Blind Testing Amps

[Sonnie Parker]

My brother-in-law bought F206's (maybe 5 years ago). We auditioned and bought them from a local dealer that drove them with a NAD integrated amp. The room was like a giant pillow, rugs, curtains, suspended ceiling, too dead for my tastes. The NAD did not do these speaker justice, it got harsh when turned up.

At home, he had a pair of Outlaw M2200 class-G monoblocks. I liked these amps at modest volume but not when turned up to where the music was in the mid 80s. I bought over a Parasound A21 and level matched and the A21 had no issues at the same volume levels with the tracks we played. He ended up buying an A21.

Now that we are both immunized, I am going to setup a listening session with the MiniDSP to compare the AHB2 to the A21 driving these speakers. He likes it loud and the F208s sound really good in is modest room, 13x15x8.
His system is using an Oppo UDP-105 as the preamp which is a nice solution and has a ML Grotti servo sub which was fairly easy to blend with the F208s without bass management.

Now that I think of it, I may have to bring 2 AHB2s

- Rich

Let me know if you want to borrow the ABX box... it really is enlightening. Joe, Leonard, Wayne and Dennis all have superb ears, exceedingly better than mine, and none of us could consistently identify any differences in the following amps over several days of testing back in 2015. When we listened and knew what we were listening to, we made notes on what differences we thought we heard, but when we used the box and didn't know the two amps we were switching between, no one could match up their same comments with any consistency... bottom line, we could not prove anyone could really hear any differences.

• Behringer EP2500
• Denon X5200 AVR
• Emotiva XPA-2
• Exposure 2010S
• Krell Duo 175
• Mark Levinson 532H
• Parasound HALO A31 (Sonnie's Main Amp)
• Pass Labs X250.5
• Sunfire TGA-7401
• Van Alstine Fet Valve 400R
• Wyred 4 Sound ST-500 MK II

 

[AJ Soundfield]

Let me know if you want to borrow the ABX box... it really is enlightening.

That's a very generous offer. He can pry my AVA ABX from my cold dead hands.
Seems you've run the gamut with speakers and amps. No wonder audiophiles eschew active speakers. Too easy, no drama.

cheers

 

[RichB]

Let me know if you want to borrow the ABX box... it really is enlightening. Joe, Leonard, Wayne and Dennis all have superb ears, exceedingly better than mine, and none of us could consistently identify any differences in the following amps over several days of testing back in 2015. When we listened and knew what we were listening to, we made notes on what differences we thought we heard, but when we used the box and didn't know the two amps we were switching between, no one could match up their same comments with any consistency... bottom line, we could not prove anyone could really hear any differences.

• Behringer EP2500
• Denon X5200 AVR
• Emotiva XPA-2
• Exposure 2010S
• Krell Duo 175
• Mark Levinson 532H
• Parasound HALO A31 (Sonnie's Main Amp)
• Pass Labs X250.5
• Sunfire TGA-7401
• Van Alstine Fet Valve 400R
• Wyred 4 Sound ST-500 MK II

You experience is interesting. When listening to amps, I like to be seated in the sweet spot fairly close the to speakers, between 6 and 10 feet (MAX).
Off angle, it goes the hello because of room modes a loss of stereo image.
Speakers matter, with efficient speakers, you should have been able to hear hiss from some of them.
Some valve amps behaves like tube amps with high-output impedance that will not remain linear with reactive speakers.

I have some reservation in introducing another component between the amp and speakers.
My session uses DSP (digital) attenuation to level match passive make-then-break switch.
I'd rather use one of these in single-blind for home trials. The persons face and switch out of sight.

In addition, the following was performed to make certain there was nothing about the configuration influencing the outcome:

Swap A/B at the passive switch
Swap outputs on the SHD.
Try multiple attenuations settings to assure the DSP was engaged for both, 0/-5.5mand -3.0 and -8.5.
Measure the voltage of both using a 0 DBFS sine wave and Fluke 87V sine-wave multi-meter.

The AT6525NC uses a linear power supply and this may have contributed to some measured instability with the test tone.
It varied from 2.75 volts to 2.862 volts . If my math is right, this difference amounts for a .2 dBV change in response.
Theoretically within detectability. There is no telling if there are similar anomalies when playing music.

After the SHD software update, I level matched again.
The AHB2 consistently measures 2.85 volts.

Your new uber amps looks great. I a big fan of regulated power supplies.

- Rich

 

[RichB]

That's a very generous offer. He can pry my AVA ABX from my cold dead hands.
Seems you've run the gamut with speakers and amps. No wonder audiophiles eschew active speakers. Too easy, no drama.

cheers

Active speakers work well for 2 channel back get to be a real pain for multi-channel.
If Harmon ever replaces the Salon2s, I think a powered lower end with low latency EQ and passive top end would be an interesting choice.
Allow the bass section to take both speaker and balanced connection, perhaps even Dante.
This lets the tubers have fun too.

- Rich

 

[RichB]

Further testing oft this amp ends in an hour. It is getting packed up for its new home in a family vacation home in Maine. We need to be ready for the renters!

- Rich

 

[Sonnie Parker]

Oh we were definitely seated in the sweet spot, and had the MartinLogan speakers setup for the best imaging, soundstage and depth acuity. I believe the best location for those speakers was about 8ft or so from the MLP. It's very important in my opinion to have your setup in it's best listening condition, as you would normally be listening to your music. Then you are simply swapping amps.

You should check out the Van Alstine ABX box info on their site... there is zero chance of it having any audible interference between amp and speakers... and I'm not sure it would be possible to get anything better. The listener would have no knowledge of what amp is A or what amp is B. And they can either control the remote or someone else can.

 

[RichB]

Oh we were definitely seated in the sweet spot, and had the MartinLogan speakers setup for the best imaging, soundstage and depth acuity. I believe the best location for those speakers was about 8ft or so from the MLP. It's very important in my opinion to have your setup in it's best listening condition, as you would normally be listening to your music. Then you are simply swapping amps.

You should check out the Van Alstine ABX box info on their site... there is zero chance of it having any audible interference between amp and speakers... and I'm not sure it would be possible to get anything better. The listener would have no knowledge of what amp is A or what amp is B. And they can either control the remote or someone else can.

The findings may hold but there are a lot of components in this doohickey.

There is some opportunity here for changing the load seen by the amplifier.
How could a valve amp drive those 15As?

If the amps are not driving woofers, that is not exactly indicative.
However, you have characterized your needs to completely valid. It might not universally translate...

- Rich

 

[RichB]

I opened the Nob switch and there was well well made with a single switch.
Also. level matches was digital and the same for both thanks to the MiniDSP SHD.

- Rich

 

[RichB]

I'll be taking the 20+ year old Sunfire Cinema amp. I'll leave the rig in place and try it here, just for fun...

- Rich

 

[RichB]

Oh we were definitely seated in the sweet spot, and had the MartinLogan speakers setup for the best imaging, soundstage and depth acuity. I believe the best location for those speakers was about 8ft or so from the MLP. It's very important in my opinion to have your setup in it's best listening condition, as you would normally be listening to your music. Then you are simply swapping amps.

You should check out the Van Alstine ABX box info on their site... there is zero chance of it having any audible interference between amp and speakers... and I'm not sure it would be possible to get anything better. The listener would have no knowledge of what amp is A or what amp is B. And they can either control the remote or someone else can.

So there is A or B and not third X, that could be A or B?

What is the site?
I found this Audio by Van Alstine (avahifi.com)


- Rich

 

[Sonnie Parker]

Oh yeah... it has some connections, but obviously you aren't using them all at one time.

Probably one of the cleanest builds of anything I've seen.

We were not using the 15A's during our amp test... we were using non-powered ESLs.

We initially used the Spatial Hologram M1 Turbo v2 speakers... and here is what Wayne wrote about those:

At the moment, the Holograms are serving as our primary evaluation tool. I will post setup details and interesting discoveries a little later. They are giving us a monstrous soundstage, the kind that eats small animals for breakfast, with extremely sharp imaging and very good depth acuity. They are extremely clear, getting into the realm of rivaling electrostatic transparency. Their in-room response is very good, with some expected peaks and dips, but still very listenable. The high frequency response is extended and smooth. The bass gives you that "Are you sure the subs are not on?" feeling on deeper tracks.

 

[Sonnie Parker]

So there is A or B and not third X, that could be A or B?

What is the site?
I found this Audio by Van Alstine (avahifi.com)


- Rich

I have uploaded the manual for you.

From Frank at Van Alstine

The ABX Switch allows seamless switching of up to two sources, two amps, and three sets of speakers.
Controlled by universal remote, usually from the listening position, the ABX switch has the capability of:

• Precise volume level matching, within 0.1 db, of any selected system.
• Infrared universal remote control.
• Blind test mode (2 of them) can force evaluation strictly by how it sounds.
• Works with or without a subwoofer.
• Programmable power up state and adjustable display brightness.
• Persistent volume settings power up the same as they were when last powered down.
• Multiple systems can be set up permanently and switched in/out instantly with remote control.
• Low noise
• Built in “Y” splitter can be used to drive two units with one source
• Allows selection of up to two speakers at the same time
• Mute entire system with a single button
• Gold plated RCA connectors for line level signal connections
• Gold plated 5-way dual banana connectors for speaker level signal connections
• DC coupled (no capacitors in the signal path).

Interesting things you can do with our ABX comparator:

If you want to make a quickie and easy blind test of two power amplifiers, for example. Attach them both to the ABX box, use the ABX box level adjustments to match signal levels from each, then simply hit the botton that turns off all the indicator lamps on the ABX box. Switch back and forth rapidly between the two amps under test a few times on the same program material and you will soon loose track of which amp is which. Then do more careful listening and when you are certain of which amp you are listening to, turn the indicator lamps back on and see if you are right. Repeat process several times. Can you really pick out what you are hearing? Once you loose the ability to hear with your eyes, all bets are off.

Of course you can do the more formal built in test procedure for the most accurate and foolproof results too.

Do you want to see if your favorite wonderful good sounding capacitor is really really better. For this you will need two identical samples of the component you are playing capacitor swaps with. Put all the good sounding parts in one sample, keep the other one stock, and run the ABX test between them. How wonderful are your capacitors now?

You can even put interconnect cables to the acid test by using two identical preamplfiers.

There are many ear opening things the ABX box can help you understand.

 

[RichB]

I am not trying to be nit picky, but the document does not provide specifications, though it does talk about gain and warn about the potential for destroying an amplifier.

Has it been measured?

- Rich

 

[RichB]

This is not directly related but this was Jon Iverson's take on blind testing (which I am in favor of):
A Different Take on Blind Audio Tests (twit.tv)

My take away, if done well, those people, that room, those sources and speakers.
Actually, that is the absolute most objective and zero based view.

All things are not created equal, like amps and cable lifters, you get the point.
Amps measure differently into different load, whereas cable lifters do not.

It is entirely possible that many of those amps are suitable, and yet... we buy things for a reason.
Additional volume is a good reason

- Rich

 

[Sonnie Parker]

I am not trying to be nit picky, but the document does not provide specifications, though it does talk about gain and warn about the potential for destroying an amplifier.

Has it been measured?

- Rich

I really don't know if it's ever been measured by anyone. I suspect at one time he had specs on the website, back when he made the second run, but I don't remember.

Of course then we'd get into the question, "Has every single piece of equipment, cable, wire, etc, that we are using in the blind testing been measured?"

It is entirely possible that many of those amps are suitable, and yet... we buy things for a reason.
Additional volume is a good reason

- Rich

Absolutely... as you already know that I have admitted that I cannot tell a difference in how amps sound, yet I keep buying different amps. Perhaps it's flashing LED lights ... power... features... cosmetics... or simply the desire to have something different.

 

[RichB]

I really don't know if it's ever been measured by anyone. I suspect at one time he had specs on the website, back when he made the second run, but I don't remember.

Of course then we'd get into the question, "Has every single piece of equipment, cable, wire, etc, that we are using in the blind testing been measured?"

Yes, but not everything is equal. My cables were 12 gauge with the exception of the amp to switch where I ran out of locking bananas so I used those for the ATI, just in case. This is decent cable that with gauge verified.
The MiniDSP, AHB2, and AT522NC (I sent this) were measured at ASR.
The Revel M126Bes were measured at Audioholics.
The make and break switch was not measured but the connections were swapped.
The performance of the source, amps, and speakers are measured. Not too bad.
Of course my sessions were not in the blind so there less confidence.

Absolutely... as you already know that I have admitted that I cannot tell a difference in how amps sound, yet I keep buying different amps. Perhaps it's flashing LED lights ... power... features... cosmetics... or simply the desire to have something different.

I'm an engineer and take great pride in owning well designed and built products.
There is nothing wrong with that. Well, maybe not for snake oil products but that is not part of this discussion.

Come to Boston and we can have another go at you

- Rich

 

[Sonnie Parker]

I'm actually looking into getting measurement equipment. It won't be the AP product like ASR has, but I don't see the need in 120dB noise testing, which is the only thing the AP would give me over what I am considering, which is a lot less money. What I am looking at is 110dB max on noise, but once you get there, anything past that is of no value (shy of mental value)... it's all inaudible by every human in the universe.

The point being... if I do ultimately decide to set something up... I'll test the ABX box, along with the SHD, HTP-1 (AHB2 if I still have one), etc, etc.

 

[AJ Soundfield]

with efficient speakers, you should have been able to hear hiss from some of them.

Those are all non-pathological SS amps, so not really. However testing with Revels negates that possibility.

Some valve amps behaves like tube amps

Valve = tube, just another name for same thing. Yes, high output impedance changes frequency response. The amps you claimed hearing differences with aren't. So your results are being caused elsewhere.

I have some reservation in introducing another component between the amp and speakers.

You should, especially a Amazon/ebay type "Nobsound" switch of unknown provenance that may be causing interaction between the amps common grounds due to lack of isolation. I don't see it being sold for controlled/blind testing at all.

My session uses DSP (digital) attenuation to level match

That could then easily be fed into the AVA ABX, which was designed specifically for blind testing and accounts for confounders like non-isolated switches (and randomization, etc, etc) which can lead to erroneous outcomes, without cognizance by those who may not understand all the nuisance variables involved. Quite common.

I'd rather use one of these in single-blind for home trials. The persons face and switch out of sight.
- Rich

I think I read elsewhere you design software. Thus familiar with GIGO concept. YMMV.

cheers

 

[RichB]

Those are all non-pathological SS amps, so not really. However testing with Revels negates that possibility.

Amplifier topology is not a guarantee of performance, otherwise there would no point to measuring them.

You should, especially a Amazon/ebay type "Nobsound" switch of unknown provenance that may be causing interaction between the amps common grounds due to lack of isolation. I don't see it being sold for controlled/blind testing at all.

I'll see if ASR wants to measure it.
The MiniDSP is not sold a dual output source device for A/B testing.
I thought it was innovative to use the MiniDSP SHD DSP to level match in the digital domain.
Technically, a better approach with only 1 D/A conversion and no additional analog processing.

That could then easily be fed into the AVA ABX, which was designed specifically for blind testing and accounts for confounders like non-isolated switches (and randomization, etc, etc) which can lead to erroneous outcomes, without cognizance by those who may not understand all the nuisance variables involved. Quite common.

Yes, but I prefer a cleaner path but that remains to be proven due to the speaker switch being used to switch speakers

I think I read elsewhere you design software. Thus familiar with GIGO concept. YMMV.

Clearly you don't believe that any sighted test has merit.
But I'm not sure that this switch is the second coming.

Product quality is achieving the requirements, which includes features working at ship time.
Pretty much all software fails to achieve this but it is a goal and I am not sure this is improving.

- Rich

 

[Sonnie Parker]

So watching the video... haven't watched all of it yet, but Jon and the host talk about "if" 1 or 2 out of 20 in the group of blind listeners can reliably tell a difference between A and B 100% of the time, that it's a problem with the testing. However, I've yet to see a published blind test where anyone could reliably tell differences between two amps 100% of the time... or even close to that mark. There may be a test session out there, but I haven't seen it yet. I've seen quite a few where no one could tell the differences 100% of the time, and when they did, the differences were so minute it wasn't necessarily they that could identify whether the difference was better or worse. So their hypothetical suggestion is really a moot point, unless again, I've missed those published blind tests, which could be. Certainly if it's out there it would be a seriously popular published article... and those "golden ears" that Jon claims those people would have would have taken up the $10,000 challenge to collect some extra spending money.

 

[RichB]

So watching the video... haven't watched all of it yet, but Jon and the host talk about "if" 1 or 2 out of 20 in the group of blind listeners can reliably tell a difference between A and B 100% of the time, that it's a problem with the testing. However, I've yet to see a published blind test where anyone could reliably tell differences between two amps 100% of the time... or even close to that mark. There may be a test session out there, but I haven't seen it yet. I've seen quite a few where no one could tell the differences 100% of the time, and when they did, the differences were so minute it wasn't necessarily they that could identify whether the difference was better or worse. So their hypothetical suggestion is really a moot point, unless again, I've missed those published blind tests, which could be. Certainly if it's out there it would be a seriously popular published article... and those "golden ears" that Jon claims those people would have would have taken up the $10,000 challenge to collect some extra spending money.

DonHo56 (ASR) recently posted on the AHB2 thread that he has consistently been able to tell the difference between a tube (ala valve) amplifier and SS. I think there is a reviewer (I forget his name) that has passed blind tests for speaker cable for god's sake, I think Jon mentioned him in the video.

John at Benchmark passed blinds with sine-waves at low level to identify crossover distortion.
I am not disputing anything really, just being careful about the facts.

Other annoying facts, amplifiers are almost never testing into reactive loads.
Do all amps (including AVR amps) sound the same and at what level.
How can you tell when they are working within their design parameters, on amps other than Benchmark?

- Rich

 

[Sonnie Parker]

I suspect there are several out there that can identify between tube and solid state.

I believe the claim has always been with solid state amps that if you are listening thru speakers to the same music and you are within the specifications of the amp (whether it is stand-a-lone, integrated or built into an AVR), that there are no differences that anyone can claim are better or worse.

Obviously when you get outside of the specs and push an amp into clipping, that's a completely different set of standards. Not sure why anyone would care about comparing those. If the amp doesn't have enough power, but more power... no reason to try to compare one that doesn't have enough power to one that does, unless you just want to prove it has more power.

I'm certainly not hammering it in stone that no one can hear differences... but I've never seen any solid prove of it. Subjective listening to me is not solid proof because it is subjective. I suspect there are indeed people out there that can hear some minor differences, although I just don't see how significant they could be. I think for the most part, the vast majority of those claiming the differences they hear are due to something going on besides the amp.

As for sinewaves, dunno... I don't sit around listening to sinewaves... only music here. As for cables... dunno why anyone would make cables that color the sound, but perhaps there are some... they should be neutral, just like amps in my opinion. But either way... hearing differences in cables doesn't validate hearing difference in solid state amps... if you know what I mean.

 

[RichB]

I suspect there are several out there that can identify between tube and solid state.

I believe the claim has always been with solid state amps that if you are listening thru speakers to the same music and you are within the specifications of the amp (whether it is stand-a-lone, integrated or built into an AVR), that there are no differences that anyone can claim are better or worse.

Obviously when you get outside of the specs and push an amp into clipping, that's a completely different set of standards. Not sure why anyone would care about comparing those. If the amp doesn't have enough power, but more power... no reason to try to compare one that doesn't have enough power to one that does, unless you just want to prove it has more power.

I'm certainly not hammering it in stone that no one can hear differences... but I've never seen any solid prove of it. Subjective listening to me is not solid proof because it is subjective. I suspect there are indeed people out there that can hear some minor differences, although I just don't see how significant they could be. I think for the most part, the vast majority of those claiming the differences they hear are due to something going on besides the amp.

As for sinewaves, dunno... I don't sit around listening to sinewaves... only music here. As for cables... dunno why anyone would make cables that color the sound, but perhaps there are some... they should be neutral, just like amps in my opinion. But either way... hearing differences in cables doesn't validate hearing difference in solid state amps... if you know what I mean.

I think we all have bounds in our minds.
For example, you'd have to be deaf to not hear the difference between some pro amps driving 100 dB efficient speakers without music playing. The noise level is too high.

Within their bounds and limits, perhaps a better is while they remain linear driving a load.
You can find measurements of amps that do not remain linear using simulated speakers.
So you must say, how linear and what load. Non-linearity is expected with Tube/Valve amps.
Yet you had an ABX test where it was not identified. An unexplained result.
Also, 100% is not a realistic goal, Harman does not use this a goal.
They have, if I recall, 80% statistically significant correlation.

I am not saying my test should be believed or determinate, I am saying that a skeptic might say that about other ABX tests as well. Harman also recognized fatigue is an issue so short samples are used.

Perhaps we are both skeptics and that is as it should be

- Rich

 

[AJ Soundfield]

Amplifier topology is not a guarantee of performance, otherwise there would no point to measuring them.

Correct, but again, there is nothing to suggest any of those amps, with proper gain structure, would produce audible hiss at LP unless the sensitivity of the speaker is very high, say >98db....extremely rare in the HiFi market where as noted, 99% are more like your Revels. None would produce hiss then unless malfunctioning. Your claims were not for hiss/noise giveaway though, which of course is a well known metric. You are claiming actual sound differences into a non-pathological load, not overdriving the amps.
That is an extraordinary claim. Thus, N-Ray, Cold Fusion, etc methods scrutiny warranted.

I'll see if ASR wants to measure it.

That would be cool, especially in the context of intended use. There are real blind test experts there, like JJ and SIY.
Beware of return policy though it seems...

Clearly you don't believe that any sighted test has merit.
- Rich

That's more than my belief.

cheers

 

[AJ Soundfield]

For example, you'd have to be deaf to not hear the difference between some pro amps driving 100 dB efficient speakers without music playing. The noise level is too high.

No one disputes this, so a bit of Red Herring. None of your speakers listed would have such a well know, accepted issue.

You can find measurements of amps that do not remain linear using simulated speakers.
So you must say, how linear and what load. Non-linearity is expected with Tube/Valve amps.
Yet you had an ABX test where it was not identified. An unexplained result.

Link??
I have high output impedance tube amps easily heard. Again, not a disputed issue at all and nothing equivalent to your claim.