Any interest in GC input buffer and power supply regulator pcb's?

[Nuuk]

couldn't they also be used as a buffer for the gainclones?

Yes they could. If they are going to be in the signal path anyway, why not use them for the buffer and save yet another circuit! They may not sound a sgood as some buffers but then buffers won't divide up the signal either.

You could try improving the X-overs with different opamps or whatever.

[troystg]

Hey Nuuk-

Great.

Would you know what other opamps are drop in replacement (if any)?

Thanks again!

Troy

[Nuuk]

Would you know what other opamps are drop in replacement (if any)?

Without knowing what is in there, I wouldn't be able to suggest anything. Take a look and tell us what you see written on each opamp.

[troystg]

They say


Logo is ST, MAL (Malaysia?)
LF353N
91B540

Per the manual.

"The filter is implemented with the Bi-Fet op-amp's IC1b, IC2a, IC2b, IC3a and IC3b."

Troy

[Nuuk]

I'm not familiar with that one but from the NS site I found:

See Also:
LMC662 - improved bandwidth, slew rate and minimum supply voltage.
LMC6032 - improved supply current per channel and input bias current.
LMC6082 - improved bandwidth, slew rate, input bias current, offset voltage.

Perhaps somebody else can recommend an alternative.

[Pedja]

Originally posted by Sheldon
Ok, now I'm going to prove that a little knowledge can be dangerous. I've got some extra j309's. How about drain to buffer output, source to ground and gate to a cap and resistor to ground, powered by =15 volts from the buffer reg.? If I understand correctly (a very dubious assumption), output from the buffer should flow to ground until voltage on the gate comes up enough to shut it off. Time would depend on the cap and resistor values. Any chance?

Generally it sounds like a mute circuit that normally can be found, say, at the output of CD players but with JFET instead of more common BJTs and controlled by the RC network. I think it can be made to work but such mute circuits are not sonically invisible. No idea if JFETs based ones could be. Switch is the cleaner solution. Though you must do the effort of switching…

I have a ground wire that connects the ground terminals of the buffer regs. I have attached the caps to that ground and had planned to connect that, in turn, to the signal ground on the chip (Brian GT's non-inverted clone). I was also going to connect the buffer input ground to the same wire. Bad idea? Should I use a separate ground for the regs and signal paths? Or are the reg. grounds low enough current to not interfer with signal?

What does supply your buffers, i.e. what does drive their regulators? Are they powered from the same transformer used for the power chips?

Pedja

[Sheldon]

Originally posted by Pedja

What does supply your buffers, i.e. what does drive their regulators? Are they powered from the same transformer used for the power chips?

Pedja

Actually, I have them connected to the output of the Rogic discreet regulator (about 24 volt). Haven't fired it up yet. Does that create any weird feedback issues?

Sheldon

[Sheldon]

Originally posted by Pedja

Generally it sounds like a mute circuit that normally can be found, say, at the output of CD players but with JFET instead of more common BJTs and controlled by the RC network. I think it can be made to work but such mute circuits are not sonically invisible. No idea if JFETs based ones could be. Switch is the cleaner solution. Though you must do the effort of switching…

Pedja

Originally, and because all this transistor stuff is new to me, I was considering some sort of timed relay. That seems to require more parts, though if I did the effort to search, I guess that pre-made circuits are probably available. The transistor thing seems simple and would take little space. Sonics are the issue. I assumed (there's that word again) that since transistors are used in these circuits that they might possibly be used for this kind of function without hurting sonics. I thought that perhaps the jfet might give a steep enough cut-off to be the sonic equivalent of a mechanical switch. Might have to try, but I don't think I have very golden ears or maybe enough patience to do a useful study. But who knows? Does anyone know how it's implemented in the 3886?

Sheldon

[Sheldon]

Originally posted by Sheldon


Actually, I have them connected to the output of the Rogic discreet regulator (about 24 volt). Haven't fired it up yet. Does that create any weird feedback issues?

Sheldon

To be clear, what I should have said is that I planned to connect the buffers and the amp boards to the regulated supply (single transformer).

Sheldon

[Pedja]

Originally posted by Sheldon
Does anyone know how it's implemented in the 3886?

As far as I can see the voltage reference of one of its current sources is made to be supplied externally.

Originally posted by Sheldon
To be clear, what I should have said is that I planned to connect the buffers and the amp boards to the regulated supply (single transformer).

If I did not misunderstood you, your buffers have their own (additional) regulators hooked to the +/-24V lines(?). Connect the grounds of these regs and caps following them by some decently sized conductor to the main ground point. Keep the overall layout tight and do not make another ground connections, that is IMO about everything you can do about the buffer and grounding in this case.

If you use an additional shunt resistor at the buffer’s input, it belongs to the signal ground.

Filter in fact rather belongs to the power chip and the ground side of the filter shunt caps goes the chip’s signal ground.

Pedja