MUFF WIGGLER Forum Index
 FAQ & Terms of UseFAQ & Terms Of Use   Wiggler RadioMW Radio   Muff Wiggler TwitterTwitter   Support the site @ PatreonPatreon 
 SearchSearch   RegisterSign up   Log inLog in 
WIGGLING 'LITE' IN GUEST MODE

Strange behaviour of Overdrive module
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author Strange behaviour of Overdrive module
djrevmoon
Hi,

my overdrive module works, but the output is very soft. I've measured it, and everything seems to be working fine. The first attenuating stage drops input from +/-8V to +/-3V or so. All opamps are getting the correct Vcc's. The output of the distortion circuit is fed into the last amplifier stage and this is where it gets weird. The last opamp should re-amplify the signal back to 8V amplitude but in stead it again attenuates the signal to +/-0.8V. But the last inverting amplifier is dimensioned correctly, the ratio of 100K/360K resistors being correct (i.e. not switched) but still the last stage attentuates in stead of amplifies. Any ideas?
Synthbuilder
djrevmoon wrote:
Any ideas?


If it sounds fine and the gain drop is experienced on both dry and wet signals then I would suspect that the output op-amp resistors aren't what they should be. Perhaps the 360K resistor is actually 36K.

Tony
djrevmoon
That was my first thought also, but nope. Actually, I did some more poking around and found i was not entirely correct in my first analysis.
The output from the first attenuator is indeed what it should be. But the dist/overdrive circuit is the part that is lowering the amplitude. The last amplifier step is simply not doing anything. This leads me to think that the opamp is not doint what its supposed to. I will do some more checken in various points in the circuit....

thanks!
Synthbuilder
It's worth noting that the middle two sections of the overdrive circuit significantly reduce the signal amplitude for higher input signals. They are at their basic level signal clippers and will limit the maximum signal.

In distortion mode the output of the tone control will limit at around +/-0.7V or so. In 100% wet setting the final output of the module will therefore be of the order +/-2.5V or so. The output may be higher in 'overdrive mode' but the harmonics will be less so it will sound softer.

If you are putting +/-8V into the module it will seem that you have a considerable gain loss through the module. It is expected that the signal input would be around 0.5V to 5V peak in normal operation.

Tony
djrevmoon
ah, so you're saying it works as designed? I'll play around with input levels and see what gives. Thanks!!
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Page 1 of 1
Powered by phpBB © phpBB Group