Interesting Nelson Pass article

[prem]

Single-Ended Class A - Pass Labs

Single-Ended Class A amplifiers have certainly hit it big in the four years since we began testing the first Aleph 0. So is this just another audio fad, or is there something fundamental about this kind of design, justifying a … Continue reading →

www.passlabs.com

 

[chander]

Very interesting - and very easy to understand too, surprisingly, most similar write-ups aren't. Are tube amps similar to a pure class A sound - - in terms of details presentation? I doubt I have ever experienced a pure class A. I know tubes present a warmer sound compared to some of the class AB I have listened together. I know no 2 pieces of equipment will ever sound same - just for my own understanding.

 

[Analogous]

Single-Ended Class A - Pass Labs

Single-Ended Class A amplifiers have certainly hit it big in the four years since we began testing the first Aleph 0. So is this just another audio fad, or is there something fundamental about this kind of design, justifying a … Continue reading →

www.passlabs.com

@prem thanks for sharing this engaging article from one of the eminent “Amp Gurus” of our times.
This (quote) from the article is going to ruffle a few feathers.

“…There has been a failure in the attempt to use specifications to characterize the subtleties of sonic performance. Amplifiers with similar measurements are not equal, and products with higher power, wider bandwidth, and lower distortion do not necessarily sound better. Historically, that amplifier offering the most power, or the lowest IM distortion, or the lowest THD, or the highest slew rate, or the lowest noise, has not become a classic or even been more than a modest success.

For a long time there has been faith in the technical community that eventually some objective analysis would reconcile critical listener’s subjective experience with laboratory measurement. Perhaps this will occur, but in the meantime, audiophiles largely reject bench specifications as an indicator of audio quality. This is appropriate. Appreciation of audio is a completely subjective human experience.

We should no more let numbers define audio quality than we would let chemical analysis be the arbiter of fine wines. Measurements can provide a measure of insight, but are no substitute for human judgment.”

 

[square_wave]

@prem thanks for sharing this engaging article from one of the eminent “Amp Gurus” of our times.
This (quote) from the article is going to ruffle a few feathers.

“…There has been a failure in the attempt to use specifications to characterize the subtleties of sonic performance. Amplifiers with similar measurements are not equal, and products with higher power, wider bandwidth, and lower distortion do not necessarily sound better. Historically, that amplifier offering the most power, or the lowest IM distortion, or the lowest THD, or the highest slew rate, or the lowest noise, has not become a classic or even been more than a modest success.

For a long time there has been faith in the technical community that eventually some objective analysis would reconcile critical listener’s subjective experience with laboratory measurement. Perhaps this will occur, but in the meantime, audiophiles largely reject bench specifications as an indicator of audio quality. This is appropriate. Appreciation of audio is a completely subjective human experience.

We should no more let numbers define audio quality than we would let chemical analysis be the arbiter of fine wines. Measurements can provide a measure of insight, but are no substitute for human judgment.”

I completely concur with his viewpoint. Measurements should be considered as the bedrock upon which the competent designer will / should "further build upon " using subjective means. The bedrock is important but it is surely a folly to just stay there.

SET is something that I have come to love. I doubt if I will even go back.

 

[arj]

What a wonderful article..a view I have not read on the pressurisation and phase of air till now and it makes so much sense..

Objective /subjective discussion is not even important here as every product is objectively designed and subjectively voiced in a wonderful combination of art and science..although these days most modern component may be going the science way and hence losing out the art...

 

[prem]

Franck Tchang with his resonators basically addresses the air issue Pass spoke about.

 

[Analogous]

I found a great quote to put on my T-shirt!!!

”Harmonic content of air is primarily 2nd order” Nelson Pass

 

[chander]

It’s not actually right to consider tubes amps as “warm” sounding which implies that the details could be missing. It’s the opposite in fact. They have predominant (of course depends on the topology too, so let’s stick to SE tube amps) 2nd order harmonics and are loaded with details.

Thanks for explaining! Brilliant!

 

[prem]

Yogibear, based on your listening experience, which of the below 3 is your preferred one

1. DHT SE
2. Pentode SE
3. Class A SS SE

 

[Kannan]

Let me share my personal experience here.

I presently own 4 NP deisgned amps from various periods.

One Adcom Class AB, another Adcom Class A Bias designed for car (which i mostly used at home), the AmpCamp (a very simple Single Ended Class A) which I am using now and another DIY under making which is broadly based on his Aleph design.

The AmpCamp which I use now is a simple 5 watt Class A amp powered by a laptop adapter.
It is a poorly measuring amp and very poorly rated in some forums like Audiosciencereview subsequent to its getting very popular in the diyaudio community.

It is ofcourse of very minimalistic design and uses feedback and 2nd harmonics primarily.

When paired with the right preamp and speakers, it sounds exceptional.
Many use a term musical which in my opinion is subjective.

It does not colour the sound in my opinion by having no exaggerations and has very clean and open midrange, good and taut lows and and good details in the highs.
Yes, with speakers needing good drive, it can struggle to provide loudness, but even therein, it delivers the full range without loss of details for near field listening.

I am running it presently on my DIY Infinity speakers which are reasonably sensitive at 89db and have also tried them on some very good power hungry speakers like the KEF R3, Revel Concerto and some floor standers at the Bangalore meet.
I have also run it on high sensitive full rangers like the vintage Altec Lansing and it has held its ground.

Overall it does its job very well keeping the measurements out, though some of the basic measurements are still well within the audiophile range.
The measurements which are normally not that audible or need high resolution gear in a properly treated room will most definitely bring out the flaws, but in normal home environment, this is an exceptional sounding amplifier.

In my experience, measurements are very important but too much clean-up can sometimes be too dull or flat sounding to an organic ear.

To add a but of naughtiness, the great Bernard Shaw once commented that "A woman can indicate with her euphoric voicing if the experience was organic or mechanical, unlike the men".

 

[prem]

Thanks yogibear for sharing your inputs.

 

[jenson]

doesn't SE class A come at the cost of wattage... Speaker matching becomes critical (or does it? As my jbl 4312s sing with apolmb with any amp)

 

[sidvee]

But again tubes watts pack much more sonic power than SS.

Just sharing my little experience and learning.

I have experienced this many times (most recently with a 25 watt SE tube amp, against a 250 watt class A sliding design), and there are technical articles with measurements that show that this is a fact in objective testing as well. However my only reservation with tube amplification of any kind (push/pull - SE etc), is that they cannot handle low impedance loads well where the SS designs reign supreme - especially in the 2 ohm and below loads.
Cheers,
Sid

 

[sidvee]

I am yet to experiment driving woofers from tube amps so have no actual experience. But will share a trick where you can drive woofers as well and have best of the both worlds, both tubes and SS and lose nothing…..

I have done bi-amping in the past with a tube amplifier for the HF and ss for LF. It worked out very well, except for the added expenses of the addition of second set of speaker cables/amps.
Cheers,
Sid

 

[nn_in]

Diy-Why not add a harmonic knob pot in preamp that has ss and tube mentioned at both extreme ends of the pot !

 

[sound1]

Diy-Why not add a harmonic knob pot in preamp that has ss and tube mentioned at both extreme ends of the pot !

"Harmonic knob pot" reminds me of Bob Carver challenge (he called them distortion pots) that Stereophile conducted, it is a very interesting read. Quite sure most of the FMs are already familiar with the article but here it goes anyways: https://www.stereophile.com/content/carver-challenge

At least in this challenge Bob tried to achieve the subjectivity using objective methods, which seems generally opposite of what objectively designed audio gears are conceived.

 

[sound1]

A little incident, it was last year or a year before that. And it was a famous audio show in Europe or US, I don’t recall.

The speakers were open baffle, by pureaudioproject, their biggest ones with four 15” woofers each side. May be like 103 dB setup. Amp was made by Thomas Mayer, Tube 46 driving Tube 46, making a max of 1.25 wpc. (My favorite tube besides EL12)

Nobody could imagine that the setup played full bandwidth with complete authority at loud volumes at a fraction of power !

Bob Carver on why Tube Amps sound much more powerful than SS amps.

 

[Hari Iyer]

Single-Ended Class A - Pass Labs

Single-Ended Class A amplifiers have certainly hit it big in the four years since we began testing the first Aleph 0. So is this just another audio fad, or is there something fundamental about this kind of design, justifying a … Continue reading →

www.passlabs.com

Thanks @prem for sharing.
I have different views on using high bias to get more juice from the output stage. This will stress the output stage and reduce component life. I would rather opt for higher anode - cathode voltage and lower bias current to get more voltage swing. My current amplifier dissipate only 13.9 watts where it has a maximum dissipation of 44 watts. Only operate at 33% of its capacity there by increasing tube life significantly without much compromise on quality.

 

[sound1]

Bob Carver on why Tube Amps sound much more powerful than SS amps.

If anyone cares to watch it beyond the answer to addressed question, the guy goes on to explain, among other things, why there is no way to attain 100% perfect audio reprodution and one needs to settle with 'believable reproduction'. IMO, the whole talk is worth a watch if you are curious about audio technicalities.