Wanted to start a new post for this. Line drivers are easy to find, and many companies make good ones. I personally really like AudioControl. However, I have not yet been able to find a crossover that suits my needs. Almost every crossover has sub, midrange, and high outputs. All I need is midrange. The crossover on my head unit is fine for the high and low end. My problem with only having one crossover for the midrange is that I use a couple different sized mids, which obviously each need there own frequency cutoff ranges.
My ideal crossover would be one with one input, and at least 3 outputs, each with the same crossover controls. The crossover would need to be a bandpass style (high and low pass crossover). I would need a high pass crossover range of about 80-100 hertz up to 600-800 hertz, and a low pass crossover range of about 2-3 khz up to 5-7 khz.
Now I'm pretty sure they don't make anything like this, as I have not been able to find anything even close to this anywhere. But what I'm thinking, is that maybe I would have to get three seperate bandpass crossovers to do this. I'm sure you guys know what I'm trying to say and do, and can probably think of several different ways to do this. Please let me know of any ideas or products that you can think of. And let me know if you have any questions or need more details.
Thanx in advance,
-Ian-
Replies (25)
swez on 09/10/2006 18:17:16
What you are talking about, are multiple stage Bandpass filters for tri-amp or quad-amped configurations. Here, we limit the frequencies each amp/speaker will get to a norrow range of operation for the speakers used in each array.
If i understand you correctly, here's the general breakdown of what is needed: We are looking at a Quad-amped array in this scenario. However, there is the option of using 3-way xovers if you so desire. It's less complex, requires fewer amp channels and a simpler install as the MR/TW share the same amp channels and use passive crossover networks. This will work just fine, requires less filters, amps and other processors as well.
Subs: A low pass filter that cuts off MB at between 80-100 Hz. Since you have a ported sub system, a Subsonic, (Infrasonic) filter is also needed. Your amp has this and the Epic 160 has a line driver too. So, the bass engine is pretty well covered already.
Midbass: If you plan to run MB speakers off their own amp channels, you'll want to use a combination of the amp HPF and add a LPF to net a clean Bandpass network for MB drivers. Your HPF will be set between 80-100 Hz. Then, you'll want a secondary LPF to block highs that will be handled by your mids and tweets. Here, a LPF with a cutoff range bertween 300-500 Hz., is recommended. That means the usable frequency range for MB is ~80-300/500 Hz. Harrison Labs "F-Mods" will get the job done for you. Avoid passive filters on your speakers as they tend to be less accurate and steal power from the speakers too. This amp system will work best if you have a Line Driver circuit to insure adequate Signal level voltage to the amp inputs.
MIDRANGE: Here, we are working with another BP filter network. The amps' HPF is set between 300-500 Hz, and basically picks up where the MB filter network cuts off. Another LP filter is needed in the chain, to block highs that will be handled by your tweets. The range of of cutoff will be fixed and should match where your tweeters operate best at. Most MR speakers are flat and fairly linear between 300/500 Hz, up to 2,000/5,000 Hz. It all depends on what power handling the tweeters can take at a given frequency band and remain reasonably flat. A line driver circuit may be appropriate here too. It just depends on how you integrate Mid/Tw's.
TWEETERS:
You can either run 1 amp and passive crossovers between MR/TW's or make them separates as well. A well matched set of Components that employs a quality crossover network and a good HPF for your crossover is all that is really needed. You don't have to futz with bandpass filters here as the passive crossover will do it for you. All that is needed here, is adequate amp channels to power your MR/TW's and use well designed passives to break out the proper signals between the MR and TW's.
May I suggest you make a detailed flow chart of devices, processors/LD's, BP filters and amp channels needed to power whatever options you desire. Once it's on paper and all crossover points are determined, then it's time to review the plan, get parts on order and began the new install.
Frankly, I do suggest keeping this plan as simple as possible. If your MIDs/TW's have good crossovers with the kit, just use 1 amp channel per set. The Comp crossovers will do the rest and one less 'black box' in the audio chain to figure out or mess you up.
Comments?
Swez
PS Keep It Simple Ian. The more black boxes you use, the more $$$ is spent and troubleshooting various stages will just make things harder in the long run.
MrBrownstone on 09/10/2006 21:43:44
Dirty little secret...all preamps come with a free line driver--and they are all created equal. Those little gain controls are your free line drivers.
Dirty secret #2, if all your crossovers on your amplifiers are of the same order (and if the amplifiers are the same manufacturer) you're getting the same order and there are no phase issues.
A lot of folks over ANALyze their equipment's specifications until they have trouble pooping. (retentive)
END PSEUDOAUDIOPHILE RANT
From there, 2 of the least important parts of your car audio system, can have an impact if they are done incorrectly, but focus your attention on the speakers and acoustic (box) design.
There's really no need to have bandpass crossover options unless you really don't like the one that comes free with your high quality component systems. I've never heard anyone's vehicle with multiple electronic crossovers that sounded better than anyone's passive crossover system from a reputable manufacturer. But hey, if you like funking around with electronics, try electrical engineering.
Line drivers are very useful when your head unit voltage is less than 4 volts,....but if it isn't, the gain control on your crossover will provide the EXACT same benefit if you choose to use an external crossover. So long as you don't use more than 3dB (about 2x the input voltage) it's a free option.
I agree with Swez's PS...KISS, black boxes are usually unnecessary and expensive. A parametric EQ is more important than all of those functions. For simplicity, just use the Xover on the amp, use the EQ for boost, and if need be, use the sub level control on the head unit and you won't really notice the difference.
That way, you are making your minute adjustments from the front of the system, and not bent over in the trunk wondering why you spent the extra money. I've personally spent over $35,000 in equipment over the years, and only $4400 was worth it.
END DOUBLE RANT
cybersailor420 on 09/10/2006 21:44:24
Hey Swez, thanks for the input, as usual :)
I had a feeling you were gonna bring up those fmods. I have no experience with them, but I'm sure they would work well for crossovers. That may be my whole solution for that... I was, however, hoping to be able to adjust my crossover points as I'm not exactly sure where I want them, and I do change my mind from time to time... but I could live with those fmods. Got a could website for them? I assume partsexpress.
I don't have component sets, so I have no existing crossovers for anything. I just have raw speakers that I pieced together. I really like them, they're cheap but can sound great with some fine tuning and a good ear.. and they get loud, which we know I like ;)
As far as the crossovers on my amps, they just don't seem to cut it. Even when I have the high pass turned all the way up to 600 HZ, my mids are still putting out way too much bass, if I don't use the crossover on my head unit, which only goes to 200 HZ. So that is out of the question.
I only need crossovers for the midrange. The crossovers on my cd player are more than sufficient for the subs and tweeters. And my sub amps have all that and more. My head unit also has a 13 band eq built in (the new one i'm lookin at has a 16 band).
So really, it's just a line driver, and a crossover setup for my mids. I guess I should tell you what mids I'm using:
http://bsless.stores.yahoo.net/pdmr5.html
http://bsless.stores.yahoo.net/pdmw6.html
I have one 4 channel amp running 6 of the 5.25"s, and one amp running 2 6.5"s on one side, and 6 power acoustik tweeters on the other side.
So I need a midrange crossover setup to run one amp for the 5.25"s, and a midrange/midbass crossover setup to run 2 channels for the 6.5"s. I hope that clarifies things for you, in order to help me :)
Thanx again, Swez. You're the man!
cybersailor420 on 09/10/2006 21:59:31
Hey Mr. B, I guess we were typin at the same time...
Yea, my head unit has "6.5 volt" preouts... I assume it's at least close to that. I only need a line driver for my mids since I'm splitting the signal for them several times.
Also, it's funny that you should mention "try electrical engineering"... I have my Bachelor of Science in Electrical Engineering from Tufts University sitting right next to me. That could explain my boldness when it comes to diving right into what some may consider an electrical nightmare :p
swez on 09/11/2006 08:04:41
This is getting crazier by the post... LOL Good that you have a bonified BSEE to guide you. I have some background in electronics, but am not a bonified BSEE. That knowledge will come in handy as you pull all these things together. Yes, this is both an electrical and acoustical nightmare bro. You said it... but it's been in the back of my mind since I saw the pics of your present install. This is like a speeding freight train w/o brakes, waiting for a stalled car on the tracks ahead. LOL
I wondered what drivers those were in the pics. Not familiar with the Pyle Logo and generally would not recommend them either. But for now, let's pair things down to a more managable package and still get the results desired.
OK, from what I see here, you have way too many MB/MR speakers in the mix. Hense, too much MB in this setup. Cancellations and impedence matching nightmares are likely. IMHO, it would be best to pair all this down to a managable package. That is, 6 MB/MR speakers of your choosing and 4 tweeters. Here, you only need enough amping power to get your SPL levels on Mids/Highs up to adequate levels. Need I say it again.... SIMLPIFY for best results!!!
Since the 5.25's are plentiful and you have 6 of them now, these can become your front stage main speakers. There is also a pair of 6.5's in the mix. Here, I would use two 5.25's in parallel (in a pod) and a tweeter w/ passive crossover per each front door mounting. This gives very good stereo imaging to the front stage and you can bridge one of your 4 channel amps to power them. All that would be needed here, is a usable HPF and a matching slope filter for your tweeters.
For the rear speakers, you can do a similar idea, but use only the 6.5's and a tweeter per side. Here again, can bridge your second 4 channel down to 2 channels, use the amps' HPF and fabricate a suitable passive crossover for the tweeters.
From there, this just leaves you the Bass Engine to deal with later. Since that is pretty well fixed and well under control, we need to focus on front and rear stage speakers, passive crossovers for the tweeters and placement for all speakers used.
OK, let's get the "Big Picture" in focus for now. Then, we dig deeper to get all the key details in line. For now, read this over carefully, draw it out manually if needed and then we can come up with an overall plan to get you from a "real fine mess", to a managable plan of attack.
Oh, got a link to specs on your tweeters? Also, what are the make and model #'s of the amps you have on hand for Mids/highs? A good link with specs on HPF crossovers & power output info, would be most helpful. The way I see this now, you may not even need Line Drivers, any active crossovers, F-Mods and such. If the next HU can supply a solid 4.0 volts to each amp, these will be unnecessary. About the only thing you may find useful now, would be a solid Digital EQ to smooth out the peaks and valleys that may appear in the MB/MR/TW regions.
Swez
PS With all the cash you're going to save on this new plan, setting aside a nice "performance bonus" for the Audio Consultant, seems like a reasonable thing to put on the table now. He's (Ol Swez) has put a lot of effort into this plan and it ain't over yet.
See, I too have a goal to reach. Am looking for a new flyrod, reel and line for same. This will be my goal for the end of the year. (My Christmas and Birthday present) and if you can help me out a bit... I'd be very satisfied with that.
Think it over as we are basically bartering skills, know how and time. Does that seem reasonable/do-able? (No, not a huge expese here either... just a token of "tangable appreciation" is the thought behind it)
I am "not saying" you have to and I will still guide you as needed. But am just floating an idea here, where both of us get something useful as we go along. Comments?
MrBrownstone on 09/12/2006 04:42:15
Let's have a laugh together since we post together!!
Back to business...when you parallel your RCA signals from your head unit or preamp equipment, the voltage doesn't go down. Remember, we're talking 6.5V ...but at a 1000 ohms (give or take). Although the reference signal is 6.5V, it's about 0.001 Watts when it's all said and done...so you can parallel quite a few lines before seeing any issues with signal voltage.
I think, but would have to test it again, that you could parallel 16 sets of RCAs before getting yourself in trouble. However, most of your amplifiers have passthrough for the other amps, so signal voltage isn't the issue.
Your main goal is to have a high enough signal voltage to excite the input side of the amplifier so that you can operate the gain control in it's more 'quieter' setting--avoiding noise.
PS Electrical nightmare? EEs are felonious for CREATING their own nightmares.
swez on 09/12/2006 14:20:30
Me thinks there is a flaw in the paralleling of many RCA outputs off a single HU channel. We know a few things about RCA circuit preamps:
1. They have a rated voltage output at ~80% of max volume (6.5 V)
2. The higher the amps' input impedence, the lower the current draw off that preamp (and visa-versa)
3. As we parallel loads (amp impedence) values, net resisitance drops in a given circuit
4. We don't know how much current draw a typical HU's RCA preamps can provide before it overloads the output current and damages the HU.
Here's an example: HU = 6.5 volts; each amp has an impedence load of 1,000 ohms
1 amp draws: 6.5 volts/1000 ohms = 0.0065 amperes (6.5 mA's)
2 amps draw: 6.5 volts/500 ohms = 0.013 amperes (13.0 mA's)
3 amps draw: 6.5 volts/333.3 ohms = 0.0195 amperes (19.5 mA's)
4 amps draw: 6.5 volts/250 ohms = 0.026 amperes (26.0 mA's)
See the picture here? The lower the impedence, the higher the current draw will be. That's Ohm's Law, pure and simple. However, we don't know the current draw limits of a given HU preamp.
If we knew that circuit could pass 50 mA's safely, no problem. That's 0.05 amperes of current and we can run a good number of amplifiers (7 ampifiers) this way. (45 mA's)
The point here is, we don't know the current limits of a HU's RCA preamps. If you look at any good manual, few show more than 2 amplifiers ("Y" cable splitters) driven off a given RCA line output. There must be a reason for that.
Anyone care to contact say Pioneer, Alpine or Eclipes and see what the preamp current maximums are? I would not be surprised if they said... "25 -30 mA's, is the maximum current draw that circuit can handle."
Anyone care to tackle that one?
Swez
swez on 09/12/2006 14:41:03
OK, I called my buddies at Crutchfield Tech and he said that 2 amplifiers are generally the limit for HU preamps. If one were to run more than 2 amplifiers off that circuit, it would be advisable to use a Line Driver/EQ or LD/Xover. He did not know the maximum current draw that circuit could take, but did say that 2 pair of amp channels is the recommended limit for a HU line out.
Case closed, unless others care to dig deeper,
Swez
PS What is the make and model # of the HU you were using when this system went on the fritz? A link would be most helpful as there are few HU's out there that produce over 4.0 volts from the RCA outs.
cybersailor420 on 09/12/2006 17:13:46
Great info there Swez, that made it more clear in my mind. I now understand what the probable cause of the output failure on my cd player(s) was.
Mid/highs amp (currently using two of these):
http://www.millionbuy.com/souega4220.html
three 30 amp fuses each
Tweeters (this is the best info I could find):
http://cgi.ebay.com/POWER-ACOUSTIK-NB-1-COMPONENT-TWEETER-2-WAY-200-WATTS_W0QQitemZ140027229332QQihZ004QQcategoryZ14943QQcmdZViewItem
Head unit:
http://www.sonicelectronix.com/item_7212.html
gotta head out of the office, but i'll be back on later.
swez on 09/13/2006 00:16:27
OK, looks like we are on the right page. This Pioneer DEH-P860MP is actually spec'd at 4.0 volts on it's manual. The Sonic web page states 6.5 volts @ 100 ohms.
So, 6.5/100 = 0.065 A's or 65 mA's of current per RCA output.
Now, if we knew the input impedence of your SS amps, and factored all this into current draw, that may well explain HU preamp failures that had been noted before. Since this circuit is not fused, a transistor junction would fail if too much current was demanded and that would explain the noise as well.
If you have amp manuals for the SoundStream EGA4220, look at the input impedence specs and float it back here.
Swez
cybersailor420 on 09/13/2006 01:02:22
No luck in the manual. I'm going to email the tech support tomorrow and ask them.
If this is the problem with my cd player, any idea what a problem like this would cost to get fixed?
MrBrownstone on 09/13/2006 01:52:14
Swez
We ran 16 sets or paralleled RCAs off 1 Eclipse unit in 2000...it worked quite well. Of course, when we got the whole preamp thing, it didn't make any difference.
We're talking about 0.026 A of current, which really doesn't make a difference. Besides, has that 'tech' from Crutchfield actually tried this arrangement? Doubt it.
If you do have the opportunity, use the pass-thru on each amplifier (most newer ones have that now) or the one on the EQ or crossover. I wouldn't worry much about signal strength since it won't change when paralleled.
PS if there's any failure from the head unit, it'll likely be using too m any connections to the Remote Turn-on wire, not the RCAs.
swez on 09/13/2006 07:25:06
Quote: "if there's any failure from the head unit, it'll likely be using too many connections to the Remote Turn-on wire, not the RCAs."
I agree 100% with that statement... what happens when we over load the REM circuit? It either shuts off the amps or it blows the power chip in the HU.
Had that problem with a Nak and a pair of JL amps and an EQ/LD. The HU REM could not support all 3 device and we wound up using a fused link off the ACC/IGN. Yes, the REM worked fine with 1 or 2 devices, but when the 3rd was inserted, the REM circuit shut off. (Auto protect)
After talking with the guy at Crutch (Think he was an older guy named Bill) we hashed out a scenario and he said that a high end HU like Eclipse or Nak might handle several splits over two, but his manuals did not show any specs on Pioneer HU's that would suggest doing more than 2 pair of splits per channel.
Am sure B, that you did as mentioned and it worked. Am not challenging your experience here. However, I don't think all HU's are as robust in some areas as the one you tried this on.
This debate is silly as the fact remains, Cyb's primary HU went on the blink with this multi-tap patch and a 2nd player did the same thing. He even tested them on his home system and the same problems were present. Bottom line, something had damaged the preamp outputs and now they are useless. (non-ground loop noise issues) We are trying to figure out the cause and avoid it on the next install.
Cyber, have no idea what the repair bill might be for your P860 player. However, if you had it bench tested by a tech and parts and labor are more than 50% of the cost of replacement HU, buy a new one.
Swez
PS Mr. B., don't really desire to debate this one with you. We know each other well enough to know that neither one is going to budge easily from our positions. (Pugnatious arn't we?) No biggie, I am not a skilled debator, nor do I wish to become one.
You can have the last word as I know you are a skilled "Master-de-bater". I just picked up my pail and shovel and moved to a different sand box. You can have this one as I have abdicated from this debate... you win. Happy now? LOL
PSS My Ex was/is a gifted debater. I am a nutz and bolts "problem solver". One likes a good verbal sparring match while the other looks for solutions. Who cares about the "what if" or playing "Devil's Advocate"? The debator is not interested in resolving problems. They just like to hash them out to the nth degree. Problem solvers are results oriented. They look for viable solutions.
Example: "Honey... just shut up and hand me the tool kit and a working flashlight. I aims to fixin' the garbage disposal and no, it's not your fault it broke"!
"OK, so I did find 2 lbs of chicken bones in there after all... nice dinner dear and the disposal is now working again. Let's go out for some ice cream... OK?" Case closed... done deal... all is right with the world again! Bedtime came early that night and it was the best night out in months.
(It really wasn't your fault sweetie. We just need a commerecial duty 2.5 HP disposal to handle all this grinding and gnashing.) GRIN
End of story... game over and out.
cybersailor420 on 09/17/2006 22:40:09
Hey guys,
sorry it's taken me so long to get back to these posts, been super busy (surf has been up, hehe).
I still haven't heard back from the tech support at Soundstream. I will send them another email tomorrow.
Mr. B, your points were well noted, and I do agree that running several amplifiers off the remote turn-on could damage the head unit. However, as Swez pointed out, I do not believe that is the case in this scenario.
After my head unit started to malfunction, I tried using a portable dvd/cd player. The head unit was still used only to turn the amps on and off, which still worked fine. But after a couple days of this setup, the portable player also started having the same noise issues. When I plugged it into my home amp, I still got the noise.
I'll get back to you guys if I hear anything from Soundstream. I'm taking my time picking out my new gear... I'll keep you posted on that progess as well.
-Ian-
Victor on 09/18/2006 00:26:01
If its a Pioneer Player, they are notoriously known for bad RCA out grounding....
Try grounding the RCA out from the HU and the noise should be gone...
Victor...
swez on 09/18/2006 07:24:48
Seems like Ian's making a point and we are trying to figure out why the system worked fine for a time, then went on the fritz.
He used his main Pioneer HU, (P860MP) until it failed and he varified the HU was generating some odd noise with his home system. He then used a portable player, (known good) and it too went on the fritz.
The common thread here, seems to be his vehicle and systems within his original install. It MAY be "ground loop" issues to a degree. However, 2 players going down after working fine, says something here. That indicates something in this install, is causing damage to the HU and a self-powered player.
The question is... "What is causing these players to fizzle out when used in this vehicle?" Ian, are all RCA outs making this noise or can we isolate it to Front, Rear or Sub only outputs?
One thing we have not discussed yet, is an "Ground Loop Isolator) or RCA isolation circuits. This is an air core transformer setup where we inductively couple the HU RCA's to the outboard amps.
Here, the HU load remains constant on one side of the ISO Transformer. (a fixed load) The other side of the ISO Tranformer, feeds your amps via inductive coupling only. This is how Ground Loop Isolators work. They de-couple the HU from amplifiers and this usually eliminates all grounding mis-matches between the HU and amp inputs.
Am wondering if this approach would be beneficial here??? Why?
1. HU RCA's see a fixed load, regardless of amp(s) impedence loads)
2. Amps get RCA signals from the Isolation Transformer only
3. This de-coupling circuit does not need hard wired linkage from HU outs to amp ins
4. Since this is inductively coupled, ground loops and impedence issues are eliminated
I would bet that most quality LD's/EQ's/Crossovers, use this circuit as well. Anyone care to inquire about this one with Audio Control products?
swez
cybersailor420 on 09/20/2006 23:25:45
Swez - am not sure exactly what you mean by "inductive coupling." do you have a link that explains this, or would you care to give me a little more info on this?
Also, how do you ground the RCA outputs? I know I read about it in a post a while back, but could not find it. This may help with some of the noise that I never seemed to be able to get rid... One noise I could never get rid of seemed to have something to do with the Daytime Running Lights. I would have no noise if the hand brake was on, or if the head lights were on... but once I took the hand brake off without the headlights one, I would get a constant hum.
-Ian-
swez on 09/21/2006 07:40:38
Quote: "One noise I could never get rid of seemed to have something to do with the Daytime Running Lights. I would have no noise if the hand brake was on, or if the head lights were on... but once I took the hand brake off without the headlights one, I would get a constant hum."
That is often a sign of ground loop noise. When those circuits are in use, you get a better ground and the noise goes away. This is not common with most installs. However, when the HU is not fully grounded with other components, or there is an imbalance of grounds to audio gear, we get noise.
One option is a "Balanaced Line Driver" that uses an isolated power supply. Read more about this here:
http://www.bcae1.com/audioiso.htm
Most of the advanced Crossovers and EQ add ons from Audio Control, offer "balanced and unbalanced" audio line in or line outs. This means the power supply in the EQ/LD/XO have an isolating transformer in their power, to supress ground loops. DC offsets do not pass through the transformer's primary and secondary coil sets. Hense, no more ground loop noise in the audio chain. This is called an "Audio Reference Isolation" circuit. (See it explained in the link given)
When we ground the RCA wires, this refers to running a dedicated ground wire from the amp chassis grounds, back to the HU and attach this wire to the HU chassis. Some RCA wire sets have a small diameter tag wire for this purpose or that wire can be used as a REM feed from HU to amps.
If your RCA's do not have this tag line, you can install one as a stand alone ground from the HU chassis, back to each amp/processor chassis and get the same benefits. This method insures all devices in the "signal path" are now grounded to the same point via your tag wire and add on splices for each amp or processor in the audio signal path.
This method works well in most applications too. Here, all audio signals now share a common grounding path and most of the time, ground loop noise is eliminated.
Is your head spinning now? LOL
swez
swez on 09/21/2006 07:58:42
Here's a section on "Ground Loop Isolators" to review:
http://www.bcae1.com/glisoltr.htm
Note the transformer employed between the input and output side RCA's. The transformer is there to block DC hum. Transformers will not pass DC signals and therefore, block all DC noise in a given circuit.
Again, better HU's, processors and amps have some form of noise isolation or suppression circuits or balanced line input/outputs. However, many good products only use OP amps and non-balance line in/out circuits. This is when we can employ the use of ground loop isolators.
swez
cybersailor420 on 09/29/2006 21:06:30
I finally got an email back from the tech support... only took about 2 weeks. Anyways, they said the input impedance of my soundstream amps is 6,000 ohms.
swez on 09/30/2006 11:25:16
Interesting number there Sailor.... if you had 3 of these amps paralleled together with "Y" cables, that's a 2000 ohm impedence load.
With a HU rated at 4.0 volts, that's ~2 mA's of current draw. (4/2000 = 0.002 A's) Seems like that is not a big number for a given channel (F,R or Sub) off the HU preamps to drive that modest load. However, 2 damaged HU's are a compelling reason to look deeper into this one.
The question here would be, how much current can the RCA preamps manage safely? I doupt any HU maker would publish that detail. However, a tech at Crutchfield recommended no more than two feeds per channel off a given HU.
Mr. B. has daisy-chained several channels in his days and reports a given RCA preamp can support well over 4 pairs. But the fact still remains... what caused your 2 HU/Sources to crap out?
Have you had a chance to send either unit in for diagnostics and repairs? It would seem to me, your P860MP would be worth repair costs if it did not exceed about 50% of the cost for a new HU. (Consider a factory refurb?)
swez
Victor on 10/1/2006 05:28:29
Well, Can you please atleast try and ground the RCA outs from the HU and check if there is any improvement in the sound...??
Victor...
swez on 10/1/2006 09:40:40
Am sure he will... once the HU is repaired or replaced.
swez
cybersailor420 on 10/1/2006 10:34:34
Hey guys,
I have yet to get my cd player repaired, but I do plan on it. I have to go to another island in order to have it done...
Once I get my head unit repaired, or put a new one in, I am going to run a ground wire from the grounding point in the back to the spot where my head unit is grounded to the chassis in the front. I will then run a wire from the frame of the head unit to this spot as well. Does this sound like a good plan to you? This should take care of any ground loop issues, right?
I also have a line driver/eq coming that has balanced inputs. I got an Audio Control EQX on ebay for $58. I figured I'll just use it for the balanced inputs and line driver for now, until I find something I really like. More on that later.
Thanx guys,
-Ian-
swez on 10/1/2006 13:16:43
Yes, proper grounding is the key to getting rid of ground loops. Also, running balanced signal lines will definitely help. With this feature, you effectively double the RCA signal strength over unbalanced lines.
If you want to weed/read some details about how balanced lines work, go here:
http://www.bcae1.com/ballndrv.htm
swez
My ideal crossover would be one with one input, and at least 3 outputs, each with the same crossover controls. The crossover would need to be a bandpass style (high and low pass crossover). I would need a high pass crossover range of about 80-100 hertz up to 600-800 hertz, and a low pass crossover range of about 2-3 khz up to 5-7 khz.
Now I'm pretty sure they don't make anything like this, as I have not been able to find anything even close to this anywhere. But what I'm thinking, is that maybe I would have to get three seperate bandpass crossovers to do this. I'm sure you guys know what I'm trying to say and do, and can probably think of several different ways to do this. Please let me know of any ideas or products that you can think of. And let me know if you have any questions or need more details.
Thanx in advance,
-Ian-
Replies (25)
swez on 09/10/2006 18:17:16
What you are talking about, are multiple stage Bandpass filters for tri-amp or quad-amped configurations. Here, we limit the frequencies each amp/speaker will get to a norrow range of operation for the speakers used in each array.
If i understand you correctly, here's the general breakdown of what is needed: We are looking at a Quad-amped array in this scenario. However, there is the option of using 3-way xovers if you so desire. It's less complex, requires fewer amp channels and a simpler install as the MR/TW share the same amp channels and use passive crossover networks. This will work just fine, requires less filters, amps and other processors as well.
Subs: A low pass filter that cuts off MB at between 80-100 Hz. Since you have a ported sub system, a Subsonic, (Infrasonic) filter is also needed. Your amp has this and the Epic 160 has a line driver too. So, the bass engine is pretty well covered already.
Midbass: If you plan to run MB speakers off their own amp channels, you'll want to use a combination of the amp HPF and add a LPF to net a clean Bandpass network for MB drivers. Your HPF will be set between 80-100 Hz. Then, you'll want a secondary LPF to block highs that will be handled by your mids and tweets. Here, a LPF with a cutoff range bertween 300-500 Hz., is recommended. That means the usable frequency range for MB is ~80-300/500 Hz. Harrison Labs "F-Mods" will get the job done for you. Avoid passive filters on your speakers as they tend to be less accurate and steal power from the speakers too. This amp system will work best if you have a Line Driver circuit to insure adequate Signal level voltage to the amp inputs.
MIDRANGE: Here, we are working with another BP filter network. The amps' HPF is set between 300-500 Hz, and basically picks up where the MB filter network cuts off. Another LP filter is needed in the chain, to block highs that will be handled by your tweets. The range of of cutoff will be fixed and should match where your tweeters operate best at. Most MR speakers are flat and fairly linear between 300/500 Hz, up to 2,000/5,000 Hz. It all depends on what power handling the tweeters can take at a given frequency band and remain reasonably flat. A line driver circuit may be appropriate here too. It just depends on how you integrate Mid/Tw's.
TWEETERS:
You can either run 1 amp and passive crossovers between MR/TW's or make them separates as well. A well matched set of Components that employs a quality crossover network and a good HPF for your crossover is all that is really needed. You don't have to futz with bandpass filters here as the passive crossover will do it for you. All that is needed here, is adequate amp channels to power your MR/TW's and use well designed passives to break out the proper signals between the MR and TW's.
May I suggest you make a detailed flow chart of devices, processors/LD's, BP filters and amp channels needed to power whatever options you desire. Once it's on paper and all crossover points are determined, then it's time to review the plan, get parts on order and began the new install.
Frankly, I do suggest keeping this plan as simple as possible. If your MIDs/TW's have good crossovers with the kit, just use 1 amp channel per set. The Comp crossovers will do the rest and one less 'black box' in the audio chain to figure out or mess you up.
Comments?
Swez
PS Keep It Simple Ian. The more black boxes you use, the more $$$ is spent and troubleshooting various stages will just make things harder in the long run.
MrBrownstone on 09/10/2006 21:43:44
Dirty little secret...all preamps come with a free line driver--and they are all created equal. Those little gain controls are your free line drivers.
Dirty secret #2, if all your crossovers on your amplifiers are of the same order (and if the amplifiers are the same manufacturer) you're getting the same order and there are no phase issues.
A lot of folks over ANALyze their equipment's specifications until they have trouble pooping. (retentive)
END PSEUDOAUDIOPHILE RANT
From there, 2 of the least important parts of your car audio system, can have an impact if they are done incorrectly, but focus your attention on the speakers and acoustic (box) design.
There's really no need to have bandpass crossover options unless you really don't like the one that comes free with your high quality component systems. I've never heard anyone's vehicle with multiple electronic crossovers that sounded better than anyone's passive crossover system from a reputable manufacturer. But hey, if you like funking around with electronics, try electrical engineering.
Line drivers are very useful when your head unit voltage is less than 4 volts,....but if it isn't, the gain control on your crossover will provide the EXACT same benefit if you choose to use an external crossover. So long as you don't use more than 3dB (about 2x the input voltage) it's a free option.
I agree with Swez's PS...KISS, black boxes are usually unnecessary and expensive. A parametric EQ is more important than all of those functions. For simplicity, just use the Xover on the amp, use the EQ for boost, and if need be, use the sub level control on the head unit and you won't really notice the difference.
That way, you are making your minute adjustments from the front of the system, and not bent over in the trunk wondering why you spent the extra money. I've personally spent over $35,000 in equipment over the years, and only $4400 was worth it.
END DOUBLE RANT
cybersailor420 on 09/10/2006 21:44:24
Hey Swez, thanks for the input, as usual :)
I had a feeling you were gonna bring up those fmods. I have no experience with them, but I'm sure they would work well for crossovers. That may be my whole solution for that... I was, however, hoping to be able to adjust my crossover points as I'm not exactly sure where I want them, and I do change my mind from time to time... but I could live with those fmods. Got a could website for them? I assume partsexpress.
I don't have component sets, so I have no existing crossovers for anything. I just have raw speakers that I pieced together. I really like them, they're cheap but can sound great with some fine tuning and a good ear.. and they get loud, which we know I like ;)
As far as the crossovers on my amps, they just don't seem to cut it. Even when I have the high pass turned all the way up to 600 HZ, my mids are still putting out way too much bass, if I don't use the crossover on my head unit, which only goes to 200 HZ. So that is out of the question.
I only need crossovers for the midrange. The crossovers on my cd player are more than sufficient for the subs and tweeters. And my sub amps have all that and more. My head unit also has a 13 band eq built in (the new one i'm lookin at has a 16 band).
So really, it's just a line driver, and a crossover setup for my mids. I guess I should tell you what mids I'm using:
http://bsless.stores.yahoo.net/pdmr5.html
http://bsless.stores.yahoo.net/pdmw6.html
I have one 4 channel amp running 6 of the 5.25"s, and one amp running 2 6.5"s on one side, and 6 power acoustik tweeters on the other side.
So I need a midrange crossover setup to run one amp for the 5.25"s, and a midrange/midbass crossover setup to run 2 channels for the 6.5"s. I hope that clarifies things for you, in order to help me :)
Thanx again, Swez. You're the man!
cybersailor420 on 09/10/2006 21:59:31
Hey Mr. B, I guess we were typin at the same time...
Yea, my head unit has "6.5 volt" preouts... I assume it's at least close to that. I only need a line driver for my mids since I'm splitting the signal for them several times.
Also, it's funny that you should mention "try electrical engineering"... I have my Bachelor of Science in Electrical Engineering from Tufts University sitting right next to me. That could explain my boldness when it comes to diving right into what some may consider an electrical nightmare :p
swez on 09/11/2006 08:04:41
This is getting crazier by the post... LOL Good that you have a bonified BSEE to guide you. I have some background in electronics, but am not a bonified BSEE. That knowledge will come in handy as you pull all these things together. Yes, this is both an electrical and acoustical nightmare bro. You said it... but it's been in the back of my mind since I saw the pics of your present install. This is like a speeding freight train w/o brakes, waiting for a stalled car on the tracks ahead. LOL
I wondered what drivers those were in the pics. Not familiar with the Pyle Logo and generally would not recommend them either. But for now, let's pair things down to a more managable package and still get the results desired.
OK, from what I see here, you have way too many MB/MR speakers in the mix. Hense, too much MB in this setup. Cancellations and impedence matching nightmares are likely. IMHO, it would be best to pair all this down to a managable package. That is, 6 MB/MR speakers of your choosing and 4 tweeters. Here, you only need enough amping power to get your SPL levels on Mids/Highs up to adequate levels. Need I say it again.... SIMLPIFY for best results!!!
Since the 5.25's are plentiful and you have 6 of them now, these can become your front stage main speakers. There is also a pair of 6.5's in the mix. Here, I would use two 5.25's in parallel (in a pod) and a tweeter w/ passive crossover per each front door mounting. This gives very good stereo imaging to the front stage and you can bridge one of your 4 channel amps to power them. All that would be needed here, is a usable HPF and a matching slope filter for your tweeters.
For the rear speakers, you can do a similar idea, but use only the 6.5's and a tweeter per side. Here again, can bridge your second 4 channel down to 2 channels, use the amps' HPF and fabricate a suitable passive crossover for the tweeters.
From there, this just leaves you the Bass Engine to deal with later. Since that is pretty well fixed and well under control, we need to focus on front and rear stage speakers, passive crossovers for the tweeters and placement for all speakers used.
OK, let's get the "Big Picture" in focus for now. Then, we dig deeper to get all the key details in line. For now, read this over carefully, draw it out manually if needed and then we can come up with an overall plan to get you from a "real fine mess", to a managable plan of attack.
Oh, got a link to specs on your tweeters? Also, what are the make and model #'s of the amps you have on hand for Mids/highs? A good link with specs on HPF crossovers & power output info, would be most helpful. The way I see this now, you may not even need Line Drivers, any active crossovers, F-Mods and such. If the next HU can supply a solid 4.0 volts to each amp, these will be unnecessary. About the only thing you may find useful now, would be a solid Digital EQ to smooth out the peaks and valleys that may appear in the MB/MR/TW regions.
Swez
PS With all the cash you're going to save on this new plan, setting aside a nice "performance bonus" for the Audio Consultant, seems like a reasonable thing to put on the table now. He's (Ol Swez) has put a lot of effort into this plan and it ain't over yet.
See, I too have a goal to reach. Am looking for a new flyrod, reel and line for same. This will be my goal for the end of the year. (My Christmas and Birthday present) and if you can help me out a bit... I'd be very satisfied with that.
Think it over as we are basically bartering skills, know how and time. Does that seem reasonable/do-able? (No, not a huge expese here either... just a token of "tangable appreciation" is the thought behind it)
I am "not saying" you have to and I will still guide you as needed. But am just floating an idea here, where both of us get something useful as we go along. Comments?
MrBrownstone on 09/12/2006 04:42:15
Let's have a laugh together since we post together!!
Back to business...when you parallel your RCA signals from your head unit or preamp equipment, the voltage doesn't go down. Remember, we're talking 6.5V ...but at a 1000 ohms (give or take). Although the reference signal is 6.5V, it's about 0.001 Watts when it's all said and done...so you can parallel quite a few lines before seeing any issues with signal voltage.
I think, but would have to test it again, that you could parallel 16 sets of RCAs before getting yourself in trouble. However, most of your amplifiers have passthrough for the other amps, so signal voltage isn't the issue.
Your main goal is to have a high enough signal voltage to excite the input side of the amplifier so that you can operate the gain control in it's more 'quieter' setting--avoiding noise.
PS Electrical nightmare? EEs are felonious for CREATING their own nightmares.
swez on 09/12/2006 14:20:30
Me thinks there is a flaw in the paralleling of many RCA outputs off a single HU channel. We know a few things about RCA circuit preamps:
1. They have a rated voltage output at ~80% of max volume (6.5 V)
2. The higher the amps' input impedence, the lower the current draw off that preamp (and visa-versa)
3. As we parallel loads (amp impedence) values, net resisitance drops in a given circuit
4. We don't know how much current draw a typical HU's RCA preamps can provide before it overloads the output current and damages the HU.
Here's an example: HU = 6.5 volts; each amp has an impedence load of 1,000 ohms
1 amp draws: 6.5 volts/1000 ohms = 0.0065 amperes (6.5 mA's)
2 amps draw: 6.5 volts/500 ohms = 0.013 amperes (13.0 mA's)
3 amps draw: 6.5 volts/333.3 ohms = 0.0195 amperes (19.5 mA's)
4 amps draw: 6.5 volts/250 ohms = 0.026 amperes (26.0 mA's)
See the picture here? The lower the impedence, the higher the current draw will be. That's Ohm's Law, pure and simple. However, we don't know the current draw limits of a given HU preamp.
If we knew that circuit could pass 50 mA's safely, no problem. That's 0.05 amperes of current and we can run a good number of amplifiers (7 ampifiers) this way. (45 mA's)
The point here is, we don't know the current limits of a HU's RCA preamps. If you look at any good manual, few show more than 2 amplifiers ("Y" cable splitters) driven off a given RCA line output. There must be a reason for that.
Anyone care to contact say Pioneer, Alpine or Eclipes and see what the preamp current maximums are? I would not be surprised if they said... "25 -30 mA's, is the maximum current draw that circuit can handle."
Anyone care to tackle that one?
Swez
swez on 09/12/2006 14:41:03
OK, I called my buddies at Crutchfield Tech and he said that 2 amplifiers are generally the limit for HU preamps. If one were to run more than 2 amplifiers off that circuit, it would be advisable to use a Line Driver/EQ or LD/Xover. He did not know the maximum current draw that circuit could take, but did say that 2 pair of amp channels is the recommended limit for a HU line out.
Case closed, unless others care to dig deeper,
Swez
PS What is the make and model # of the HU you were using when this system went on the fritz? A link would be most helpful as there are few HU's out there that produce over 4.0 volts from the RCA outs.
cybersailor420 on 09/12/2006 17:13:46
Great info there Swez, that made it more clear in my mind. I now understand what the probable cause of the output failure on my cd player(s) was.
Mid/highs amp (currently using two of these):
http://www.millionbuy.com/souega4220.html
three 30 amp fuses each
Tweeters (this is the best info I could find):
http://cgi.ebay.com/POWER-ACOUSTIK-NB-1-COMPONENT-TWEETER-2-WAY-200-WATTS_W0QQitemZ140027229332QQihZ004QQcategoryZ14943QQcmdZViewItem
Head unit:
http://www.sonicelectronix.com/item_7212.html
gotta head out of the office, but i'll be back on later.
swez on 09/13/2006 00:16:27
OK, looks like we are on the right page. This Pioneer DEH-P860MP is actually spec'd at 4.0 volts on it's manual. The Sonic web page states 6.5 volts @ 100 ohms.
So, 6.5/100 = 0.065 A's or 65 mA's of current per RCA output.
Now, if we knew the input impedence of your SS amps, and factored all this into current draw, that may well explain HU preamp failures that had been noted before. Since this circuit is not fused, a transistor junction would fail if too much current was demanded and that would explain the noise as well.
If you have amp manuals for the SoundStream EGA4220, look at the input impedence specs and float it back here.
Swez
cybersailor420 on 09/13/2006 01:02:22
No luck in the manual. I'm going to email the tech support tomorrow and ask them.
If this is the problem with my cd player, any idea what a problem like this would cost to get fixed?
MrBrownstone on 09/13/2006 01:52:14
Swez
We ran 16 sets or paralleled RCAs off 1 Eclipse unit in 2000...it worked quite well. Of course, when we got the whole preamp thing, it didn't make any difference.
We're talking about 0.026 A of current, which really doesn't make a difference. Besides, has that 'tech' from Crutchfield actually tried this arrangement? Doubt it.
If you do have the opportunity, use the pass-thru on each amplifier (most newer ones have that now) or the one on the EQ or crossover. I wouldn't worry much about signal strength since it won't change when paralleled.
PS if there's any failure from the head unit, it'll likely be using too m any connections to the Remote Turn-on wire, not the RCAs.
swez on 09/13/2006 07:25:06
Quote: "if there's any failure from the head unit, it'll likely be using too many connections to the Remote Turn-on wire, not the RCAs."
I agree 100% with that statement... what happens when we over load the REM circuit? It either shuts off the amps or it blows the power chip in the HU.
Had that problem with a Nak and a pair of JL amps and an EQ/LD. The HU REM could not support all 3 device and we wound up using a fused link off the ACC/IGN. Yes, the REM worked fine with 1 or 2 devices, but when the 3rd was inserted, the REM circuit shut off. (Auto protect)
After talking with the guy at Crutch (Think he was an older guy named Bill) we hashed out a scenario and he said that a high end HU like Eclipse or Nak might handle several splits over two, but his manuals did not show any specs on Pioneer HU's that would suggest doing more than 2 pair of splits per channel.
Am sure B, that you did as mentioned and it worked. Am not challenging your experience here. However, I don't think all HU's are as robust in some areas as the one you tried this on.
This debate is silly as the fact remains, Cyb's primary HU went on the blink with this multi-tap patch and a 2nd player did the same thing. He even tested them on his home system and the same problems were present. Bottom line, something had damaged the preamp outputs and now they are useless. (non-ground loop noise issues) We are trying to figure out the cause and avoid it on the next install.
Cyber, have no idea what the repair bill might be for your P860 player. However, if you had it bench tested by a tech and parts and labor are more than 50% of the cost of replacement HU, buy a new one.
Swez
PS Mr. B., don't really desire to debate this one with you. We know each other well enough to know that neither one is going to budge easily from our positions. (Pugnatious arn't we?) No biggie, I am not a skilled debator, nor do I wish to become one.
You can have the last word as I know you are a skilled "Master-de-bater". I just picked up my pail and shovel and moved to a different sand box. You can have this one as I have abdicated from this debate... you win. Happy now? LOL
PSS My Ex was/is a gifted debater. I am a nutz and bolts "problem solver". One likes a good verbal sparring match while the other looks for solutions. Who cares about the "what if" or playing "Devil's Advocate"? The debator is not interested in resolving problems. They just like to hash them out to the nth degree. Problem solvers are results oriented. They look for viable solutions.
Example: "Honey... just shut up and hand me the tool kit and a working flashlight. I aims to fixin' the garbage disposal and no, it's not your fault it broke"!
"OK, so I did find 2 lbs of chicken bones in there after all... nice dinner dear and the disposal is now working again. Let's go out for some ice cream... OK?" Case closed... done deal... all is right with the world again! Bedtime came early that night and it was the best night out in months.
(It really wasn't your fault sweetie. We just need a commerecial duty 2.5 HP disposal to handle all this grinding and gnashing.) GRIN
End of story... game over and out.
cybersailor420 on 09/17/2006 22:40:09
Hey guys,
sorry it's taken me so long to get back to these posts, been super busy (surf has been up, hehe).
I still haven't heard back from the tech support at Soundstream. I will send them another email tomorrow.
Mr. B, your points were well noted, and I do agree that running several amplifiers off the remote turn-on could damage the head unit. However, as Swez pointed out, I do not believe that is the case in this scenario.
After my head unit started to malfunction, I tried using a portable dvd/cd player. The head unit was still used only to turn the amps on and off, which still worked fine. But after a couple days of this setup, the portable player also started having the same noise issues. When I plugged it into my home amp, I still got the noise.
I'll get back to you guys if I hear anything from Soundstream. I'm taking my time picking out my new gear... I'll keep you posted on that progess as well.
-Ian-
Victor on 09/18/2006 00:26:01
If its a Pioneer Player, they are notoriously known for bad RCA out grounding....
Try grounding the RCA out from the HU and the noise should be gone...
Victor...
swez on 09/18/2006 07:24:48
Seems like Ian's making a point and we are trying to figure out why the system worked fine for a time, then went on the fritz.
He used his main Pioneer HU, (P860MP) until it failed and he varified the HU was generating some odd noise with his home system. He then used a portable player, (known good) and it too went on the fritz.
The common thread here, seems to be his vehicle and systems within his original install. It MAY be "ground loop" issues to a degree. However, 2 players going down after working fine, says something here. That indicates something in this install, is causing damage to the HU and a self-powered player.
The question is... "What is causing these players to fizzle out when used in this vehicle?" Ian, are all RCA outs making this noise or can we isolate it to Front, Rear or Sub only outputs?
One thing we have not discussed yet, is an "Ground Loop Isolator) or RCA isolation circuits. This is an air core transformer setup where we inductively couple the HU RCA's to the outboard amps.
Here, the HU load remains constant on one side of the ISO Transformer. (a fixed load) The other side of the ISO Tranformer, feeds your amps via inductive coupling only. This is how Ground Loop Isolators work. They de-couple the HU from amplifiers and this usually eliminates all grounding mis-matches between the HU and amp inputs.
Am wondering if this approach would be beneficial here??? Why?
1. HU RCA's see a fixed load, regardless of amp(s) impedence loads)
2. Amps get RCA signals from the Isolation Transformer only
3. This de-coupling circuit does not need hard wired linkage from HU outs to amp ins
4. Since this is inductively coupled, ground loops and impedence issues are eliminated
I would bet that most quality LD's/EQ's/Crossovers, use this circuit as well. Anyone care to inquire about this one with Audio Control products?
swez
cybersailor420 on 09/20/2006 23:25:45
Swez - am not sure exactly what you mean by "inductive coupling." do you have a link that explains this, or would you care to give me a little more info on this?
Also, how do you ground the RCA outputs? I know I read about it in a post a while back, but could not find it. This may help with some of the noise that I never seemed to be able to get rid... One noise I could never get rid of seemed to have something to do with the Daytime Running Lights. I would have no noise if the hand brake was on, or if the head lights were on... but once I took the hand brake off without the headlights one, I would get a constant hum.
-Ian-
swez on 09/21/2006 07:40:38
Quote: "One noise I could never get rid of seemed to have something to do with the Daytime Running Lights. I would have no noise if the hand brake was on, or if the head lights were on... but once I took the hand brake off without the headlights one, I would get a constant hum."
That is often a sign of ground loop noise. When those circuits are in use, you get a better ground and the noise goes away. This is not common with most installs. However, when the HU is not fully grounded with other components, or there is an imbalance of grounds to audio gear, we get noise.
One option is a "Balanaced Line Driver" that uses an isolated power supply. Read more about this here:
http://www.bcae1.com/audioiso.htm
Most of the advanced Crossovers and EQ add ons from Audio Control, offer "balanced and unbalanced" audio line in or line outs. This means the power supply in the EQ/LD/XO have an isolating transformer in their power, to supress ground loops. DC offsets do not pass through the transformer's primary and secondary coil sets. Hense, no more ground loop noise in the audio chain. This is called an "Audio Reference Isolation" circuit. (See it explained in the link given)
When we ground the RCA wires, this refers to running a dedicated ground wire from the amp chassis grounds, back to the HU and attach this wire to the HU chassis. Some RCA wire sets have a small diameter tag wire for this purpose or that wire can be used as a REM feed from HU to amps.
If your RCA's do not have this tag line, you can install one as a stand alone ground from the HU chassis, back to each amp/processor chassis and get the same benefits. This method insures all devices in the "signal path" are now grounded to the same point via your tag wire and add on splices for each amp or processor in the audio signal path.
This method works well in most applications too. Here, all audio signals now share a common grounding path and most of the time, ground loop noise is eliminated.
Is your head spinning now? LOL
swez
swez on 09/21/2006 07:58:42
Here's a section on "Ground Loop Isolators" to review:
http://www.bcae1.com/glisoltr.htm
Note the transformer employed between the input and output side RCA's. The transformer is there to block DC hum. Transformers will not pass DC signals and therefore, block all DC noise in a given circuit.
Again, better HU's, processors and amps have some form of noise isolation or suppression circuits or balanced line input/outputs. However, many good products only use OP amps and non-balance line in/out circuits. This is when we can employ the use of ground loop isolators.
swez
cybersailor420 on 09/29/2006 21:06:30
I finally got an email back from the tech support... only took about 2 weeks. Anyways, they said the input impedance of my soundstream amps is 6,000 ohms.
swez on 09/30/2006 11:25:16
Interesting number there Sailor.... if you had 3 of these amps paralleled together with "Y" cables, that's a 2000 ohm impedence load.
With a HU rated at 4.0 volts, that's ~2 mA's of current draw. (4/2000 = 0.002 A's) Seems like that is not a big number for a given channel (F,R or Sub) off the HU preamps to drive that modest load. However, 2 damaged HU's are a compelling reason to look deeper into this one.
The question here would be, how much current can the RCA preamps manage safely? I doupt any HU maker would publish that detail. However, a tech at Crutchfield recommended no more than two feeds per channel off a given HU.
Mr. B. has daisy-chained several channels in his days and reports a given RCA preamp can support well over 4 pairs. But the fact still remains... what caused your 2 HU/Sources to crap out?
Have you had a chance to send either unit in for diagnostics and repairs? It would seem to me, your P860MP would be worth repair costs if it did not exceed about 50% of the cost for a new HU. (Consider a factory refurb?)
swez
Victor on 10/1/2006 05:28:29
Well, Can you please atleast try and ground the RCA outs from the HU and check if there is any improvement in the sound...??
Victor...
swez on 10/1/2006 09:40:40
Am sure he will... once the HU is repaired or replaced.
swez
cybersailor420 on 10/1/2006 10:34:34
Hey guys,
I have yet to get my cd player repaired, but I do plan on it. I have to go to another island in order to have it done...
Once I get my head unit repaired, or put a new one in, I am going to run a ground wire from the grounding point in the back to the spot where my head unit is grounded to the chassis in the front. I will then run a wire from the frame of the head unit to this spot as well. Does this sound like a good plan to you? This should take care of any ground loop issues, right?
I also have a line driver/eq coming that has balanced inputs. I got an Audio Control EQX on ebay for $58. I figured I'll just use it for the balanced inputs and line driver for now, until I find something I really like. More on that later.
Thanx guys,
-Ian-
swez on 10/1/2006 13:16:43
Yes, proper grounding is the key to getting rid of ground loops. Also, running balanced signal lines will definitely help. With this feature, you effectively double the RCA signal strength over unbalanced lines.
If you want to weed/read some details about how balanced lines work, go here:
http://www.bcae1.com/ballndrv.htm
swez
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