SOLVED Byzantium Flanger "Fuzzing" at high input volume

H

he2718

New member
Hi all,

I built the Byzantium Flanger and it's almost working.
I adjusted the clock with the oscilloscope, however for lack of a function generator I had to adjust the other two trim pots by ear. It's flanging beautifully and I got it very close to some sound samples I fount on YT.
However at medium to high volume on the e string and high volume on the a string on bass it makes a dirty almost fuzz like sound. I think *something* is overdriving/ clipping at higher input voltages. But what and why?
I would be glad for any help/ pointers/ suggestions to find the issue...

Best regards
Henrik
 
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falco_femoralis said:
Try swapping your op amps. Not the clock chips, but the op amps themselves. If you get a bad one they can be noisy like this
Click to expand...

Thank you so much swapping the op amps on the audio board solved it immediatly!

blackhatboojum said:
Sounds like your bias is off. You can use this site to generate and feed a sine wave into it.
Click to expand...

I was thinking the same however I tested it by just lowering the bias very much and it still was doing the strange sound...

Thanks for all the other hints as well, you guys are the best!

Kind regards
Henrik
 
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blackhatboojum said:
Sounds like your bias is off. You can use this site to generate and feed a sine wave into it.

Online Tone Generator - generate pure tones of any frequency

www.szynalski.com www.szynalski.com

Set all knobs to minimum. Probe pin 1 of q5 with your oscilloscope and adjust the bias to a clip free wave form at its peaks, while sweeping the manual knob.
Click to expand...
I was also trying this method, however did not know how to achieve the "0db" level on the 200Hz signal the original boss manual is asking for... If you have a suggestion I might come back to finetuning my bias like that...
 
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he2718 said:
I was also trying this method, however did not know how to achieve the "0db" level on the 200Hz signal the original boss manual is asking for... If you have a suggestion I might come back to finetuning my bias like that...
Click to expand...
You can measure the the ac voltage of the signal with your scope or multimeter. .78v is 0db
 
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blackhatboojum said:
You can measure the the ac voltage of the signal with your scope or multimeter. .78v is 0db
Click to expand...
It seems I lack some understanding. Since dbm is in mW I thought voltage conversion would depend on the (input?) impedance of the pedal... Is there an assumption or convention behind the conversion? Some explanation would be welcome!

Hiwever, following your advice I readjusted the bias today measuring both the input voltage as we'll as the probe point with the two channels of my scope and the clip free bias point did not really shift between .65 and 1.0v rms input signal... Since it sounds good as well I think it's fine.

Best regards
Henrik
 
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he2718 said:
It seems I lack some understanding. Since dbm is in mW I thought voltage conversion would depend on the (input?) impedance of the pedal... Is there an assumption or convention behind the conversion? Some explanation would be welcome!

Hiwever, following your advice I readjusted the bias today measuring both the input voltage as we'll as the probe point with the two channels of my scope and the clip free bias point did not really shift between .65 and 1.0v rms input signal... Since it sounds good as well I think it's fine.

Best regards
Henrik
Click to expand...
Technically, you are correct. Precise voltage conversion is dependent on input impedance. In the audio world, it’s an assumption, based on the old telephone standard of 600 ohms.
 
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