JG´s Nobrainer and Nobrainer Discrete

[Joachim Gerhard]

The tube buffer whould ad that kind of distortion. It is only 0.05% and mainly second.
With a pure sinewave i can not hear better then 1% but i can hear when " natural" distortion from a tube is added.
It sounds more full, dynamic, rich.
The soundstage is bigger and better focussed.

 

[Joachim Gerhard]

This guy did research why CD does often not sound satisfying :BURWEN BOBCAT
As far as i know he adds reverb and " distortion " to the signal to improve CD sound subjective.
I really do not have another explanation.
There is a lot of dead accurate amps on the market that sound sterile.
Maybe it is not possible to make a perfect recording so some nhancement is ok.
Also there is no perfect loudspeaker and no perfect room.
What we hear is the complete chain. So when it sounds wrong, it is wrong. Even when everything is " perfect ". If it would not be so then an AD797 is the solution. It is still the lowest distortion opamp on the market. It is used by Audio Precission, Stanford Research and other in analysers. I simply think that " input plus undistorted gain is output " is not true. The AD797 is perfect. See my measurement on MPP and the Blowtorch thread. I also tried various exotic measurements but i could not find anything worse then -120dB.

 

[RCruz]

In this case I believe I do not miss any induced distortion... as a matter of fact this "little amp" is far from analytic or sterile IMO. It sings beautifully now creating a credible wide soundstage. The 103 I use for comparison is a "lean" amp, no fat whatsoever, so I do not miss it.

I will use it with my soon to be monitors (already have some drivers... need a box and a crossover) in my lab room.

It will partner my old pedja buffer (this one has a warm envolving sound) and my latest paradise build

 

[Joachim Gerhard]

cool

 

[RCruz]

I am currently using lme49710 and so I could build the input without a coupling cap. I will try to get some of those in metal can version (I know that LME49720 metal can sounds much closer to a discrete design than it's plastic LM4562 version).

I will also try the other opamps you referred to. Anyway I am quite happy with the results so far.... been listening to it all day and I really find it "musical sounding".

 

[Joachim Gerhard]

Well, Frans and i did not engineer any sound into it but i had a good feeling that this is better then the usual gainclone.

 

[Joachim Gerhard]

Thanks for finding the idle sweetspot.

 

[RCruz]

You can try the LME49870 that can stand plus-minus 22V so you get more power.
You could also try the LME49880. It is a JFet double.
You can simply stack the input opamps ( parallel them ) and connect the output together with a 10 Ohm resistor. Then you have double the current drive. I learned that simple trick from Douglas Self and it works.

This is very interesting.

I do not get clearly how and why to connect the outputs together with a 10r.

Where do I connect the output ?

Can you draw something ?

 

[RCruz]

I got the idea now, one 10r on the output of each opamp.

Now why do we need those resistors ? To eliminate possible differences between opamp outputs ?

 

[Joachim Gerhard]

The resistors decouple the outputs so that they do not inflence each other. Yes, simple one resistor each at the outputs and then the resistors come together to make the new output.
Jan Didden was sugesting also to split the feeback loops in two. I tried it and it is not necessary.

 

[RCruz]

this arrangement will provide double current output so more current capability also in the output stage.... more power and better bass control.

Does this affect current on the output drivers ?

 

[Joachim Gerhard]

No, but i think the distortion may be less because the double opamp has an easier time to drive the output stage.

 

[RCruz]

So to get more power I would need more current on the output buffer.... that would lead to more output devices right ?

 

[Joachim Gerhard]

Yes, the drivers then have to be reconfigured too to suplly double the current.
You will only get more poer into low impedance that way. The output voltage is always limited by the opamp supply and the opamps used are not rail to rail.

 

[RCruz]

I see.... I really like this output stage that is stable using CFP without the need of any compensation. I have seen designs that need a cap in the negative driver to be stable.

The biasing circuit is also extremely clever (particularly the floating mirror, now with a super stiff ccs).

I will try the LME49870 that can stand plus-minus 22V so I get more swing an more power.

After that I will build another amp with a discrete input stage (I am already collecting info and will start sim soon)

I am doing this for learning purposes... never built a solid state amp before although I have done it with tubes. In the mean time I am also learning how to sim and scope my builds.

 

[Joachim Gerhard]

Great. What discrete design did you chose ?

 

[FdW]

I see.... I really like this output stage that is stable using CFP without the need of any compensation. I have seen designs that need a cap in the negative driver to be stable.

The biasing circuit is also extremely clever (particularly the floating mirror, now with a super stiff ccs).

I will try the LME49870 that can stand plus-minus 22V so I get more swing an more power.

After that I will build another amp with a discrete input stage (I am already collecting info and will start sim soon)

I am doing this for learning purposes... never built a solid state amp before although I have done it with tubes. In the mean time I am also learning how to sim and scope my builds.

You should try OPA501/502, it will go to +- 40V

 

[RCruz]

I just asked Bigun permission to use his single transistor input stage.

 

[Joachim Gerhard]

OK, a singleton. Why not.

 

[RCruz]

Bigun just gave me a green light but he does not have the time to look into the global schematic so here it is hoping you and Frans will get interested to develop it a bit.