Simple 100W power amp

[JMFahey]

Not exactly
Most had 60V/uSec Slew Rate at full power (a more meaningful rating than simple "Frequency Response" which is usually measured ar 1W); the biggest ones (such as the one shown) "only" 45V/uSec.
The choice of the best Recording Studios in the World, including the BBC.
http://www.hhamplification.co.uk/dbf...s/mosfetvx.pdf

[djk]

Barely meets the Jung criteria of 0.5V/µS per peak volt of output.

I would prefer to see a little more current available to push all that gate capacitance.

"The choice of the best Recording Studios in the World, including the BBC."

Hyperbole, no comment.

(my standards are a bit higher than theirs)

[nigel pearson]

MOS FET's ( Exicon ) only need about 1 mA to work acceptably . Sure the gate capacitance at up to 1nF is a problem . My experiments say 5.6 mA is about optimum . 600 Watts at 20 kHz for music ? More like 10 W and hope the tweeters can cope , ears of the punters won't . 8mA is not my cup of tea ( too good ) . This seems to be a default value in many amps . Distortion caused by not bandwidth limiting such an amp is folly . There is no value in entertaining mice . Myself I would have the amp as hi fi with one set of outputs . Then bandwidth limited with other FET's switched in . I would have a heat-sink for normal use backed up with fans for fairground use . The punch offered by many FET's is a positive , plenty of HF maybe not ?

I was in Cuba recently . I am sure their amplifier was fine . I just wish I had brought some Motorola horns with me . It would have been nice to hear 3 kHz and above . A few other bits and I might have integrated them nicely ( stop them quacking also ) .

Now to the crunch . I bet that an over engineered power supply and what I have just described will sound better to the punters more than most of the sterile hi fi amps . The bonuses are . Robust ,simple , no emitter resistors . Can be driven by a ridiculously small VAS and can sound silky smooth . What must be remembered is many who bought these amps were changing over from valve equipment . They wouldn't tolerate the unpleasant squeaks of typical hi fi . Most people who enjoy this forum would last 5 minutes in that world . And now the crunch . At the drop of a switch this amp with no complexity becomes a nice domestic amp . The usual criticism of the Hitachi design was it is too simple to deal with HF distortion . The Hitachi graphs say totally different to that . An op amp with serious current . To me this is as serious a defect in understanding . Like saying a diesel car could never win a race , or if it did only something minor like Le Mans !
https://www.google.co.uk/search?q=go...%3B1400%3B1050

[JMFahey]

Hyperbole, no comment.

Hyperbole is something pulled out of thin air .... this is *fact* ... and I see it hurts.
Just google "HH " and "BBC" and you'll get a million hits.
All mentioning something like "commonly used by many broadcasting studios, including the BBC. " , "many of which are still in use in studios all over the world" and so on.

(my standards are a bit higher than theirs)

Well, *this* is hyperbole.

What must be remembered is many who bought these amps were changing over from valve equipment . They wouldn't tolerate the unpleasant squeaks of typical hi fi . Most people who enjoy this forum would last 5 minutes in that world .

Well, that's a quite precise evaluation of the situation.
Just adding that not only they were changing from "valve equipment" but from "the best valve equipment"
Oh well.

[nigel pearson]

100 % right . I will have a drink on Thursday with John . I think Carlsbor was his favourite fairground amp . He has repaired everything I have ever named , uses Turbo Sound himself . As you say about makes and quality .

HH proves that something that others would dismiss have successful commersial lives . When I see amps that are 70% protection systems I despair . It is possible to build things that are simple and work .

[Aniket]

Originally Posted by vedmitraa

Here is a circuit of 2n3773 8 pairs,70-0-70 volt d.c. 42 volt output at 0.497% distortion power output 887 watts into 2 ohm

With just 24mA bias per device, and 9.3nV DC offset. 980W@2R ultra low THD of 0.169% @ 20kHz, with 5 pairs MJL21193/4. THD could be further reduced using more output pairs.
Just simulated my design, wonder it would perform like this in real.

Regards,
Aniket

[nigel pearson]

I think you could build it with a pair of devices and try 8R . How is it at 100 W 8 R ?

24 ma should be excellent as bias .

I often still use TO3 devices . I have no problem using flying wires to the PCB . That way adding a few is not difficult .

I have even run transistors in buckets of water . It sometimes works well enough until the water contaminates . 1 bucket per device . I think I have gone to 70V before now ?

My dream is to put some TO3's with their heads in a water pipe . It should work reasonably well . Not perfect as the die is on the connection side . A pump will be needed . Isolated TO3P even better . 90% could be in the water .

[JMFahey]

Originally Posted by Aniket

Just simulated my design, wonder it would perform like this in real.

Why, of course not.
There's a ton of important parameters that simulation is not considering which will affect end results big way.

[AndrewT]

Aniket,
ask the simulator what current is passing R3 and R4?

[Aniket]

1.079 and 1.08 mA through R3 and R4 respectively. Images attached.

Regards,
Aniket