Pass Labs.

[Gorgonzola]

Gorganzola I` like to know what preamp are you using with your Purifi power Amp? also are you suggesting that the Crown amps would be a better choice oppose to the Pass X350? also would you agree the Purifi amp would not be the Power amp to try to power the larger Maggies 3.6, 3.7i, 20.1, 20.7, 30.7`s ?

I guess it's about time I answered you questions here ... sorry, I haven't been following this thread carefully.

The preamp I am presently using to drive my VTV stereo Purifi amp is the Sonic Frontier Line 1 SE+ which is a tube preamp somewhat famous for it's "neutral", not especially tubey sound.

I'm certainly not suggesting that the Crown would be better to drive those Magneplanars, (I've owned the MG16 QR's), than would the Pass Labs X350 (or X360.8 or whatever). This are a matter of taste: Pass and Purifi, (I've owned both makes), don't sound the same. I don't know about Crown but is probably sounds different from either of them.

I'm not suggesting either that the Purifi wouldn't be good with the Maggies. It puts over 400 wpc into the Maggies' 4 ohm load which ought to be plenty in a medium room and sensible listening levels. Again, it's a matter of taste whether you would prefer the Pass or the Purifi.

 

[Grumpish]

I have heard Nelson Pass designs tend to sound good at lower volumes compared to most other SS amplifiers but that also tends to true of most really good sounding amplifiers.

I have a Pass F6, one of the designs that Nelson Pass makes available to the DIY community, and can confirm that - it sounds really good into my efficient floor standers on acoustic material, but is less impressive on the kind of music that has to be listened to at the threshold of pain - but then it is a 25w pure class A amplifier (makes a good heater) with fairly low gain, so runs out of steam quite quickly.

 

[Ralph_Cramden]

Pass isn't an engineer. He has a BS in physics, but a Master's in BS. He markets his "guru" status well.

 

[BrianP]

I've never heard a Pass amplifier, but I've read several interviews where Mr. Pass expressed a preference for low levels (up to 1%) of phase-inverted second harmonic. He believes that this "sweetens" the sound in the manner of an EL-34 based triode amp. Seems it would also avoid the tube amp drawbacks of heat, unreliability, and voltage instability into a complex impedance.

The audibility of this less than 1% distortion is certainly debatable -- many dogmatists would categorically deny it without ever actually listening (so then why even bother to measure it?) -- and its audibility (if any) is unlikely to be detected in a high-pressure ABX test. HOWEVER, if one spent an extended period with such an amplifier listening to favorite music (not test tones), and then did the same with an ultra-low distortion amplifier, and then went back again, I suspect that the subliminal effect of the distortion could lead to a definite preference for one or the other.

In situations where you WANT that second harmonic at high levels, such as an electric guitar amplifier, it's a whole different story. Many years ago I built an EL-34-based practice amp from a published design, and it had a gorgeous, sweet, singing tone with wonderful sustain when I cranked it up. Probably close to 100% THD, but mostly second harmonic, and not at all harsh and ugly like solid state distortion.

 

[Yasofnos]

I have owned Nelson's First Watt J2 and First Watt SIT-3. I know they measure quite poorly.
They are beautiful sounding amplifiers, the best sounding solid state amps I have ever owned. I have also owned the Benchmark AHB2 which measures extremely well, but I would never say it sounded beautiful.

 

[jtgofish]

I have owned Nelson's First Watt J2 and First Watt SIT-3. I know they measure quite poorly.
They are beautiful sounding amplifiers, the best sounding solid state amps I have ever owned. I have also owned the Benchmark AHB2 which measures extremely well, but I would never say it sounded beautiful.

Would love to hear a SIT-3.I own a Bakoon Amp 5521 which is the best sounding SS amp I have used[by far] .There is an article somewhere that rates the Bakoons and the SIT 3 as the best sounding amps they have come across.Very different designs though.

 

[jtgofish]

The best value Nelson Pass amplifier is not a Pass Labs or a First Watt.It is an Usher R1.5.A very good sounding and very well built Threshold copy on which the patent had expired.

 

[Wes]

Pass isn't an engineer. He has a BS in physics, but a Master's in BS. He markets his "guru" status well.

You seem unaware of his amplifier designs.

 

[Rottmannash]

I found a link to an Audioholics review and measurements of the X350.5. Quite a powerful, expensive and very heavy beast.
https://www.audioholics.com/amplifier-reviews/x350.5-review

 

[Ralph_Cramden]

You seem unaware of his amplifier designs.

Quite aware. Douglas Self, Bruno Putzeys, other real engineers have done much better designs.

 

[Ata]

I wouldn't think it was a controversial statement - Pass has been fairly clear over the years that minimum distortion isn't the design goal. You'll see this in reading articles at First Watt and Pass DIY. The various Zen amps and the related Amp Camp amp have high distortion, and own it in their docs. The Pass Labs amps measure rather better, and seem to meet their specs, but won't be winning prizes for low distortion. Are they 'low enough'? That's your call. A case could be made that between the lenient audibility thresholds and the typical levels of distortion in speakers it will be inaudible, or that you like the distortion profile. You can test the latter using Distort.

As for your amps, the XP30 doesn't seem too bad. I haven't seen measurements for the XP350 but you can have a look at Stereophile's measurements for other Pass Labs power amps and get a flavour then compare with some of the better measuring amps here.

At the end of the day if you're happy with your amps then don't worry.

Sorry for my ignorance, but if an amp is not designed to minimise distortion, what objective measurement is it designed/optimised for, noise / power efficiency / output impedance / stability / power rail noise rejection / reliability? Or, is it designed to "sound" best? In engineering school they taught us class A offers the lowest distortion, as compared to, say, class AB or B (there was no class D back then, or at least not in our textbooks). So if distortion is not an objective, why design a class A?

I am not saying Pass amps don't sound good, a friend has a DIY clone that sounds good, and I subscribe to minimalism in engineering design, just curious what the Pass Labs design objectives would have been.

 

[jtgofish]

Quite aware. Douglas Self, Bruno Putzeys, other real engineers have done much better designs.

Yes and of course nothing good has ever come from people working outside of their formal qualifications.Nor from people who have the ability to promote their ideas or business.How dare they!

 

[jtgofish]

Sorry for my ignorance, but if an amp is not designed to minimise distortion, what objective measurement is it designed/optimised for, noise / power efficiency / output impedance / stability / power rail noise rejection / reliability? Or, is it designed to "sound" best? In engineering school they taught us class A offers the lowest distortion, as compared to, say, class AB or B (there was no class D back then, or at least not in our textbooks). So if distortion is not an objective, why design a class A?

I am not saying Pass amps don't sound good, a friend has a DIY clone that sounds good, and I subscribe to minimalism in engineering design, just curious what the Pass Labs design objectives would have been.

I do not think anybody has proposed that low distortion is not desirable.Just that there is a desirable threshold [say 1%] below which there are no audible benefits.And that the pursuit of lower distortion of itself may be counter -productive within the bigger picture of overall sound quality.You can buy any number of cheap P.A. type power amps which have low distortion.That does not mean they sound any good.The Dartzeel NHB 108 is widely recognised as one of the best sounding amplifiers ever made.Its distortion is typically between 0.5% and 1% and its designers have never claimed it to be a low distortion design because they have concentrated on other performance critera which they consider more important for sound quality.Using no negative feedback being one of them.

 

[somebodyelse]

Sorry for my ignorance, but if an amp is not designed to minimise distortion, what objective measurement is it designed/optimised for, noise / power efficiency / output impedance / stability / power rail noise rejection / reliability? Or, is it designed to "sound" best? In engineering school they taught us class A offers the lowest distortion, as compared to, say, class AB or B (there was no class D back then, or at least not in our textbooks). So if distortion is not an objective, why design a class A?

I am not saying Pass amps don't sound good, a friend has a DIY clone that sounds good, and I subscribe to minimalism in engineering design, just curious what the Pass Labs design objectives would have been.

Assuming you're talking about Pass in particular, not J. Random Person's choice of design goals, https://www.firstwatt.com/faq.html and https://www.passdiy.com/about should give you a fair idea of his thinking, at least for that subset of his amps. The docs for each of the amps in the sections I linked originally go into more detail about the goals and choices for the specific amps. Some are fun and simple educational tools so builders can make something uncomplicated and see the effect of various alterations (the Zen variations), rather than practical amplifiers, but that doesn't stop people using them in their stereo system. Others are Pass Labs designs that are no longer in production, but usually measure rather better than the simpler ones, and obviously have different design goals. Another reason to build Class A is that there's a demand for them from people with very deep pockets...

 

[SIY]

I fail to see an assumption.

We all do, when it's our own.

First, the question asked me was, "Have you ever spent time with a Pass Labs amplifier?" Nothing ambiguous about the question or my answer.

Big assumption is that the "tuning" has any actual audible effect. You assume it does. I haven't seen anything to demonstrate that, it is merely asserted. Our ears are highly sensitive to many things, but distortion with program material is not one of them.

Now, if I change the output impedance, the frequency response may change, and may even be enough to be audible. But that change isn't amp "voicing," since it will be different from speaker to speaker. And of course, it can be cheaply achieved with an accurate amplifier and a resistor.

Someone else in this thread tried stealing a base by slipping in "high pressure" into a statement about ears-only testing. This of course is utter bullshit. Ears-only testing has established remarkable sensitivity to many audible factors (e.g., frequency response, localization, level, data compression...), but is only criticized when it shows null results for cherished and profitable claims. Sorry to chunk this into the same reply, but I'm on my phone at a truck stop.

 

[dtaylo1066]

It sounds silly to me to argue about one's qualifications in terms of his or her degree in physics or EE. I don't see much Pass product marketing happening, and he seems quite clear and transparent in his writing and philosophy regarding design, performance and circuitry. An objectivist is likely to dismiss his products out of hand. So be it.

As to similar "B.S." or marketing, why would Topping state the following on their website: "Each product will enter the hearing adjustment stage after achieving excellent parameters and performance during the R&D process, then we will again check whether the parameters are still excellent after getting the satisfactory sound, which process is repeatedly refined." If one takes that at face value, they are designing to a sound and not just specs. Per one side of this argument, they are then full of bullshit. Would not the best measurements produce the best sounding DAC or amp?

 

[Wes]

Quite aware. Douglas Self, Bruno Putzeys, other real engineers have done much better designs.

you are not looking at his history, which predates them by decades

a partial list was generously posted by someone upthread

 

[ta240]

We all do, when it's our own.

Which, is why I asked.

First, the question asked me was, "Have you ever spent time with a Pass Labs amplifier?" Nothing ambiguous about the question or my answer.

Again, I was just curious if it was his first watt line or the pass line; as some people don't differentiate between them and call them all Pass. In a fraction of the time it took you to dance around the question you could have answered it but everyone enjoys a good dance now and then. And, in reality, if I was only interested in making assumptions I wouldn't have asked the question; I could just assume without posting anything and go about my day. I think you mistook my interest in what amp(s) you listened to as a challenge to your result rather than looking for more data points to add to the current knowledge I had on the situation.
Everyone that asks a question isn't making a challenge; some are looking to learn from the answer.

Big assumption is that the "tuning" has any actual audible effect. You assume it does. I haven't seen anything to demonstrate that, it is merely asserted. Our ears are highly sensitive to many things, but distortion with program material is not one of them.

If we can't hear distortion then why is it measured here and why are amps rated based on it? That would mean the Amp Camp Amp is now recommended because Nelson's 'tuning' on it resulted in nothing that can be heard. I guess I shouldn't have thrown mine out; because it was good to listen to after all.
The caveat that is often added to the 'all amps sound the same' statement is usually something to do with them operating correctly with low distortion. Since his amps have a variety of distortion levels as well as harmonics they seem to fall outside of the 'sound the same' claim... but there goes another assumption.

Looking at the square waves for his latest DIY SIT offering (if I'm reading them properly) they show boosted treble and it also has fairly high distortion levels (into the 2% range). The boosted treble would really seem to me to be a 'voicing' aspect as that helps with 'the details sound amazing' comments. The distortion, when high enough, will show with the sound; and time after time the amps with high enough distortion have been referred to as sounding warm. To me, that sure seems like voicing.

Someone else in this thread tried stealing a base by slipping in "high pressure" into a statement about ears-only testing. This of course is utter bullshit. Ears-only testing has established remarkable sensitivity to many audible factors (e.g., frequency response, localization, level, data compression...), but is only criticized when it shows null results for cherished and profitable claims. Sorry to chunk this into the same reply, but I'm on my phone at a truck stop.

Each side chooses to endorse the method that fits their results. Posters get blasted on this site for claiming they can hear a difference in an ears-only test, but similar tests that result in no difference found get brought up as proof; even when sighted. Amir refuses to do blind tests before measuring the equipment; which is really no different than me listening after the salesman tells me what I'm about to hear. So, I do acknowledge that generally every side picks the methods and results that fit their agenda.

I'm still very curious about the marketing hype you referred to. That is a fairly common thing to see said about him and I have yet to see anything like that from him or his companies.

 

[ta240]

Sorry for my ignorance, but if an amp is not designed to minimise distortion, what objective measurement is it designed/optimised for, noise / power efficiency / output impedance / stability / power rail noise rejection / reliability? Or, is it designed to "sound" best? In engineering school they taught us class A offers the lowest distortion, as compared to, say, class AB or B (there was no class D back then, or at least not in our textbooks). So if distortion is not an objective, why design a class A?

I am not saying Pass amps don't sound good, a friend has a DIY clone that sounds good, and I subscribe to minimalism in engineering design, just curious what the Pass Labs design objectives would have been.

To quote Nelson Pass "we do these things so you can listen longer". His entire goal is to have amps that produce sound that his fans enjoy listening to for long periods of time.

Aren't there different kinds of distortions where some are actually pleasing to some listeners and some aren't even noticeable. If that is the case then it is only necessary to remove the unpleasant ones and worrying about the others is a waste of time for anything other than the spec sheet.

 

[Wes]

I am gonna buy a First What amp.