Power Scaling is Flawed?

[mooreamps]

Has anybody noticed that this thread is still one of the top google hits on searches for the words "power scaling"? And it comes up bold: "Power Scaling is Flawed?".

Ya, I see that. I also see one of my amps comes up on page three..


But, I also see you and Kevin come up on page one and page two.. I think that is very noteworthy....


-g

[Mickey_C]

Well, I didn't think of the advertising angle - somebody start a thread on my amps here quick!

But seriously, I think it kinda sucks that one of the top hits on Power Scaling is that it's flawed. That's not really cool, as it's not really correct.

Anyway, how did MEF get so high on the search engines?

[mooreamps]

I did not take it as a statement of power scaling being flawed. I took it as a question : Is power scaling flawed ? Thus, gives us the opportunity to present our point of view, that it is not.

-g

[MilbertCom]

We don't think the concept is flawed. It works well in GAGA-50. Milbert Amplifiers, Most Musical Amplifiers

[Steve Conner]

Good grief! Is that David Berning on the line?

In any case, since it's a popular thread that people are using as an advertising/SEO soapbox, I think it's only fair to warn people that all of Berning/Milbert's amplifiers are throbbing masses of MOSFETs, ferrite thingies, and switchmode technology generally.

I'm sure they work and sound great, and I love the ZOTL concept, it's one of the cleverest amplification ideas I've seen. But you have to ask yourself whether they're really in the spirit of tube amplification. For instance, there are probably only three people on the planet who could fix one if it blew up on you, and two of them are aliens.

And, MEF places highly on search engines because it's awesome.

[Diablo]

Say Steve, can you explain in layman's terms how that Gaga-50 Milbert amp works? I went to their website and couldn't figure out a darn thing. Yeah, it's missing the OT. So what is connected to the plates of the power tubes? What sets the load lines for the tubes? How do you convert the high voltage - low amperage of the output tubes to low voltage - high current to drive the speakers?

Is there a link to a soundclip? If it sounds like ass, then I'm not so interested in how it works.....

[Steve Conner]

I've written about it in more detail before, and you can also look up David Berning's patent.

But to cut a long story short, the two sides of the PP OT are replaced by two switchmode DC-DC converters running at several hundred kilohertz. They draw current off a low-voltage bus (derived from the wall voltage by yet another switcher) and step it up to 400V or so for the tube plates.

Each converter supplies one of the power tubes, and as the tubes vary their plate currents in response to the audio signal, the input currents on the converters' low-voltage sides get modulated in the same way. So, the difference between the input currents of the two converters works out the same as the current that would be induced in the speaker winding of a real OT. And likewise, as the speaker voltage varies, that reflects back through to the plate voltages of the tubes.

The whole thing is mathematically the same as a real OT, except that it responds clean down to DC and doesn't saturate. The tube circuitry driving it can be just the same as an ordinary tube amp, too.

[teemuk]

Say Steve, can you explain in layman's terms how that Gaga-50 Milbert amp works? I went to their website and couldn't figure out a darn thing. Yeah, it's missing the OT. So what is connected to the plates of the power tubes? What sets the load lines for the tubes? How do you convert the high voltage - low amperage of the output tubes to low voltage - high current to drive the speakers?

Is there a link to a soundclip? If it sounds like ass, then I'm not so interested in how it works.....

Read the ZOTL patent:
http://davidberning.com/images/paten...ent5612646.pdf

The power tubes are coupled to the load through a pair of bridged DC-DC switching power converters. That is a switching circuit where a high-frequency square wave signal modulates the output signal (from tube plates) so that the resulting signal can drive a set of switching MOSFETs. The output signal is low-pass filtered to get rid of the HF switching residuals. Basically it's like a push-pull tube output coupled to a class-D amplifier but with different modulation technique than the usual PWM.



No, it doesn't sound like ass. In fact, when Milbet's site still had soundclips it sounded like a typical tube amplifier voiced for kind of "blues-ish" distortion.

[MilbertCom]

Lots of clips and jams from the June 2012 NY Amp Show:
Milbert Amplifiers GAGA clips

Guitar + Bass amplified thru GAGA and GAGA D-60 + drums.
Various musicians and session players stopped in to jam.
Great show, lots of fun.

GAGA's had their power generally turned/stepped down and played with a variety of tubes thru different cabs/speakers.
(we're not allowed to say 'scaling' without licensing the trademark, but we think the overall concept works well)