I bread boarded the Joe's Diode-Compression Opamp (2N5087/2N5089). it sound really nice by itself and in a Dist. plus type thing I tried, but it's noisy as hell. it has alot of noise and high pitch squeel. I tried the advanced version as well, and it too, as well as the tone maybe, is VERY noisy and squeely.
I tried a hi cut cap to ground on the input and out put and a hi cut cap in the feedback loop... nothing...
help... plz?
A little update. I got rid of the nasty oscillations with an inverting stage, but this crkt is still very noisy. Am I doing some thing wrong?
Sometimes you need a filter cap on breadboards, even if the power supply is well-filtered. I run into this a lot.
Other then that, make sure the output is near 4.5v, adjusting the 6.8k resistor if it's off. It also might need a more stable bias, use 10k/10k voltage divider, filtered by a 10uF or so cap, then the 1M going to the input. I think the input resistance is less than a real opamp.
The basic version is probably best for most purposes, the only advantage to the more complicated one is to drive a bigger load.
I use a chip to do the voltage dividing, and it's really precusr and stable. by board is filter aside of the existing power supply filtering.
I succeded in quiting the beast down :) now I'm very happy with the nosie floor. thing is, it's has alot of bass at high gains (500k pot /.1uf->2k4) and with a pair of Si doides it doesn't clip as hard as say, a tube screamer.
Any thoughts?
When I had mine partially working, I used GE diodes for a lower clipping threshold. I'm also wondering if a Darling transistor for Q3 might help raise the output level. 8)
Here's what I found...
output [lower
Noise Floor [lower
Sound [different, opinion is it's a good improvement [only a/b'd Vs. LM741] I'd venture to say that the compression amp works handily in the DS-1 Cologne.
Looking for bigger boosted outputs?...look elsewhere...
Looking for great sounding/otherwise performing OA...there 'ya go !
Pretty large difference I notice, really for once likin' the DS Sound, it still boosts, not as much.