kimonostereo wrote:
Spent the day taking this pedal apart and adding sockets to R4 as Keith suggested. Tried a bunch of lower values I had in my spare parts bin and found 100K worked the best.
The bright peak is now gone and it sounds much closer to my original signal when engaged. I wasn't sure I could live with the brightness of the sound, but now I really like it. 100% worth the time and effort to disassemble the pedal for this mod.
I didn't have any resistors higher than 100k that wasn't over 220k, so not sure if it would improve things. I can only say I liked 100k better than lower values I tried. YMMV.
byoc wrote:
The signal is split into a high pass filter and a low pass filter and then the two signals are mixed back together. A lot of mid range should be missing. This is normal because the low pass filter has a roll off frequency of about 75Hz @ 6dB per octave. I'm not sure what exactly the high pass filter roll off frequency is because it's not an RC filter that can be calculated....it's just really small decoupling cap that only lets in high frequencies, but I would probably guess it to be around 7k5Hz. 6dB per octave isn't very sharp, so all the midrange between 75Hz and 7k5Hz isn't completely missing, but it's going to definitely sound a lot thinner than your bypass signal. In order to get the overall volume level back up to about unity gain with bypass, the remaining frequencies need to be boosted. So the higher frequencies are going to be very prominent.
These were the frequencies selected by Fender. The intention of this pedal is to sound like the vibrato channel on a brown face Fender. It's not meant to sound "transparent". You can modify it to be more transparent, but this may have an effect on the actual harmonic tremolo.
You can let more low frequencies into the high pass by replacing C4 with a larger value cap.
You can let more high frequencies into the low pass filter by reducing R4. This might actually be the way to go even though allowing more highs to pass when your complaint is that it's too bright may sound counterintuitive. You'll actually be letting more low mid range in. But you'll also be increasing the volume/output of the low pass filter, so you'd be increasing the amount of low signal that is ultimately mixed back in with the high pass filter. This will allow you to turn down the level trimmer, thus reducing the highs.
I have one of these in the mail coming my way right now!
I definitely want to do this mod. Where on the board are R4 and C4? I noticed in the images theyre labeled by the value of the cap / resistor, rather than the sequence in the circuit
Also, is there a way to decrease the minimum speed?
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