madbeanpedals::forum

General => Open Discussion => Topic started by: garfo on June 17, 2024, 04:14:14 PM

Title: Summing stage with Blend circuit bleeding noise
Post by: garfo on June 17, 2024, 04:14:14 PM
Hi guys, I thought that I should ask the Peeps opinions on where to look in order to improve a little issue.
I have a design that, as many pedals, blends the clean signal with the Distorted signal. For this, I am using a Pan circuit with an inverting opamp stage. The Center of the Pot connects to VR (2x 10k resistors with a 39uf filtering cap.
The circuit works really well, except that, when completely on the clean side, there is bleeding from the distorted tone when the gain is up. I thought that the 39uf cap would be enough to filer everything, but it doesn't seem to do the trick.
I guess the question is, any idea where to look?
Title: Re: Summing stage with Blend circuit bleeding noise
Post by: jwin615 on June 22, 2024, 11:50:05 PM
Can you post a schem or some other form of info?
Title: Re: Summing stage with Blend circuit bleeding noise
Post by: madbean on June 23, 2024, 02:59:52 AM
Quote from: garfo on June 17, 2024, 04:14:14 PMHi guys, I thought that I should ask the Peeps opinions on where to look in order to improve a little issue.
I have a design that, as many pedals, blends the clean signal with the Distorted signal. For this, I am using a Pan circuit with an inverting opamp stage. The Center of the Pot connects to VR (2x 10k resistors with a 39uf filtering cap.
The circuit works really well, except that, when completely on the clean side, there is bleeding from the distorted tone when the gain is up. I thought that the 39uf cap would be enough to filer everything, but it doesn't seem to do the trick.
I guess the question is, any idea where to look?

You may need to set the blend control so that the distorted path is grounded when turned to fully clean. Regardless of a cap in-between, if there is series resistance b/w the two halves of the circuit there can be some bleed. If you can post the portion of your schematic with the blend control it would help.
Title: Re: Summing stage with Blend circuit bleeding noise
Post by: jwin615 on June 23, 2024, 04:37:38 PM
Another option is to use a MN taper and cut the trace at the end of the wiper
Google "no load MN blend"
Bassists have been hip to it for a bit.
Or use a pot with a switch at the end that breaks the circuit, but those get pricey.