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Testing audiophile claims and myths - Page 154

post #2296 of 3085

Just found this thread. Have to say, props to the OP for collating such a broad set of results!

post #2297 of 3085

No offense to the people in this thread, but while I agree to an extent about cable differences, you will never sell me saying power amps "all sound the same".

 

I have a pair of Quad SS 99 monoblocks which I used paired with Dynaudio floor standing speakers. Now, a few years ago one of these amps started losing gain, and I bought a really CHEAP (40 euros, ~50 bucks) amp to replace them temporarily, while I get them fixed.

 

Now, both when I got the cheap amp, and when I got my Quads back, the difference was night and day. Even my father who is an engineer and was rolling his eyes at me was dumbfounded - the Quads really were far superior, the sound is more dynamic, more airy, more subtle and precise without a doubt.

 

Maybe you'll argue that the replacement amp was "too cheap", and indeed, it is a piece of crap (pardon my French) amp, and perhaps you are right. Maybe a decent 150-200usd amp would compete with my Quad monoblocks, but until I hear it for myself, I won't be easily convinced.

 

Keep in mind that I would be quite happy to be proven wrong. I would sell any gear I own that's beaten or equalled by cheaper gear instantly.


Edited by elmoe - 2/5/14 at 7:50am
post #2298 of 3085

The problem with the cheap amp probably was power, not sound quality. Compare equivalent power ratings and see what you get.

post #2299 of 3085

The Quads are 155W into 8 ohms, my el cheapo amp 100W into 8 ohms, so not THAT much difference. Especially since I don't listen to music very loudly. The speakers are Dynaudio Audience 62s - IEC Long Term Power Handling: 150 watts. They're pretty easy to drive - Dynaudio recommends around 65W amp for a small sized room...


Edited by elmoe - 2/5/14 at 9:28am
post #2300 of 3085

100 watts per channel for $50?! Wow. What amp was that?

post #2301 of 3085

It was heavily used - bought it from a musician friend of mine.

 

Inter-M R300 (not Plus).

 

 

Never did any research on it, but it seems to be pricey! 300e or so, never thought it would be that expensive.


Edited by elmoe - 2/5/14 at 10:42am
post #2302 of 3085

Ah. That explains it. The capacitors were probably toast. How old is it? I looked one up on ebay and it looked like the late 80s.

 

I think you would get different results with a modern inexpensive solid state amp that hasn't been "rode hard and put up wet".

post #2303 of 3085

It's about 15 years old give or take a couple of years.

 

So you're telling me a modern, cheap solid state amp will perform just as well as my Quad monoblocks? I am incredibly tempted to buy one and test this out, because if it turns out to be true I will sell the Quads in a heartbeat. What would you recommend?

 

If I open up the Inter-M and take pictures, would you be able to tell if it is damaged? Because it still seems to work fine...


Edited by elmoe - 2/5/14 at 11:23am
post #2304 of 3085

I use a Yamaha AV receiver and I'm very happy with it, but you'll have to check to see if that's the best choice for you feature wise. Try one in the Yamaha RX series with Aventage in the name. Those are the best receivers Yamaha makes. I also hear that Onkyo and Dennon make excellent receivers. But I don't know model numbers on those.

 

I couldn't tell if the amp is damaged from pictures. From what I'm told, capacitors go south after a while, especially under heavy use. It's usually more cost effective to just get a new amp than it is to recap an old one. Solid state components have come a long way in 15 years.


Edited by bigshot - 2/5/14 at 2:26pm
post #2305 of 3085
Quote:

So you're telling me a modern, cheap solid state amp will perform just as well as my Quad monoblocks?

obviously not all/any amp - probably not even "most" mass market consumer "home theater in a box" - many will be objectively compromised

 

and there are reasons to believe the numbers on the side of the box aren't adequate for an informed decision

 

scraped from diyAudio, Dr Geddes and his wife have published measurement and listening test research - his contribution is the GedLee Metric - weights low level nonlinearity high, broad smooth low order distortion much less - and gives better correlation in his published listening tests

 

Quote:
Originally Posted by gedlee
You can believe it or not, but its true. I tested about five amps that I had and the Pioneer was the best.

People always take my statements out of context. Once one has good electronics - and clearly price and "personal perception" don't correlate with good - then the only thing that matters is the speaker and the room (source material being a given). I have never said that any piece of junk electronics is fine. Only that very inexpensive and readily available electronics place the electronics into the "insignificant errors" category.

I know that this is not a popular position and it's not one that I have always held, but I have studied this problem intensely and this is my conclusion. It is, by the way, the same one as held by Flyod Toole and Lauri Fincham and a whole host of other well know audio researchers. It's amp designers and marketers who seem to hold contrary beliefs
Quote:
Originally Posted by gedlee
No hardly - I don't "favor it", but I was severely chastised for using it at RMAF when, in fact, no one really knew if it was any good or not. It works just fine as my measurements show. I would not use this amp for many applications, but it suited my point at the time, which was that loudspeakers account for 99% (well you could argue 98%, but you get my point) of the audio systems sound quality.

The amp is a Pioneer DSX-V912 - a receiver. The point is that it was on sale at Costco for $150.00. I bought several of them for home theater use. I used my test to measure the amps and they were quite good actually. Especially for chip amps. I was measuring a lot of chip amps (a survey of capability) and most were pretty bad. As a chip amp this unit definitely stands out. It compared quite favorably to a very well engineered discrete amp that I also use.

I also tested several other receivers and they were almost universally bad.
Quote:
Originally Posted by gedlee
Crossover distortion is a particularly insidious form of nonlinearity because it happens at all signal levels and there is no comparable mechanism in a loudspeaker to mask it. The question was asked if I have a way of identifying crossover distortion in an amplifier.

Yes, I do.

You see the situation with crossover distortion is that the % distortion increases with falling signal level. This is exactly why it is so audible since this is directly opposite to our hearing.

One could therefor ***** crossover distortion by looking at THD as the signal level goes lower, which is a typical measurement. The problem is that virtually all of these THD versus level measurements are THD + noise. When this is the case, the rise in THD at lower signal levels is actually the noise and NOT the distortion, but it is impossible to tell which is which. SO this test actually masks the real problem. One would have to track the individual harmonics of the waveform, but then the noise floor is still an issue.

Hence the measurement problem is one of noise floor and how to measure distortion products down below this floor.

This is done by averaging. But normal averaging can only lower the noise floor so much - down to the noise power. But if I have a signal and I average this signal synchronously then I can raise the net signal to noise level. This too is common. But if the signal does not exactly fit the time base then I need to window it and the resultant spectral leakage makes this synchronous averaging less effective.

I use a signal that exactly fits into the time base of the A/D taking the data. This means that I don't have to use a window and I can synchronously average a signal to noise ratio that is about 20 dB better than a simpler test could achieve. This means for example that the input signal needs to be something like 976 Hz, not 1000 Hz, which doesn't exactly fit the window.

I actually had to generate the input wav file in FORTRAN using quad precision, special random number generators and rounding techniques, because the test signals needed to have a 120 dB dynamic range - very difficult with 16 bits.

I use a signal that starts out low and goes up in level. I plot out the results as the signal drops into the noise floor. This test shows vast differences in amps that measure identical with standard tests.

It also shows that my Pioneer amp - you know the "really crappy" one that I get criticized for using at RMAF - is an extremely good amplifier. As good as the best that I have tested with this technique.

 

[spellchecked some of the quotes]

post #2306 of 3085

Most modern solid state amps that are operating within spec and not designed to be deliberately colored are audibly transparent. The only time they wouldn't be if there was insufficient power or incorrect impedance settings. Some amps may measure better than others, but it's only a theoretical difference. It wouldn't be something you hear with human ears.

post #2307 of 3085

I don't know that Geddes pursuit of low level/crossover distortion deep into the noise floor is warranted - but some AB amps, audio chip amps do show rising distortion as output level goes down - well above the noise floor

 

and this really isn't captured in the side of the box specs - although easily seen with THD vs Power sweeps - preferably at a number of frequencies

 

Geddes has the listening test results for our greater sensitivity to these distortions

 

 

many consumer mass market amps still game the power specs - although you can now find the weasel words if you look closely since the FTC set some standards

post #2308 of 3085
Quote:
Originally Posted by jcx View Post
 

some AB amps, audio chip amps do show rising distortion as output level goes down - well above the noise floor

 

As the level goes down, the noise floor of the room takes over.

post #2309 of 3085
Quote:
Originally Posted by jcx View Post
 

I don't know that Geddes pursuit of low level/crossover distortion deep into the noise floor is warranted - but some AB amps, audio chip amps do show rising distortion as output level goes down - well above the noise floor

 

and this really isn't captured in the side of the box specs - although easily seen with THD vs Power sweeps - preferably at a number of frequencies

 

Geddes has the listening test results for our greater sensitivity to these distortions

 

 

many consumer mass market amps still game the power specs - although you can now find the weasel words if you look closely since the FTC set some standards

 

So what you're saying if I'm understanding everything properly is that finding a "cheap" amp that's also good is kind of hit or miss? I looked into receiver prices for brands like Onkyo, Denon etc, and for the Wattage I need, the prices are pretty much hand in hand with my Quad amps, so it doesn't really seem worthwhile to make a switch just so I can get AM/FM radio and a remote control...

post #2310 of 3085
I have a very nice portable amp that is supposed to be able to drive headphones up to 600 ohms. Would there be any benefit in a desktop amp?
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