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Budget ABX gear/method "good enough" to compare amps, DACs, audio sources?

AaronDC

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Jan 13, 2021
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Hi.

I'd like to do some blind AB comparisons between amplifiers, DACs and digital audio sources. I feel that I don't need gold-standard double-blind, but just enough subtlety to be able to overcome my preconceptions about the gear that I have and gear that interests me. I've been searching high and low for a device that will get the job done well enough to allow me to make unbiased evaluations for myself. There seems to amazingly little available as far as real budget ABX equipment goes. I was thinking of having a friend randomize with a tossed coin and switch devices with something like this:

This one for $75 would work to compare 2 amps:
https://www.ebay.com/itm/Two-2-Amp-...s-Selector-Switch-Combiner-SP-71/265101125751

I'll need an RCA version to compare DACs and audio sources. This one is $28:
https://www.ebay.com/itm/2-in-1-Out...Signal-Selector-Switcher-Speaker/265018475122

Do you think this looks good enough for my purposes? Any other suggestions under $100?

Thanks!
Aaron
 

Bob-23

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Jul 3, 2019
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It's important to switch instantaneously: our accoustic memory is extremely short, in particular, when dealing with, expectedly, small differences, thus, a toggle switch or a push button is optimal.

If you do the switching yourself, it's optimal, to find a push button which gives you not the slightest hint to the amp it's actually switching on: both positions of the button should be indistinguishable, not only with regard to the height of the button, but also with regard to their respective switching noise (which maybe different in both positions). If you don't find such a switch, you may try to obfuscate before yourself which position of the switch is switching which amp, for instance, by winding/twisting the cables leading to the switch box.

It's very important to equalize the output voltages of the amps: even very small voltage differences - that don't yet appear as loudness differences - may make the amp sounding better: 'more open'. Get a 1 khz test-tone from youtube, and a sensitive multimeter to do that. (That doesn't have to be expensive, the very cheap, but astoundingly capable Aneng 8008 does it.) Voltage difference shoudn't be higher than 1%.

If you're on diy: On Rod Elliotts ESP you can find the schematics for a simple one with relays. It's the last project. "AB-Switch Box
Can you really hear the difference between amps or cables?"
https://sound-au.com/

Good luck! And don't be shocked!
 
OP
A

AaronDC

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Jan 13, 2021
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Hi Bob. Yes, I do DIY, although I am new to it. Actually I came across the Rod Elliotts ESP and considered it, but was scared off by the stern warning about not using it with an amplifier with a bridge-tied-load output because I'm not sure how to determine if any of my amps fit that description. Despite the simplicity, I was also wondering what parts to get. I tried to make a BOM on Digikey but there are so many parameters/choices, I got a bit lost. Know where I could find a BOM for that? I didn't see anything on the site.
 

somebodyelse

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You can use DPDT relays in place of the SPDT ones to switch both speaker terminals instead of just one.
 

bryanl9581

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Mar 11, 2021
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Russound makes some speaker switch boxes that have volume controls so you can level match. I had one and it worked ok. I now have a more expensive one but it has paid for itself a few times over since I could not tell the difference between a pricy amp and a reasonably priced one.
 
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