Buzzing Forum-Vibe

[poorboy]

Hi all,  is the second time i write here... im a newbie and have a problem.. i hope someone can help me...
I've build the RedHouse mod version of Forum-Vibe
LFO is ok now,  the pedal works..
it seems all solders are ok..... but the out signal is low (the effect sounds ok)  and the buzz is more than signal... the effect sound is low fi...
Im using a 18v DC power supply with two LM317T powerboard based.. the DC out,  is fixed to 15,5 volts...
I need to follow the signal path with audio probe to discover where the buzz born.. someone can help me?  tnx a lot...

[lonewolf]

is it like a hum? check all your grounds first..and the in/out jacks..are you using true bypass or grounding the bulb?

[poorboy]

hi Lonewolf... i've used this
 http://www.classicamplification.net/forumvibe/fv_mod_11.htm

but i've build this
 http://www.classicamplification.net/forumvibe/fv_rh_07.htm
the noise is like bzzzzzzzz
... and a bit of hum.
When effect is on the buzz go up and down.. with lfo frequency...

must use another wiring?
ps.. the mix/dry mod seems dont works.. no effect on trimmer rotation...
ps.. what do you mean with "grounding the bulb".. is another wiring type.?

[poorboy]

Ok friends... i getup early this morning... strange dreams of mutant  buzzing vibes threw me down from bed...
I discover the buzz source... the vibe is unboxed .... removing the effect from my pedals flight case the noise disappears... yeahhhh,!
Now.. the only problem is the mix/dry mod.. i think is not working 'couse on trim rotation i heard no different  sound... suggestions?

[lonewolf]

I built the neovibe and wanted to do the mix mod and tried it using the 2 75k resistors(R34-35) and the 47k trimmer(TR3) and got the same result.(couldnt find 76k).switched to a 220k trimmer and eliminated the 2 75k's/47k trim and that worked great..could definately hear the change when I turned the trimmer..

[poorboy]

I built the neovibe and wanted to do the mix mod and tried it using the 2 75k resistors(R34-35) and the 47k trimmer(TR3) and got the same result.(couldnt find 76k).switched to a 220k trimmer and eliminated the 2 75k's/47k trim and that worked great..could definately hear the change when I turned the trimmer..

ok,  i will try 220k trim  and... hemm instead the two resistors must use two jumpers.. right?  sorry..  im just a newbie...
tnx Lonewolf

[lonewolf]

yes jump the resistors and if you cant find 220k you could use 200k or 250k

[poorboy]

great.. tnx

[RedHouse]

Hey Poorboy, next time you're down at your local second-hand store scrounging for parts/stuff, look around for a tin box, the kind that candy or shortbread cookies come.

I happen to have a Peppermint Bark box but you can use any tin box you will find.

Glue a piece of rubber (or something wires won't poke through) into the botton inside the box, and drill-n-mount your periferal stuff (jacks/pots/switches, etc).

This is one I specifically use for Vibe testing, it has both pin-cables and alligator flying leads:



The boxes Bottom and Sides will act as a ground-plane reducing hum significantly while you test/debug your builds.

If you are debugging hum-specific problems, you can place the tin top onto the box to check how your circuit sounds fully enclosed, but then pop it back off easily to do work on the circuit. You may have to sand off some paint on the corners to allow good contact for the lid.

[poorboy]

wow, this is brilliant ... I want one too... tnx Brad for the good idea!!

[poorboy]

It's me.. again
last two questions.. after i will disappear in the fog.. maybe
1) what is the optimum distance between the bulb and the LDRs?
2) i use a 18v dc power adapter.. after i put 2 powerboards with LM317T... what is the best dc value for this effect... im using 15,5 vdc for both powerboards...

[lonewolf]

there is no simple answer regarding the bulb/ldr placement..I tried a lot of ldr/bulb combinations and it sounded best with the hermetically sealed ldr's flat on the board facing up ...thats the way the originals were.I owned one...mostly reflective light..the bulb offset trimmer makes a big difference also..it allows you to dial in most any bulb for the smoothest effect..eliminating the choppy sound..

[poorboy]

Thanks for the answer Lonewolf
Your opinion about the dc in?  or over 15vdc there's no difference?

[poorboy]

ok... i was jocking.. THIS is the last question
I'd like use the rotary switch to make the multivibe mod...
for the caps is not specified the unit: are they  F or uF? (except 470pf cap of course).
I think uF couse in the schematics C6, C8 etc are uF... right?
Tnx