So what are some genuine Class A amplifiers?

[Ric Vice]

I cannot think of any bass amplifiers that were class A, the Walter Woods Mi-100-8 was class A/B Pre Amp and Power Amp with a switching power supply. So
it's an analog amplifier with SMPS power supply

 

[madmaskbass]

Avalon U5 is Class A isn't it? I know it isnt an amp but the conversation kind of shifted into a different realm and I am interested in the "magic sauce" style of this preamp that is generally related to Class A that just does great things to sounds. From memory Phil Jones also works in this realm.

 

[bobyoung53]

nope. george harrison or paul mccartney or whoever got it wrong when he claimed that.

agedhorse just answered, said it was class A up until about 10-15 watts, I never heard either of The Beatles say that, was very common knowledge amongst guitarists years ago, especially When Queen were big.

 

[agedhorse]

Avalon U5 is Class A isn't it? I know it isnt an amp but the conversation kind of shifted into a different realm and I am interested in the "magic sauce" style of this preamp that is generally related to Class A that just does great things to sounds. From memory Phil Jones also works in this realm.

Most signal level circuitry is class A or contains class A stages. Most opamps are class A input and VAS stages but many use push-pull output stages with current source biasing, which can be B, AB or A depending on the intent of the design team.

For the most part it doesn't matter much imo.

 

[dkelley]

agedhorse just answered, said it was class A up until about 10-15 watts, I never heard either of The Beatles say that, was very common knowledge amongst guitarists years ago, especially When Queen were big.

Damn. Brian may.

Hell its been a long day lol

I never considered it class A at band playing volume. I do defer to agedhorse of course. But is it a class A amp? I don't consider it class A if it isn't class A unless it stays in class A.

I can't believe I thought it was one of the beatles.... but honestly I do think paul played one for some of his guitar solos.

 

[Jeff Scott]

Chris used a couple of AC30s for bass in the early days.

 

[AlexanderB]

Class D amps can and do achieve these specs also.

Like I said, I have never seen one, though. Do you have an example of a class D PA power amp (or something "bass rig friendly) with wide band distortion numbers that low? The best I have seen is this:
NewClassD Amplifier Modules
That is still on somewhat "calculated" level, as this only measures the DIY module. An actual implementation might mean compromises that reduce performance. As typically seen, the distortion starts to rise in the mid range, than getting worse in the treble region.

 

[bobyoung53]

Damn. Brian may.

Hell its been a long day lol

I never considered it class A at band playing volume. I do defer to agedhorse of course. But is it a class A amp? I don't consider it class A if it isn't class A unless it stays in class A.

I can't believe I thought it was one of the beatles.... but honestly I do think paul played one for some of his guitar solos.

I think the Beatles used them in the studio, I know they used a lot of Vox tube amps. It was common knowledge years ago that it was a class A amp, I was surprised when he said it was only class A until 15 watts, but hey he knows a lot more than I do. Brian May used to use 9 of them onstage, eight blacks ones and one white one don't know if they were all on. He put them on the map in the US. They were huge here during the 70's, I saw them in early 1977 at Springfield MA Civic Center.

 

[bobyoung53]

Chris used a couple of AC30s for bass in the early days.

View attachment 3967983

Did I ever tell you I know a studio owner who claims to have an Ampeg B-12 that he says Chris used to use in the studio for the distorted top end? I used it once at an outside gig, I didn't sound like Chris Squire

 

[beans-on-toast]

I think the Beatles used them in the studio, I know they used a lot of Vox tube amps. It was common knowledge years ago that it was a class A amp, I was surprised when he said it was only class A until 15 watts, but hey he knows a lot more than I do. Brian May used to use 9 of them onstage, eight blacks ones and one white one don't know if they were all on. He put them on the map in the US. They were huge here during the 70's, I saw them in early 1977 at Springfield MA Civic Center.


View attachment 3968153

The old AC-30's had a drawer in the back. They run so hot that Brian's tech slides them out for better cooling. Some people remove some of the unused preamp tubes to help in that respect.

Brian uses three amps at once. There's s a switching system to bring other's in or out. It isn't unusual for Brian to blow speakers while playing so they do have some spare speaker cabinets, nine in total. See the Premier Guitar video in this link. Neat stuff.

Brian May Fryer AC30

 

[dkelley]

I think the Beatles used them in the studio, I know they used a lot of Vox tube amps. It was common knowledge years ago that it was a class A amp, I was surprised when he said it was only class A until 15 watts, but hey he knows a lot more than I do. Brian May used to use 9 of them onstage, eight blacks ones and one white one don't know if they were all on. He put them on the map in the US. They were huge here during the 70's, I saw them in early 1977 at Springfield MA Civic Center.

It's funny how common knowledge works, eh? LoL

Been reading that claim for 40 years, probably, too, just like everyon else, but always followed by someone correcting him (not to his face, but in the print article I was reading).

Just different sources of news/information I guess. I leaned towards reading the technical side, and I tend not to take the artist's word for fact of how something electronic is designed, or why it actually sounds how it does. I'd heard him claim it was the class A amps forever, but always followed by someone saying... "of course, it really can't be classified as Class A, and this is why..." LoL

I was probably too much of a nerd.

 

[Jeff Scott]

Did I ever tell you I know a studio owner who claims to have an Ampeg B-12 that he says Chris used to use in the studio for the distorted top end? I used it once at an outside gig, I didn't sound like Chris Squire

I don't recall ever reading anything where he mentioned that. Interesting (I would have thought he got his distortion from the AC30). Or, max'ing out his Marshall.

BTW, I never sounded like Chris, either. For some bizarro reason I always sounded like me.

 

[agedhorse]

Like I said, I have never seen one, though. Do you have an example of a class D PA power amp (or something "bass rig friendly) with wide band distortion numbers that low? The best I have seen is this:
NewClassD Amplifier Modules
That is still on somewhat "calculated" level, as this only measures the DIY module. An actual implementation might mean compromises that reduce performance. As typically seen, the distortion starts to rise in the mid range, than getting worse in the treble region.

Yes, the IcePower parts measure similar to the linear amps you mentioned. THD rising above 1kHz is common in both linear and class d amplifiers, it's related to the reduction of global feedback applied in order to maintain loop stability, it's not specifically a class D or class AB phenomena.

Key Specifications
• 700 W @ 1 % THD+N, 20 Hz – 20 kHz, 4 Ω
• 117 dBA dynamic range
• THD+N = 0.005 % @ 1 W (4 Ω, 1 kHz)
• THD+N = 0.0008 % @ 50 W (4 Ω, 100 Hz)
• CCIF IM distortion = 0.0003 %, 10 W, 4 Ω, 18.5 kHz / 1 kHz

 

[BogeyBass]

But the market likes tube pres.
So regardless of THD specs.

All goes out the window with a tube pre.
Doesn't Really matter.

Even without tube pre....
Doesnt really matter

 

[AlexanderB]

But the market likes tube pres.
So regardless of THD specs.

All goes out the window with a tube pre.
Doesn't Really matter.

Even without tube pre....
Doesnt really matter

Like I said, I think the "nasty" transient of electric bass will mask certain kinds of distortion, and some players even prefer the unlinear behaviour of some "less than perfect" SS amps. (Or better, "SS amps that were never even designed for accurate reproduction of the input signal".)

Myself, I do not like tube preamps at all, and while never claim to have "golden ears", I can tell the tonal difference between my two SS preamps that measure very similar when no eq is used. Transients and clarity (lack of "mud") are different.

 

[AlexanderB]

Yes, the IcePower parts measure similar to the linear amps you mentioned. THD rising above 1kHz is common in both linear and class d amplifiers, it's related to the reduction of global feedback applied in order to maintain loop stability, it's not specifically a class D or class AB phenomena.

Key Specifications
• 700 W @ 1 % THD+N, 20 Hz – 20 kHz, 4 Ω
• 117 dBA dynamic range
• THD+N = 0.005 % @ 1 W (4 Ω, 1 kHz)
• THD+N = 0.0008 % @ 50 W (4 Ω, 100 Hz)
• CCIF IM distortion = 0.0003 %, 10 W, 4 Ω, 18.5 kHz / 1 kHz

Well, the "bass rig friendly" (but expensive) Bryston 4B3 does below 0.005% THD 20Hz to 20kHz at 300W.
Again, I have never seen that level of performance from anything class D...

 

[callofcthulhu]

II even did a Bing search or two, but its all about "class D", couldn't find or identify any class A bass amps?

There's your problem.

It's not 1999. There is only one reliable search engine.

 

[BogeyBass]

Lol , Not necessarily a search engine problem, but was funny regardless.
My buddy showed me Google when it was still on the college server.
Slooooooowww, but when you got results it was pretty amazing at the time.

Anyhoo, no searches came up for Class A Bass Amps.
Because nobody makes them. pointless topology for bass

Even for HiFi With Class A/B in ridiculous low distortion ratings.
I guarantee the 1 to 3 % speaker distortion is more, but inaudible, no matter how fancy the
drivers are.
It just doesn't matter.
Even simple class A/B topologies have more than enough performance.

Good news is the Bee Gees and the evening news is just as annoying with
.00005 THD or .5 THD lol
The cover band I seen last week,
I dont think reducing crossover distortion would have helped them in any way.
Class A or A/B or D tube or solid state...they sucked lol

 

[agedhorse]

But the market likes tube pres.
So regardless of THD specs.

All goes out the window with a tube pre.
Doesn't Really matter.

Even without tube pre....
Doesnt really matter

Hey, we agree!

Well, the "bass rig friendly" (but expensive) Bryston 4B3 does below 0.005% THD 20Hz to 20kHz at 300W.
Again, I have never seen that level of performance from anything class D...

Well, ok.

At $6k for a power amp, I think your argument is kinda-sorta absurd. Don't you think? I could be equally absurd comparing to a cheap linear amp with much the same results.

Here's a class D amp that's less than .008% THD (PLUS noise) for as high as it's measured (for bass applications, the second harmonic of 6.7kHz would be 13.4kHz which isn't important for normal players)

And for dog whistle folks, here's an IM plot showing distortion with combined 18kHz and 19kHz, which is less than .005% at 1200 watts for any single harmonic (6dB -100dB = -94dB). Very low.

 

[bobyoung53]

I don't recall ever reading anything where he mentioned that. Interesting (I would have thought he got his distortion from the AC30). Or, max'ing out his Marshall.

BTW, I never sounded like Chris, either. For some bizarro reason I always sounded like me.

I was wondering myself when he said it, this guy is not prone to telling tales though. The B-12 actually sounded really good, you'd never know it was a what 25 watt amp?