Current project: 1kW

[Frisbee78]

Hi everybody!!

I thought I'd share the schematic of my current (and first) project to the community:
Full size (big)
Half size (still big but not as much)

It's from a French magazine published in 98 and is supposed to sound real, real good. I'll tell you when I get it done

The author called it "the monster" and gave these specs:
- Power: 1x1035W into 8 ohms (bridged) or 2x350W into 8 ohms
- S/N ratio: > 120 dB
- Bandwith @ 1dB: 1 Hz to 227 kHz
- Rasing time: 1.2 µs @ 10 kHz

It feaures 6 pairs of MJ15025/MJ15024 (12 in total) and the PSU is powered with 5 toroidal transormers adding up to 1500VA...

Now that's lethal (well for ma at least )

[Richard C]

Very erm.... strange. At a glance, I can't say I'd be tempted to spend time and money on this design

[Frisbee78]

Very erm.... strange. At a glance, I can't say I'd be tempted to spend time and money on this design

Strange? Why strange?

[Richard C]

It seems complicated yet when used as a stereo amp has undesirable capacitor coupled outputs, when used bridged then a crude phase splitter is employed at the input.

What controls bias? and how is NFB applied (if any)?

There are some very basic and not particualrly linear stages in this design and considering its complexity it doesn't look promising.

[dmfraser]

Lets see. No feedback. No use of differential amplifiers. Will have so-so power supply rejection. THD will be high. Transient response may be better. Darlington output is low efficiency. There are a lot better, and simpler, ways to generate a kilowatt these days.

[Frisbee78]

It seems complicated yet when used as a stereo amp has undesirable capacitor coupled outputs, when used bridged then a crude phase splitter is employed at the input.

What controls bias? and how is NFB applied (if any)?

There are some very basic and not particualrly linear stages in this design and considering its complexity it doesn't look promising.

Got your points.
The coupling capacitor are rather large beasts of 22 000 µF... I hope that such values won't affect the output signal too much. But then again, it's more of an amp meant to be used bridged.
As for the input phase splitter, no interferences whatsoever can be seen on the graphs near the 0v line.

Sorry, but I have no idea of what control bias or NFB are... I don't speak English as my first language and I still have plenty of technical vocabulary to learn for electronics & amps...

I agree on its complexity. But the results look good, so?

Lets see. No feedback. No use of differential amplifiers. Will have so-so power supply rejection. THD will be high. Transient response may be better. Darlington output is low efficiency. There are a lot better, and simpler, ways to generate a kilowatt these days.

Yes, no feedback, but do amplifier always really need them? If the design is made to do without and manages that lack well, then I don't see the problem. Going to an extreme, I could even quote Nelson Pass himself: "In the hands of mediocre designers, feedback was often overused to cover up design sins elsewhere in the circuit...". No feedback, no lies?...
Differential amp? Sorry, I'm clueless again
Same with PSU rejection. What is it?
THD... mmm... Yes, THD... How do you measure that?
Transient response. Another unknown term... :/
Darlington output might not be the most efficient solution but... it's a solution... And if using plenty enough of transistors then why not?
I'm sure that since the article was published in 98, better, simplier and more economic designs came to light. But... when I started that project, well, erm... it was 98... (I know )

Thanks guys for your feedback.

[Workhorse]

Originally posted by Frisbee78

Got your points.
The coupling capacitor are rather large beasts of 22 000 µF... I hope that such values won't affect the output signal too much. But then again, it's more of an amp meant to be used bridged.
As for the input phase splitter, no interferences whatsoever can be seen on the graphs near the 0v line.

Sorry, but I have no idea of what control bias or NFB are... I don't speak English as my first language and I still have plenty of technical vocabulary to learn for electronics & amps...

I agree on its complexity. But the results look good, so?



Yes, no feedback, but do amplifier always really need them? If the design is made to do without and manages that lack well, then I don't see the problem. Going to an extreme, I could even quote Nelson Pass himself: "In the hands of mediocre designers, feedback was often overused to cover up design sins elsewhere in the circuit...". No feedback, no lies?...
Differential amp? Sorry, I'm clueless again
Same with PSU rejection. What is it?
THD... mmm... Yes, THD... How do you measure that?
Transient response. Another unknown term... :/
Darlington output might not be the most efficient solution but... it's a solution... And if using plenty enough of transistors then why not?
I'm sure that since the article was published in 98, better, simplier and more economic designs came to light. But... when I started that project, well, erm... it was 98... (I know )

Thanks guys for your feedback.

MY Friend AmpmaN Requests u to donot attempt this amplifier because u donot have enough level of understanding of electronics related to amplifiers and u also seems that u dont have relavant knowledge in amplification systems.

Some Facts about this amplifier.
No Negative Feedback.
Poor power supply rejection ratio.
Nil common-mode rejection ratio.
No differential pair at input.
slew rate is inadequate as compared to its power rating.
Thermal compensation and biasing is inadequate.
Higher components of Total Harmonic Distortion at output.

Regards
AmpMan.

[Circlotron]

Originally posted by amp_man_1
Thermal compensation and biasing is inadequate.

Ampman, you just hung yourself. In another thread (I will look for it if you like) you made the claim that you never use thermal compensation and yet here you say that another circuit's thermal compensation is inadequate.

I was going to say more but I have decided not to.

Edit -> Changed my mind. http://www.diyaudio.com/forums/showt...119#post304119

[Workhorse]

Originally posted by Circlotron

Ampman, you just hung yourself. In another thread (I will look for it if you like) you made the claim that you never use thermal compensation and yet here you say that another circuit's thermal compensation is inadequate.

I was going to say more but I have decided not to.

Edit -> Changed my mind. http://www.diyaudio.com/forums/showt...119#post304119

MY Friend Circlotron
Yes I still made that claim that I never use Thermal compensation but:
That is in the case of MOSFETS not in the case of BJTs , so understand the logic.

Regards

AmpMaN

[Richard C]

Originally posted by Frisbee78

Yes, no feedback, but do amplifier always really need them? If the design is made to do without and manages that lack well, then I don't see the problem. Going to an extreme, I could even quote Nelson Pass himself: "In the hands of mediocre designers, feedback was often overused to cover up design sins elsewhere in the circuit...". No feedback, no lies?...

If an amplifier is intended not to use feedback then open-loop linearity is paramount as there is no mechanism to reduce distortion.

This amp appears to be designed to encourage distortion rather than reduce it.

1000W with >50W distortion...

Don't do it