Dx Blame ES .... based into the Blameless, i am trying a new amplifier

[destroyer X]

We are putting the wheel to run.... others, maybe you, will prefere to sit over the wheel.... i hope with some pleasant moments with the wheel, you may turn more kind.

Not having anything clever, or kind to say, it is better not to say things.

Carlos

[wahab]

Originally Posted by BV

Reinventing wheel, gentlemen?
Slones 11.4 'Blameless'
It is very old idea, in many books and schematics. And capacitive loading VAS with 470pF to GND is very suboptimal way to stabilize amplifier- loading means increased distortion at higher frequencies.

Hi, bv..
The idea is way older than slone or doug selfs designs..
as far as i remember, it was vastly used in japanese
amps by the 70s, so the reference you mention also
reinvented this wheel...

Anyway, what was discussed was not the enhancement
of the Vas, but the current limitings around this stage..

About this, i will add that a resistor in serial with the bc546
protect only this one from excessive currents, while using
a zener allow current limiting of both bc546 and bd139 vas.

[AndrewT]

Originally Posted by godfrey

Hi Carlos

Perhaps you could put a resistor at the collector of Q6, to drop some voltage and share the power?

Regards - Godfrey

Originally Posted by wahab

This idea work, godfrey, but then, this transistor s collector will see a signal appearing due to the transistor functionning in a common emitter mode.
So a capacitor should be added in paralel with this resistor to keep
the collector in ground in AC mode...

q6 is effectively a constant current fed emitter follower.
A resistance in the collector to ground lead will see a nearly constant voltage drop even when the VAS and it's EF are passing audio signals.

Add in this extra resistor to limit the dissipation in the To92 device. I think this was suggested about 5months ago.

[PMA]

BV is right, capacitive loading of VAS to GND is probably the worst possible compensation method.

[wahab]

Originally Posted by PMA

BV is right, capacitive loading of VAS to GND is probably the worst possible compensation method.

Agree, pavel , but only in the case of a single differential amp.

With a symetrical differential, Vas collector to ground compensation
can work quite well.

[BV]

Hi, wahab
It was no reference, only example how can it (current limiting in VAS) be done other way, avoiding also VAS saturation and rail" sticking"..

Vas collector to ground compensation
can work quite well.

Anyway, loading VAS iwith capacitor is worsening its linearity and SR, excessive current is needed.

[taj]

Originally Posted by PMA

BV is right, capacitive loading of VAS to GND is probably the worst possible compensation method.

Pavel (and BV, and Eva too for that matter),

I thought it was obvious given how many years Carlos has been here talking about this, but apparently not, so listen up: Carlos has priorities with his projects:

1) great sounding amplifier
2) stable within reason
3) easy and cheap to build for anyone

You will notice there is no mention of distortion in that list. There are other threads for that. Eva, I refer you to item #3.

..Todd

[wahab]

Originally Posted by BV

Hi, wahab


Anyway, loading VAS iwith capacitor is worsening its linearity and SR, excessive current is needed.

Well, i m somewhat off topic, but just want to mention that
i used to think so as well till i did some tries and had some
good results with this much decried way of compensation scheme.

As i mention it, it didn t work with simple differential topology
but with a symetrical differential ,it yielded some fairly good
specs when the amp wa loaded with a complex load...

[PMA]

Originally Posted by taj

Carlos has priorities with his projects:

1) great sounding amplifier
2) stable within reason
3) easy and cheap to build for anyone

He is not the only one, so please refrain from empty words. We are trying to point at obvious mistakes, I have not said a simple word about THD.

[tinitus]

Just want say todays posts have been a pleasure