dod fx 40 eq

[chalieroundeye]

hi, i gues this would apply to build, or at least maybe modifying my stomp box, anyway, does anyone know what causes hiss even when the effect is off? like the bypass mode when i turn the EQ off it still gives me this hiss that i dont get when its not activated, any idea what to do?

thanks!

Joe

[Mark Hammer]

Just about every pedal that uses a momentary footswitch and electronic switching is NEVER "out of circuit".  The footswitch and circuitry change something within the overall circuit that makes the effect not be heard, but the input and output buffer circuits needed in order to use the FETs for switching always remain on.

In most instances, the buffers themselves are intended to contribute little hiss, and most amps/speakers tend not to make it audible even if it gets that far.  In your case, it appears the hiss IS audible.

One suggestion is to see if there are lower-noise transistors that can substitute for what is in the input/output stage of your pedal.  Sometimes there are.  Although use of a transistor that costs maybe 90 cents more may seem simple enough to us, it may well shave off part of the profit margin for companies, and may also be in shorter supply than large-scale manufacturers require to sustain their product line (i.e., if they turned out 50 pedals a month, maybe....but not if they want to turn out thousands in a year, year after year).

A second suggestion is that you might consider replacing the resistors in the input/output stages with 1% metal-film ones for lower noise.  This won't affect the noise level heard when the effect is in circuit, just what you hear when it is bypassed.

A third suggestion is to remove/shunt the input cap on the pedal.  Craig Anderton used to incorporate an AC/DC (cap/no-cap) switch in some of his designs to reflect the fact that an input stage without caps would have less noise, but since you couldn't always assure absence of stray DC at your input it was nice to have a cap around.

A fourth suggestion is to make the EQ part of some loop pedal that can provide true mechanical bypass with a DPDT or 3PDT stompswitch.  That way, the bypassing is done off the EQ pedal itself, completely removing the input/output stage of the pedal from your signal path.

[chalieroundeye]

ok thank you very much, i will look into it!

Joe

[jimbob]

Ive really messed around w a lot of different eq's, but a lot of them do that after-hiss thing--DOD esp!!  My new mxr m108 i expected it to do that as well--but to my suprise no problm-- i still need my NOIsE GATE FOR IT ANYWAY --HAHHAHA---never perfect-In so very in search of the  perfect sound setup--i swear ill never find it! But ill keep building/ buying/looking!