No-global-loop amplification

[thimios]

I measure according to pdf manual, at tp1.
Do you see something wrong?

 

[thimios]

Do you want another test in tp2?

 

[thimios]

Hi Valery, apologize
A bad gnd connection on second probe give the problem!
Here is again.
First picture Tp1.
Second picture Tp2.

 

[vzaichenko]

OK, cool - it's better to measure at TP2 - same shape but higher amplitude - less noise. Very good in terms of phase alignment.

It looks like you didn't reach the minimum - if the trimmer is at its limit - amend the value of the resistor that is in series with it.
The green one will go down to some 100mV RMS and become somewhat corrupted - then that's a pure error signal.

 

[thimios]

R33=750R,is this the one to reduse?

 

[jwilhelm]

That's the resistor to alter if you've bottomed the pot.

 

[thimios]

Ok, thanks Jeff.
I will try this soon.

 

[thimios]

Ok, no need for R33 decreasing.
As soon as we test at Tp2 this time, trimmer act in the opposite direction, plenty of room

 

[vzaichenko]

ОК, now it's good. In fact, around 50mVpp is a very good result, confirming the open-loop distortion of the amplifier is rather low and the bias is at its optimum position.
You're all set man!

 

[thimios]

Ok, let's go for the second chanel

 

[vzaichenko]

 

[thimios]

Some progress in the 21'century protection system.

 

[thimios]

C1 in the bom (relay board) is 7,5mm lead spacing but on the pcb is 5mm.
I can't find a 50v one with 5mm lead spacing.
I found this EEU-FK1V222L but at 35v.
I think that this will be suitable.

 

[thimios]

I measure 18v on C1,so a 2200uf/25v is fine here.

 

[jwilhelm]

Yes 25V should be fine there.

 

[thimios]

I'm using CD-02-05-264 Wakefield-Vette | Mouser Canada. I used 43-77-20G Aavid | Mouser Canada in the past but found them a bit too fragile.

Hi jeff, are you using any thermal paste between this and heatsink?
I mean for the 567-cd-02-05_264

 

[thimios]

Close to finalize for the second chanel.
Unfortunately 2 caps, 10pf & 27pf are missing.

 

[thimios]

Hi Valery, how critical is the C18= 27pf?
I found a ceramic 27pf common type and a 33pf NPO.
This will be just for test, then i will order the right type.
The same for C11=10pf.I found a ceramic 10pf NPO.
I'm in a hurry to listen the Simpelstark in stereo mode.

 

[jwilhelm]

Hi jeff, are you using any thermal paste between this and heatsink?
I mean for the 567-cd-02-05_264

Wakefield recommends using this in place of thermal paste. Just bolt it up dry, it'll melt onto the surfaces as soon as things warm up.

 

[thimios]

Thanks Jeff!
The coincidence test of holes before soldering.