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Quick question. Built an HM-2 clone which works great. If I connect it to a Buff n Blend I get a high pitched oscillation at higher volume/gain levels. If I pull those knobs back, I don’t get the oscillation. Is there any way around this? I’ve tried a 10k resistor in place of the jumper, but I’m not sure this issue is even related to that resistor value since it doesn’t sound like the loop is overpowering the signal. Even without a guitar plugged in, I get that oscillation. Any help would be appreciated. Thanks!
Are you connecting the HM-2 to the SEND and RETURN of the BnB? If so, try a higher value resistor in place of the jumper. If you are sending the output of the HM-2 directly into the INPUT of the BNB, the signal will be too strong when it reaches the MPF102.
Understood! I’m using the send and return off the Buff n Blend so I’ll try a higher resistor value and report back!
OK I added resistance to R5 (the jumper) using various values up to 200k and still the same issue. I can actually hear the oscillation without the 3pdt being pushed. So if I just plug in, my guitar is going to the input of the Buff n Blend. The send is going to the input of the HM2. The HM2 out is going to the return of the Buff n Blend. And the output of the BNB is wired to my output jack. If I just plug that in, I can hear a high pitched oscillating hum without the 3pdt turned on. I can adjust the knobs of the HM2 circuit and hear the oscillation being affected, although the distortion itself isn’t coming through. Once I turn on the 3pdt, I get the distortion effect and the full HM2 sound, but that oscillation is present at high gain/high treble/high volume.
Hmmm. You say that the oscillation changes when the HM-2 controls are changed. That makes me wonder if the oscillation is being created within the HM-2. When the HM-2 is connected to the BnB, it only passes through 2 resistances on the way to the output. Its signal does not pass through the MPF102.
Do you have oscillation from the HM-2 when sending its signal directly to the amp? If so, there is an with the HM-2. If not, there may be an issue with the BnB. we will need good clear photos of both sides of the BnB as well as photos showing all external wiring including the HM-2 connections.
There is no oscillation issue when it’s not run through the Buff n Blend. Before I do anything else, I’m going to double check my values on the BNB. I’m wondering if I populated that wrong. I’ll post photos and such here if I can’t sort it out.
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