Kind request of opinion - minimal schema with darlingtons.

[beppe61]

Dear Sirs,

searching the web for info on simple amps schematics using darlingtons I found the schematic I am attaching.
It is so simple that I even wonder if it could work!
Nevertheless I find it intriguing.
I would like to hear some comments on it.

Thank you so much.
Kind regards,

bg

[edl]

Let's refer my post there:
http://www.diyaudio.com/forums/showt...797#post781797

Regards,

[beppe61]

Originally posted by edl
Let's refer my post there:
http://www.diyaudio.com/forums/showt...797#post781797
Regards,

Dear Sir,

thank you greatly for your extremely kind and valuable reply.
So this kind of circuit do not intrigue only me !
I find it even exciting.
Tell me please, have you built your circuit?
How does it sound?
I am sure its potential is very great indeed.
As I am not so sure that to sound good an amp must be complex!
In the next days I will study your thread in depth.
Any your advice would be extremely welcome, appreciated and valuable to me.

Thank you so much again.
Kind regards,

beppe

[sousmielie]

Hi beppe

I have built this amp a while back, it isn't one of the baddest sounding amplifiers out there. I would recommend it. It's very cheap to build and uses common parts. I have done some modifications to the circuit to improve on quality and boosted the power output. I'll have to look where I put the circuit, then I'll post it here.

I haven't been on diyaudio for some time, but I'm glad to be back!

Cheers,
Werner

[lineup]

Originally posted by beppe61
It is so simple that I even wonder if it could work!
Nevertheless I find it intriguing.
I would like to hear some comments on it.

Yes, it is simple.
I am not sure it is really Hi-Fi.
But I think it will work.

Here is many Solid State Power Amplifier Schematics


For example:
This very interesting and original 100W 2SC2922 2SA1216 Amplifier
See my attachment.

[ilimzn]

Yes, very interesting and very thermally unstable original amplifier

[beppe61]

Originally posted by sousmielie
Hi beppe
I have built this amp a while back, it isn't one of the baddest sounding amplifiers out there. I would recommend it.
It's very cheap to build and uses common parts.
I have done some modifications to the circuit to improve on quality and boosted the power output.
I'll have to look where I put the circuit, then I'll post it here.
I haven't been on diyaudio for some time, but I'm glad to be back!
Cheers,
Werner

Dear Sir,

thank you very much for your very interesting reply.
I am attaching (for me writing in English is not the easiest thing) some words I wrote in another similar thread regarding topologies using darlingtons.
------
I would like to explain my interest for simple amps using just a single pair of darlington in the output stage.
During the last 6 months I have tried a number of integrateds and power amps in my system to drive a quite demanding pair of Dynaudio speakers.
Most failed to give an adequate bass response (i.e. fast, deep, powerful and damped).
The best power amp I listened in my system has been two English monos rated 45W/8ohm that I had the opportunity to open and see inside.
I could see in each mono:
1) a toroidal transfo made by ILP type:5322 S.N.:2102
2) two good sized filter caps
3) 7-8 small plastic case bjts (in TO92 case I think)
4) a single pair of TIP146/TIP141 per channel.
This has been by a long margin the best amp I tried in my sistem.
On this basis I am now very interested in very simple topologies.
My dream would be to find a kit of a power amp with just 4-5 bjts that could be used along with the output pair of point 4).
This kit with a very powerful power supply could have the potential to sound very good IMHO.
The sound of the monos pair I mention it is very good even with demanding speakers.
The monos have been circulated among a number of audio friends of mine.
Every time the judgement has been positive to say the least.
If I were good at cloning that woudl be my target.
As I said I will study all the minimalist designs I will find that could be used with a single darlington output pair.
-----

So I will be waiting any your kind and precious further information.
Thank you very much again for your very valuable advice
Kind regards,

beppe

[beppe61]

Originally posted by lineup
1) Yes, it is simple. I am not sure it is really Hi-Fi.
But I think it will work.

2) Here is many Solid State Power Amplifier Schematics


For example:
3) This very interesting and original 100W 2SC2922 2SA1216 Amplifier
See my attachment.

Dear Sir,
thank you sincerely for your kind and helpful reply.

1) Did you build it? I feel that you are not very optimistic about the resulting sound. Am I wrong?
2) Thank you very much for the link.
I found it today along with the schematic googling for "TIP142".
3) Very interesting indeed. Excellent Sanken output stage and very basic circuit as well.
Did you build it? How about its sound? Do you think it would be miles better than the darlingtons circuit?
As I wrote above I found a truly great sounding amp with just a single pair of darlington at the output.
Ok. The whole circuit is quite more complex, with about other 9 bjts (4 BC556, 4 BC546 and 1 BC555) besides the output pair (tip146/tip141).
So I became interested in circuits using darlingtons.

Thank you very much indeed.
Kind regards,

beppe

[beppe61]

Originally posted by ilimzn
Yes, very interesting and very thermally unstable original amplifier

Thank you Sir.
This is unfortunate.
It was too good to be true, or as someone say too simple to be good.
Why life has always to be complicated ?
It is a real pity.
Are you aware of any system to make it more stable?

Thank you very much indeed.
Kind regards,

beppe

[ilimzn]

Yes, Beppe, the bias network for the MOSFETs on the input has to be made in such a way to have a negative temperature co-efficient, i.e. not with ordinary resistors, other measures would involve putting a low value resistor in the emitter of each output BJT (altough there is a tradeoff involved here, regarding damping factor). The simple amp in that schematic has another problem, which is hum induction into the input due to the way the MOSFETs are biassed from the power supply, but this could be cured with a few caps. Cascoding could be greatly improved by connecting the caps to the common point of the input MOSFET sources, this would make the nonlinear Cgd of the MOSFET dissapear and the distortion drop by removing the mechanism that introduces it, rather than trying to correct it via NFB.
The circuit reminds me very much of Jean Hiraga and all the above being said, it's not a bad idea at all, just needs some work into making it a real world amp.