Pass Labs F7 Class A Stereo Power Amplifier Preview

[ski2xblack]

Peng, if you're curious about those who have heard such amps, look back at my post #24. It seems Matteos and I are describing the exact same thing, I'm just a bit less forgiving of the cost factor coming from a DIY perspective.

 

[PENG]

Peng, if you're curious about those who have heard such amps, look back at my post #24. It seems Matteos and I are describing the exact same thing, I'm just a bit less forgiving of the cost factor coming from a DIY perspective.

I did read your post #24 and #26 but I just read it again. My point was simply, on a topic like this, people are going to make subjective comments so it really isn't strange, but of course if Matteos felt that way then he felt that way. I also don't consider those subjective comments/opinions meant to be "bashing" the product as such.

 

[mr sarnoff]

$3K sems a bit rich to me for an 25wpc power amp with admittedly small parts count and maybe an unproven design .


I've seen folks spend $10K and more on billet aluminum CD transports and $4K on an Audio something brand 3 meter PCM data cable the 5K billet aluminum DAC they bought cant read any better through R6 bulk TV Coax and where a $100-$200.00 retail or a decent DIY DAC with a SABRE ASIC or two and a New Japan Radio op amp or two gain staged in it with a clean PSU can sound every bit as good and some of them spend all that money and much more and dont treat the rooms.


Some try to do double duty as an HT with their music systems which are often not the same goals or desired results anyway (been there and done that ..you don't want muti channel or two ch. music and LFE (all at real THX levels *from each multi channel speaker array ) at the seated positions for long trust me. ) For music a bad room is hard to impossible to play safely through anyway.


FWIW now I have a Crown XTi 2002 at 1000W 2Ω, 800W 4Ω, 475W 8Ω feeding JBL LSR LSR 6332 L/R monitors and also 2 self powered reference subs in an professionally engineered acoustically controlled dedicated music studio/ PC game room addition outside of the normal living spaces running out of a pro interface pre amp and professional digital audio workstation PC and mixing configuration and a modest Schiit Audio stack on this PC for the phones in here

Note all that stuff in the playback chain and the speakers outside of the windows 10 PC digital Audio workstation/game build are professional THX PM3® Certified items .

I've been an expert level enthusiast (reading Audioholics for many years also ) and owned some reasonably decent stuff off and on for over 40 years that include a Citation II (Duece) EL 6884 P/P tube amp and matching Citation One pre amp ,a Phase Linear 700B and the usual TOTL or nearly so Pioneer Silvers and some newer Sony ES gear ,Altec model 19's and the EV Sentry IV's I still own and that Crown amp can put all those amps to bed in a minute and cleanly too .




The long and short of all this is in that not small room (on a good /recording mix more often copy's of 24 bit mixes and digitized analog mixes sourced originally from the labels here ) that mess all sounds as good as it needs to for me in that size room and bigger and can probably astonish a few spendy 'audiophiles' like it has done with some music producers and artists I know and outside of the addition that costs maybe more than a new luxury car this side of a Bentley it doesn't cost like spendy audiophile gear and at some point it's all about the room anyway and money is often better spent on speakers and room treatments and if you need more power a modern pro amp like a decent Crown or QSC can often deliver all that fine just don't get the inexpensive bottom feeders that are usually outsourced and noisy anyway....OTOH I've always liked McIntosh audio gear so ......

 

[mr sarnoff]

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 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..

FWIW I tried my arguably decent Sony ES 140 wpc AVR on my JBL LSR6332 speaks in the music /game room addition and the Crown XTi 2002 amp in there handily put all that out of my mind in a minute.

OTOH I can imagine that Luxman would be excellent in the right room on the right speakers but what would be equally good in the same room on the same speakers at much less money is always an arguable and interesting question that you wont convince some spendy 'audiophiles' of in a forum .

ppfffttt I wont mention the other one where they hang out

 

[mtrycrafts]

......

How many of those JBLs do you have? all 3 fronts?

 

[matteos]

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.

If you are using a Denon 3805 as your amp.. I think most dedicated amps / preamps will make your speakers sound better. Most AVR's are no match for a good stand alone amp. I think the 3805 was sort of in the middle of the range?

The first Watt amps are a good fit for your R900's (Love these!) But will be a bad fit for the LS50s.. They're not sufficiently sensitive.

Another point. The J2 at least is using (Now, no longer available) JFET transistors.. Only a handful of amps have used these historically (I think as they are hard to get a hold of)... Anyway they have significantly more gain compared to MOSFETs and less distortion. NP was able to use these in a circuit similar to SET amps.. Kind of gives you the best of both worlds as you don't have to run ridiculously sensitive speakers to get that musicality.

I'm not sure what he did with the amp the thread is based on, but I'm sure he's trying something equally awesome with the parts that he has.

 

[cutedaddy]

Never found any reason for the bad rep of negative feedback, other than the fact it contains the word 'negative'. Negative feedback (as i presume Putzeys' article will also state, probably the article of his i read long ago) is one of the most positive things engineers have at their disposal to mitigate distortion, specifically the back EMI caused by dynamic piston driver operation.

I am very glad indeed to find Audioholics.com mentioning Putzeys' name and addressing this issue, as BP is one of the pioneers of modern day class-D amplification, lifting the class from an inferior but efficient topology, to the topology of choice for anyone who wants the very best performance any amplifier can deliver, at any price. Its efficiency has now become merely an added bonus.

Benchmark measuring gear manufacturer AP needed to develop new, more sensitive gear to even measure the distortion of Putzeys NCore topology, rendering the science of amplifier design sort of 'accomplished'. No design of any description will audibly improve on NCore, since there already is no audible distortion left.

Perhaps if we will find a speaker design that has equally low levels of distortion (THAT would indeed be the holy grail of audio reproduction!), something about the amp might become audible, but even then i seriously doubt it. Pass Labs must be, in my opinion, launching yet another redundant improvement in amp technology, the claim to fame of which will be corroborated by subjective listening tests only, and only when these tests are performed by non-professional audiophiles.

 

[PENG]

If you are using a Denon 3805 as your amp.. I think most dedicated amps / preamps will make your speakers sound better. Most AVR's are no match for a good stand alone amp. I think the 3805 was sort of in the middle of the range?

But I did compare it with a few separate preamp/amps I also owned, a Marantz vintage preamp and preamp, a 250W Halo power amp, 300W Bryston power amp, and a Cambridge audio preamp (Class A). The 3805 held its own extremely well, using the R900 and the LS50+Rythmik sub. I did not do the same comparisons with my 1028Be that has better resolution than the R900, though I highly doubt it will make much difference. I must say I do like separates regardless.

Another member, ADTG also owned a few high end preamp/amps and found his AVR-3312 held its own too, powering some higher end speakers than mine.

Obviously YMV..

 

[matteos]

But I did compare it with a few separate preamp/amps I also owned, a Marantz vintage preamp and preamp, a 250W Halo power amp, 300W Bryston power amp, and a Cambridge audio preamp (Class A). The 3805 held its own extremely well, using the R900 and the LS50+Rythmik sub. I did not do the same comparisons with my 1028Be that has better resolution than the R900, though I highly doubt it will make much difference. I must say I do like separates regardless.

Another member, ADTG also owned a few high end preamp/amps and found his AVR-3312 held its own too, powering some higher end speakers than mine.

Obviously YMV..

I can't speak to your experiences but Denon is one of my favorite brands ive owned multiple avrs and have a poa 1500 pra 10000 that I will never get rid of.. I did have the Aver one thing lower than the 3805 I didn't like it. But I think it was the dac. Sure yours is is a lot better. The only Denon I didn't like. Wish you could hear my setup.. as is not much use paper speccing about these things. I think the beauty of these shots I'd the simplicity of design. Apologies for the tips. I'm posting from a truly broken phone.

 

[PENG]

I can't speak to your experiences but Denon is one of my favorite brands ive owned multiple avrs and have a poa 1500 pra 10000 that I will never get rid of.. I did have the Aver one thing lower than the 3805 I didn't like it. But I think it was the dac. Sure yours is is a lot better. The only Denon I didn't like. Wish you could hear my setup.. as is not much use paper speccing about these things. I think the beauty of these shots I'd the simplicity of design. Apologies for the tips. I'm posting from a truly broken phone.

I owned a Denon AVR-1705 and a 1912 briefly and have to agree if you want to get to the point of diminishing return you have to go with their 3000 series or higher (especially for the newer models), basically models that have multi channel pre-outs will typically do the trick. After that, it is a matter of power output that rules.

 

[mr sarnoff]

How many of those JBLs do you have? all 3 fronts?

Very Nice spot and speakers and etc. you have there !

Only 2 JBL LSR6332 and they are left and right imaged its a 2.1/ or 2.2 ch. capable l music system not surround sound but maybe 3 in front could be interesting anyway but I'm not sure about what I would feed 3 of them channel wise on a 2 ch source perhaps a L/R blend

A newer 40" Sony 1080P TV used as a main PC, You Tube ,PC game or DAW monitor more than a TV in there is at the front center of the workstation desk between the JBL's nearly in each corner on the frt. short wall of a rectangular room facing nearly straight out and slightly towed in for the sweet spot at the desk and slightly further back than the screen and desk anyway whereas the near field JBL LSR 308's are closer of course.

OTOH I'm not foolish enough to make an argument that all that sounds remarkably better or better than a decent audiophile /enthusiast consumer configuration ( some surprisingly modest and or vintage also ) in a good room of any kind either or even a vinyl vs digital argument having grown up with all that and starting with console pull tube amps and DIY speakers and so on ........just that it all sounds very good here for not unreasonable new gear /speaker costs IMO although the JBL LSR6332 weren't exactly cheap either but not as spendy as some well regarded speakers

 

[mtrycrafts]

Very Nice spot and speakers and etc. you have there !

Only 2 JBL LSR6332 and they are left and right imaged its a 2.1/ or 2.2 ch. capable l music system not surround sound but maybe 3 in front could be interesting anyway but I'm not sure about what I would feed 3 of them channel wise on a 2 ch source perhaps a L/R blend

...

I changed the center in the pictures to that 6332. Very nice speaker indeed. The Tis are too tall to have in the center and the older JBL I built in the pictures was getting just old. Was hard to replace them, had it for a good while.
ps. found a very good deal on my 6332, so it made the transition less painful.

 

[Johnny2Bad]

The F7 does have a relatively low steady-state power rating, but transient power is said to be through the roof. Did you notice any evidence of clipping in your listening tests?

 

[lukesky518]

I am currently using a First Watt F6 ( completely different than the F7 ) but with the same basic pretense...simplicity . My preamp is a Cary SLP-05 , for about 7 years or so . The amps I have owned in the last 5 years .....Belles A150 hotrod , VTL ST-85 , Cary V12 ( racing version) , Bottle Head 300b mono blocks , Transcendent Sound Mini Beast , Conrad Johnson Classic 60 , Aragon 4004 mk 2 and some I cant remember . The F6 is more musical than all of them ( to me , in my system ). BTW , the Aragon measured better than all of these but sounded the worst .

 

[TLS Guy]

Let me start by saying it is my right to guess that Mr. Pass could not tell it apart from his other SS amps using the first watt in a DBT. Another thing, +ve feedback? Wow, I wouldn't want to spend 3K experimenting. Still, for 3K it seems like an affordable toy for die hard audiophiles.

Well, my power amps are all +ve feedback. Peter Walker did not call it that as he was afraid of just your reaction. Instead he called it feed forward! But it is +ve feedback, but actually feed forward is a more descriptive and accurate term for it.

I have always thought that Nelson Pass has used a lot of Peter Walker's ideas in his designs.

The thing is that Peter Walkers amps are much simpler than all the circuitry designed to overcome the problems of class A/B. The amp boards are small with a low component count.

Here is a Quad 909 amp board, 250 watts into 4 ohms class A and it makes very little heat as the power transistors are biased heavily to B, and the class A amp feeds forward to correct the dumpers and sets the class A spec.

Elegance in design! It does not cost 3K either.

 

[lukesky518]

The 909 is a nice amp for sure . A few corrections ( I think ) . Nelson Pass came out with the Stasis amp/circuit in the late 1970's with Threshold . Paul Walker came out with his version in 1978 . I believe the release dates are so close that neither would have had the time to copy the other and market their own version . Also , there is no way that is a 250 wpc class A amplifier .

 

[TLS Guy]

The 909 is a nice amp for sure . A few corrections ( I think ) . Nelson Pass came out with the Stasis amp/circuit in the late 1970's with Threshold . Paul Walker came out with his version in 1978 . I believe the release dates are so close that neither would have had the time to copy the other and market their own version . Also , there is no way that is a 250 wpc class A amplifier .

No, Peter Walker published the theory and details in December of 1975, at the introduction of the 405. Peter had no secrets and welcomed peer and public review.

I considered Peter a true friend. I was in Canada at the time and was his Western Canadian agent for a while, and we had a lot of shared discussions and experiments on the further iterations of the 405.

In my view Pass is the plagiarist. Peter Walker had a very high code of personal honor and would never stoop so low.

 

[PENG]

Well, my power amps are all +ve feedback. Peter Walker did not call it that as he was afraid of just your reaction. Instead he called it feed forward! But it is +ve feedback, but actually feed forward is a more descriptive and accurate term for it.

I have always thought that Nelson Pass has used a lot of Peter Walker's ideas in his designs.

The thing is that Peter Walkers amps are much simpler than all the circuitry designed to overcome the problems of class A/B. The amp boards are small with a low component count.

Here is a Quad 909 amp board, 250 watts into 4 ohms class A and it makes very little heat as the power transistors are biased heavily to B, and the class A amp feeds forward to correct the dumpers and sets the class A spec.

Elegance in design! It does not cost 3K either.

I happen to know feed forward quite well and I am not sure that's what Mr. Pass was talking about. Why would he call it feed forward then? Anyway, I guess you could be right.

Regarding those Quad amps that you like so much, they didn't have the best bench test results in the Miller Audio research Avtech lab. Regardless, you've got me very curious about them, almost enough to want to try one if I can find one at reasonable cost.

 

[TLS Guy]

I happen to know feed forward quite well and I am not sure that's what Mr. Pass was talking about. Why would he call it feed forward then? Anyway, I guess you could be right.

Regarding those Quad amps that you like so much, they didn't have the best bench test results in the Miller Audio research Avtech lab. Regardless, you've got me very curious about them, almost enough to want to try one if I can find one at reasonable cost.

Just get a little more curious and get it satisfied.

The trouble with bench testing is that it tests under resistive load conditions. A speaker is anything but. This always bothered Peter and he was always at pains to really try and make his amps performance independent of load as far as possible.

Now I will concede one thing. I have used these current dumpers most of my life now. So my speakers were designed and voiced using those amps. So it is certainly possible my designs are optimal with those amps.

I have long thought that ideally amp and speaker should be designed as a single entity.

 

[lukesky518]

"Now I will concede one thing. I have used these current dumpers most of my life now. So my speakers were designed and voiced using those amps. So it is certainly possible my designs are optimal with those amps." He probably voiced the amps as well to obtain what he wanted . BTW ......I think it is a bit unfair and irresponsible to call Nelson Pass a plagiarist , especially without proof . He has many patents and gives his schematics , time and experience to the DIY community . Not only that , to most audiophiles , his work is the pinnacle of solid state design , build and sound quality .