Mulder
Addicted to Fun and Learning
If I want to blind test two different amplifiers with the same pair of speakers and the same preamp/DAC, what do you recommend I use to switch between the amplifiers.
You'll want to place a 220 ohm 2 watt resistor across the outputs of the tube amp. That way when you switch away from the speakers it won't go into oscillation from having no load. Otherwise you could cause damage to the tube amp. That was one of the reasons I thought it good to ask.I am going to compare a Purifi-Class D with an EAR Tube amp.
ABX tests done correctly allow you to switch between A, B and X as often and early as you like. Which makes them tricky for amp testing.I personally prefer to do AA, AB, BA, BB testing, where the switching is random, and the test is to be able to distinguish A from B with statistical validity. I find that ABX testing where X has to be identified as either A or B doesn't work for me, as by the time I've heard X, I've forgotten what A and B sound like, so end up guessing. The AB, BA, AA BB test, with rapid switching back and forth is exquisitely sensitive to small differences. It also just requires the answer 'same' or 'different'.
S
The most important thing is that the ground is separate and is switched in the same way as the + line.If I want to blind test two different amplifiers with the same pair of speakers and the same preamp/DAC, what do you recommend I use to switch between the amplifiers.
I did that recently with a friend. What we did was the following (not ideal but as good as we could). Streamer WiiM Ultra -> Optical -> Marantz HD-DAC1 -> Fixed out -> Amp1 -> Variable out Amp2 | Both speaker out connections to a speaker switch A | B.If I want to blind test two different amplifiers with the same pair of speakers and the same preamp/DAC, what do you recommend I use to switch between the amplifiers.
That's a totally inadequate way to level match. You MUST use a voltmeter and tone and get levels equal to within 0.01V. any other method is invalid.Volume matching with REW and a calibrated Mic feeded by Pink noise...
Thanks for the technical correction but… There is nothing I MUST do, we did what we liked and we didn*t notice any difference in level between the two. Besides you should not move your head while listening, the slightest movement will give other results… it was good enough for usThat's a totally inadequate way to level match. You MUST use a voltmeter and tone and get levels equal to within 0.01V. any other method is invalid.
You surely are not obliged to do something. But if you do not follow the recommendations, your test will be pointless and you do not need to share results of improperly done test. Of course, your choice only.There is nothing I MUST do, we did what we liked
No, you don't have to hold your head still.Besides you should not move your head while listening, the slightest movement will give other results…
If you have an ABX testing box you get to choose if you are listening to A, B or X for each trial in a test. You can switch between them as often and as quickly as you like. When I start a new test I typically just jump back and forth between A and B to determine what I think is different between the two DUT. Once I think I have identified a difference I just jump between A and X . If I hear them as the same I then ID X as A, if you hear them as different you identify X as B and then move onto the next trial in the test which re-randomizes the identify of X. At that point I just keep going between A and X and get through 10 or 15 trials in the test.I personally prefer to do AA, AB, BA, BB testing, where the switching is random, and the test is to be able to distinguish A from B with statistical validity. I find that ABX testing where X has to be identified as either A or B doesn't work for me, as by the time I've heard X, I've forgotten what A and B sound like, so end up guessing. The AB, BA, AA BB test, with rapid switching back and forth is exquisitely sensitive to small differences. It also just requires the answer 'same' or 'different'.
I think it was way better than knowing which amp was playing and then have some flavor for the most expensive. Even if the test was not perfect by the book it's way beter than thinking that the most expensive gear must be better than the cheaper one...I 'd say it depends on what You want to accomplish with the test. If the goal is to perform objectively valid sound quality test, then it is actually fairly demanding, as can be concluded from the comments on this thread. On the other hand, if You just want to find out if there is a difference in sound quality that is big enough for You to clearly notice it, and pick the one you prefer, things become much easier. You still want to be blindfolded, and have somebody to do the switching for You, but You can overlook the absolute accuracy of level matching, head movements, the time it takes to perform the switching etc... finer details. Yes - they all do matter when You are searching for truth, but not so much, if You just want to find out if You clearly favor one above the other in practice.