speaker level to line level adapters - AVS Forum
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post #1 of 25 Old 07-08-2012, 05:00 AM - Thread Starter
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i ran into a problem when i bought a receiver and found out that it doesnt have preouts for my 2 channel amp to power my 4 ohm speakers, im trying to find a way to connect my receiver (denon avr 1610) to my b&k 2 channel amp, i came across harrison labs x connect speaker to line level converter. does anybody have an experience with these?

http://store.hlabs.com/pk4/store.pl?section=13

will this work?
is this a viable solution?
thanks in advance
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post #2 of 25 Old 07-08-2012, 05:59 AM
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Originally Posted by soup dragon View Post

i ran into a problem when i bought a receiver and found out that it doesnt have preouts for my 2 channel amp to power my 4 ohm speakers, im trying to find a way to connect my receiver (denon avr 1610) to my b&k 2 channel amp, i came across harrison labs x connect speaker to line level converter. does anybody have an experience with these?
http://store.hlabs.com/pk4/store.pl?section=13
will this work?
is this a viable solution?
thanks in advance

There are bunches of these things, more often found and used in the realms of car audio.

What they basically do is very simple and should be hard to screw up. Nobody has the time and money to actually try them all.

On the evening of the 4th I was listening to a very large well-optimized 9.2 system that was based on a mid-priced receiver driving gizmos like these, and thence into some very heavy stuff. It sounded magnificent!

Modern power amps, particularly when driving a high value resistive load such as these, generally have such low distortion and noise that adding another good amp after them has no (zero) audible consequences.

IME up to 5-20 generations of amps and couplers like these can be hooked up before a reliably audible difference can be heard. Since they raise the source impedance of the amplifier as seen by the cables to the next amplifier in the chain, keeping cable lengths reasonable may be a priority. Probably not.
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post #3 of 25 Old 07-08-2012, 09:02 AM - Thread Starter
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thanks for the reply, hope it works well with audyssey
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post #4 of 25 Old 07-08-2012, 09:37 AM
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Originally Posted by arnyk View Post

Modern power amps, particularly when driving a high value resistive load such as these, generally have such low distortion and noise that adding another good amp after them has no (zero) audible consequences.

That's what I was thinking too. The OP's receiver outputs 75 watts per channel, so less his B&K puts out appreciably more, there seems little reason to even use a separate power amp.

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post #5 of 25 Old 07-10-2012, 12:49 PM - Thread Starter
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in adding the x connect, will the speaker terminals act like a preamp out (more like transferring sound rather than driving speakers) the xconnect has gain controls, do you think setting it to maximum will transfer most of the driving to the amp
thanks in advance
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post #6 of 25 Old 07-10-2012, 01:23 PM
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the xconnect has gain controls,

It's passive, it can't have any gain.

The xconnect consists of a voltage divider and proabably a transformer for the isolation they suggest it has.
All it does is reduce the voltage from the power amp, using a resistive voltage divider.
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post #7 of 25 Old 07-10-2012, 05:15 PM - Thread Starter
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im pretty ignorant with these terms and gadgets, but can it function like i thought it would. will it convert it to a preamp in terms of drawing power from the receiver and have the external amp do the work, or will it draw power like its driving speakers? i just want the receiver to give more juice to the rear channels rather than spending it on the fronts which already has a separate amp to drive it. the denons 75 watts per channel (rms) which is only true if 2 channels are driven and if 4 channels cause im only running it 4.1 (with a phantom center); its going to be much less. i dont drive my system loud, but with a lot of headroom i think the sound is going to be more robust and open even when played at moderate levels.
thanks in advance
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post #8 of 25 Old 07-11-2012, 05:42 AM
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or will it draw power like its driving speakers?

It's not a speaker , it's a high impedance voltage divider. It will dissipate a very small amount of power. The power amp you connect it to will supply the power to drive the speakers you connect to it.
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post #9 of 25 Old 07-11-2012, 05:50 AM
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Quote:
Originally Posted by soup dragon View Post

im pretty ignorant with these terms and gadgets, but can it function like i thought it would. will it convert it to a preamp in terms of drawing power from the receiver and have the external amp do the work, or will it draw power like its driving speakers? i just want the receiver to give more juice to the rear channels rather than spending it on the fronts which already has a separate amp to drive it. the denons 75 watts per channel (rms) which is only true if 2 channels are driven and if 4 channels cause im only running it 4.1 (with a phantom center); its going to be much less. i dont drive my system loud, but with a lot of headroom i think the sound is going to be more robust and open even when played at moderate levels.
thanks in advance

Each speaker output is serviced by a separate amplifier inside the receiver. Leaving aside power supply issues, nothing you do to one amplifier module is going to allow another amplifier module to use the power the first one puts out.
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post #10 of 25 Old 07-11-2012, 06:14 AM
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Quote:
Originally Posted by soup dragon View Post

im pretty ignorant with these terms and gadgets, but can it function like i thought it would. will it convert it to a preamp in terms of drawing power from the receiver and have the external amp do the work, or will it draw power like its driving speakers? i just want the receiver to give more juice to the rear channels rather than spending it on the fronts which already has a separate amp to drive it. the denons 75 watts per channel (rms) which is only true if 2 channels are driven and if 4 channels cause im only running it 4.1 (with a phantom center); its going to be much less. i dont drive my system loud, but with a lot of headroom i think the sound is going to be more robust and open even when played at moderate levels.
thanks in advance

Confirming what SAM64 said well - The power drain of a class AB power amplifier (what you find inside just about every audio power amp) is highly dependent on the load. The products we are talking about draw negligable amounts of power, so each output stage's drain on the receiver power supply will be minimal. This will be confirmed by a negligible temperature rise as compared to the receiver just sitting there powered up, no speakers attached, idling.

These devices turn just about any SS receiver into a preamp that can also drive speakers.
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post #11 of 25 Old 07-11-2012, 08:01 AM - Thread Starter
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thanks for the info, it is very helpful
so you think a car application speaker to line level converter that claims a 30w max will suffice and not will not overload
considering that it doesnt really take much power from the receiver
thanks
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post #12 of 25 Old 07-11-2012, 09:31 AM
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Originally Posted by soup dragon View Post

thanks for the info, it is very helpful
so you think a car application speaker to line level converter that claims a 30w max will suffice and not will not overload
considering that it doesnt really take much power from the receiver
thanks

On second look, I see a larger problem. The device you linked seems to have a feature that will affect the low frequency response of your system adversely.

"Built in Subsonic filter 37 Hz"

Try this one instead:

http://www.bossaudio.com/auto/high-lever-to-low-level-converter-b65n/
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post #13 of 25 Old 07-11-2012, 11:45 AM - Thread Starter
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thanks
how about this product?

http://www.sonicelectronix.com/pictures_new.php?id=4993&picture_id=305363
do you think this will work?
i know harrison labs is a reputable manufacturer of audio products, do you think its worth the extra dollars minus the 2 extra channels?
thanks in advance
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post #14 of 25 Old 07-11-2012, 04:42 PM - Thread Starter
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will the hlabs subsonic filter affect the system even if the crossover for the fronts is 80hz?
thanks in advance
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post #15 of 25 Old 07-11-2012, 05:10 PM - Thread Starter
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thanks for the link arnyk
ill try the boss, its half the price of the hlab hope it works
thanks for your help
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post #16 of 25 Old 07-12-2012, 02:00 PM
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be careful when choosing a line-level adaptor like the ones linked in this post, a lot of them are designed for car stereos, so they will only handle 20 watts.
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post #17 of 25 Old 07-13-2012, 04:11 AM
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Originally Posted by WagBoss View Post

be careful when choosing a line-level adaptor like the ones linked in this post, a lot of them are designed for car stereos, so they will only handle 20 watts.

Shouldn't be a problem as you don't have to run the amp or receiver that drives the line-level-adptor to full output. These products have gain controls so you can drive the power amp to full output without taxing whatever drives the adaptor.

It's not really an issue of choice, but rather an issue of setup. Don't turn the gain on the adaptor all the way down. and this issue will be moot.
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post #18 of 25 Old 09-24-2012, 11:58 AM
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I realize that this thread is a few months old, but I'm going to revive it for a little more technical discussion.

I'm trying to do something very similar to what Mr. soup was trying to do with a system I'm working on now. The goal is to add external amplification to some relatively power hungry front stage speakers. I would let the receiver continue to power the surround speakers. As I work through this in my mind, it seems that it would provide two main benefits. First the external amplifier would provide much more headroom for the front speakers. And second it might clear up some headroom from the receiver for the surround speakers.
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Originally Posted by JHAz View Post

Leaving aside power supply issues, nothing you do to one amplifier module is going to allow another amplifier module to use the power the first one puts out.
This comment refutes my second advantage mentioned above. But is it fair to leave aside power supply issues? What most commonly causes a receiver to clip/distort? Is it the individual power amplifier stage asking for a higher voltage than its supply voltage due to preamplifier gain being too high? Or is it the common power supply letting its output voltage dip due to excessive current draw? (Or is it some other failure mode I haven't thought of?) If it's the latter, I'd think that reducing the demands on the common power supply could provide benefit to the remaining channels driven by the receiver.

And another concern I had with a setup like this is phase matching. Every time you run a signal through a power amplifier you get some kind of phase shift, right? In the standard use case of a budget receiver like the one mentioned every channel is fed through an identical power amplifier, so their phase shifts should all match. But the addition of external amplification for only some of the channels would mean that some channels will have gone through one stage of power amplification and other channels will have gone through two stages. Is this cause for concern?

I'm not into "thumbs upping" or "liking". Don't take it personally. Just assume that I found your post helpful. Unless it wasn't.
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post #19 of 25 Old 09-24-2012, 12:16 PM
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Originally Posted by pitviper33 View Post

But is it fair to leave aside power supply issues?

It depends on your receiver and how it's spec'd. Does the power rating claim XX watts with all channels driven at once, or is it vague about that? biggrin.gif
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What most commonly causes a receiver to clip/distort? Is it the individual power amplifier stage asking for a higher voltage than its supply voltage due to preamplifier gain being too high? Or is it the common power supply letting its output voltage dip due to excessive current draw?

It's simply asking the amp to put out more power than it's capable of.
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Every time you run a signal through a power amplifier you get some kind of phase shift, right?

Phase shift and number of stages is almost never a problem, though polarity should be verified.

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post #20 of 25 Old 09-24-2012, 06:14 PM
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Ive been using one of these for about 6months now to feed 2 additional subs, as my amp has no "sub out",
and the subs have no "speaker level in".
Works perfectly, with no issues.



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post #21 of 25 Old 09-24-2012, 08:37 PM
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Forgive me if my understanding is a little basic. Most of what I know about amplifiers is what I learned in a few EE classes years ago, so the operation of a modern AV receiver is certainly a lot more complex. I'm trying to learn.
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Originally Posted by Ethan Winer View Post

It depends on your receiver and how it's spec'd. Does the power rating claim XX watts with all channels driven at once, or is it vague about that? biggrin.gif
It's simply asking the amp to put out more power than it's capable of.
The particular amplifier I'm using in this setup is quite ambiguous in its claims. That's been the case for pretty much every receiver I've worked with that was in the price range to not have preouts.
So when you say the amplifier has been asked to put out more power than its capability, what does that mean? The amps I worked with way back when didn't have any power limits that I remember, other than thermal failures. They would clip voltage when trying to output greater than their supply voltage, but they'd gladly deliver as much power as they were allowed to until they got too hot. Do the amplifiers in a modern AV receiver behave differently? As I said in my previous post, I can understand the power supply having current/power limitations if that's what's happening. Reducing load on a few channels should help that.
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Phase shift and number of stages is almost never a problem
Can you elaborate here? Those very simple amplifiers I worked with in the past, if memory serves, exhibited a pretty significant phase shift at the output. Are you saying that this isn't true of the amplifiers in question? Or do you mean that it's there but would be imperceptible?

As I said above, I'm sure that my understanding is overly simplistic. And even what I learned in labs and classes was long enough ago to be a little foggy. You might say that I know just enough to be dangerous.biggrin.gif

I'm not into "thumbs upping" or "liking". Don't take it personally. Just assume that I found your post helpful. Unless it wasn't.
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post #22 of 25 Old 09-25-2012, 03:58 AM
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Originally Posted by pitviper33 View Post

I realize that this thread is a few months old, but I'm going to revive it for a little more technical discussion.
I'm trying to do something very similar to what Mr. soup was trying to do with a system I'm working on now. The goal is to add external amplification to some relatively power hungry front stage speakers. I would let the receiver continue to power the surround speakers.

How do you know that there is currently a problem?

Is the receiver audibly distorting, or is it just a matter of you being uneasy in your mind?

Is this one of these quests for better sound with no specific goal?

Got any measurements that support your apparent belief that the receiver's front amps are clipping?
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As I work through this in my mind, it seems that it would provide two main benefits. First the external amplifier would provide much more headroom for the front speakers.

If there is already adequate headroom, then adding more will be free of any tangible benefits. How much headroom is adequate? For a modern power amp, almost none at all. These amps work almost perfectly until the power is just a bit below clipping.

Don't fall prey to the audiophile myth that amplifiers sound better when they are run well below maximum output.
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And second it might clear up some headroom from the receiver for the surround speakers.

Same question. How do you know that your receiver is running out of power when you are listening to music with it?
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The most productive way to improve the headroom of an audio system is to add a good subwoofer. Got one?
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But is it fair to leave aside power supply issues?

Receivers generally have just one power supply, and all things considered, this is a good thing. While amplifying music, it is unlikely that the number of channels being driven or how they are driven significantly affects the power available to the remaining channels. All of the numbers you've seen that show the receiver's output sagging when all of the channels are driven are based on non-musical waveforms and resistive loads that put an unrealistic load on the power supply.

You can check this out by popping the covers on your receiver and use a voltmeter to measure the voltage across its power supply capacitors. If the DC voltage drops by 10% or more, then that is somewhat significant. Ever done that?
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What most commonly causes a receiver to clip/distort?

Amplifiers whether in receivers or not, are usually pushed into distortion by the gain being turned up to the point where the output stages run out of power supply voltage.
Quote:
Is it the individual power amplifier stage asking for a higher voltage than its supply voltage due to preamplifier gain being too high?

Yes, that is the usual case.
Quote:
Or is it the common power supply letting its output voltage dip due to excessive current draw?

Depends on how the receiver is being used.

If we are on the test bench driving resistors with a steady sine waves near maximum rated output applied to every channel, then the power supply will likely sag under the load and the maximum output of the receiver's power amps will be reduced on the order of 50%. This looks worse on paper than it sounds if you were crazy enough to sit around and listen to sine waves. 50% of the power is only a 3 dB loss which is just about audible.

If we are in the listening room listening to music through speakers, then the situation is vastly different. Music has at least 6 times less energy than a pure sine wave with the same voltage. The speaker draws something like half as much power as an equivalent resistive load because the impedance of the speaker varies strongly across the audio band. Furthermore, multichannel recordings that drive all channels to full output and just sit there and grind, are very rare if they exist at all.
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I'd think that reducing the demands on the common power supply could provide benefit to the remaining channels driven by the receiver.

That is true, if there is actually a problem.
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And another concern I had with a setup like this is phase matching. Every time you run a signal through a power amplifier you get some kind of phase shift, right?

Yes, but that phase shift may be reasonable in the normal audio range, and large only at the extreme frequencies.
Quote:
In the standard use case of a budget receiver like the one mentioned every channel is fed through an identical power amplifier, so their phase shifts should all match.

The common power supply neither helps nor hurts. The phase shift in the power amps is based on their own properties. One of the functions of a good power amp is to ignore what its power supply is doing, within reason.
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But the addition of external amplification for only some of the channels would mean that some channels will have gone through one stage of power amplification and other channels will have gone through two stages. Is this cause for concern?

Generally no. Power amps just don't have that much phase shift in the normal audio range, and the phase shifts due to the speakers and different locations in the listening room are always far larger.,

If you are sitting at different distances (inches, feet) from your speakers, the sound from them undergoes massive shifting due to the time it takes sound to pass through the air. 1 foot of air causes about 1 millisecond of delay, which causes 360 degrees phase shift at a relatively low 1 KHz. At 10 KHz its 3,600 degrees! At 1 KHz the phase shift in a power amp is just a few degrees.

Many 2-way speakers run the tweeters with reversed polarity as compared to the woofer. The phase shifts in speakers and rooms are massive and tend to wash out whatever little changes happen in the power amps.
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post #23 of 25 Old 09-25-2012, 04:56 AM
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Thanks for the detailed reply Arny!
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Originally Posted by arnyk View Post

How do you know that there is currently a problem?
Is the receiver audibly distorting, or is it just a matter of you being uneasy in your mind?
Is this one of these quests for better sound with no specific goal?
In this case, I THINK I can hear distortion. Truth is I don't have the experience to reliably identify one failure mode over another. So I can't say with confidence that what I'm hearing is clipping. What I can say with confidence is that when something very loud happens on screen, the sound picks up a definite harshness. With the master volume set a bit lower, the harshness in those same scenes disappears. One possible explanation for that, at least in my mind, is that the amplifier is beginning to distort.
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Originally Posted by arnyk View Post

Got any measurements that support your apparent belief that the receiver's front amps are clipping?
None. I couldn't think of a way to get any useful measurements without an oscilloscope, and a fairly advanced one at that. I don't have one. (I'd love to have one, but they're far more expensive than a few voltage dividers and a used amplifier.) Is there another way to measure?
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Originally Posted by arnyk View Post

The most productive way to improve the headroom of an audio system is to add a good subwoofer. Got one?
Yes I do. And I've played around with some different crossover points, but I found that going very high with them was leading to localization of the subwoofer. It's entirely possible that this was my mind playing tricks on me. But try as I might, I can't forget where that darn subwoofer is to re-run the test.
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Originally Posted by arnyk View Post

Receivers generally have just one power supply, and all things considered, this is a good thing. While amplifying music, it is unlikely that the number of channels being driven or how they are driven significantly affects the power available to the remaining channels. All of the numbers you've seen that show the receiver's output sagging when all of the channels are driven are based on non-musical waveforms and resistive loads that put an unrealistic load on the power supply.

You can check this out by popping the covers on your receiver and use a voltmeter to measure the voltage across its power supply capacitors. If the DC voltage drops by 10% or more, then that is somewhat significant. Ever done that?
I haven't done that, though I'm planning to. Truth is that in my setup, I haven't heard anything objectionable coming from the surround channels. The idea that they might receive a little more headroom from the proposed change is just a handy side benefit.
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Originally Posted by arnyk View Post

Generally no. Power amps just don't have that much phase shift in the normal audio range, and the phase shifts due to the speakers and different locations in the listening room are always far larger.,

If you are sitting at different distances (inches, feet) from your speakers, the sound from them undergoes massive shifting due to the time it takes sound to pass through the air. 1 foot of air causes about 1 millisecond of delay, which causes 360 degrees phase shift at a relatively low 1 KHz. At 10 KHz its 3,600 degrees! At 1 KHz the phase shift in a power amp is just a few degrees.

Many 2-way speakers run the tweeters with reversed polarity as compared to the woofer. The phase shifts in speakers and rooms are massive and tend to wash out whatever little changes happen in the power amps.
Your point that phase shifts happen all over the place, particularly at higher frequencies, is well received.

I'm not into "thumbs upping" or "liking". Don't take it personally. Just assume that I found your post helpful. Unless it wasn't.
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post #24 of 25 Old 09-25-2012, 11:17 AM
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Originally Posted by pitviper33 View Post

So when you say the amplifier has been asked to put out more power than its capability, what does that mean? The amps I worked with way back when didn't have any power limits that I remember, other than thermal failures. They would clip voltage when trying to output greater than their supply voltage, but they'd gladly deliver as much power as they were allowed to until they got too hot.

If an amp clips for voltage, then you asked too much from it. But amps also have a current limit. So whether the limit is voltage or amperage, if it clips then you hit its limit. Which limit you hit first depends on the impedance of your speakers and the design of the amp's power supply.
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Can you elaborate here? Those very simple amplifiers I worked with in the past, if memory serves, exhibited a pretty significant phase shift at the output. Are you saying that this isn't true of the amplifiers in question? Or do you mean that it's there but would be imperceptible?

Phase shift in audio gear is generally at the frequency extremes: at the low end due to coupling capacitors, and at the high end due to normal roll-off and stray capacitance etc. But phase shift is not audible anyway unless it's a huge amount, such as thousands of degrees.

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post #25 of 25 Old 09-25-2012, 06:52 PM
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I would have found a good audio service shop- NOT a so-called "upgrader" - and had them install a POST fade output for you. This would have given you a line level output that follows the master gain dictated by the on- board volume control and then fed to a second amp. Easy as pie for any e-tech.
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