Amp Camp Amp - ACA

I know what gauges I need. Can anybody identify what type or brand the wires for the kit are? Or simply identify some quality wire for power, signal, and output?


Bear in mind that I've barely made apprentice amp builder status and that I'm not blessed with golden ears - in my case, I opted for generic offerings. The important factors that I looked out for (after gauge) was (in no particular order):

  • Solid versus multi-strand
  • Tinning of the copper wire strands
  • Temperature rating of the insulation (if you're concerned you can take this to the next level and check the build/design standard)
So, on that basis I landed on multi-strand (less prone to damage due to manipulation), tinning (minimise copper corrosion), temperature rating ca. >=85°C (given how warm Class A amps get, it seems sensible to select wire with insulation that can handle a bit of heat, so the higher temp rating the better {within limits, i.e. $$}). Even so, life's a compromise and there are varying shades of grey that will be influenced by personal taste/rationale.



Hook up wire can attract a swag of opinion, e.g.:
Best Hookup Wire? (for component internal wiring)
You could check that thread to gather intel. Probably best to avoid sending this thread on a tangent.


Good luck with your journey.
 
Just built up and ACA. Looking at the amp in bridged mode using RCA input as per
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. The input and output are the same polarity.

When the XLR is used pin 2 (+) connects to the R input and if the speaker is connected as above the the input and output polarity are out by 180 degrees.

Am I correct in my observation?
 
I wrote a very lengthy explanation why it is not so, and while doing it I think you may be right.

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Rembmer that each ACA channel will invert the phase.

So... in bridged mode, the black cable is hooked to the same channel as the input (left) which will be reversed, and that output (which is inverted) is input into the right channel which is re-inverted (correct original phase). So, as you mention... that will yield correct absolute phase in the speakers.

Now, in balanced XLR, you should get the same thing...
-------------------------

So, the hot pin (pin 2) will get inverted, so to preserve absolute phase, that should go to the 'black' output. So pin 2 should go to the left channel of the amp, but it is connected to the right channel of the amp.

Maybe I'm missing something obvious, but I think you may be right here. :(

6L6? You are the master here, what are we missing?

Regards,
Rafa.
 
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With a balanced source. The inputs to pin 2 and 3 of the XLR are equal in amplitude but opposite in polarity. Its purpose is really to reject noise in high noise environments. It could be debated for years as to whether it sounds any better. And, for those that love the 2nd harmonic distortion of the ACA. Using it in the balanced configuration, cancels the distortion.

A good diy project that would really help one to understand it would be an unbalanced to balanced converter amplifier.

It is because the balanced source is equal in amplitude but opposite in polarity that you use the two (-) speaker posts: to feed your speaker. Rather than a single end playing against ground. Each end plays against each other. Doubling the output amplitude and canceling the noise.

In that mode you don't hear the turn on growl - because the noise is cancelled. Or CMR. Common Mode Rejection.
 
With a balanced source. The inputs to pin 2 and 3 of the XLR are equal in amplitude but opposite in polarity. Its purpose is really to reject noise in high noise environments. It could be debated for years as to whether it sounds any better. And, for those that love the 2nd harmonic distortion of the ACA. Using it in the balanced configuration, cancels the distortion.

A good diy project that would really help one to understand it would be an unbalanced to balanced converter amplifier.

It is because the balanced source is equal in amplitude but opposite in polarity that you use the two (-) speaker posts: to feed your speaker. Rather than a single end playing against ground. Each end plays against each other. Doubling the output amplitude and canceling the noise.

In that mode you don't hear the turn on growl - because the noise is cancelled. Or CMR. Common Mode Rejection.


But isnt the noise that's canceled using balanced lines all external noise, rather than internal noise from the amp? I'm confused.
 

6L6

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6L6? You are the master here, what are we missing?

I think you are right - in XLR, as you say, "red" (pin 2, hot, standard phase) will get inverted by the amp, so that should be speaker black.

Pin 3 ("white", reverse phase) will be inverted by the amp, and should be speaker red.

Of course, the output is taken from both of the black speaker posts.

SO...

If my thinking is correct, the photos in the guide (for XLR) are incorrect...?

3Ll1moh5kG5ZiIVL.large




But here's the thing... Absolute phase is best tested in your system, and you choose what sounds best to you. I had a friend over recently, listening to his new factory-made SIT-3 (fantastic amp, as good as you can possibly imagine) and then we switched to the M2x with Norwood buffer -- it sounded really good, enjoying it immensely, holding its own against the SIT-3 quite well. But I was listening to a recording I've known since I was a child (and never get tired of) and thought something wasn't quite in the right spot... So I reached down, inverted the speaker wires, and immediately my friend shouted out "Wow! What did you do??" because it sounded about 98% as good as the SIT-3.



Both amps are non-inverting. Sometimes things don't make perfect sense.