If tubes amplifiers measure poorly, why are they perceived as sounding better?

[Magz]

A 1600W space heater would be welcome here this week (11°F, getting down to about 7°F / -14°C by Thursday). I'm tempted to fire up the 300B amp sitting in the corner.

Re the 833 amp, I'm not sure how you can get 200W out of it. Class A SE has a max efficiency of 25%. Plate dissipation is about 350W, which means that running full tilt, the max output power would be about 85W or so.

The magic of Class A2. It's pure Class A1 up to about 40W, then moves into Class A2 and draws up to 180-200mA grid current in addition to the 160mA idle plate to cathode current.

No worry about blocking distortion as the input tube is direct coupled to the 833C...no coupling cap.

 

[Sir Sanders Zingmore]

The magic of Class A2. It's pure Class A1 up to about 40W, then moves into Class A2

What are Class A1 and Class A2 ?

 

[SIY]

What are Class A1 and Class A2 ?

A1 doesn't draw grid current. A2 does. Basically, you run the drive positive.

 

[SIY]

draws up to 180-200mA grid current

That is WAY above the tube's ratings. Hope you have spares.

 

[Daverz]

People say it's the 2nd order harmonic distortion, but a competent push-pull amp will have inaudible distortion. Perhaps this is true for flea-watt single-ended amps, but those are going to require going down another rabbit hole of high-efficiency speakers.

IMO there are 2 factors:

• The inconvenience and expense, as in the cartoon.
• Load dependency, which adds some bass warmth with most speakers.

 

[Magz]

That is WAY above the tube's ratings. Hope you have spares.

Been running the same pair for 10 years now. No issues. Haven't even had to adjust the bias very much. Rock solid.

 

[SIY]

Been running the same pair for 10 years now. No issues. Haven't even had to adjust the bias very much. Rock solid.

I'm guessing you aren't running much into the grid current range.

I remember the sims you posted on diyAudio. Did you ever post experimental measurements? That would be interesting to see.

 

[Magz]

In reality, the amps spend almost all their time in A1 and move into A2 on transients. The extra power is very useful in that situation, but running full time in A2 would make me deaf!

 

[Magz]

I'm guessing you aren't running much into the grid current range.

I remember the sims you posted on diyAudio. Did you ever post experimental measurements? That would be interesting to see.

I did post sine and square wave measurements on the completed amps as part of the build thread. If anyone is interested, the entire thread is here:

The Midlife Crisis - My 833C Amp Build

-My wife, upon seeing the 833C triodes in person - "That's not an amp, that's a Midlife Crisis!" -My reply, "Hey, it's cheaper than a Corvette..." So was born my 833C SET monoblock project. The 833C is a ruggedized version of the 833A, with thick graphite plates capable of 400W dissipation...

www.diyaudio.com

 

[SIY]

I did post sine and square wave measurements on the completed amps as part of the build thread. If anyone is interested, the entire thread is here:

The Midlife Crisis - My 833C Amp Build

-My wife, upon seeing the 833C triodes in person - "That's not an amp, that's a Midlife Crisis!" -My reply, "Hey, it's cheaper than a Corvette..." So was born my 833C SET monoblock project. The 833C is a ruggedized version of the 833A, with thick graphite plates capable of 400W dissipation...

www.diyaudio.com

Can you link to the post? That thread is ENORMOUS.

 

[Cbdb2]

If you’re not plugging a Les Paul or a Strat into it, avoid tubes…

You forgot P-bass.

 

[Magz]

After some hunting through the thread, here are screenshots of a 2kHz square wave through the driver stage and on the outputs. Not bad considering the parasitics inherent in a 60lb output transformer!

 

[SIY]

After some hunting through the thread, here are screenshots of a 2kHz square wave through the driver stage and on the outputs. Not bad considering the parasitics inherent in a 60lb output transformer!

What's the load? Voltage level?

Did you run anything like a THD vs power curve to verify what power you can actually get?

Thanks much, the work is beautiful, and I'm sure it's expensive as well!

 

[Magz]

What's the load? Voltage level?

Did you run anything like a THD vs power curve to verify what power you can actually get?

Thanks much, the work is beautiful, and I'm sure it's expensive as well!

4 ohm resistive load.
To be honest, as it was 10 years ago I don't remember all the details, but I remember the dummy load got hot!
That's the extent of the testing done, as I was eager to get the amps installed for listening after spending damn near a year planning and building them.
Maybe after I retire this year I can go back and do more measurements, but they sound so good, and they are so, so heavy to lug down to my basement lab...definitely a 2-man job.

 

[Magz]

Thanks much, the work is beautiful, and I'm sure it's expensive as well!

If you're ever in Central New Jersey I'm always open to hosting a listening session.

 

[SIY]

If you're ever in Central New Jersey I'm always open to hosting a listening session.

Thanks much! I'll bring the beer.

 

[JSmith]

However, many people say tubes sound better. How is this possible?

A warm glow...


JSmith

 

[Keith_W]

A1 doesn't draw grid current. A2 does. Basically, you run the drive positive.

Isn't Class A2 basically Class B, but with more bias towards Class A?

 

[genesisaudiorack]

From a casual observation tube equipment measures poorly compared to solid state. However, many people say tubes sound better. How is this possible? From personal experience, I have noticed some poorly measuring tube amps will raise the hairs on the back of my neck while listening to Sade. It is as if she were breathing on my neck and ears. However, I have also noticed I do not get this same physical reaction with some very well-measuring solid-state amplifiers. The scientific part of me says this is bullshit but my physical response is undeniable. How can I get these two sides of my brain to agree? I want to believe if it can't be measured it does not exist yet the goosebumps on my neck do not lie. Has anyone else had this experience?

someone somewhere will piss on my toes for saying this.

out of all the solid state amps ive heard, one of the outstanding ones was MSB, for some reason it was great, and it was on a s5 speaker. in the last nine of so months the mcintosh's ive heard were okay-okay. but here the thing, most amps in the solid state range to me sound generally neutered, missing boom, and sorta flat sounding. some people say, "you need to eq" but im its still as a standard in reference setup just flat and ball less. the msb, and like one other amp impressed me but they were really expensive.

now ive learned that when listening to most tube amps at low to low-mild volumes you'll never hear any of the tube amp "distortion" complaint solid state guys tout, but when you drive a tube amp it will have that tube shimmer/distortion but that's supper distinctive and different in every amp. then there are some high end amps with tubes, and you can turn those things up to 100-110 db and there zero distortion, you get that tube BOOM, and there's a sound stage. some amps dont really break up, but you pay for that loudness volume quality. im sure there are affordable great sounding tube amps too.

the guys who talk about tube distortion its true, but can we hear it? maybe in bad tube amp circuits, or noisier circuits when turned up with unstable transformers. there are some phenomenal mono block setups out there that are just like full on turbo charged amps. and the tubes serve near zero drawback. the solid state guys may be technically right but they are bias. some tube amps right out of the box dont need any real eq except for room correction. they have a concerto boom and snare snappiness similar to a high speed paper snapping. its just insane how some of these amps work. i like tube amps. and when i finds a solid state that i feel sounds as good or better i can afford, i will deff let people know i got it.

tube amps can be crappy and they can be brilliant. when i got my first hifi tube amp i thought it was great till i learned about loud music.

 

[LTig]

someone somewhere will piss on my toes for saying this.

out of all the solid state amps ive heard, one of the outstanding ones was MSB, for some reason it was great, and it was on a s5 speaker. in the last nine of so months the mcintosh's ive heard were okay-okay. but heres the thing, most amps in the solid state range to me sound generally neutered, missing boom, and sorta flat sounding. some people say, "you need to eq" [..]

... and they are right. The boom is the result of the output impedance of the tube. It's higher than typical solid state amps and leads to kind of a slight loudness effect, depending on the impedance curve of the speaker. You can get the same effect with solid state amps with EQ, or by adding a resistor in series to the speaker, thereby increasing its output impedance.