Seventh Circle Audio

by **Thepilgrimsdream** » Sun May 15, 2011 5:37 pm

I just assembled my first preamp.

It all went well. I think the biasing got me a little confused at the end. I think I got it though.

I have it set for the extra 6db of gain for ribbon mics.

It sounds great until the last 3 clicks of gain. It gets really noisy. Before then its quiet as a mouse and then i crank it up a little more for the ribbons and it gets really noisy.

I am not too electrical savy, so i will have my electrician friend help me.

What could i have done wrong?

by **tpryan** » Tue May 17, 2011 11:15 am

Try moving the ground jumper at J4.

by **Thepilgrimsdream** » Thu May 19, 2011 1:18 pm

I moved it. The noise just changed. Its more of a buzz/hiss sound around 5k-10k.

I can seem to here it from gain positions 7-12. Its just extremely bothersome starting at around 9 or 10

by **tpryan** » Mon May 23, 2011 11:55 am

Are you using SC99 op-amps? Can you post some photos of both sides of the board?

by **Thepilgrimsdream** » Sun Jun 12, 2011 7:34 pm

Yes the SC99's Its not working at all now. power comes on, but generates no signal.

http://www.flickr.com/photos/andidreamt ... 827322808/

http://www.flickr.com/photos/andidreamt ... 827321348/

by **Thepilgrimsdream** » Sun Jun 12, 2011 7:36 pm

This was my first one, so it was a sloppy soldering job. If you need a bigger picture size, i can email it to you.

by **tpryan** » Mon Jun 13, 2011 10:58 am

Are the voltage regulators hot?
Does one op-amp get warmer than the other?
What are the DC voltages at the SC99 pins?

Seventh Circle Audio

J99 noise high gain

J99 noise high gain

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