Ruby guitar amp noisy when plugged with DC adapter

[ChopSauce]

The fact that we are at least three perfect unknowns to having experiences noise when using this sort of amp, but when using batteries, is something to doubt from luck alone ruling the process... 

Do you guys have ay other idea that might work?

Seems to be a common problem. Maybe you can try one or two CRC filters in series between the adapter and the amp?

This is a solution I did not tested, NB. But - like you - I experienced that just one (as big as 100 uF) cap was not enough, while additional(s) (R, C) filter(s) does(/do) seem to be required for proper filtering, if I'm reading well: http://www.valvewizard.co.uk/smoothing.html

The suggested CLC filter might be even better.

[anotherjim]

I think the 100uF cap in the design should be there even when using a battery. It's required to keep the amplifier stable when short high current pulses occur. It will not help much if a PSU with poor regulation is used. To be more tolerant of the PSU, it wouldn't harm to fit a 470uF to 1000uF capacitor across the DC supply input.

When the PSU is a switching type, it adds fast switching noise to the problems. Then a 100nF ceramic disc capacitor should be added across the 100uF one. This small cap works better for high frequencies than the bigger electrolytic ones.
It also aides amplifier stabilty and ought to be there even for battery use.

Finally, read the small print on the PSU. If it says something like "For office/IT use only" it will be too noisy for audio.

[iainpunk]

true, but an Inductor the requires size is quite quite expensive, a power resistor is cheaper,
another option is the ''capacitance multiplier'' it uses smaller capacitors and higher resistors and a transistor to take out noise and/or ripple (if the ripple is small enough, less than 0.6v) form the power line.


cheers, Iain

[ChopSauce]

... a 100nF ceramic disc capacitor should be added across the 100uF one. This small cap works better for high frequencies than the bigger electrolytic ones.

Not to hijack this thread / interfere with the problems of the original poster, but I tried that (polyester film cap with magnitude order about 10 nF, though) too. The PSU was a Boss, the small model, for a single pedal. Didn't solve my noise problem.

Hence my first suggestion.

[anotherjim]

Cheap eBay kit
See the big capacitor C9?
This is for a cheapo kit intended for use with a psu. They don't include the extra 1000uF for no good reason.

[anotherjim]

Actually, and just to make me look stupid, I've got a horrible feeling that the 1000uF on that board could be the speaker output! Duh!

[iainpunk]

Actually, and just to make me look stupid, I've got a horrible feeling that the 1000uF on that board could be the speaker output! Duh!

haha, was just about to post that and then saw you corrected yourself,


cheers, Iain