Pass Labs F7 Class A Stereo Power Amplifier Preview

[PENG]

This seems like a commercial version of his First Watt DIY kits. Without the diy savings, this amp seems a bit ridiculous.

Oh, regarding the kool-aid comments and ability to tell them from others in blind tests, this whole realm is a side branch of the single ended tube amp part of the audiophile rabbit warren. All of the First Watt amps have differing distortion profiles, some low enough to pass an a/b test, some with predominant 2nd harmonics, some with predominant 3rd but little 2nd... These amps do in fact sound a bit different from each other. They forego the complexity that would result in more power such as additional gain stages or more complex output topology, or that would produce better specs (many use absolutely no global negative feedback, or very little). How else would one get those chocolaty mids?

I think you may be right, but have you actually heard one of those and heard the difference? Mr. Pass seems to be one of those in the go by ears instead of specs camp, for that reason I wouldn't want to pay $150/WPC as I consider that would be a risky bet on $ for improved SQ.

 

[highfigh]

You cannot just use the power consumption and output specs to calculate or even estimate efficiency to compare products made by different manufacturers because they don't necessarily use the same methodologies, terms of reference etc. Class A or not, efficiency also varies with load (though less so with A than AB) among other things. Practically speaking, only the manufacturers themselves know the basis of their power consumption specs, assuming they always bench test and specify this spec for their products under the same conditions.

I have previously listed many examples to show how one would be misled using power consumption figures for such purposes. Depending on the specific purposes, power consumption specs can still be useful, such as when comparing power outputs of products in the same line, made by the same manufacturer but only when comparing in relative sense.

I'm not saying it's any way to state much of anything about an amplifier's output, especially if the piece has additional circuitry. OTOH, there's no such thing as free energy, so it can indicate this at some level but it hardly tells the whole story. It's never a good way to determine overall efficiency, only relative and maybe for roughly determining the needs of the electrical circuit when assembling a whole system. I have seen and heard people talking about their equipment, with them thinking that the consumption is the power output.

 

[highfigh]

I think you may be right, but have you actually heard one of those and heard the difference? Mr. Pass seems to be one of those in the go by ears instead of specs camp, for that reason I wouldn't want to pay $150/WPC as I consider that would be a risky bet on $ for improved SQ.

From the review- "Although we haven't been blown away by how Pass Labs amplifiers have tested on our bench, we did thoroughly enjoy our listening sessions with the X350.5 unit we reviewed."

IIRC, the main measurement that was seen as 'bad' was high DC offset- it would be interesting to find out if this results in a perceivable characteristic in the sound. I guess the amp's target market may be people who are less concerned with $/Watt.

 

[ski2xblack]

I think you may be right, but have you actually heard one of those and heard the difference? Mr. Pass seems to be one of those in the go by ears instead of specs camp, for that reason I wouldn't want to pay $150/WPC as I consider that would be a risky bet on $ for improved SQ.

Yeah, I have heard a couple First Watts. They're very pleasant sounding, in the same way that single ended tube amps are pleasant. I'm sure the F7 follows suit. In my experience, these hyper simple, single ended designs, either tube or ss, all share a peculiar resolving power that more complex topologies fail at. Whether from being genuinely more resolving (utter absence of crossover distortion? Minimal parts in the signal path?), or simply the result of ear-friendly, low order harmonic distortion and clipping behavior, or some combo of both, it's pretty obvious when you hear it. That kooky crystalline clarity is their only redeeming quality, IMO. And, while beguiling, it's not enough to put up with all of their limitations.

Agreed on the risky bet part...that's a lot of coin for such an odd beast.

 

[PENG]

I guess the amp's target market may be people who are less concerned with $/Watt.

Agree, but as I said I considered the risk is high that this little amp won't give me audibly better sound. I think the odd is high that even my 12 years old AVR will sound just as good or better (in certain ways) at higher volume. If there is a money back guarantee including say shipping one way, then the risk would be acceptable, to me anyway. The bottom line is, even such specialty amps are supposed to be designed to amplify the signal transparently, without introducing a particular "sound".

 

[ski2xblack]

The bottom line is, even such specialty amps are supposed to be designed to amplify the signal transparently, without introducing a particular "sound".

Not when it comes to First Watt amps. They are distinctly within the "amp as processor" realm. Mr. Pass goes on at length about this at his website:

There is no such thing as a perfect amplifier. All audiophiles and their associated equipment have specific needs, but in each case there is such a thing as a best amplifier - the one that makes you happy.

First Watt exists because I wanted to explore a variety of amplifier designs in what I think of as neglected areas - amplifiers that might not fit into the mainstream and are probably not appropriate to my more commercial enterprise, Pass Labs.

With oddball characteristics and output power ratings of 25 watts or less, First Watt is not for most people. If you have efficient loudspeakers, listen at reasonable levels and are obsessed about subjective performance, then you probably have come to the right place.
...
First Watt amplifiers are routinely compared with tube amplifiers, although I make a point that they are not designed to mimic tubes as such [but they do]. These amplifiers share some of the characteristics of the better tube products in that they have simple circuits with minimal or no feedback and emphasize performance of individual gain devices. In some ways they are better than tubes, in other ways perhaps not.​

 

[PENG]

In that case, no thanks, I have no time for amps that adds favor to the original recording.

 

[highfigh]

Agree, but as I said I considered the risk is high that this little amp won't give me audibly better sound. I think the odd is high that even my 12 years old AVR will sound just as good or better (in certain ways) at higher volume. If there is a money back guarantee including say shipping one way, then the risk would be acceptable, to me anyway. The bottom line is, even such specialty amps are supposed to be designed to amplify the signal transparently, without introducing a particular "sound".

I would say it's possible for the sound to be different, given the low NFB but it would be necessary to make sure the preamp/power amp interface is correct for both/all amplifiers tested and any other circuitry remains the same- only the power amp should change during the test. I will say that if several variables change, sonic differences are pretty easy to hear. I installed a Denon AVR-X6200 a couple of weeks ago and before I did, I set it up here, to do the firmware update and to take it for a test drive. I didn't have any problems with the sound and in the installation, it sounds great, but I don't think it sounds as good as my Parasound P5/A23 combo. That said, the DAC may/may not sound different, but I doubt it would be possible to isolate the one in the P5, so it's a moot point.

If I had enough time, I would have run the Denon's output into the A23 and its own power amp, to listen for differences and similarities.

 

[PENG]

If I had enough time, I would have run the Denon's output into the A23 and its own power amp, to listen for differences and similarities.

I hope you will have another opportunity to do it. With analog controlled preamp volume, you don't usually have to turn it up much, 10 O'clock is typically more than enough for me, so when you do an A/B with a modern AVR volume match is must. As I mentioned before, I A/B my 3805 with A21 using 2 different preamps and while I couldn't say they sounded exactly the same, any difference would be extremely difficult to verify in even a single blind test. I have no experience with the newer Denon AVRs though. Regarding DACs, the lower end X4200W has the same DAC as the SR-7010, so the X6200W may have a better one though unlikely. In terms of specs, there is no doubt the P5/A21 combo is far superior.

 

[highfigh]

I hope you will have another opportunity to do it. With analog controlled preamp volume, you don't usually have to turn it up much, 10 O'clock is typically more than enough for me, so when you do an A/B with a modern AVR volume match is must. As I mentioned before, I A/B my 3805 with A21 using 2 different preamps and while I couldn't say they sounded exactly the same, any difference would be extremely difficult to verify in even a single blind test. I have no experience with the newer Denon AVRs though. Regarding DACs, the lower end X4200W has the same DAC as the SR-7010, so the X6200W may have a better one though unlikely. In terms of specs, there is no doubt the P5/A21 combo is far superior.

The X4200 is hardly "lower end". I spec'd the 6200 mainly for the extra power (it's in a fairly large room) and for the fact that the customer isn't using 4K now, but they will in the future- I don't like using AVRs that I know will be obsolete in two years.

Net time I need to install something at this level, I'll try to take the time- I have been extremely busy this Summer and just wasn't able to do this test. It's in a room where I thought it would be very difficult to have good sound, but they decided to use a larger rug & sofa group and place it closer to the speakers, so the sound doesn't pass by it and hit the back wall/floor the way it seemed at the beginning of the project.

 

[slipperybidness]

From the review- "Although we haven't been blown away by how Pass Labs amplifiers have tested on our bench, we did thoroughly enjoy our listening sessions with the X350.5 unit we reviewed."

IIRC, the main measurement that was seen as 'bad' was high DC offset- it would be interesting to find out if this results in a perceivable characteristic in the sound. I guess the amp's target market may be people who are less concerned with $/Watt.

Yeah, I would say that high DC offset is bad! VERY BAD in fact!

 

[TLS Guy]

Yeah, I would say that high DC offset is bad! VERY BAD in fact!

Yes, it will be very bad if it is high enough to move the woofer cones away from their neutral position.

 

[highfigh]

Agree, but as I said I considered the risk is high that this little amp won't give me audibly better sound. I think the odd is high that even my 12 years old AVR will sound just as good or better (in certain ways) at higher volume. If there is a money back guarantee including say shipping one way, then the risk would be acceptable, to me anyway. The bottom line is, even such specialty amps are supposed to be designed to amplify the signal transparently, without introducing a particular "sound".

But even the reviewer stated that they enjoyed the listening session, so it must sound good, maybe excellent. What power level do you think you normally operate in/at/on (I figure I might as well use more prepositions, if I'm going to end a question with one)? If it's in the 5-10 W range, it should be able to handle a good range of music, unless you like to test equipment with the Telarc version of the 1812 Overture and it's real cannon. With sufficiently sensitive speakers, it really should be enough power for a lot of people- when I was younger and just getting into audio, I had a Sony 30W integrated amp and it sounded great with all kinds of music. OTOH, all of the reviews showed it outputting 56W/channel, both channels driven, at rated distortion.

 

[PENG]

But even the reviewer stated that they enjoyed the listening session, so it must sound good, maybe excellent.

I used to believe what reviewers said but learnt to ignore most subjective reviews. YMMV..

What power level do you think you normally operate in/at/on (I figure I might as well use more prepositions, if I'm going to end a question with one)? If it's in the 5-10 W range, it should be able to handle a good range of music, unless you like to test equipment with the Telarc version of the 1812 Overture and it's real cannon.

On average 0.1 to 0.3W per channel most of the time with peaks to 20W +/- 5W approximately, based on the VU meters verified by a multimeter with very fast response time.

With sufficiently sensitive speakers, it really should be enough power for a lot of people- when I was younger and just getting into audio, I had a Sony 30W integrated amp and it sounded great with all kinds of music. OTOH, all of the reviews showed it outputting 56W/channel, both channels driven, at rated distortion.

I wouldn't mind one of those Luxman, e.g. https://onahighernote.com/shop/mono-stereo-amps/m-600a-pure-a-stereo-amp/, https://onahighernote.com/shop/integrated-amps/luxman-l-590ax-pure-class-a-ii-integrated-amp/

Those should give me enough power and headroom for one of my 2 channel system, currently powered by an A21. It still won't sound different than my old Denon 3805 but I am sure their look and price tag will help me imagining and hallucinating..

 

[highfigh]

I used to believe what reviewers said but learnt to ignore most subjective reviews. YMMV..



On average 0.1 to 0.3W per channel most of the time with peaks to 20W +/- 5W approximately, based on the VU meters verified by a multimeter with very fast response time.

I didn't see a dynamic headroom spec, which I think they should all post. I remember some well-received amplifiers in the past that were said to provide a very dynamic sound with plenty of power, then they hesitated to post the headroom spec because they might have been good for .1dB, from rated power. Once they started under-rating their amplifiers, the wheels fell off of that spec.

I don't know of many multimeters that react quickly enough for any frequency, other than 60Hz. Does it have a peak hold setting?

I wouldn't mind one of those Luxman, e.g. https://onahighernote.com/shop/mono-stereo-amps/m-600a-pure-a-stereo-amp/, https://onahighernote.com/shop/integrated-amps/luxman-l-590ax-pure-class-a-ii-integrated-amp/

Those should give me enough power and headroom for one of my 2 channel system, currently powered by an A21. It still won't sound different than my old Denon 3805 but I am sure their look and price tag will help me imagining and hallucinating..

If you were to do a listening test, would you be comparing the sound with the Denon as the front end, when comparing the amplifiers? I'd like to do this and compare the front ends with one power amp, then compare the power amps with the AVR's preamp. If I had the time.

 

[PENG]

If you were to do a listening test, would you be comparing the sound with the Denon as the front end, when comparing the amplifiers? I'd like to do this and compare the front ends with one power amp, then compare the power amps with the AVR's preamp. If I had the time.

I have done both, using the Denon as an integrated amp and using it as a preamp. By the way, the speakers used were LS50 and R900. The preamps used were an vintage Marantz and a class A Cambridge Audio.

 

[slipperybidness]

But even the reviewer stated that they enjoyed the listening session, so it must sound good, maybe excellent. What power level do you think you normally operate in/at/on (I figure I might as well use more prepositions, if I'm going to end a question with one)? If it's in the 5-10 W range, it should be able to handle a good range of music, unless you like to test equipment with the Telarc version of the 1812 Overture and it's real cannon. With sufficiently sensitive speakers, it really should be enough power for a lot of people- when I was younger and just getting into audio, I had a Sony 30W integrated amp and it sounded great with all kinds of music. OTOH, all of the reviews showed it outputting 56W/channel, both channels driven, at rated distortion.

I"m curious, did the amp just happen to match well with the speaker load used for the listening tests?

How would it sound with a different set of speakers?

In the ideal world, an amp would be load invariant.

 

[highfigh]

I"m curious, did the amp just happen to match well with the speaker load used for the listening tests?

How would it sound with a different set of speakers?

In the ideal world, an amp would be load invariant.

When I set up the 6200, I used my speakers, which I built around 5 years ago and I used music I could repeat. It takes about two minutes to switch from the P5 to anything else because the back of my rack is open and I have banana plugs and my system is two channel. The speakers in the system I installed are Dynaudio Excite 14 LCR and Dynaudio in-ceiling for the rears. I asked, but they didn't want to bother with the extra speakers the AVR can drive, so....big improvement over the crappy little speakers he had before and the old AVR is pre-HDMI, so this is much better for now and in the foreseeable future. I used a Velodyne sealed sub, because the room is very live, acoustically, and I didn't want anything to make it more boomy than anyone wants.

The last time I installed the same model of Dynaudio speakers, I compared them to mine and used them as a model for setting the level of my tweeters, relative to my woofers. I made no changes to my speakers when I connected the Denon and I would say it leaned toward a warmer sound than the Parasound but, again, I didn't use the P5 to drive the Denon's power amp.

In the theater where it was installed, it sounds very good, without ANY equalization of any kind. Considering the room's acoustics, I was very pleasantly surprised. They put down a large rug very close to the cabinet at the front, it extends almost to the side walls (which are 30' apart) and it extends about 18' from the cabinet, with a large, soft pit group for seating. These do a great job of taming the room and I was also very surprised by the bass response- much better than expected.

When I listen to speakers and systems, I want to hear an even response, that doesn't have zones where the sound disappears or is excruciatingly strong in a range where I'm sensitive. When I or the music produces a frequency sweep, I want to hear it as evenly as possible and my system does that nicely. I would like to take all of the credit, but I have to think I have some happy accidents that are helping. The theater doesn't have the same height my system does, nor did the Denon when I listened to it here. The main difference in speaker placement between my place and the theater is that my speakers are 34" tall with the tweeters a little below ear level and the bottom of the Dynaudios are 4" above the floor, behind cabinet doors with a black screen. I haven't heard them since the screens were installed, so I assume I'll be doing a good amount of equalization.

 

[matteos]

I've got a First Watt J2 mated with a set of KEF R900s...

The clarity of the amp is astonishing. There is a resolution that you get from it I've not gotten from any other amps I have used, either SS or tube.. It really imparts a sense of the recording space.

There is all the volume you need out of 25 watts with 90db efficient speakers. I can say other amps I have such as one with 175 watts do make the bass a little more stout, but like all things there are trade offs and this is such a small difference anyway it's fine.

I find the bashing here kind of strange. Especially over the cost.. I've read reviews here of amps and speakers I'll never afford. It's not like $3k is a price that is so far out of reason. I think NP has designed so MANY loved amps that he can really do whatever he likes...

 

[PENG]

I've got a First Watt J2 mated with a set of KEF R900s...

The clarity of the amp is astonishing. There is a resolution that you get from it I've not gotten from any other amps I have used, either SS or tube.. It really imparts a sense of the recording space.

There is all the volume you need out of 25 watts with 90db efficient speakers. I can say other amps I have such as one with 175 watts do make the bass a little more stout, but like all things there are trade offs and this is such a small difference anyway it's fine.

I find the bashing here kind of strange. Especially over the cost.. I've read reviews here of amps and speakers I'll never afford. It's not like $3k is a price that is so far out of reason. I think NP has designed so MANY loved amps that he can really do whatever he likes...

Those who heard such amps might also find it strange that you heard such difference. IMO the moment this started one can expect diverse opinions/comments because this is a mostly subjective thing. Regarding the cost, if that amp can make my R900 and/or LS50 sound even just audibly better, I will not mind paying 3K or even 6K.