'nother MN3005 Aquaboy issue

[maysink]

I was able to mitigate the faint, high-pitch whine (original post here) by decreasing the max delay trimpot but I still have an issue of the delay effect bleeding into the bypassed signal.

With the feedback pot dime'd, I get the effect's self-oscillation faintly bleeding in to the bypassed signal. I finally got around to installing some shielded wire from the switch to the output jack but that did nothing. I tested continuity between the stomp switch lugs to make sure it's functioning and it's all good.

I'm wondering if anyone has a suggestion on why this might be happening and/or a clue on how to track the culprit down. It would be my uneducated guess that, all things working correctly, a bypassed effect should not ever bleed into the (clean) signal.

**EDIT**

Just read this on the new pork barrel docs:

"As with all clock-driven effects, bleed-over (clicking) is possible. Use proper lead dress: keep wires separated as much as possible and use shielded cable on the FX in and out. If you do have clicking, you can try placing a 100pF ceramic cap between pins 1 and 5 of IC4 on the underside of the board. This will provide extra DC filtering at the chip."

So maybe this is a normal issue and I need to use shielded wire elsewhere and make sure my wiring's tight?

[jkokura]

yes.

[madbean]

I wouldn't necessarily start re-wiring everything with shielded wire....I'd say put one more shielded wire between the FX output on the board and the switch and see if that helps. Just run the extra ground directly to the switch.

[maysink]

So I used shielded wire on all 4 in/out points and this did not eliminate the problem osicillation-in-bypass problem but it did slightly lessen it. Of course, since I never run pedal in full-on oscillation mode it's not really an issue.

However, I WAS able to get a tad more out of the delay trimpot w/o any more noise so there's that!

[madbean]

Are you running anything before/after the pedal when you get this problem?

What kind of power supply are you using?

[maysink]

I've only noticed it when the AB is all by itself. I'm running a BBE supa charger at either 9 or 12volts into the AB. Again: only when I dime the feedback knob does the self-oscillation bleed into the bypass signal. And it's fairly quiet--noticeable--but not loud. Also, the mix knob will make effect the oscillation bleed's level.

Also, also, I top mounted the jacks & power plug in a 125B enclosure so the jacks are quite close to the board (output jack is damn near on top of the mn3005 chip).

[gtr2]

I had this problem with a deluxe memory boy.  It stopped when I used it with a wall wart by itself instead of powering with the same source as my other pedals.  I don't know if that would help, but I'm just throwing it out there. 

[maysink]

You're an f'ing GENIUS!!! Gave the AB it's own adapter and NO oscillation in bypass! Thanks, GTR2 (insert real name here)!

PS: is it common knowledge to give analog delay pedals a dedicated power source? never had this issue w/ my BYOC digital delay. But it's obviously digital.

[jkokura]

I don't know, but if you think about it, the old DMM's used to have their own built in AC power cord. It's probably having to do with power filtering and such that they do I think. They often require quite a bit of power also, and they're better run on a power supply rather than battery.

Jacob

[madbean]

Hmm...maybe the BBE does not have isolated outputs? It would be nice to find a solution that does not require its own wallwart. There should be sufficient filtering on the board.

Just as an aside, you should maybe get your DMM and test to make sure the BBE is putting out a rock solid 9v.

[gtr2]

Well at least we kinda narrowed it down...  I've heard though other forums people complaining of "clock noise" with the Aqua Puss and some have no issues.  The specs say the Aqua Puss reissue draws 16 mA and one isolated output will put out 100 mA on your BBE supra.  I just wonder if some of these analog delays are very sensitive to different power supply filtering depending on the chip used???  That's beyond me...  The deluxe memory boy had to be powered separately but my carbon copy has no issues at all running with the same power supply as everything else.  I got rid of the deluxe memory boy, so my research stops there.

Josh

[madbean]

IIRC, the Aqua Puss used a regular 9v input. But, I believe some units used the 3005 and later units used the 3205. If you've ever seen a guts shot, all the wires were zipped together and ran to two jacks at the top of the enclosure. So, obviously there was no clock issue with those.

I do think a large ceramic cap from Vcc to ground right under the MN3101 might help. Haven't had a reason to do that myself, but it should help filter noise out if a sufficiently large enough cap is used.

[maysink]

I think the supa charger is confirmed to have isolated outputs. I DMM'd two plugs' ground connections and there was no continuity. I'm thinking the DMM would have squak'd if they shared a common ground.

Also, the oscillation-in-bypass-cancelling adapter I tried is an isolated 9v @ 300 mA (morley brand adapter) which is 3x a supa charger's output. Weird. I haven't tested if the stand alone adapter will let me squeeze more max delay time from the internal trimpot but it's on my todo list.