mods for the m-audio audiobuddy

[edanderson]

as promised, some mods to make the audiobuddy tolerable. the cap mods greatly reduce the low end roll off. also, the stock caps are crappy quality. changing the opamps reduces HF distortion and extends the HF frequency response.



the key is to raise most of the cap values, but still have the caps fit. the nichicon HE series from mouser or panasonic FM from digikey should work. don't go crazy raising the values much higher than this because it probably wont help.

change the red circled caps to 47uf/50v or higher (63v if you can fit them)
change the blue circled caps to 22uf/25v
change the yellow cirled caps to 100uf/25v
change the green circled caps to 470uf/35v or higher

change the four purple blobbed opamps to NJM5532L (mouser), especially the two by the XLRs
add TO-220 heatsinks to the voltage regulators, make sure they don't touch anything that could cause a short circuit.

dont bother changing:
the two opamps between the 1/4" jacks drive the meter LEDs
the far right opamp is a charge pump for the phantom power voltage multiplier
the four caps by the phantom power switch are for the voltage multiplier

please don't PM me. ask any questions in this thread.

ed

[rodabod]

I may start calling this the Audiobastard instead of the Audioenemy.

Did the original NJM opamps already have compensation caps? Is the preamp free of any oscillation with the new opamps?

Did you notice any improvement in noise levels? I remember the preamp being pretty useless on some quieter sources.

[edanderson]

i could not get the new opamps to oscillate. the 5532 is internally compensated, as i suspect the 45x0 series is also - not really enough pins in a dual 8 pin for compensation caps.

the 5532 itself is quieter, but the design pretty much limits the noise performance. so no, not much improvement there.

ed

[redear]

Nice, thanks. I have one of these from back in my Merantz 4 track days and I have been wondering how to improve it a little. Seems simple enough.

[thisplace]

Hm 9 year old thread ... But does anyone have the image / diagram Ed Anderson is referring to re "caps with the red circles...purple blobs..." Etc? It must have been removed from the op...and is like to do these mods!

[Drone]

Not on the Internet Archive or in google images, and Ed Anderson hasn't posted in 5 years.

[thisplace]

Well it's the red and blue I don't get mostly because it seems the both replace 1mu 50v caps (8). So I don't get how you'd put on a 25v.... The others are fairly obvious

[Drone]

Maybe the increased capacitance is more important if the voltage rating on the original is overspec'd, lowering to a lower voltage lets you get a larger capacitance value for the same physical size.