Two more for troubleshooting BrianGT GC

[kneadle]

Hello all,

I'm in the process of burning-in my BRAND NEW BrianGT Gainclone, which is my very first active electronics project ever. It sounds great, but not without a little lovin' and tender talkin'.

In the picture below, the amp depicted therein can produce almost absolute quiet amplification; I have to hold my ear directly against the cone of the speaker to hear the amp's self noise.

Here are two things I discovered that might be helpful for all those newbies who follow all the directions but find that you have a horrible buzz or hum in the circuit.
[list=1][*]Check wire polarity EVERYWHERE
I checked and double-checked, but I still missed one: I had the RCA posts wired in reverse. The sleeve is the neutral (OG), not the inner wire. Duh. I was getting so much RFI that a Cubs game broadcast five years ago was coming in loud and clear. And I'm a Cardinals fan.[*]Check the household circuitry
I had my amp plugged into one circuit, and I was feeding it a signal that was coming from a unit plugged into another circuit. I'm not entirely sure why, but this can introduce a situation where the mains are bringing in lots of noise. That same circuit also has my cable TV/internet things on it. Cable TV is bad for ground noise, I think.[/list=1]

If you've searched like I have, but come up empty, try those.

Dave

[kneadle]

PS--note the judicious use of plastic zip ties. Oh yes. It worked.

[kneadle]

Ah dangit....wrong picture...

Grounds are important. Here's a different picture of the same amp and different heatsink.

Sorry about that one.

[soundNERD]

thats a huge heatsink. where did you get it?

[kneadle]

The one in the second picture is salvaged from a Pioneer VSX-402, out of which I salvaged a dandy Tx. That heatsink is temporary while I burn it in. The blue one in the first pic is a computer heatsink that will look lovely in my wife's red living room.

Dave

[jtsjf]

Nice job, Dave! I'm glad to see you have it up and running now.
Two things I also do just to tidy up the whole mess are to clip off the excess leads from the back side of the boards. It doesn't do anything, but makes it look better. I suppose it's one less thing to touch and cross wires also. Also, twist the AC lines to/from the transformer. Again- probably doesn't do much (it's supposed to reduce Rf), but it makes it look nice.
Do you have an enclosure yet?
Good use of zip ties. I'm a big fan of them as well.
Jason

[kneadle]

I just bought some shrink tubing for the mains leads, and the enclosure building just took a huge step backwards when I saw the price for a can of spray shielding.

A 30-second job just turned into a much longer process. I'm building the enclosure out of the same shelf I built the Hohlflutes for my wife, so I need to go the necessary extra step and shield the interior with aluminum foil, I suppose.

Dave

[Colin]

so I need to go the necessary extra step and shield the interior with aluminum foil, I suppose.

[/B]

Maybe not - there are a few amplifiers around which avoid metal casework entirely. The DNM amps use acrylic and the Russ Andrews amplifiers use wood. Both claim the lack of metal shielding improves the sound.

Colin

[kneadle]

I've been listening to it for three days while I build a preamp for it; the amp is still totally exposed. One screw serves as the star ground, screwed into the wood. That's all.

There's just no noise. It's quieter than some of my consumer-level equipment. I just can't get over it. Perhaps you're right to suggest I leave well-enough alone.

Dave

[Nuuk]

I have found the same thing. The best sounding GC's that I have built are the ones that are just built on a lump of wood, so my 'final' vesion will be built along those lines too.