SuperOPA

[Terry Demol]

Re: yes you are right

this is just a project for 50W class A 🙄

i have taked inspiration from Accurphase design 😉
so in the original schematic
the output bipolar was in reversal mode

but my idea is use output resistor as negative feedback

I think you got the idea from Fred Forssell's original design.

http://www.forsselltech.com/downloads/schematics/Class A JFet Opamp.PDF

Everything up to Q7 looks good.

You could have at least re drawn it. 🙂

cheers

Terry

 

[Stee]

better use MPSA to drive

see new SuperOPA

RA/RB 560R/8K2

 

[AndrewT]

that's a crib of MOX discrete opamp.
Where is your attribution?

 

[Stee]

sorry

now is better

do you think it's possible increase voltage from +/-15V
to +/- 30V on first block? (final stage don't have voltage gain)

 

[Stee]

we need more power

see another cut and paste
with SFS - Stee Final Stage
most famous crossing biasing

 

[U102324]

Re: we need more power

see another cut and paste
with SFS - Stee Final Stage
most famous crossing biasing

Hi Stee,

I did this amp some time ago and only completed it around June when pushed by one of my audio buddies. See if there is anything useful in it that you can use.

http://digisec.co.za/ras/music/Schematic HP Amp Rev 10.pdf

Kind regards

Nico

 

[Stee]

NICO many thanks

🙂

best accuracy on VAS
maximum biasing on FINAL (with NTC self-control)

how many voltage can modulate this super driver? +/- 35?

 

[U102324]

Re: NICO many thanks

🙂

best accuracy on VAS
maximum biasing on FINAL (with NTC self-control)

how many voltage can modulate this super driver? +/- 35?

Hi Stee,

You are welcome. I will keep following your amp design until it is completed and then try your design out myself. Nice going.

Nico

 

[U102324]

Re: Re: NICO many thanks

Hi Stee,

You are welcome. I will keep following your amp design until it is completed and then try your design out myself. Nice going.

Nico

Sorry I did not answer you, what you need to watch is the power dissipation, there is quite high current flowing so choose the transistors wisely.

I have used it with 30V but was limited with what I had in my junk box.

Nico

BTW this is your design, only some small suggestions by me.


😉

 

[Stee]

thanks a lot Nico

can you sell me one finished Amp like your pdf schematic?
then i will try to increase voltage to 60V 🙄

 

[U102324]

Re: thanks a lot Nico

can you sell me one finished Amp like your pdf schematic?
then i will try to increase voltage to 60V 🙄

Hi Stee,

I am sorry but I am not a kit person. I design something and build it, If I like it I keep it a while and then make another design.

I have gerbers of the PCB layout for this amp that I will e-mail you, but I made this particularly for a high performance headphone/line amp.

I wanted for a while to change the design for use with lateral MOSFET output stage. Maybe I do it in the next few weeks.

Cab you make PCBs?

Nico

 

[Stee]

very good man

my next experiment start from final stage
then i will try your great OPA-driver

 

[Stee]

Mosfet drive variation

Now this idea come to be IGBT-similar
Because within BJT drive
There isn't any current limiting for the transistor bases.
This will most likely kill one or more parts.

for mosfet biasing need swap red leds
with a series of power diode (3x)
until have 2.1 Vsg --> Class A current 😎

 

[Stee]

Stee Final Stage pseudo-IGBT

update schematic 😱

 

[john65b]

Would an Aikido Front End work with this output setup?

 

[Stee]

i don't know

if you have a schematic, will be very intresting😉

 

[john65b]

Here - you can call it the STEE-KIDO.

I have a lot of 6SL7's and 6SN7's...as well as 2SA1943/2SC5200, and a few 2SJ74/2SK170 too...

 

[Stee]

yes very good

but there is one super expert here
that can say (from simulation)
THIS new circuit works!?

today I'm testing full BJT version
with OPA driver

 

[john65b]

That expert is NOT me.

Io non sono bravo a niente!!

 

[stinius]

That expert is NOT me.

Io non sono bravo a niente!!

Oh don't be so shy, yust admit it.🙂 🙂 🙂 🙂