My Gainclone Buffer.

[lgreen]

A number of posts have appeared regarding buffers and the Gainclone. I have made an inverting GC (LM3886) with a differential buffer (INA134) using low noise regulators and a separate transformer for the buffer power supply. This amp is here and on my web page.

Here is the power supply and buffer schematic, note that I can accept XLR or RCA inputs, in the event of using RCA inputs, the negative XLR input is simply grounded through a switch which works well. I would not attempt to use 2 different sources connected simultaneously though as each would be connected directly to the other.

[gregjpeters]

Looks good. How does it sound? What is the output impedence of those opamps? Is the circuit for those INA devices that simple? No feedback or anything? Sorry I'm not familiar with these devices. Do you use a volume control pot/att before or after the input buffer in this case? Would you min posting the schematic of the power amp section? Have you used any filtering on the power amp input like the valve/jfet buffered types? Looks very promising. Anyone else tried it?

Cheers,

Greg.

[lgreen]

Entry about the sound is here.

I have no idea about the output impedance of the opamps or the Linear Technologies regulators, didn't measure them and didn't see them on the datasheet. Someone else might know. I picked these because of their low noise characteristics and because I wanted to try something surface mount. A picture of the full board is here.

Yes, the INA134 is quite simple, no feedback. I think you connect a pin to ground and that's not shown in the schematic, oops.

You could use a 50K pot before or after the buffer. A schematic of the power amp section is here. This has the pot after the buffer, but I've put it before as well (actually using fixed resistors once I got the gain I liked).

I have not tried filtering like the valve/ jfet buffers you see others making here. I am going to use this for a few months after I get my stereo room back together before making any design changes.

[cpemma]

Originally posted by lgreen
Yes, the INA134 is quite simple, no feedback.

On-die feedback resistors, beat that for short signal path, you gaincloners...

Farnell UK stock, fairly modest £2.64 for the dual.