PSA 150 S (pure sound amplifier)---help needed

[sergiu2009]

Hello DIYaudio, I'm new on this forum (only 4 months, but have learned alot from all of you) so i need your help.
Here is a schematic that my colleagues have had developed from alot of other schematics---only the good things from each one, on " Forumul Electronistilor" wich is just like diy audio (only in romanian language); can somebody trace its origins and can tell me if it can deliver good sound quality (ex. some simulations, personal opinions)?
I want to say that we made some simulations but, we (other colleagues) didn't have all of the transistor models in LtSpice, so the results where inaccurate.
We have already initiated a group buy for the components, and i am hoping that all of you could help me to tweak this interesting design for better results and sound quality.
I have attached the BOM and the schematic.
Please excuse my rough english.
Regards

Sergiu

[sergiu2009]

It delivers:
PSA-150S - Vers.A 2x120W/4R/2x38-44Vcc - 100W/8R/2x46-52Vcc - Final tansistor 2SA/2SC...
PSA-150S - Vers.B 2x150W/4R/2x42-48Vcc - 120W/8R/2x50-58Vcc - Final transistor MJL

[sergiu2009]

I forgot, to say that the amp has short circuit protection just in case..

[sergiu2009]

i'm sory , but i forgot to post the schematic for the mono block, so here it is:
Imageshack - psa150s.jpg

[steph_tsf]

High collector voltage on input transistors. Noise ? Reliability ?

Q109 really needed ? Have you compared with/without ?
Purpose of JP101 ?

R128 R129 cause ground pollution. Need proper cautious wiring.
R144 R145 cause ground pollution. Need proper cautious wiring.

C111 (bias filter) 1µF optimal value ? Have you tried more ?

Is the amp stable when suppressing C116 C117 C118 C119,
shorting R150,
suppressing C122 C123 C124 C125,
shorting R151,
and placing a single V+ to V- decoupling cap like 220µF ultralow ESR ?

C109 C110 : allow mutiple choices, more than just WIMA and Nichicon.
Is there a version with FET input and no capacitor in the feedback path ?

DZ101 DZ102 : better without ?
C101 C102 C103 : allow mutiple choices, more than just WIMA and Rohm.

RC compensation network may be needed in parallel with R120 R121.
R = 6.6K
C = 1.8pF

No lowpass capacitor after L101, the output coil ?

F101 F102 rating ?

[sergiu2009]

for JP 101 is something like a controller, that is under construcion, but in our case its not needed..
C111 (bias filter) 1µF optimal value ? Have you tried more ?---i didnt tried, i think that walue is optimal..
i dont know the value for the L101, but it will be winding on the R162, i will try to talk to the creators tomorrow..
F101-102 ---5.2 amps---just to be sure

[sergiu2009]

hello,
F101,102 5.2 amps for the 150 w/4 ohm version
it work without JP101,102 wich are for a controller that is under construction..
that's what i was hoping to get help for: to find a solution that doesnt includes capacitors in the signal path
C111 (bias filter) 1µF optimal value ? Have you tried more ?---i didnt tried, i think that walue is within 0.1 and X uF, but it wouldn't have an influence in the sound ..

regards
sergiu

[sergiu2009]

to be specific: the jp 101 it is necessary for eliminating the cascode on the VAS
--please excuse my rough english--
in my opinion q 109 has to do with the miller efect
if we short r150, r151 we wouldn't have done much good, because of their small values,

[tiefbassuebertr]

I cannot recommend to choose this mirror symmetric circuit for a homemade resp. diy amplifier.
In the schematic from post #1 and in the theory the negative half is a mirror image from the positive half. This means, that all even-numbered harmonic distortions goes to zero.
This isn't so in the real world, because PNP BjT haven't a mirror image character from NPN counterparts. Even the most professional engineers don't respect this. Additional there is the risc of unwanted oscillation through parasitic effects causes through spread capacity and inductitity of the PCB wires.
Most commercial products that I know, where the topology from post #1 is inside, don't sounds really better than products with an easier topoloy like that one from Mr. Nelson Pass.
For this reason I hate such topologies.

For perfect transmission you need a circlotron like "Sumo 9" - go to
SUMO Power Amp
or a SuSy topology (also much easier than that one from post #1).

Nearly the same audible results you will get with the german diy amp "Black devil" (very easy to build and very fine results by the use of a good power supply and high quality caps, eg from ftcap, Husum) go to post #13 about
Your opinion about this schematics?
The whole paper you will find here:
http://www.eserviceinfo.com/download...0Poweramp.html
Some years ago about
http://www.experience-electronics.de/englisch/index.htm
this amp was available as kit.

An additional solution for you are the "Circlophone" amplifier or the "Circlomos" from the member "ELVEE".
If you want to send me an PM, use my e-mail address and not the PM aera here on diyaudio:
kirschner-hifi@tiefbasswiedergabe.de

[AKSA]

Terrific summary, Tief. Agree with everything you have said.

Do you have a 'Black Devil', which has attracted my attention also?

Hugh