OK guys,
We have coached others on Stock HU's being amped. Some say... use LOC's from the HU to amps via RCA's while many amp makers have the option to use speaker level inputs, direct to the amp as well.
Seems like the amp makers must think this is an OK option or they would not have the extra circuits to provide that option.
We know most decent Aftermarket HU's have internal amps and RCA outs. The RCA's range from 1.5 -5.0 volts of signal. Most amps are fine with that range now.
Most (if not all) Stk HU's, do not have RCA outs. But they do have speaker level output values that often exceed 12 watts. (even more if factory amps are installed)
But, the speaker outs can put out more AC signal voltage to an amp. The amps with this feature have attenuator circuits to bring HU amped voltage, down to usable reference voltages. That's what an LOC does as well.
What's the rest of the story here?
Swez
PS I am curious as I have tried both options and could not detect any real differences in bass performance. That may be true of bass... but less true of full range?
Replies (6)
Victor on 12/14/2004 13:50:08
Personally i have not found much difference between the performance of the RCA and the Speaker level outputs..
unless not properly installed.. the speaker level outputs work well..
distortion or signal interference cud be an issue to consider.. but for all the installs i have done i have not face much problem getting good sound from the speaker level outputs too..
Victor..
ttocs on 12/14/2004 15:40:12
I agree that it depends on the install. I have seem more noise in systems not using rca's, and tapping the signal at the rear speakers. When I used an loc, I always put them behind the radio to get the signal.
I have used the high level inputs on JL amps(500/1, 1000/1) and never had a problem. They are supposed to use a different way to convert the high level signal that is better. I believe it........
swez on 12/14/2004 16:29:35
Yeah, that's kinda where I stand on the issue. The biggest concern I can see, is that speaker cables are not shielded. There is some inductive and capacitive impedance issues as well. But why not use a twisted pair of speaker lines to blank out noise or a 2 conductor with a shielded jacket.
In live Pro Audio and Studio applications, we use very low signal voltage sources (uV range) like microphones. Often, the cable lines in a "Snake" are 100 - 250 feet from the board. They are very thin, 3 conductor, balanced lines. (in most cases) RF noise? Yeah right... lighting, mechanical effects motors, explosive flash detonation, lasers... you name it. It's all part of the game. Not to mention many guys are now using RF signal, (wireless) mikes, connections from instruments and all kinds of on stage gizzmos too. The biggest headache on a sound crew's mind are ground loops and feedback elimination.
And too... talk about gain factors. Again, most boards have preamps and filters to block incoming noise. They take a few uV-mV signals, amplify these to a few volts, then back to the amps at stage area that commonly need less than 1 volt input (0.707 volts RMS is reference voltage I believe) to reach full amplification. I'll have to confirm these specs to be sure... but in all, a pretty solid noise blanking platform is available here.
I cannot help but wonder why RCA's are so expensive for HT and Car Audio applications. It seems like total overkill to me. Yes, a solid, skuff resistant jacket makes sense as does reasonable strand count wires and grounding jackets... but the rest seems like a bunch of "hogwash" to line someonelses pockets with OK stuff that is not superior to high grade electronic signal wires. I have even heard of some folks using CAT5 lines as signal transfer lines for Car Audio.
Any comments on these? Fire away as I am listening for solid proof and maybe debunking common myths.
Swez
ttocs on 12/14/2004 23:10:10
I personally gained alot of sound when I switched out a super cheap rca's for a monster cable set. I don't ask why the stuff sounds better, I just install it.. I'll change my title to install monkey GRIN ...........
swez on 12/15/2004 05:23:57
OK, that can probably be explained by better conductivity of the wires you now use. (ohms per linear feet) Cheap cables use small conductor lines, shielded with a braided ground.
Small diameter wires can have high resistance and maybe poor inductance/capacitive impedance issues to. High resistance means less power to amp from source unit right? (OK, so we drop 0.5 volts in 20') That may or may not be a big issue here. Most 4 volt source units will manage that loss and most amps have gain adjustments to compensate for such a minimal loss.
However, I am thinking that inductive/capacitive issues, are the primary concern here. Coaxial cables have capacitive impedance as there are 2 conductors in very close proximity to each other, separated by an insulator. That forms a capacitive load. Depending on the amount of C impedance, we can lose some low frequency dB signal along the way. (a HPF effect)
On the other hand, wire acts like an inductive load. (especially when coiled. Is braided shield wire more like a coil? (a LPF effect) That means we may lose some high frequency dB along the wire length.
If the 2 values are about the same, (C & I impedances) it's a wash and they cancel each other out with no ill effects or audio degradation is noted. That's my theory on this whole subject of wires. Can anyone show me otherwise?
Again, I am not an expert on these matters at the moment. But I am trying to make sense of it all and maybe, learn something useful to pass on to others. (Where are you Sky Pilot?) This is an electrical engineering topic. Am sure there are rational ways to proof this all out... but will struggle through it until the issue is clear.
Thanks for your patience and thoughful inputs,
Swez
MrBrownstone on 12/16/2004 00:27:37
I'd recommend that you convert the speaker level signal to RCA right away near the head unit, then run the RCA all the way to the amp. HUs and speaker wire are felonious for noise, and that's the main reason people go to aftermarket HUs other than for more/better features.
SQ will be identical provided you have a high enough output to make a difference. Noise can be mitigated with getting a HIGHer VOLTAGE signal to the amp, and using a low (quiet) setting on the amplifier.
What you really should concern yourself with is the end result of your system. Are you looking to ever run front, rear and subwoofer amplification? If so, might as well plan for the end result first. If not/never, you're on the right track
We have coached others on Stock HU's being amped. Some say... use LOC's from the HU to amps via RCA's while many amp makers have the option to use speaker level inputs, direct to the amp as well.
Seems like the amp makers must think this is an OK option or they would not have the extra circuits to provide that option.
We know most decent Aftermarket HU's have internal amps and RCA outs. The RCA's range from 1.5 -5.0 volts of signal. Most amps are fine with that range now.
Most (if not all) Stk HU's, do not have RCA outs. But they do have speaker level output values that often exceed 12 watts. (even more if factory amps are installed)
But, the speaker outs can put out more AC signal voltage to an amp. The amps with this feature have attenuator circuits to bring HU amped voltage, down to usable reference voltages. That's what an LOC does as well.
What's the rest of the story here?
Swez
PS I am curious as I have tried both options and could not detect any real differences in bass performance. That may be true of bass... but less true of full range?
Replies (6)
Victor on 12/14/2004 13:50:08
Personally i have not found much difference between the performance of the RCA and the Speaker level outputs..
unless not properly installed.. the speaker level outputs work well..
distortion or signal interference cud be an issue to consider.. but for all the installs i have done i have not face much problem getting good sound from the speaker level outputs too..
Victor..
ttocs on 12/14/2004 15:40:12
I agree that it depends on the install. I have seem more noise in systems not using rca's, and tapping the signal at the rear speakers. When I used an loc, I always put them behind the radio to get the signal.
I have used the high level inputs on JL amps(500/1, 1000/1) and never had a problem. They are supposed to use a different way to convert the high level signal that is better. I believe it........
swez on 12/14/2004 16:29:35
Yeah, that's kinda where I stand on the issue. The biggest concern I can see, is that speaker cables are not shielded. There is some inductive and capacitive impedance issues as well. But why not use a twisted pair of speaker lines to blank out noise or a 2 conductor with a shielded jacket.
In live Pro Audio and Studio applications, we use very low signal voltage sources (uV range) like microphones. Often, the cable lines in a "Snake" are 100 - 250 feet from the board. They are very thin, 3 conductor, balanced lines. (in most cases) RF noise? Yeah right... lighting, mechanical effects motors, explosive flash detonation, lasers... you name it. It's all part of the game. Not to mention many guys are now using RF signal, (wireless) mikes, connections from instruments and all kinds of on stage gizzmos too. The biggest headache on a sound crew's mind are ground loops and feedback elimination.
And too... talk about gain factors. Again, most boards have preamps and filters to block incoming noise. They take a few uV-mV signals, amplify these to a few volts, then back to the amps at stage area that commonly need less than 1 volt input (0.707 volts RMS is reference voltage I believe) to reach full amplification. I'll have to confirm these specs to be sure... but in all, a pretty solid noise blanking platform is available here.
I cannot help but wonder why RCA's are so expensive for HT and Car Audio applications. It seems like total overkill to me. Yes, a solid, skuff resistant jacket makes sense as does reasonable strand count wires and grounding jackets... but the rest seems like a bunch of "hogwash" to line someonelses pockets with OK stuff that is not superior to high grade electronic signal wires. I have even heard of some folks using CAT5 lines as signal transfer lines for Car Audio.
Any comments on these? Fire away as I am listening for solid proof and maybe debunking common myths.
Swez
ttocs on 12/14/2004 23:10:10
I personally gained alot of sound when I switched out a super cheap rca's for a monster cable set. I don't ask why the stuff sounds better, I just install it.. I'll change my title to install monkey GRIN ...........
swez on 12/15/2004 05:23:57
OK, that can probably be explained by better conductivity of the wires you now use. (ohms per linear feet) Cheap cables use small conductor lines, shielded with a braided ground.
Small diameter wires can have high resistance and maybe poor inductance/capacitive impedance issues to. High resistance means less power to amp from source unit right? (OK, so we drop 0.5 volts in 20') That may or may not be a big issue here. Most 4 volt source units will manage that loss and most amps have gain adjustments to compensate for such a minimal loss.
However, I am thinking that inductive/capacitive issues, are the primary concern here. Coaxial cables have capacitive impedance as there are 2 conductors in very close proximity to each other, separated by an insulator. That forms a capacitive load. Depending on the amount of C impedance, we can lose some low frequency dB signal along the way. (a HPF effect)
On the other hand, wire acts like an inductive load. (especially when coiled. Is braided shield wire more like a coil? (a LPF effect) That means we may lose some high frequency dB along the wire length.
If the 2 values are about the same, (C & I impedances) it's a wash and they cancel each other out with no ill effects or audio degradation is noted. That's my theory on this whole subject of wires. Can anyone show me otherwise?
Again, I am not an expert on these matters at the moment. But I am trying to make sense of it all and maybe, learn something useful to pass on to others. (Where are you Sky Pilot?) This is an electrical engineering topic. Am sure there are rational ways to proof this all out... but will struggle through it until the issue is clear.
Thanks for your patience and thoughful inputs,
Swez
MrBrownstone on 12/16/2004 00:27:37
I'd recommend that you convert the speaker level signal to RCA right away near the head unit, then run the RCA all the way to the amp. HUs and speaker wire are felonious for noise, and that's the main reason people go to aftermarket HUs other than for more/better features.
SQ will be identical provided you have a high enough output to make a difference. Noise can be mitigated with getting a HIGHer VOLTAGE signal to the amp, and using a low (quiet) setting on the amplifier.
What you really should concern yourself with is the end result of your system. Are you looking to ever run front, rear and subwoofer amplification? If so, might as well plan for the end result first. If not/never, you're on the right track
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