How to fix (if possible) a problem of hiss on a DanEcho stomp box

[BrunoCH]

Dear DIY folks,
I have a problem with my DanEcho delayjavascript:void(0);. It makes an hiss or kind of whistle noise even when it is off. The noise seems to be related to the speed button as it changes in frequency (going higher) when the speed is increasing. Is this problem known by somebody? Is it possible to fix it?javascript:void(0);
Thanks in advance.
Regards.
Bruno

[Mark Hammer]

That sounds like clock noise, and a mismatch between the clock frequency and what the lowpass filters are set to.  Alternatively, there may be  something preventing one or more of the caps to ground one usually sees in the lowpass filtering in such pedals from actually connecting to ground.  This would have the effect of providing less lowpass filtering than is needed at ALL delay settings, which might explain why the noise is there even at shorter delays.  In some of the earliest delay pedals, sometimes manufacturers would make a choice to have juuuuuuust as much lowpass filtering as was needed to keep clock noise in check while maintaining as wide frequency response as possibel in the delay path.  Sometimes, at the longest delay times, you'd hear a touch of the whine you describe (which most people would "fix" by turning the treble down on the amp), but it was rarely the case that the whine would be audible at ALL delay times, which suggests something wrong with the filtering.

Alternatively, is there anything that sounds like there might be some error in any other on-board noise-reduction, like a compander chip?

[BrunoCH]

Thank you Mark,
I guess your point about the connection to ground is part of the problem. I discovered that by making the power plug swinging in its hole, the noise get weaker and even disappear.
Regards
Bruno