Author Topic: Current Lover - Double Swoosh Noise when rate light reaches its brightest.  (Read 385 times)

79_455

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Hello

I've finally built my first pedal... The flanging Sounds fantastic... but Im having an issue finding out where or whats causing the double swoosh noise im hearing.

(1) Project Name - Current Lover
(2) General description of the problem - Double swoosh sound occurring when rate led goes to its brightest.
(3) Steps that you have taken to try to resolve the issue -  I have done this alignment procedure below

1.   Clock Trimmer (Freq Counter):  Set Feedback=0%, Range=100%, Rate=0%, Switch=Filter Matrix (left position).  Measure pin 1 of IC4 with frequency counter.  Turn clock trim pot until frequency is 70 kHz.
*****This came out perfectly***** See First Picture

2.   Bias Trimmer (O-scope): Set Feedback=0%, Range=100%, Rate=0%, Switch=Filter Matrix (left position).  Place 200 Hz 1V p-p (or ~p-p V of your guitar PU output) sine wave into the input jack of pedal.  Measure pin 7 or 8 of IC2 (MN3007).  Adjust bias trimmer until there is no clipping.  The output waveform will have an amplitude ~1.5 V p-p.
**** This step did not let me get an output over 0.5V no matter where i turned the bias to.. but the trimmer was turned clockwise until the wave stayed clean***** Picture 2 is what bias was set at...Picture 3 is what it looked like when bias trimmer was turned fully clockwise. So i dont know if something is wrong there..

3.   Set T1 (O-scope): Set Feedback=100%, Range=100%, Rate=50%, Switch=Flange (right position).  Turn off signal generator.  Set T1 at full counter clockwise.  Measure signal at output of pedal (tip wire of output jack).  Signal should grow in and out with the clock (will be ~2V p-p at max). Adjust T1 trimmer until signal significantly diminished (barely visible).  There is a sweet spot where the signal will go from ~1V p-p to almost nothing.
***I followed this step through with no issues****

4.   Set T1 (Amp): Set Feedback=100%, Range=100%, Rate=50%, Switch=Flange (right position).  Turn off signal generator. With no input, plug out put of pedal into amp.  Turn feedback trimmer clockwise until a horrible high-pitched tone breaks all the windows in your house.  Reduce (turn CCW) until horrible noise subsides.  Donít go to far, you want to be slightly below the horrible noise to have good flanging.
***Did this as well and it worked.. trimmer was in same spot after i retried the previous step******

5.   Set Vol (O-scope): Set Feedback=50%, Range=50%, Rate=50%, Switch= Filter Matrix (left position).  Apply 3Khz 0.5V p-p sine wave to input jack.  Measure output jack.  Output signal pulses up and down. Set vol trimmer until output is minimum 0.5V p-p
*** This step i followed through as well with no issues**********

(4) List any substitutions you used for parts/values - r30 is 39k  - r10 is 47k -c20 is 47pf

You can hear the swoosh when the guitar volume is off faintly... but its super loud when the volume is full and strings muted.

The flanging sounds fantastic.. just that noise thats the problem..

Im running it off a 9V boss psa-120

Any help would be appreciated..

If need be ill send a file of the sound..

Thanks!




Bio77

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You can cut R10 even lower ~1-10k.  That will give you enough room on the trim to bias it. 

Also, for step 3/4, I like the amp version better now a days. Also, I like the rate fast enough that I don't have to wait too long for the LFO sweep to make adjustments.  If you hear the double swoosh with no input, then back off T1 and see if that helps.  If you aren't hearing the sound with no input, you'll have to wait for one of the BBD Jedi to give advice.

Good Luck!

79_455

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Hi Bio

Thanks for the reply!

Regarding r10 and biasing.. do the second and 3rd picture look like what theyre supposed to look like for the output waveform on the BBD?

Is the reason i cant get over .5v  on the BBD output because that resistor is still too high? ( i can just short it and see if anything changes.. but id need to know what output waveform im looking for on the scope.. )
If anyone has output pictures from all the IC outputs, that would be a great help as i dont understand how a flanger works in completeness.

Regarding T1 -  i backed off it completely and youd still hear the double swoosh from the rate..

When i flipped the switch back to left, i got a slow rising mod sound.. that sounded like modulation from the gorf or space invaders video game.. faint but you could still hear it but no double swoosh..

Thanks again!

Bio77

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Oh, sorry, I misunderstood your pictures.  Picture 2 looks good.  No need to change R10.  You can try lowering the p-p voltage on the input sine wave a little, so, it looks less like a square wave.  That can give you a bit more resolution, but it looks like you are biased right in the middle.

79_455

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Im glad to hear that its correct! as the flanging sounds great...

Its just those other noises, if i could get rid of or find out whats causing the double swoosh... that would solve everything!


Bio77

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If lowering T1 doesn't help, maybe try setting the clock for a different frequency.  Check online, maybe people have better luck with different settings. 

If that doesn't help, I don't know.  I'm getting beyond my knowledge base.

79_455

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No worries..

How would you describe the double swoosh noise that repeats more frequently as rate is turned up?

Ill post it in a separate post..

Again thanks for your help!