DC adjustable double-Sziklai Power Diamond Buffer

[mtlin12]

I have designed another 0 dB Diamond Buffer Power Amp.

I use this Power Buffer with my SRPP+Cathode Follower TUBE E-80
pre-amp to make a pretty good sound Non-Global-Feedback Amp.

With some changes from my ULTIMA-SDDB small Class-A power Amp and headphone amp ,
see my last thread at sziklai-darlington diamond buffer (SDDB) for power output stages ,
I desided to design this 0 dB Power Amp with double-Sziklai output stage.

The INPUT stage is similar to LH0033.PDF fast buffer, but with cascode
stage for JFET high voltage protect. So the output DC level can be
adjustable by tunning the CCS current.

About 40W with my tube pre-amp the output power can be achieved. ( not yet totally tested )
The bottleneck is the 2SK246BL's limited breakdown voltage only
50V, if use LS844 it will be better 60V.

My Taiwan made E-80 tube amp.

[amplifierguru]

Why not use a 2n7000 60V DMOS FET? Doubt it would be suitable for your current sources though with Idss=1mA for starters, but input. MOS in OK?

Greg

[SkyChu]

If Output power only is 40W, Why you use +/- 38V in output stage ?

The 2SK246 is limit 50V, Why don't to use Cascode by Q7 and Q12 ?

[mtlin12]

hi, Greg,

I think MOS is not suitable for the input FET here.

DMOS FETs are Enhancement type FETs, the Vgs will be positive
voltage from gate to source.
But JFETs are depletion type, the Vgs will be NEGTIVE voltage
from gate to source.

The source voltage of the Input JFET Q8 will higher than the input
(gate) voltage, if we set it to be Vbe, then we can get pure DC
output Buffer without using capacitors or DC-servo ckt.


hi, skychu,

I have a DZ T270 27-0-27 power transformer in my hand, so I use
this to get a +/-38V DC.
But I lower the voltage of the cascode Q7 (Q12) voltage to about
25V, and providing the Q14 (Q15) CCS sufficient voltage.

The voltage of the output tage can be lower to +/-25V,
only I have no other AC output voltage.

[SkyChu]

Originally posted by mtlin12
But I lower the voltage of the cascode Q7 (Q12) voltage to about
25V, and providing the Q14 (Q15) CCS sufficient voltage.

Is it "cascode" circuit of Q7 (Q12) ?

[mtlin12]

You are right, it is just a normal common drain JFET with voltage reference.

[mtlin12]

I think the 40W Power of this 0dB Diamond Buffer is enough, if we
make two Buffers as BTL with a high output Balanced Tube pre-Amps like ARC REF MKII.

The maximum output could be triple or quadruple, about 150W!

[amplifierguru]

What's the purpose of all this eclectic, complex, 'solution without a problem' electronic lego?

Have you heard of elegant simplicity? Or, indeed elegant sufficiency?

Cheers,
Greg

[mtlin12]

Hi Greg,

I think my amplifiers no matter with amplitude or not, basically are
designed with simple structure , though look like complex circuit.

Since my first My Ultima DB-01 Dual JFET+DB Head-Amp announced
on Head-Fi at 10-18 2003, I began to design with the same structure
using the same cascode JFET differential input stage, plus single-
ended JFET+CCS voltage amplitude stage, I want to design a high voltage gain
and large current output, so they can be pre-amp headphone amp
as well as a power amp ---- my 150W ULTIMA-1 .


And I love the diamond buffer and JFET's sound .

But they are all Global-Feedback designed, since I bought my SRPP
tube pre-amp, I think my power amp maybe can eliminate the
differential input stage and voltage gain stage, just use a SIMPLE
common drain JFET stage as input buffer plus a SIMPLE Power
Diamond Buffer to drive not only the headphone but also the
speakers.


True, it came to be the same complex as my first amp, but I use
only one pair SANKEN 2SC2922/2SA1216, to have large cuurent
gain. And some circuit are for remote stand-by control optional.
LEDs are for CCS and power on indicators.

All BJTs are very cheap small signal except the driver and output
stage, total cost is not very high.

NGF 0dB Amp without the no-useful or no-benefit voltage ampltude
stage maybe can achieve better noise, THD, phase-shift, ...

I think it can sound more elegantly with the tube, but without
output transformer.

[Workhorse]

Hello Mtlin,

One of my Friend has built your headphone amp, i have also listened to the immaculate sound of that amp...its a great gift to DIYER'S ......

cheers,
Kanwar