• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

Double Blind tests *did* show amplifiers to sound different

DonH56

Technical Expert
Technical Expert
Patreon Donor
Joined
Mar 15, 2016
Messages
3,422
Likes
4,531
Location
Monument, CO
#21
Caveat: I have not really followed this thread.

My assertion is usually weasel-worded as "most SS amps operated within their linear region driving most typical speakers will sound the same". Lots of ambiguity because I have not listened to, let alone measured, a large sample of amps connected to a similarly large sample of speakers any time recently. Treat all that follows as opinion.

As an aside: I respect Kal's opinions, and he has certainly opined that he can hear differences among amplifiers. In some cases I have had no problem picking out amplifiers as well so am not hard over on the "all amps sound the same" camp. But it's complicated...

I suspect few of us would have a problem distinguishing a SS amp from a tube amp. The differences, measured and heard, are large enough to be clearly audible on most speakers. One time I designed an OTL tube amp with differential stages and all that jazz, including feedback to (try to) keep it from blowing up speakers if an output tube shorted, and managed to get halfway decent specs out of it. The result? "Too SS-like." I made one of the input stages single-ended again, restoring most of the tube-like distortion characteristics, and then folk agreed it sounded more like a tube amp should. The high output impedance of a typical tube amp, coupled with the fixed-tap output transformer, makes them pretty load-sensitive. One reason I have always felt on ESLs many (most?) tube amps offer gorgeous midrange, somewhat poor highs, and poor bass (where the load is usually pretty high, a mismatch for the transformer).

SS amps generally have low enough output impedance and sufficient frequency response (i.e. the feedback loop can be closed over the audio band) that they will drive most speakers with aplomb. Unfortunately there are a lot of speakers out there that present an "interesting" load impedance. Speakers with wild excursions in impedance magnitude and phase (I have seen <2 to >100 ohms, and with phase changes well over 90 degrees) can represent a very difficult load for an amplifier. ESLs tend to drop dramatically in impedance at high frequencies (the panel is one big capacitor, after all, and of course the transformer is in the picture as well), and that is where feedback falls off as well, so the amp's output impedance increases just when you want it lower. There are stability issues and such that can cause strange things to happen with some speakers.

The gain structure and noise floor of the amp is in play as well; one of things I (many people) found years ago was, in blind testing, an amp with a higher noise floor was readily distinguished from another amp. We did a test with two tape (yes, 1/2" tape at that time) loops playing the same music selections using a couple of big SS amps (have forgotten which, Krell, Threshold, and Levinson were in the store at that time, among others). The speakers I've forgotten but I think were either Magnepan MG-20's or B&W 801's ca. 1982'ish. We might have run with both speakers, too long for me to recall. We inserted a 2 s silence between the selections on one tape, and went straight from one selection to another on the other. The selections were a mix of music but did not have very quiet (silent) passages. Gain matched the channels, natch. With the 2 s gaps, people easily picked out the "noisier" amp, and commented how it "filled in" gaps between piano notes, drum strikes, and such. Without the gaps, nobody was able to tell the two amps apart. IIRC the noisier one was class A but had fairly low SNR, like 80 - 90 dB unweighted, whilst the other amp was something like 100+ dB.

To me the differences in amplifiers are really the difference in how the amp plays with a particular pair of speakers, and of course how close to exceeding the amp's linear range you are. Horn speakers generally require less power but their high sensitivity means more susceptibility to noise (hiss). Panels, ESL and planar-dynamic, tend to be lower impedance and lower sensitivity so push an amp closer to its linearity limits but noise floor (SNR) may be less an issue. And so forth.

FWIWFM - Don
 

Fitzcaraldo215

Major Contributor
Joined
Mar 4, 2016
Messages
1,427
Likes
541
#22
Don, bravo. An excellent post.

Needless to say, I agree completely. I do not think all amps sound the same into real world speaker loads, even if the amps seem the same into "standard" loads for the purposes of measurement. I think it is a matching problem, although the differences are not necessarily sonically earth shaking, in terms of my own experience. Somehow, usually always, the music always emerges from the speakers.

If we could have access to a database of measurements of any and all amp-speaker conmbinations, that would indeed be wonderful. But, we don't.

If there were someting better that the highly imperfect practice of listening with our own imperfect ears, I would be all in favor. But, we don't.
 

Blumlein 88

Major Contributor
Joined
Feb 23, 2016
Messages
7,282
Likes
8,031
#23
Don, bravo. An excellent post.

Needless to say, I agree completely. I do not think all amps sound the same into real world speaker loads, even if the amps seem the same into "standard" loads for the purposes of measurement. I think it is a matching problem, although the differences are not necessarily sonically earth shaking, in terms of my own experience. Somehow, usually always, the music always emerges from the speakers.

If we could have access to a database of measurements of any and all amp-speaker conmbinations, that would indeed be wonderful. But, we don't.

If there were someting better that the highly imperfect practice of listening with our own imperfect ears, I would be all in favor. But, we don't.
I have in plenty of my comments on the matter indicated amps and speakers still need matching, and there are real though usually small differences. Same of microphones and mic pre-amps. In between I think we have transparency all the way for any competent gear. Not all gear is competent nor is all gear designed to be transparent. You can't sell a 'house' sound unless you have one that isn't transparency. Something I have in mind, but never gotten around to is something I think modern reviewers of amps/speakers should do in all reviews. Have a circuit to connect at the speaker terminals, reduce voltage in a transparent way, and feed an ADC. Then make those test listening tracks available for download.

Yes your own speaker/system colorations would be on top of those of the review system, but I think it would let you hear how amp/speaker combos differ in most instances.

Sonic Sense has done something similar for studio monitors. They record with a good quality omni condenser mike at about 1 meter various studio speakers. This is in a well treated fairly large studio that is on the dead side. Seemed like plenty of gotchas that would ruin such a simple minded idea. We record speakers so you can hear what they sound like remotely. I wished they used different, better and more music. Yet as goofy as it is this I have found lets you get a really good handle on the balance of response differences between various monitors. Recording speaker output at the speaker terminals would be several steps up from that in validity for remote comparisons.

Here is one example if you would like to try it.
 

DonH56

Technical Expert
Technical Expert
Patreon Donor
Joined
Mar 15, 2016
Messages
3,422
Likes
4,531
Location
Monument, CO
#24
Don, bravo. An excellent post.

Needless to say, I agree completely. I do not think all amps sound the same into real world speaker loads, even if the amps seem the same into "standard" loads for the purposes of measurement. I think it is a matching problem, although the differences are not necessarily sonically earth shaking, in terms of my own experience. Somehow, usually always, the music always emerges from the speakers.

If we could have access to a database of measurements of any and all amp-speaker conmbinations, that would indeed be wonderful. But, we don't.

If there were someting better that the highly imperfect practice of listening with our own imperfect ears, I would be all in favor. But, we don't.
Thanks Fitz. To your last point, if more people tested with more complex loads, we'd be able to better see the variation among amplifiers. There's the cube test that stresses magnitude and phase, and any number of more realistic test loads, that might show very measurable differences among amplifiers in a THD or even better an IMD test. Something like load pull tests routinely performed on RF amplifiers. Square wave testing, preferably into those loads, would be a good stability test. And so forth. Probably too much work for too few people who would understand the results.

My Maggies are a fairly benign if low-impedance load. Most amps handle them fine, provided they can handle a 3-4 ohm load and have enough power given their low sensitivity. I'm interested to see how the Salon2's perform with the same electronics.
 

bravomail

Senior Member
Joined
Oct 19, 2018
Messages
403
Likes
145
#25
the methodology they used and the number of people listening - makes it as unscientific as it could. while I would agree that all amps should sound the same, my short experience with DAC/Amps shows that every one of them have a distinct sound. I don't have that many.
Schiit Modi3/Magni2 - best so far, clean, transparent, powerful
Yamaha AVR 683 - more musical, but less details
Schiit Modi3 to Yamaha 683 - improves things, much easier to pick dialog details in the movies.
Galaxy S7 edge phone - very good and detailed
Hifime Sabre 9018 - good, "sweet" sound, I suspect some harmonic distortion
FX-Audio X6 - good, strong, "dark" sound, pleasant, but less details
Sabaj Da2 (SMSL Idea) - harsh sound
SMSL M3 headphone out - harsh sound, less details than Modi3/Magni2
Speaka USB dongle (XtremPro) - harsh, boomy and muddy sound

For the life of me, I don't know where that harshness comes from. Certainly, Amir measurements don't show it. But it makes listening for longer time absolutely impossible. I tried 2 headphones with each "device" - AKG K7xx and Audiotechnica M40x. Not very demanding.
 

Xulonn

Addicted to Fun and Learning
Patreon Donor
Joined
Jun 27, 2018
Messages
622
Likes
1,564
Location
Boquete, Chiriqui, Panama
#26
the methodology they used and the number of people listening - makes it as unscientific as it could.
Please describe the robust scientific methods - including double blind techniques - that you used used to achieve your results.

Or do you just have horrible hardware incompatibility problems that are causing severe distortion?
 
Top Bottom