Kind request of opinion - minimal schema with darlingtons.

[beppe61]

beppe
I build that at least 15 yrs ago,or at least something similar
I agree with you regarding simplicity and quality, but what is important to say that PS is equally or even more important part of that style preamps
same as in NS10 or SL10 or Fet1 etc

Thank you very much for your very kind and valuable reply.
I think that what you say is very important and completely true.
My point is that maybe it would be better to adopt simple gain stage topologies and then make all the bigger efforts to build a really great power supply.
One case that confirms the fundamental importance of the power supply are the Tom Evans phono preamps.
I have a friend who owns one.
With the standar power supply is quite good, but with the "deluxe" PS using those famous ultra low-noise Lithos regulators is absolutely stunning.
And I am not completely sure but it should be built around off-the-shelf op-amps (the signal amplification circuit of course, not the regulators).
Your words have convinced me completely that I should start studying PS schematics in more depth.
Because there the magic is.

Thank you very much.
Kind regards,

beppe

 

[beppe61]

That is good preamp, beppe61.
People do not think simple can be good. But they are wrong!
I have built such preamp and used them.
But nobody is interested.
Because they like Advanced and Complicated.
They think they get better result, but maybe only get more problems.
The more parts - the more possible troubles.
Here is my version of your amplifier.
Uses an output buffer stage of 2 transistors.
I have posted it 3-4 times, already ........
And here it is again:

Dear Sir,
thank you so much for your very kind and precious reply.
I am completely ignorant in electronics but I think that one should think at the purpose of the unit.
Let's take a line preamp, for instance.
A line preamp must provide voltage gain (2 or 3 time usually) and current gain, to drive adequately also low impedance.
That can be easily achieved with just two good active devices working in their conditions of best linearity.
I saw the thread about the Blowtorch preamp by John Curl.
One of the best preamp around.
I read an interview with JC who stated that he has returned for this TOTL preamp to more basic topologies with the conviction that they have bigger chances to sound very good.
Thank you very much for kindly disclosing your schematic with us.
Very interesting indeed.
Do you use it currently? What kind of PS do you use?

Kind regards,
beppe

 

[beppe61]

Exactly - it would be very thermally unstable and it's a big question if it could survive longer than a few minutes to begin with.
...
SOA ratings of most Darlington BJT packages are nothing to write home about, unfortunately.

Dear Sir,

Thank you so much for your very kind and thorough explanation.
you have given me material to study for the next three months !
You mention in the end the poor SOA ratings peculiar of many Darlingtons.
Nevertheless I have been very impressed with the performance of an amp using just a single pair of TIP141/146 as output devices: very powerful even with low impedance loads and reliable too.
Thank you so much again.
You have prevented me to burn my mother's curtains!

Kind regards,
beppe