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Do tube amps REALLY clip more gently than solid state?

Head_Unit

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I have read this assertion many times as a supposed reason tube amps are great. I like tube amps and remember fondly a couple I got from my uncle, but this "gentler" thing has always bugged me. My recollection and now recent mini-survey of Stereophile measurements shows all amps' distortion zooms up very steeply at clipping. Here at ASR a bunch of solid-state amps all zoom up; I didn't find any tube amps. Not all amps distortion "zoom up" exactly the same, but they all hit a point where it goes up steeply. Some amps' distortion ramps up somewhat slowly before the zoom point however those ramps are below 1% so to me that does not count as "gentler."
Back to the asssertion that tube amps clip "more gently":
--> Is this truth? Or myth?

Note: in another thread @paulbottlehead asserts "Zero feedback SET amps clip softly enough that they would be an odd basis for comparison." Really? Maybe. I did find one test where the distortion while still zooming up does so not *quite* as fast as usual:
https://www.stereophile.com/content/line-magnetic-audio-lm-518ia-integrated-amplifier-measurements
Now I do have a degree in electrical engineering but as I specialized in loudspeakers I know just enough about amps to be dangerous ha ha. Makes me think:
- If clipping is gentler, doesn't that imply the power supply is soft? Because a true hard clip should always generate the same kind of harmonic signature in an idealized perfect amplifier I believe.
- In a tube amp can't the output transformers add a degree of softness?
- If there is a "gentler" thing wouldn't it be more about global feedback than tube versus solid state?
 

paulbottlehead

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The LM-518IA is not a zero feedback SET amp.

207cayin.7.jpg

This is more of what I was referring to. It's kind of a straight line to a point, then it cranks up into harder clipping.
 

mhardy6647

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The LM-518IA is not a zero feedback SET amp.

207cayin.7.jpg

This is more of what I was referring to. It's kind of a straight line to a point, then it cranks up into harder clipping.

... as opposed to the archetypal solid state, push-pull Class AB "checkmark" signature
(this one a Mac MAC-7200 stereo receiver, from Stereophile)
1220MACfig05.jpg

" Fig.5 McIntosh MAC7200, 8 ohm tap, distortion (%) vs 1kHz continuous output power into 8 ohms"
source: https://www.stereophile.com/content/mcintosh-mac7200-stereo-receiver-measurements
OK , maybe it's a left-handed checkmark.

EDIT: and, from the late 1970s, a similar graphic from a Sansui G2000 receiver's marketing brochure :)

1642271634555.png

source: https://www.hifiengine.com/hfe_downloads/index.php?sansui/sansui_g-2000_brochure_en.pdf

:cool:
 
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Sal1950

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Tube or SS, If your amp is clipping you need a bigger one. ;)
A bit of sarcasm but still true.
IMO one of the most important details of a great sounding system is
one that has plenty of headroom.
 

DanielT

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Damn what pointless laws there are. You may not sell your own DIY tube amp (in Sweden) but someone else (who does not DIY the tube amp may sell it). Fu**** stupid. Of course, those who are DIY friends give the assignment to commission (a hamburger) to fix it.

So what the he** am I burning on that tube amp. Measure W and soft clipping (see attached picture), single end, power tube 300B. It will be a match vs HK 670, 80 W in 8 Ohm.

Speaker, JPW P1, 89 dB, 2.83 V / 1M

I blow on. We'll see .:p

HiFi is about having fun. Everything is an illusion.:)
 

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DanielT

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That's kind of crazy since you have Lundahl there to supply you with some nice parts!
I will return with more pictures tomorrow, plus listening test. Observe subjective impressions then! Best to say.:)

So over and over again there will be subjective impressions and yes I know this with bass response tube amp, maybe elevated midrage (possibly) damping factor and so on and that it can affect, create assumed opinions bias and so on what I think of the sound.

Those who get a rash about my reported impressions tomorrow, please do not read this thread.:)

THIS IS Fun! :)
 

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Sal1950

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Those who get a rash about my reported impressions tomorrow, please do not read this thread
You must really love the sound of distortion. :facepalm:
 

DanielT

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You must really love the sound of distortion. :facepalm:
Well, give me a little more confidence. It's just gadgets for me, I bought HKn this summer for $90. I plan to sell it later this spring. I can just as easily connect and compare with:


I have no special tube amp feelings in itself, ... as you see on commission (to me)..so. :)
 

DVDdoug

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I believe it's true that tubes tend to soft-clip compared to transistors & MOSFETs. Guitar players generally like the way tube amps sound when overdriven. I think the audio-output transformer (required for tube power amps) also contributes to the "tube sound" of a guitar amp.

But it also depends on the circuit design. A tube amp can be designed to behave like a sold-state amp and vice-versa. For example, a tube or transistor circuit with high open-loop gain and negative feedback ("corrective" feedback) will tend to have low distortion, flat frequency response, and linear output up to the point where it hard-clips.
 
OP
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Head_Unit

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The LM-518IA is not a zero feedback SET amp.

207cayin.7.jpg

This is more of what I was referring to. It's kind of a straight line to a point, then it cranks up into harder clipping.
Yeah THAT looks like what I had in mind. But I think pretty rare? And is it really to do with the tubes or is it the feedback? And how many tube amps really look like that? Corollary, are there any solid state amps looking like this Cayin?
 
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Head_Unit

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If your amp is clipping you need a bigger one. ;)
A bit of sarcasm but still true.
Yes, I've really come around to thinking about this. People recommending upgrades to like 100 watt outboard amps from AVRs...gee that is not really going to get you much headroom eh?
 

paulbottlehead

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Yeah THAT looks like what I had in mind. But I think pretty rare? And is it really to do with the tubes or is it the feedback? And how many tube amps really look like that? Corollary, are there any solid state amps looking like this Cayin?
Oh man, loaded questions here for sure! What you should find is that most single ended triode amps that are zero feedback amps will do this, though whether they will do it in the LF region can depend a bit on the quality of the output iron.

Some of the Ayre amps kinda do this:
ayrv1fig7.jpg


I actually have a V1XE here that I could bring to Amir's house, but maybe I'll save that for a time when there isn't a creek running down his driveway since that thing is dang heavy.
 

DanielT

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Do I get a milk shake as well?!? :D
He he.Of course I help my friend plus it is of fun to test a tube amp for a few weeks.:)

Today there will be little experiment. I'm buying a new converter (I don't know where the old one went). Then I plug in a little here and there, including with and without sub. Will see if I can drive tube amp into overdrive with the help of Luxors pre out.
Dad's old solder from the 70's. Would you look at that. Search and you will find.
Measures up with dB app when I listen. I'll be back .... later today.

Edit:
By the way, if you have the roads past Gothenburg (Sweden) this spring, feel free to come and visit. Björn can probably arrange accommodation at the folk high school. No date nailed yet. You do not need to bring your own DIY, you are most welcome anyway. Send a PM.:)

 

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DanielT

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Now I have tested! I could not get hold of any high-low converters. They were out of stock. So no sub included in the test. Nevermind. You see I play quite loud. It fixes it easily and there more volume to turn on, if I want.:)

The sound then? Well, it sounds nice. Not because I hear any difference from HK 670 other when I turn up the volume really high. Especially if I use Luxorn as a pre amp with the loudness plus max on the bass tone control. Then the bass gradually becomes more and more "blurred" and "blurred" , at higher volume. . But it goes to high volume then. You can not listen to it for a long time. Too high volume.

That tube amplifier together with maybe 95 dB (or more) tube amp kindly sensitive speakers for sensible headroom. Plus active subwoofer that takes care of everything below about 80-100 Hz and relieves tube amp, then.. yummy. :)

Although actually my 89 dB sensitive speakers, 2.5 meters (around) listening distance is enough.I play some light pop music with it. It's probably not the most dynamic type of music / recordings. If I were to put on something really demanding, it would surely be scared.I will continue to listen with that tube amp. Advantage, of course, cozy tube glow when it gets darker later in the evening.:D

Note, I have not tried to do the same with Luxorn as pre amp and HK 670. That is max with bass plus loudness. Will test that and see how it sounds.

Watercolors because I will paint the lamps, VU meter on Luxor. I will also fix the cabinet as well, with new buttons and color .... when I have the energy and desire to do that.

With that, I have learned, uh,.. I do not really know.o_O..Well, it is important to match with the right type of speaker, when a tube amp with so little power is used. I knew that before. Everyone knows that, so nothing new under the sun there.Probably high sensitivity horn speakers + single end tube amp.It kind of belongs together , I think. Old school Hifi.

Edit:
Speaker, JPW P1.Two-way speaker. Sealed, 20 liter box, 8 Ohm, 89 dB, 2.83V / 1M.
Speaker elements:
Bass element: VIFA M21WG-09-08

Tweeter: VIFA D19TD-05-08

Add a link, so you will have some sweets to look at:


Edit 2:
Now I have checked the speakers with HK 670, max power bass + loudness. There is even a visible difference in how the bass element moves. I can push the 8 "at the bottom if I want.
So those were probably the differences I could see / hear tube amp vs HK 670.It's probably output transformers in the tube amp that saturate, which makes up for the lack of bass (compared to HK 670), when I pull on really properly a lot that is.
Despite the low stated power on the tube amp, it feels in some strange way that there are more W. If it depends on how it clip? I do not know. Maybe it's so.:)
 

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tvrgeek

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Maybe it comes from the output transformers not passing as high a frequency spike as bi-polars can generate. Just a thought.
 
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Head_Unit

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Some of the Ayre amps kinda do this:
ayrv1fig7.jpg
That to me looks like a fairly hard clip; above 1% the slope is pretty steep. Maybe those tubes actually have transistors inside! It's a conspiracy to drive us insane! And they're controlling our COVID microchips from this!
OR maybe I need to take a nap...
 
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