[sdiy] Jim Dunlop Cry Baby Wah-Wah.. 500mH inductor replacement .. Found a small professional MuMetal shielded matching transformer @ 530mH on primary..

[rburnett at richieburnett.co.uk]

I'd be concerned about any stray capacitance across the huge 140H 
secondary!  Even the smallest amount of stray capacitance across the 
secondary winding is going to look like a much bigger capacitance across 
the 530mH primary winding due to the transformer turns ratio.  This 
reflected capacitance will detune the Wah down in frequency by some 
amount.

-Richie,



On 2024-07-08 15:06, Jean-Pierre Desrochers via Synth-diy wrote:
> To possibly solve my HUM induced problem in my Cry Baby Wah’s 500mH
> inductor
> 
> I saw that some expensive  Wah’s  (like the Clyde Wah’s) use
> MuMetal shielded inductor
> 
> to get rid of any surrounding EMI.
> 
> These shielded inductors are not available from any sources..
> 
> A company named Fulltone uses custom made inductors like these
> 
> But would not sell any..
> 
> BUT… last weekend  I checked my parts bins and found some
> 
> professional matching transformers the size of what I’d need.
> 
> MICROTRAN S111-S
> 
> I checked the actual inductance of windings and found that
> 
> The primary reads 530mH (DC resistance at 60 ohms). ! ß-
> 
> Secondary reads 140H (DC resistance at 2000 ohms).
> 
> See the picture :
> 
> I was wondering if using the 500mH primary inductance only,
> leaving the secondary wires unconnected would harm the transformer.. ?
> 
>> On 2024-06-13 19:46, Jean-Pierre Desrochers via Synth-diy wrote:
> 
>> 
> 
>>     Hi list,
> 
>> 
> 
>>     I have a guitar pedal board that uses 8 pedals.
> 
>> 
> 
>>     The first pedal (receiving the guitar) is a Jim Dunlop Cry Baby
> Wah-Wah.
> 
>>     The following pedal is a switchable  overdrive with high gain.
> 
>> 
> 
>>     Then the pedal chain goes on with 6 other pedals to a final
> tuner
> 
>>     that drives a guitar amplifier. Ok.
> 
>> 
> 
>>     4 of these pedals are powered with there separate AC supplies
> (9VAC,
> 
>>     9VAC, 7.5VAC & 22VAC).
> 
>> 
> 
>>     The other pedals are powered using 9VDC standard BOSS supplies.
> 
>> 
> 
>>     Here is my problem :
> 
>> 
> 
>>     Since the Wah-Wah is connected at the 'head' of the pedal chain
> and
> 
>>     uses an internal 500mH inductor in its circuit
> 
>>     it acts like the secondary of a transformer picking up 60Hz
> 
>> 
> 
>>     from all the nearby transformers of the board.
> 
>>     I had to unsolder the inductor from the inside PCB and,
> 
>> 
> 
>>     using short lenghts of wires connected to it … place it in the
> 
>>     Wah-Wah housing
> 
>>     at a 'specific' place and angle to get the less 60Hz pickup.
> 
>> 
> 
>>     This is annoying..
> 
>> 
> 
>>     Now I can play with a little back ground hum when the Wah-Wah is
> 
>>     activated..
> 
>>     I  was wondering if I could use an active inductor simulator
> circuit
> 
>> 
> 
>>     In place of the 500mH passive inductor.. (??)
> 
>> 
> 
>>     Feasable ??
> 
>> 
> 
>>     Here is the  Jim Dunlop Wah-Wah schematic :
> 
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