How are this schematic ?

[rubydac]

6N23P + KT88 push pull with regulation power supply preamp.

Can I modify it to integrated amplifier by change Av and use passive volume ?

PCB or HARD WIRING ?

Thanks
Rubydac

[Miles Prower]

Originally posted by rubydac
6N23P + KT88 push pull with regulation power supply preamp.

Looks pretty good, except for:

#1)

I would change the tail load to a CCS made from cascoded BJTs. It isn't all that much more involved, and it works better.

#2)

This is especially bad. You already have a negative rail and fixed bias. It would be much better to give each final its own bias adjust pot. Use 10R sense resistors in each cathode. That way, each final can be adjusted for current balance to really minimize the DC magnetization current. What you have there won't give good balance between phases unless you use matched sets (more $BUX). Of course, matched sets aren't guaranteed to remain matched once they go into service.

PCB or HARD WIRING ?

What I do is to use a modified "dead bug" method of construction. Build each subsystem on copper clad circuit board with connection pads etched into the copper with a Dremmel or some similar engraving tool. The ground planes of each board are individually connected to the DC neutral.

[rubydac]

My new CCS design
I used DN2540 instead of BJT.

[kevinkr]

I noticed that you do not have a bypass cap across pins 4 - 7 of your op-amp, I do note that you have a zener across these pins which is the right thing to do. ARC commonly used a 30V zener in this location.

I recommend a dip for thermal considerations, which should be socketed for easy replacement in the event of a mis-hap.

I don't quite get what you are doing wrt to a reference.

Everything appears to referred to the regulated output, but for absolute predictability the reference needs to be referred to ground which is the only defined point in the system.

Take a look at some of the supply schematics on legacy ARC products which can be found on their website.

Using this approach you can regulate everything if you so choose.

FWIW it's a good thing you replaced your BJT based CCS - as drawn it would not work.

[rubydac]

This's its PCB layout, any comment ?

Thanks
Rubydac

[kevinkr]

How about breadboarding some of this first - particularly the HV power supply circuitry prior to committing to a pcb?

[rubydac]

I don't have breadboard I never use hard wiring (less skill)
I design from my friend layout he suggest me to this design.

But I decide to use JFET as input amplifier.

Thanks
Rubydac

[rubydac]

My PCB design was completed with suggestion of antique soundlab fan's. Next week I think my BARED BOARD PCB will be succes by local pcb maker shop.
Anyone have any comment ?

Thanks
Rubydac