hello all
i just finished the Mad Bean Sunking pedal. It all went pretty well except my pots were wired backwards. genius that i am... ::)
anyway, it sounds pretty good and as expected except when the effect is engaged there is a faint but audible high pitched squeal present. you can here it when i'm not playing with amp at a reasonable volume. i tried wiggling wires and even replaced the wires from OUT to SWITCH to OUTPUT JACK with shielded mini cable (grounded by the AC adapter jack). nothing helped. it's not 60 cycle hum but something far higher in frequency. dogs would hate it! charge pump chip is 7660 CPA.
anyone experience this? or from another pedal?
chain: 1989 Fender Strat Plus with Hotrails -> Sunking -> 1948 Gibson GA30. Amp grounded at chassis. AC adapter for Sunking 9.7VDC. The Gibson is the only amp i have around at home right now so cannot test with another quite yet. gotta hit the studio...
thanks for any insight or suggestions,
andy
Try replacing it with the "SCPA" version. Or, you can use a TC1044 or MAX1044
REF: http://www.madbeanpedals.com/forum/index.php?topic=194.0
Looks like I have typo in the build docs: I labeled it SPCA.
ok cool thanks.
which MAX1044 do i want? CSA, CPA, ESA or ESAT?
i want to order a MAX1044 and the 7660SCPA to see which is more quiet.
thanks!
andy
Pretty sure this is what I've ordered in the past:
http://www.mouser.com/ProductDetail/Microchip-Technology/TC1044SCPA/?qs=sGAEpiMZZMuCocSLMfZw/9572jYUh8Cw42A68P5EkeI%3d
BTW: Ive noticed a whine when unboxed, however, mine always goes away once it's in the enclosure (probably added shielding/ground).
so it appears the "SCPA" version of these chips is the way to go.. both the 1044 and the 7660.
i'll check my local electronics shop for these.
could i have a grounding issue? my ground run is from the AC adapter. the middle lug on the 3PDT and the middle tab (jack barrel) of the input jack connects to it (no battery option). the middle lug of 3PDT also runs to the ground on the board. output jack is grounded via chassis (no connection to ground tab). output wires shielding grounded back at the negative of AC adapter jack. (shielded cable added later, no change to squeal.)
thanks!
andy
Most likely it is the oscillator in the charge pump causing the whine. IIRC, when pins 1 and 8 are connected together, the oscillator frequency is scaled upwards by some factor. It could be that in the case of the the "CPA" version, this frequency is still audible in audio applications.
the 7660SCPA chip solved the problem.
thanks!
andy
Hi guys !
I've got the same problem on my SUNKING !
In my pedal the IC3 is a 7660SCPAZ .
What's wrong ???????
Thank's
Gwen
...same issue here. The MAX1044 solved it for me.
Thanks for clearing this up! Now to put mine together!!