Rotary Switch to compare 2 Amplifiers?

[CauliflowerEars]

Another member suggested getting this Rotary Switch to A/B test two amps with the same pair of speakers.
Unfortunately, I wasn’t able to get more clarification, and I’m not an engineer (sorry).
I don't want to fry anything, so would like to double check, how to connect everything
(Aiyima A07, Fosi V3, Topping E50 DAC, Elac DBR62 speakers):

1) With speakers, seems there are 2 options:
a. 4 cables (2 sets of 2 cables) coming out of the 1 set of speaker binding posts?
One set for amp 1, the other set for amp 2?
b. Do 1 speaker per 1 amp (I know it's not perfect, but at least something).
2) Is the following assumption correct?

Switch position 1:
Amp 1:
* Connect both cables of the Left speaker output to 5.
* Connect both cables of the Right speaker output to 1.
Speakers:
* Connect both Left speaker cables to 6.
* Connect both Right speaker cables to 2.

Switch position 2
Amp 2:
* Connect both cables of the Left speaker output to 7.
* Connect both cables of the Right speaker output to 3.
Speakers:
* Connect both Left speaker cables to 8.
* Connect both Right speaker cables to 4.

 

[olieb]

Another member suggested getting this Rotary Switch to A/B test two amps with the same pair of speakers.
Unfortunately, I wasn’t able to get more clarification, and I’m not an engineer (sorry).
I don't want to fry anything, so would like to double check, how to connect everything
(Aiyima A07, Fosi V3, Topping E50 DAC, Elac DBR62 speakers):

1) With speakers, seems there are 2 options:
a. 4 cables (2 sets of 2 cables) coming out of the 1 set of speaker binding posts?
One set for amp 1, the other set for amp 2?
b. Do 1 speaker per 1 amp (I know it's not perfect, but at least something).
2) Is the following assumption correct?

Switch position 1:
Amp 1:
* Connect both cables of the Left speaker output to 5.
* Connect both cables of the Right speaker output to 1.
Speakers:
* Connect both Left speaker cables to 6.
* Connect both Right speaker cables to 2.

Switch position 2
Amp 2:
* Connect both cables of the Left speaker output to 7.
* Connect both cables of the Right speaker output to 3.
Speakers:
* Connect both Left speaker cables to 8.
* Connect both Right speaker cables to 4.

With this switch you can only compare in mono.
For stereo (2 amps with summed 8 terminals switched to 2 speakers (left+right) with summed 4 terminals, that is 12 terminals all together.) You need a version with 16 terminals. This is an example but there are others. STEREO switch

Amp 1:
* Connect both cables of the Left speaker output to 5.

This is not a good idea. This will create a short as you connect plus and minus terminal of the left amp. Chances are good that this might destroy it.

Speakers:
* Connect both Left speaker cables to 6.

This is not a good idea either as the speaker works with the difference in voltage between its terminals. Connecting both will make this difference vanish and there will be no sound (no matter whether you fried your amp or not ;-).


My proposal was not 100% serious as I do not expect to find (big) differences between amps and even less between Fosi V3 and Aiyima 07. But it should work and the big question here is whether the contacts are reliable and have low enough contact resistance for the task. But being certified for 63A that should be ok. And as switching from "1" to "2" always passes over "0" where all is off there will be no shorts possible (if you connect correctly).
But of course caution is always important and you can check with button cells/AAAs as Amps first.

Here is a table for switching 2 Amps to the same speakers.
These switches always patch odd to even terminals.
So amps are connected to the odd numbered terminals and the speakers are connected to the even numbered.

 

[CauliflowerEars]

My proposal was not 100% serious as I do not expect to find (big) differences between amps and even less between Fosi V3 and Aiyima 07.

Thank you. I will probably need to compare 4 amps altogether, so that's why I wanted to make sure I have a good way.

But of course caution is always important and you can check with button cells/AAAs as Amps first.

Ah, so you've never used such a switch for comparing amps?
With the battery test, if the batteries go as amps, do I connect the actual speakers on the other side .... ?
Would the batteries create sound through the speakers?

Here is a table for switching 2 Amps to the same speakers.

Looking at the MONO table, doesn't it basically suggest 1 speaker per 1 amp?
There are 4 speaker cables mentioned, so 2 speakers (unless I can connect 1 speaker to both of amps ... )

If the mono switch only allows 1 speaker per 1 amp, it might be possible to do it easier:
1. Wiim - set to MONO.
2. DAC - connect with the standard 2RCA-2RCA cable, but the other end of the cable goes: white to amp1, red to amp2.
3. Speakers: Left to amp1, Right to amp2.

Since it's going to be in mono anyway, I suppose the DAC connection would work fine?

 

[olieb]

Ah, so you've never used such a switch for comparing amps?
With the battery test, if the batteries go as amps, do I connect the actual speakers on the other side .... ?
Would the batteries create sound through the speakers?

No, I didn't.
With a tiny battery of 1.5V you can connect the speaker, there can be no damage. The amp is more in danger anyways.
When connecting or moving the wire on the battery pole there should be sound (pop, rustle) from the corresponding speaker. But only from the right combinations of course.

So for position 1 (meaning Amp 1 is active):
connecting the battery to terminals 1/5 should produce sound in left speaker
connecting the battery to terminals 9/13 should produce sound in right speaker
but nothing with other combinations of odd numbered terminals.

for position 2 (meaning Amp 2 is active):
connecting the battery to terminals 3/7 should produce sound in left speaker
connecting the battery to terminals 11/15 should produce sound in right speaker

 

[Pareto Pragmatic]

Thank you. I will probably need to compare 4 amps altogether, so that's why I wanted to make sure I have a good way.

Is there some reason not to use something like this: https://www.amazon.com/SOLUPEAK-P3-Amplifier-Speakers-Selector/dp/B0BGHMGY7J

Two amps and two sets of speakers can be connected. No need to wire and make sure you do it right, just standards connectors. You might even find a use for this in the future.

There are two amp/one set of speaker options as well for less money, and other brands as well.

 

[olieb]

Looking at the MONO table, doesn't it basically suggest 1 speaker per 1 amp?
There are 4 speaker cables mentioned, so 2 speakers (unless I can connect 1 speaker to both of amps ... )

If the mono switch only allows 1 speaker per 1 amp, it might be possible to do it easier:
1. Wiim - set to MONO.
2. DAC - connect with the standard 2RCA-2RCA cable, but the other end of the cable goes: white to amp1, red to amp2.
3. Speakers: Left to amp1, Right to amp2.

Yes, that is the idea of MONO. Might be more interesting when comparing speakers instead of amps. As speakers are better to be compared in MONO whereas for amps STEREO is reasonable if one hopes to find differences in imaging.

But if you want to compare amps you need to use the IDENTICAL speaker(s). Otherwise you will "hear" differences in speaker units and positions. And these are presumably much greater than differences between amplifiers.

 

[olieb]

Is there some reason not to use something like this: https://www.amazon.com/SOLUPEAK-P3-Amplifier-Speakers-Selector/dp/B0BGHMGY7J

That is absolutely the right thing. And of course much more convenient with the binding posts.
But it is a bit more expensive, about 5 times the price if you want to compare amps.

Amazon.com

EDIT: If this Solupeak is interesting one could add a little bit and get a switch with VU-meter bling. This seems to be the hot thing at the moment. There is (for another 40h) a kickstarter project from Fosi.

https://www.kickstarter.com/projects/fositechnology/fosi-audio-lc30-vu-meter-amplifier-speaker-selector?_sc_p=lid%3A6470d901311c433493ba8ed2aea98f38-%2Algt%3A1703069626%2Aseg%3A&mktg_wl=

 

[DVDdoug]

If you want to be "serious" (scientific) -

If you don't already have one, get a multimeter and run some test tones (which you can generate with Audacity) and level-match (adjust the volumes so the voltage to the speakers matches). You don't need an expensive meter. It doesn't have to be super-accurate, just repeatable. (A 10% difference is about 1dB and it should be better than that.)

Then get somebody to help you with a blind ABX Test Their job is to flip a coin to get a "secret" random sequence (usually about 10 times). Then they have to switch between A, B, and X without you being able to see what is being selected. (There should also should not be any clues, like "clicking" because you can't know when it's actually switched or not.) And hopefully, none of the amplifiers "pop" when connected/disconnected because that's another clue.

Your job is to ask for A, B, and X and try to identify X. You can ask to hear A, B, and X repeatedly until you identify or (guess) what X is. Then record your choice and go to the next trial (the next coin-flip).

And of course, if your partner wants to participate you can switch roles (with a new set of coin-flips unknown to him/her).

ABX Probability Chart




P.S.
Don't worry if the coin flips don't "look random" or if you don't end-up with an equal number of heads & tails... That's just the nature of true-randomness and it doesn't foul-up the experiment. The main point is that the subject doesn't know what X is, or if it's changing or not with each trial.

 

[mhardy6647]

AVID Comparator.
Scan0023 by Mark Hardy, on Flickr

source: https://www.worldradiohistory.com/Archive-All-Audio/Archive-Audio/70s/Audio-1978-11.pdf