The Aleph-X

[stefanobilliani]

Originally posted by nar
Stephanobilliani,

The VR doesn't seem to vary enough DC offset for me.

Looking at Grey's original schematic,I made a mix from Rtirion and

V2 is now 250 ohms

R26 is 470 ohms

R24 is 221 ohms

What are the values you use for those resistors ? Thanks.And which is your latitude for offset ( VR at max,DC offset and VR at min,DC offset ? )

Maybe I can't vary bias diff.pair enough

Which is your value for the Magical Resistors ?

In your version,how many power mosfets ( i.e P240 ) do you use for the whole amp ? ( I don't think about the 9610s )

Great thanks for reply.

Regards,

The need for changin imput to ground rsistors (R19 R29) from 10k to 68k was the first thing when I tested the circuit, as the absolute dc wasn't good .I say 15 or so volts.
The resistors from the output to the sources of the diff pair are 4.7k and for me is hard taming the dc offset varing this ones .
I notice large variations of dc as you report , changin this resistors.
VR2 give large variations also but the position depends by the current trough the output mosfets.
For me R24 is 475, VR2 220, R26 330.4 mosfets/channel R5 R6 etc. 0.33 ohm.
Setting VR1 and VR3 for the max current VR2 voltages variations are from -11 to + 5 volts.
Rails : +/- 15 volts

Stefano

[nar]

Ok,so I changed a lot of stuff.

I went to 2k2 for the famous magical resistors.

I got 475 ohms for R24,332 ohms for R26 and a 200 ohms trimmer,like in Grey's version.

I re-ran the circuit,and this time I can adjust absolute DC to 0V !

But varies + and -,I have to wait for temperature equilibrium for

precise 0V.Around 0V,the offset goes - 30mV and then to +30mV,and again.

My bias is now a little over 4 A. Sink temperature is OK.

I have to wait 2 hours.Listening !

What a pleasure


Thanks Staphanobilliani !!!

PS:The draw of the Aleph Current Sources seems higher than the output stages.In other terms,more draw on V+ than on V-.I have no explaination.The values for R 39 and R 35 are 221 and 100 ohms respectively...

If the to92 NPN for output stage sense was limiting current...I have no clue yet however.

Regards

[joke]

Can some one please tell me what capacitors voltage I should use for C1,C3,C5,C6 - 220uF...will 6.3V be enough...
I was thinking to use BG 220uF/6.3V NX tipe...

Thanks
Josip

[grataku]

joke,
I used 220uF, 35V panasonic FC in my prototype. They fit the ver1.0 pad spacings

[wuffwaff]

Nar,

how do you know there´s more current through the current sources? If there´s less through the output stages then where is that current gone? I mean it can´t dissappear can it


william

[jh6you]

Originally posted by joke

220uF/6.3V

For C1 and C6, 220uF/6.3V okay.
But, for C3 and C5, I recommend minimum 12V rating.

JH

[swede]

wuffwaff: ;=) Nope, in that case mr Kirchoff would be turning in his grave...

//magnus

[nar]

Hi everyone,

Could someone give me the recipe to adjust the AC current source gain to 50 % ???

I have a BF generator non balanced out,and a good multimeter but non True-RMS type.I have no scope

But I guess it must be simple to adjust when having clear explanations

Thanks for feedback

Regards

Anael

[Peter Daniel]

Some info is here: http://www.diyaudio.com/forums/showt...887#post133887

There was also an old thread where everything was nicely explained. You might try to search it or I will find it in a meantime.

[UrSv]

Originally posted by nar
Hi everyone,

Could someone give me the recipe to adjust the AC current source gain to 50 % ???

I have a BF generator non balanced out,and a good multimeter but non True-RMS type.I have no scope

But I guess it must be simple to adjust when having clear explanations

Thanks for feedback

Regards

Anael

Been covered in several threads but essentially I think you could do this:

Disconnect R10 (or whatever the resistor is called that feeds back to the current source). Run a signal into the amp driving a constant load and measure the voltage variations on the source resistors of the output stage. Now connect R10 (...) and adjust until that variation is half of the original value. Then the contribution from the current source is half.