Amplifier Distortion- The Ultra Low vs. the Intentionally High (Subjective)

Ultra low Total Harmonic Distortion seems to be an appealing trend in some popular contemporary amplifiers- but so does Intentionally High THD (e.g. tube amplifiers).

For example, tests of the Benchmark AHB2 reveals the following THD-
.0004% THD @ rated power into 8 ohms,

Primaluna ProLogue Premium-
.1% THD operating, > 1% @ rated power. That is 250X more THD at operating power and 2500X more at rated !

The differences should be obvious, right? Are they? How does it present itself- (high frequency issues, congestion or lack of continuity with complex material, lack of bass, other?) s

 

I have completely stopped paying attention to those distortion numbers after my NOS DAC (which all measure terribly) blew my mind. Tube distortion tends to be even order and pleasant to the ear. Yes, I feel like I can hear it, and it comes through as sparkle and a tiny bit of grit at times, but there's something about it that, to me, makes it sound more natural and alive. My primary system is solid state, besides the DAC, and my other stuff I own right now is all tube, and I'm regretful of my decision to build out my primary system with low sensitivity + solid state, because I find the cheap, THD heavy second system more fun to listen to, despite its flaws, or maybe even because of them. I've come to find the pristine clean of solid state a bit boring and look forward to the day I switch my main system to all tube.

 

Archimago's Musings: BLIND TEST RESULTS Part III: "Is high Harmonic Distortion in music audible?" Subjective Descriptions

 

I've never encountered it with my tube amps because I'd never ever be able to push them to the level that I'd experience distortion - without police being involved.

So always crystal clear at all volume levels. Distortion is a concept I learned about when younger using crappy equipment.

 

I would question whether many amplifier makers intentionally add distortion. I think it is more that it is inherent in the tube amp design and topology and often a lack of a negative feedback loop.

 

thanks, i'm aware of that thread. i'm more interested in hearing from people who have been at the extremes as outlined in the opening post. with amplifiers becoming ultra low distortion as a selling point, who has made the switch and what did they find.

 

I can definitely hear the harmonic distortion in tube amps, but it heavily depends on the song and the instruments present in a given song. I mostly notice it in the reverb tails of electric guitar. Only seldom do I find it objectionable. I don't notice it quite as much with tube preamps and tube-buffered gear.

 

Totally down with tube distortion. Would love to hear some of the beloved solid state amps with higher distortion.

(push pull w/neg feedback atm)

 

I think distortion signature more important then actual THD...
I know I am in minority, but for my ears in chain source - pre - amp - speakers amplifier, if properly made, makes the smallest difference.

 

I would also question whether a designer would intentionally "add" distortion when in fact any tube equipment can be designed to measure and even sound like solid state. If you look at specs and measurements of tube equipment from manufactures like ARC and McIntosh their preamps and amplifiers are generally designed to have the lowest possible noise and distortion and often measure and compare favorably with solid state equipment. I recently read a review of a Cary integrated (an SLI-80HS) in Stereophile and though the reviewer raved about the sound the amp reproduced, when the amp was placed on John Atkinson's test bench and put through its paces and compared to typical solid state amps, measured quite poorly especially considering the amp was designed around tubes using solid state rectification and push-pull outputs (KT88s and 6922s) which in another implementation could be made to measure quite well. So maybe the designer isn't intentionally adding distortion they are (subjectively) relaxing the parameters of design which could otherwise result in a cleaner measuring amplifier.

 

Most people cannot hear up to 2% distortion. Audiophiles with trained ears may be able to hear 1% distortion. Some like a little distortion on rock and roll music. The Fisher 500B is a perfect example. In stock form it is very pleasing. Modified with paper oil capacitors and best tubes, the Fisher 500B is very different. But those audio transformers still provide that pleasing distortion when upgraded.

 

High praise coming from an owner of the cleanest sounding amplifier on the market !

 

What I think I am hearing may be objectionable on the recording but "amplified" by the system and more audible at higher, somewhat already harsh frequencies- example 3-8Khz.
I have heard a super clean system sound incredible in those frequencies but it could also have been a super clean recording.
When a recording has intentional compression or distortion for effect, it seems as if that pushes some less clean / tube based systems into objectionable sound. Not high volume either, just moderate volume.
I wonder if recorded distortion + system distortion = harsh listening ?

 

This is, IMO, the essence of tweaking a tube system. There's already distortion in the recording, so how does that get rendered. In my experience, the tubes you use, but also the ICs and speaker wire can help clean up the distortion as it is added to what is already in the recording. That bloom that you get with tubes can also be bloom in relation to distortion. At this point, I feel like I've found some basic ways to mitigate it. However, as tubes are always in a state of slowly degrading, it's a moving target and learning to listen is required.

 

This may be of interest to some:

Audio distortion and feedback - Passlabs

 

Where the AHB2 really earns its keep is the silent noise floor and woofer control at lower volumes.

 

I can easily hear distortion in set amps when driven too hard. Never noticed it in any other type of gear, unless it' s an electric guitar

 

It is about much more than distortion. The lowest-distortion-possible race of the '70s created many amplifiers with vanishing levels of distortion, which nonetheless sounded like crap. Much like mastering, it's all about the implementation of the circuit, and, frankly, careful listening to parts used. Generally, the obvious differences to me are that tube amplifiers (at least at reasonable price levels) with higher distortion have less transparency and detail than a solid state amplifier with much lower distortion, but to me SS sounds a bit less lifelike. That has been the tension in my audio journey, finding the right balance between detail and emotion in a combination of components, but I have never considered the distortion of a particular piece as part of my buying decision. It has always been about listening.

JohnK.

 

I recently went from a PrimaLuna Integrated to the AHB2. I love the PL, but I think the AHB2 is doing everything an amp should do, which is faithfully amplify the signal being sent to my speakers. Subjectively, the sound coming from the two is very similar, but the most obvious difference (besides better bass output, which like you said in another thread is to be expected) is the pinpoint imaging and level of clarity at high volumes. I’m no electrical engineer nor a long time audiophile, but my intuition is that the harmonic distortions create a very subtle smearing effect that a lot of people find pleasing, since it sounds more “alive”... because we never hear things perfectly in the real world, so hearing things “perfectly” in our music, to some, robs it of authenticity.

In my mind, however, if what we as listeners are after is the faithful reproduction of what the artists and mastering engineers intended us to hear, the lower the distortion the better. This obviously comes with all the caveats that measurements aren’t everything, and that what sounds best to one might not be another’s cup of tea.

 

Well said.

 

I think our hunter tracker brains hear harmonic distortion as the information that allows us to differentiate orientation in space, so some people learn to listen for that enhanced illusion and even seek out recordings that do it well. Others focus in audible distortion. Some hear both and pick their best solution.

 

Hi guys,
Very good discussion and I touched upon this topic yesterday when I posted the measurements for the Pass Amp Camp Amp:

MEASUREMENTS: Pass Amp Camp Amp (ACA) 1.1. The crossroads between objectivism and subjectivism, and reconsidering von Recklinghausen.

For me, one of the central questions as an audiophile (one who loves music and sound) is which of the paths do I want to choose?

1. Take the route of "fidelity" / "transparency" / "accuracy" to the source (LP, CD, streaming). If this is the case then we'd be going with that Benchmark amp since the low THD means the linearity of the device is essentially perfect. Whatever is on that source recording will be amplified without "extra" frequencies added or other distortion within the amplifier use situation. One can be objective about this with better measurements to a point where audibility is exceeded; no need to spend more money or upgrade after that.

2. Take the road to "euphonia". Whatever it takes to sound good! 2nd order harmonics can sound good like in the ACA. Obviously too much noise, too much distortion will distract and won't sound good anymore. Tubes can certainly provide this kind of personalized "tuning" for euphonic sound.

Either path is great and can only be determined by each of us... Of course, nothing wrong with having both an ultralinear Benchmark AHB2 and a tube amp/SET/Pass ACA .

 

I have owned and sold the champs among both tube and tranny power and pre amps.
To my mind there are several moving parts at play in the distinctions between the two.
It is NOT all just about the THD numbers.
It ain't that simple.

Depending on the circuit topology, power supply type and size, output design, input stage design, type of tube, bias levels and on and on and on.
The MAIN thing I take away from the debate is that tubes, even push-pull class B tube amps---"breathe" a little easier since the tubes pass electrons pretty easily and they "flow" pretty well---even cheap tube amps.

Tranny amps push their electrons through silicon or "sand" if you will. And this junk "resists" the flow until it gets nice and "hot". Thus tranny amps tend to sound better running harder. And when I gain stage my setups I try to push tranny inputs closer to "hot" levels to maintain the "flow."
If the input stage of a power amp, for instance, is set real soft and low coming out of the preamp---that amp may sound rather dead on arrival.
But the same power amp hit with a couple of volts to "wake it up" will sound much more "tube like."

Now as for distortion---this is typically low enough at normal listening levels to not be noticeable with either type amp. But pushed---the tranny amp may clip into an ugly harsh tone, while a tube amp will slowly turn into "mush" as you push it.

So what it the "take away" from all my tales of how the world works?
Well, first of all the power section MUST like playing with the load your speakers present upon it. So EITHER type of setup is dependent on a great "match up" when the speaker pushes back electrically (it IS a motor, after all---and it WILL "push back" into the amp!).

Once you get THAT part figured out as to what power sections play well with your speakers, I would suggest that top of the line amp designs of either stripe will not be as big a deal as in days gone by when power and control went lacking due to insufficient design margins.

In other words to make a long story short---I have heard the best of each designs pitted against each other and under a fair test the best stuff all sounds pretty great.
Low power flea amps and super sensitive speakers, SETs and so forth are a totally different problem as these approaches are mostly for "experimenters."

But if the system parameters include nice power margins the good stuff is pretty similar in presentation---at the top rungs at least.
Distortion is only one part of the presentation and the better, modern, hefty tube designs have marginalized this issue in some cases.

Or maybe I am crazy, don't know beans and am just flat out wrong about EVERYTHING my whole life and should just shut up as I am nothing but a fool.
On the Hill.

 

I'd just be careful about this myth about the 70's and vanishing levels of distortions claimed.

Remember back in the day in the 80's and 90's when we also saw crazy specs like "1000W PMPO" and stuff like that out of boomboxes? This was all marketing nonsense of course! Actual measurements of amplifiers in the 70's did NOT demonstrate crazy 0.00001% THD+N or some such results using standard loads and proper measurement technique. Bruno Putzeys discussed this as well in his article on feedback.

These days, we might not hype numbers as much, but we of course hype in other ways (like expensive cables making a difference, or MQA "deblurring", etc...).

I do have a few vintage refurbished amps/receivers from the 70's and 80's here. I'll see about measuring one of these at some point to show you what the results look like...

 

[/QUOTE]...because I find the cheap, THD heavy second system more fun to listen to, despite its flaws, or maybe even because of them. I've come to find the pristine clean of solid state a bit boring and look forward to the day I switch my main system to all tube.[/QUOTE]
I just accidentally came across this forum... I built a quite unique ultra-low distortion SE tube amps (design is here: Ultra-low distortion valve hybrid amplifier - Valve Radio ), with THD of about 0.005% near clipping and obviously reducing to nill at lower power (as single ended class A does not produce that "nasty" harsh crossover distortion). I found that sound is not distinguishable from sound of a quality solid-state amp.
So I would say there is no market for zero distortion tube amps.
Those who prefer undistorted pristine sound feel free to use good transistor amps.