Can you hear a difference in Sound between Audio Amplifiers?

[Goliath]

I second this notion. I went from parasound to nad m27 and I didn't need to be scientific because the sound difference was very apparent. I think it was the noise floor difference, because the background has been very black.

Yep, I'm sure the difference would be readily apparent given the lack of scientific rigor in the testing. Zero controls, etc.

Certainly not discounting your subjective experience, but before you can isolate what you think you heard to noise floor you would have to eliminate all the "other factors" which you had not done (weren't scientific etc).

A difference may have been heard possibly due to ... level mismatches, expectation bias, visual cues, what the wife heard/reviews, weight, mood swings, priming the pump, imagination skill etc.

Certainly could be noise floor related, but there are many other possible causes too, all unaccounted for in the casual, uncontrolled listening session.

 

[Steve81]

Yep, I'm sure the difference would be readily apparent given the lack of scientific rigor in the testing.

I can also hear a difference between the Outlaw amp on my main system and the Emotiva amp on my second setup. No blind test needed. The Outlaw's massive transformer hums, whereas the Emotiva is essentially silent. There's also bit of hiss on a couple of the channels, whereas the Emo exhibits no hiss. The Outlaw already went back once for service, which cost a pretty penny in shipping, so theoretically it's functioning as it should be. Fortunately for me, I can mitigate these problems to an extent as the hum can be dithered by the noise of a cooling fan, and I only use 5 of the 7 channels on the Outlaw amp, so I don't have to use the noisier ones.

 

[AcuDefTechGuy]

I don't think that was relevant because regardless of how low or high the volume was, the benefit was apparent. I am not an audiophile but I attempt to disprove that the two amps sounded different but the difference was undeniable. Just unfortunate that it cost me $2450 more than the outlaw amp..like i said though, I went from a budget a/b outlaw, and the parasound a52, to a class d, but some reviews say that the nad m27 is similar to a51 but the matter has a little more weight

The point is, if the processor volume is the same, but one amp has a gain of 27dB and the other amp has a gain of 28dB, most people will prefer the amp with the 28dB gain.

So you have to compare 2 amps with the EXACT SAME VOLUME. You have to eliminate human BIAS and other power of suggestion. Knowing that one amp costs $2450 MORE than the other amp is enough bias to skew the results.

 

[Jared J. Crandall]

I certainly understand your reasons for being skeptical, so let me expound: I have in the past changed gear and have had to stretch to determine what the differences were. The differences were very subtle and I would be skeptical over my findings, but when switching from the outlaw to the nad, the differences were very apparent and undeniable. I bought both at the same time and had the incentive to return the nad because it was so much more expensive, so by all means I would be happy to be proven wrong. The difference in sound was like switching from a low quality receive to a higher quality one I e. Very apparent difference.

For a little background, I had ran audyssey two times with each amp, used the same source, and volume matched--although I didn't use a dB meter but went from what audyssey calibrated to be reference. Each time the difference was very apparent. I even still wanted to keep the outlaw so I attempted to adjust the pre/pro to see if I could create the same effect, but to no avail.

 

[Jared J. Crandall]

The point is, if the processor volume is the same, but one amp has a gain of 27dB and the other amp has a gain of 28dB, most people will prefer the amp with the 28dB gain.

So you have to compare 2 amps with the EXACT SAME VOLUME. You have to eliminate human BIAS and other power of suggestion. Knowing that one amp costs $2450 MORE than the other amp is enough bias to skew the results.

Yeah, a bias to save $2450 and prove that they are the same. I responded to your question elsewhere.

 

[Jared J. Crandall]

I can also hear a difference between the Outlaw amp on my main system and the Emotiva amp on my second setup. No blind test needed. The Outlaw's massive transformer hums, whereas the Emotiva is essentially silent. There's also bit of hiss on a couple of the channels, whereas the Emo exhibits no hiss. The Outlaw already went back once for service, which cost a pretty penny in shipping, so theoretically it's functioning as it should be. Fortunately for me, I can mitigate these problems to an extent as the hum can be dithered by the noise of a cooling fan, and I only use 5 of the 7 channels on the Outlaw amp, so I don't have to use the noisier ones.

FYI. I used to have an outlaw 7500 and it too had a hum, but I bought emotiva's power supply and the hum was gone. It is the one intended to eliminate the noise, worked like a charm.

 

[Goliath]

I can also hear a difference between the Outlaw amp on my main system and the Emotiva amp on my second setup. No blind test needed.

Yes, but I think it's doubtful hum/hiss would be audibly relevant at typical seated distances and when playing music. Music is a fantastic masking source for hum/hissing.

 

[Jared J. Crandall]

I bought

Did you compare BEFORE you BUY or AFTER you already BOUGHT the amp?

I bought the nad m27, had buyer's remorse for spending so much, so I bought the outlaw believing that amps don't makena difference, but when I used the outlaw the extra magic was gone, then I began doing those testing. So both were tested at my home.

 

[AcuDefTechGuy]

I certainly understand your reasons for being skeptical, so let me expound: I have in the past changed gear and have had to stretch to determine what the differences were. The differences were very subtle and I would be skeptical over my findings, but when switching from the outlaw to the nad, the differences were very apparent and undeniable. I bought both at the same time and had the incentive to return the nad because it was so much more expensive, so by all means I would be happy to be proven wrong. The difference in sound was like switching from a low quality receive to a higher quality one I e. Very apparent difference.

For a little background, I had ran audyssey two times with each amp, used the same source, and volume matched--although I didn't use a dB meter but went from what audyssey calibrated to be reference. Each time the difference was very apparent. I even still wanted to keep the outlaw so I attempted to adjust the pre/pro to see if I could create the same effect, but to no avail.

So the comparison was not done within seconds, but within an hour of each other? And you were using ROOM CORRECTION Audyssey to compare the 2 amps?

 

[Steve81]

Yes, but I think it's doubtful hum/hiss would be audibly relevant at typical seated distances and when playing music. Music is a fantastic masking source for hum/hissing.

Not when the music is intentionally silent for a moment or two.

 

[Steve81]

FYI. I used to have an outlaw 7500 and it too had a hum, but I bought emotiva's power supply and the hum was gone. It is the one intended to eliminate the noise, worked like a charm.

I've thought about trying their CMX-2 in the past (usually out of stock when I looked), but the fan solution does its job and has a practical benefit beyond just masking the noise.

 

[Jared J. Crandall]

So the comparison was not done within seconds, but within an hour of each other? And you were using ROOM CORRECTION Audyssey to compare the 2 amps?

Look, I have heard plenty of amps and I sometimes believe I hear differences between certain class a/ ab amps but I remain skeptical, however, going to the nad m27 was very apparent, enough so that I didn't have to put forth hours and hours of effort to vouch for the differences, the difference was very apparent. So, no, I did not work in a vacuum, I do not have an a/b tested that can switch between amps on the go, I didn't check voltage, air pressure, weather , etc. But the sound was very apparently there. I've returned a lot of equipment whenever I was dubious about any supposed improvements. I couldn't tell the difference in movies between a parasound a52 and outlaw, but the difference was apparent in the nad. Maybe it was the class d or maybe it was simply a much better amp, I don't know, but the difference was as clear comparable from going to a low quality pre/pro to a high quality pre/pro

 

[Goliath]

I certainly understand your reasons for being skeptical, so let me expound: I have in the past changed gear and have had to stretch to determine what the differences were. The differences were very subtle and I would be skeptical over my findings, but when switching from the outlaw to the nad, the differences were very apparent and undeniable. I bought both at the same time and had the incentive to return the nad because it was so much more expensive, so by all means I would be happy to be proven wrong. The difference in sound was like switching from a low quality receive to a higher quality one I e. Very apparent difference.

I'm sure there were differences. I believe you.

Certainly possible the one amp was playing a little louder than the other. Most people don't level match (including me) while listening casually at home, and this can lead to all sorts of (unintended) sound quality differences.

The other point that needs to be driven home is that listening while sighted can introduce all manner of biases into the "listening". Knowing what you are listening to can introduce a bias that can readily explain what you heard.

Simply switching between two amplifiers in an uncontrolled listening session can introduce a host of variables leading to very obvious differences.

For a little background, I had ran audyssey two times with each amp, used the same source, and volume matched--although I didn't use a dB meter but went from what audyssey calibrated to be reference.

That's not level matching and running Audyssey in itself is a big enough confounder to contaminate the results.

Level matching requires a multimeter hooked up across the speaker terminals using a selection of frequencies to measure against. You measure the voltages across the terminals at those frequencies and ensure both amplifiers are within +- 100th of a volt (+- 0.1 dB or better).

A small level difference can lead to the perception of an audible difference. Hence the importance of level matching. Just remember, level matching is just one variable. There are many others.

Each time the difference was very apparent. I even still wanted to keep the outlaw so I attempted to adjust the pre/pro to see if I could create the same effect, but to no avail.

I've heard very audible differences between AVR's and integrated amps myself while listening casually and simply switching them manually.

I've also heard people hear very audible differences between AVR's and integrated amps when no switching was done - ie a phantom switch. Go figure.

 

[Steve81]

I'm sure there were differences. I believe you.

Something worth keeping in mind regarding Jared's amplifier:

http://sound.westhost.com/articles/amp-classes.htm

All Class-D amplifiers need the output filter - it is essential to prevent radio and TV interference. We know that a passive filter must be designed to suit a particular impedance, but what is the ideal? The problem is that there isn't an ideal, and loudspeaker makers make no attempt to standardise on a designated impedance at (say) 20kHz. A nominal 8 ohm speaker may well be 16 ohms (or more) at 20kHz, due to the semi-inductance of the tweeter's voicecoil.

In the above graph, you can see the effect of loading a filter with 3 different impedances. Should a reviewer's (or customer's) speaker happen to be 16 ohms at 20kHz, then there will be a boost of 3dB at 20kHz with the filter shown. The response isn't deliberately done that way to look bad - it's a simple filter that's fairly typical of those used on commercial Class-D amplifiers. Some listeners will report that the amplifier has 'sparkling' high frequencies, and another will complain that it's 'harsh' and/ or 'ear piercing'. It's neither, it's simply a matter of an impedance mismatch. Some Class-D amps use a Zobel network at the output in an attempt to provide a predictable load impedance at 20kHz and above.

In the past we have never had to worry about impedance. The amp has a very low impedance, speakers have a variable impedance that has a nominal quoted value, and no more needed to be said. Class-D has changed that, but no-one is taking notice. If speaker makers were to add a network that ensured a specific and standardised impedance at 20kHz and above, many of the disparaging claims about Class-D amps would just go away. Don't hold your breath.

Suffice it to say, real differences are indeed quite possible with Class D amps.

 

[Jared J. Crandall]

Parasound and Outlaw are low quality and the NAD class D amp is high quality, huh?

I said that poorly. All excellent quality, but I prefer what I heard from the nad.

 

[Goliath]

So, no, I did not work in a vacuum, I do not have an a/b tested that can switch between amps on the go, I didn't check voltage, air pressure, weather , etc. But the sound was very apparently there.

How do you know the difference you heard had anything to do with sound waves? For that you would have to listen blind because that's all you can do - listen. To sound. Using the ears. No peeking. No clues.

Listening casually involves using your ... eyes, expectations, prior knowledge, brain post-processing effects (this can include imagination) and also ears. Clearly, there is a whole lot more going on than simply "hearing" sound.

Add in level mismatches, slow manual switching, etc, etc, etc and it's no wonder people experience readily audible differences in casual listening. Hence the need for controls.

 

[Jared J. Crandall]

Something worth keeping in mind regarding Jared's amplifier:

http://sound.westhost.com/articles/amp-classes.htm


Suffice it to say, real differences are indeed quite possible with Class D amps.

Thanks for the information. I personally believe the amplifier has a better noise floor and if overall more quiet. That was the only real phenomenon I heard--or didn't hear--which made everything sound bettter.

On a similar note: I have relatively good home theater equipment, a very well treated room, yet still have a hard time noticing differences in most amps--with the nad an exception; however, when I owned a hd800, I could easily notice differences in amplifiers. Maybe the number of variables for home theater and stereo listening add a big layer of complication

 

[Goliath]

Something worth keeping in mind regarding Jared's amplifier:

http://sound.westhost.com/articles/amp-classes.htm


Suffice it to say, real differences are indeed quite possible with Class D amps.

Yep, and I fully accept that. It's certainly possible the amp affected the sound waves/sound field audibly. However, it's not the only possibility. There is a way to find out...

 

[Steve81]

Yep, and I fully accept that. It's certainly possible the amp affected the sound waves/sound field audibly. However, it's not the only possibility. There is a way to find out...

To what end? Jared is sharing his experiences on an audio forum, not writing a technical paper for AES. If you're in agreement that there's nothing outrageous in suggesting that his particular amplifier sounds different from a conventional class A/B, that's about as far as it needs to be taken.

 

[Goliath]

To what end? Jared is sharing his experiences on an audio forum, not writing a technical paper for AES. If you're in agreement that there's nothing outrageous in suggesting that his particular amplifier sounds different from a conventional class A/B, that's about as far as it needs to be taken.

Well, this is a discussion forum. Namely a "can you hear ... etc" discussion. I said his amp possibly may have affected the sound audibly. It's also possible, due to how the amps were compared, that Jared caused the difference. Psychogenically. Also possible differences were heard due to set up differences. Who knows.

This can happen when the "listening" is uncontrolled. We won't know either way, but there is no harm in discussing the possible causes in a technical thread about "hearing" differences.