Watts?

[teemuk]

Just adding:the article....

Additionally, all tube preamps tested were single-ended and all transistor preamps were push-pull. This fact alone biased the measurements to be what they were; and henceforth those results were seriously criticized in several rebuttals to that article, including one that even presented mic preamp design producing similar harmonic spectrum as the amps tested by Hamm. Conclusion of all of these rebuttals: Overall circuit design is far more important factor than the device choice.

Secondly, I can't really agree with any of the theories Hamm presented about the harmonics and their musicality. They seem nice on paper but everyone who has listened and compared signals with dominant even versus dominant odd order distortion will know that neither really sounds all too great or musical as is. Different, yes, but none any better or more "musical" than the other. They both sound like distorted signal and distortion of even order is no less apparent than distortion of odd order - no matter how convincing it sounds on paper.

Furthermore, in the context of guitar amps, I trust you will not find any classic guitar amp design that would not produce both great amounts of odd order harmonic distortion, as well as harmonics of very high order. Both something deemed horrible due to Hamm’s article (and perhaps so if you want a clean output signal from a mic preamp or HiFi amp) but also something you will evidently encounter from all guitar amp designs if they are overdriven.

[J M Fahey]

Additionally, all tube preamps tested were single-ended and all transistor preamps were push-pull. This fact alone biased the measurements to be what they were

Well, that's a very important point I didn't remember by heart.
That alone explains the "even vs odd harmonic" myth.
Anyway I respect Mr Hamm because he clearly worked in good faith, and bench tested the preamps, referred to actual scope waveforms and distortion analyzer curves, much more than what can be said from many "desktop warriors" who came after him.
Yes, the article *is* dated, (sigh), but honest.

[imaradiostar]

So maybe it's not a tube/solid state phenomenon, it's a behavior near clipping point phenomenon. Sorry if I was citing an article that wasn't legit. I always thought it compared op-amp, single ended transistor and single ended tube circuits. Perhaps I was mistaken.

Regardless, class D bass power amps seem to be the wave of the future and I think they're very impressive.

jamie

[J M Fahey]

Hi jamie.
It's more legit than many,that's for sure !!
It's just that some people (not talking about you, of course), "read" only the little bit that matches their previous ideas and forget the rest.
Or to say it in other words, data is good, conclusions a little too quick.
Good luck.

PS: and yes, any behaviour described there, including single ended assymmetry, grid rectification, soft clipping, whatever, *can* be recreated with Op Amps, in the right configuration.

[imaradiostar]

I also wanted to say, in case my earlier posts were unclear, that there is absolutely no way a class D amp with a 55 volt supply is going to produce more than 378 watts into 4 ohms, given clean sine wave output. It's just not physically possible!

Is it possible if there is some sort of scheme to boost that 55 higher than the +- 55 volt swing a mosfet bridge would allow? If yes then higher output is possible.

A transformer will, in certain conditions such as changing speaker impedance, overshoot the available supply voltage because of the inductance of the output transformer. I do not know of any solid state amps that exhibit this behavior.

jamie

[J M Fahey]

A transformer will, in certain conditions such as changing speaker impedance, overshoot the available supply voltage because of the inductance of the output transformer. I do not know of any solid state amps that exhibit this behavior.

Well, this is a property of the output transformer itself, not of the devices driving it.
Since most Tube amps have one, and most SS ones do not, it's easy to associate that behaviour to the active devices involved, while in fact it's not so.
In the search of the Holy Grail I have built SS, output transformer power stages and they showed beautiful peaky front edges when overdriven.
The amplitude of said peaks was around 10/15% of the voltage of the square wave itself; I could easily duplicate the waveforms from the "Twin type" Tube power amp which was my reference.
I gave up because although the sound was clearly "edgier" (in a good way) than a similar conventional SS power amp (which typically dulls when overdriven) , it didn't move me one inch closer to the biting-yet-smooth bluesy sound I was after.

[teemuk]

I also wanted to say, in case my earlier posts were unclear, that there is absolutely no way a class D amp with a 55 volt supply is going to produce more than 378 watts into 4 ohms, given clean sine wave output. It's just not physically possible!

Perhaps I need to restate what I wrote earlier:

"The amp runs two class-D switching amps in bridge, each powered by pair of 55V rails."

In theory, that is capable of creating 110 Vpeak across the load, maybe closer to 100Vpeak in reality considering device losses. Do the math, 1000W average power rating is a piece of cake.

[imaradiostar]

Perhaps I need to restate what I wrote earlier:

"The amp runs two class-D switching amps in bridge, each powered by pair of 55V rails."

In theory, that is capable of creating 110 Vpeak across the load, maybe closer to 100Vpeak in reality considering device losses. Do the math, 1000W average power rating is a piece of cake.

No need to be snippy- I was doing the math and it didn't work.

That said, a pair of them bridged is a very different thing and you're totally right. That should be capable of 1200 without any trouble, assuming you can bridge into 4 ohms without mosfets going "pop!"

jamie

[Enzo]

80% of cheap car audio systems which announce "1000 Watts" are just flat out lies. Unless you elevate the 12 VDC rail, you don't get more than 36 WRMS off a "regular" car receiver. Pioneer has this very clear on their sets, you'll notice they are almost all rated at 35 WRMS. Any higher power amplifiers that aren't a complete fraud must have step up DC-DC converters in them.

And they do, they have switching power supplies that create any voltage they want for power rails out of the 12v car system.

This discussion comes up on a regular basis, and always devolves into the same turf defense and positions. I bet if I start a thread on which bus is the better one to get to work on, it would soon turn into some guys telling us that busses are big air poluters, then counter arguments about how mass transit is more efficient, and that one stinky bus is less polluting than 40 cars, and so on, and after several pages of it, I'd still be standing there wondering which bus to take.

[tubeswell]

Amplificadores Valvulados

Cool looking site jmaf!

[imaradiostar]

And they do, they have switching power supplies that create any voltage they want for power rails out of the 12v car system.

This discussion comes up on a regular basis, and always devolves into the same turf defense and positions. I bet if I start a thread on which bus is the better one to get to work on, it would soon turn into some guys telling us that busses are big air poluters, then counter arguments about how mass transit is more efficient, and that one stinky bus is less polluting than 40 cars, and so on, and after several pages of it, I'd still be standing there wondering which bus to take.

Sorry if I was being a troll. I didn't mean to make things worse. You're right though...we've lost sight of the topic.

jamie

[jmaf]

Amplificadores Valvulados

Cool looking site jmaf!

Thanks, tubeswell. Appreciate you dropping by. Do you read Portuguese?

[jmaf]

And they do, they have switching power supplies that create any voltage they want for power rails out of the 12v car system.

I remember the first time I delved into schematics for Rockford Fosgate car power amps. I thought "this part looks like an oscillator, and why do they have this transformer here and...hey it's an inverter!" and then I learned why. You can't get 600 W RMS @ 4OHMs from 12 VDC.

This discussion comes up on a regular basis, and always devolves into the same turf defense and positions. I bet if I start a thread on which bus is the better one to get to work on, it would soon turn into some guys telling us that busses are big air poluters, then counter arguments about how mass transit is more efficient, and that one stinky bus is less polluting than 40 cars, and so on, and after several pages of it, I'd still be standing there wondering which bus to take.

I just threw the car audio comment in there because they were talking about the 55 V rails and I had no idea what other example to give. About helping folks decide what bus to take, I think the electricity to SPL discussion has pretty much run its course. And yes, you're right Enzo, this is probably the most frequently asked question of all FAQ's and it pretty much always ends where this one ended - talking about something else.

In any forum I've been to you just have to wait a week or so before someone asks "why tube watts are louder than transistor watts".

[Enzo]

jmaf, I wasn't even thinking about the car stereo reference being off topic. I was just thinking in general how the same positions will quickly line up across the no-man's land whenever this comes up. And the question fades away while the "tubes are the ultimate item" guys square off against the "solid state can do anything tubes can" crowd.

[jmaf]

jmaf, I wasn't even thinking about the car stereo reference being off topic. I was just thinking in general how the same positions will quickly line up across the no-man's land whenever this comes up. And the question fades away while the "tubes are the ultimate item" guys square off against the "solid state can do anything tubes can" crowd.

It's interesting how some topics do indeed quickly converge. Being a nearly 14k post veteran you probably see these topics starting and go oh sh@t here we go again.