High speed amplifier


Paid Member
2001-02-25 7:10 pm
Northern Iliinois
I'll go out on a limb (I think it's fairly well supported though :) ) and say you're barking up the wrong tree if you looking for a "Pass-like" design with a full power bandwidth at 400KHz.

Circuitry-wise, Spectral does a lot of things to get the speed and bandwidth they advertise. Many of these techniques fly in the face of "simpler is better".

Maybe you may get a little closer to what you want by looking at Borbely's All FET designs?

And pay some attention to recent discussions around here about phase margin. Many really wide bandwidth, very fast designs are not easily made acceptably stable driving a wide range of loading scenarios.

High speed and driving difficult loads is hard to obtain at the same time without stabilityproblems.... You need to have an outputstage with very low zout and phase change to do such a design. It is a hard task!

You need very fast BJT's, JFET's and MOSFET's .. What i mean is > 100MHz so you can control the phase change through each stage ... At the same time the openloop gain has to be low in each stage.

For an amp with good stability:

The single ended ZEN amplifier from www.passdiy.com It is a singlestage design and in theory it should have a phase margin of 90 degrees with perfect mosfet's (fast)!!

Thats a really good example on a stable amplifier and simple too.

Normaly i would say that a phasemargin of 60 degrees would be a good margin.. I would think that the ZEN amplifier would meet this requirement with no problem at all.. But i have not tested or done any sims on a ZEN....

Good stability is more important than wide bandwidth!



Disabled Account
2002-03-14 10:27 am

I'm driving my Manger's (Zerobox 109) with a 15W SOZ in a horizontal bi-amping setup. Low frequencies are handled by a politically incorrect Yamaha power amp...

Manger's bandwith recommendation only means that you should be aware of e.g. tube amps with an upper limit of 50-100kHz. She/He doesn't say that the faster the amp the better it sounds. Manger demoes his speakers with Vincent SP 991 power amps and although I cannot find any technical info I don't think that these are of extraordinary bandwith.

Btw what is the bandwith of a SOZ?
For Reinhard and Superstition!

The Vincent 991 specs:

Technische Daten SP-991
Endstufe Mono

Übertragung: 10 Hz - 20 KHz +/- 0,5 dB
Nennleistung Class A 8 Ohm: 100 W
Nennleistung RMS 8 Ohm: 300 W
Eingangsempfindlichkeit: 2 V
Klirrfaktor: < 0,1% (1 kHz 1 W)
Geräuschspannung: > 95 dB
Eingangsimpedanz: 47 kOhm
Netzanschluss: 230 V/50 Hz
Masse: L 430 x H 180 x T 530 mm (x2)
Gewicht: 30 kg

I have a Vincent Hibrid 226 it looks like been made in China...the quality of the solder and the execution of the solder job is very poor...