Reducing DC offset on a NIGC?

[GregGC]

Originally posted by Optical



Yes it seems the input cap was dictating the bass responce.. i changed a few around and now it sounds good..

I havent measured the freq responce, how do you do that?
i have some ideas but im not sure on how reliable my soundcard is for a flat responce..

I have 2 working good sounding GC's now so im not sure if i should test my luck but i think i'll try out the 6k8/220k config you suggest.. would i need to change the resistor from -ve to ground to a 6k8 too?

Originally posted by Optical
Oh, the method with the cap between the cap to ground didnt sound as good, the bass was there but the mids were off...
I was using a 100uF small electrolydic though. not sure how much of an influence it played..

If you like it the way it sounds leave it the way it is and enjoy it. Changing to 6.8k/220k doesn't require to change the +in res. to gnd (leave it 22k). I'm not sure what the resistor you are talking about (-ve to gnd) is. You should have 22k from +In to gnd, 6.8k(before it was 22k) between -In and gnd, and 220k (before it was 470k) between out and -In.

To measure the Frequency response: Sin. wave generator at the input and measure the output singnal keeping the input level constant. See at which frequencies (high and low) you get amplitude equal to 0.7 of 1khz. Those would be your -3dB frequencies. No rules but I'd rather see them outside of 5 Hz and 80kHz range. In my case: 2Hz and 160kHz.

[GregGC]

Originally posted by uvodee
A few weeks ago I followed te schematics of the 'ultimate gainclonce'. It turned out to be a hit and no no 'nasty side effects'.

I could not measure any dc anywhere and the thingies (insulated on an apex heatsink, that was it) played for weeks.

So when my brother in law came by yesterday he took them home after leaving behind some hard earned dollaaaars.
I made one last night, istarted whel after midnight till about 3 pm.
Same config, same hardware (I have stock for 5 stereo's) same toroid etc...
and every. let's say 45 seconds to one minute i get a non defined noise accompaning the music. Something i would describe as oscillating and sometomes a very present HUMM.
What did I do wrong??? I thought I did exactly the same thing. I use the simple schematic-ultimate gainclone with very few components (2 caps 1000uf, 2 resistors 680 & 22k and one pot 22k)

I replyed on the other thread you had the question.