[oldearwax]

pi filter & diode bridge ??

 

[ESL57]

Here is a riddle. What have I done ?

You have made a mod so that the uln2003 chip does not directly control the relays, now they are isolated with optocouplers and I add a diode to each coil of the to protect the transistors of the optocouplers. Do I take power or GND in the analog source, I can't see it through the blu tack balls

 

[ESL57]

New mod, attempt to raise the LT1763 to 1.3v (pin 2 disconnected from the pcb), in addition to changing the capacitors for other low noise ones suggested by B0bb, and I will comment if it works correctly.

 

[ESL57]

Perfect, values:
R1= 150k
R2= 9K1

 

[b0bb]

New mod, attempt to raise the LT1763 to 1.3v (pin 2 disconnected from the pcb), in addition to changing the capacitors for other low noise ones suggested by B0bb, and I will comment if it works correctly.

Nicely done, very clean.

 

[Xoverman]

Perfect, values:
R1= 150k
R2= 9K1

If you reduce the values noise will go down.

 

[ESL57]

If you reduce the values noise will go down.

Yes, I could do it, for example it's better like this:
R1= 1K5
R2= 91R
Or even lower values?

 

[Xoverman]

You have made a mod so that the uln2003 chip does not directly control the relays, now they are isolated with optocouplers and I add a diode to each coil of the to protect the transistors of the optocouplers. Do I take power or GND in the analog source, I can't see it through the blu tack balls

you are right, very good.

 

[ESL57]

tienes razón, muy bien. : xf_cool:

I understand, my little doubt was that the original relays are 5vdc, and from what I see they have changed to 24vdc relays.

 

[Xoverman]

I expected that the bass would be even more transparent with this MOD than with the ferrite MOD.
But that did not happen. Instead the midrange became more transparent. Reverb and voices became much more transparent.
Elvis fever (take 1) 1960 blew me away. I've never heard his voice so clear.

The bass precision has remained of course. So another small step forward.

By the way, the fine cables are "star quad cables" made by myself. They help minimize inductive radiation.

 

[Xoverman]

I understand, my little doubt was that the original relays are 5vdc, and from what I see they have changed to 24vdc relays.

Yes, PCN-124D3MHZ,001

https://www.mouser.de/ProductDetail/655-PCN-124D3MHZ001

 

[oldearwax]

you are right, very good.

No fly-back diode (built-in uln2003) across the relay ?

 

[b0bb]

This is missing from the schematic

 

[Xoverman]

oh man, i was in a hurry

 

[Xoverman]

Yes, I could do it, for example it's better like this:
R1= 1K5
R2= 91R
Or even lower values?

I think that's fine, how about you B0bb?