PnP Treble Booster crackles

[dudiluty]

Hi all !

I've made a Rangemaster Treble Booster clone in a vintage tabacco housing. It is loaded with a NOS germanium OC71 PNP transistor.

It works and sound good but when i'm using it and use the volume pot of my guitar it starts to crackle(sounds like a dirty pot). But when i switch the TB off or get it out of the chain it stops. I have read that it has something to do with the DC that is going through the pot...

Is there a way to solve this ?

Here are some photo's of the pedal and the schematic i used.

https://www.dropbox.com/s/jp6kxg36kmvrcxc/20210121_051220.jpg?dl=0

https://www.dropbox.com/s/3gi6ylwsk3cdp2b/Rangemaster Treble Booster.jpg?dl=0

https://www.dropbox.com/s/al641b8z699bzoz/20210114_202924.jpg?dl=0

Thanks.

Marco

 

[ErikH]

That is normal with a PNP circuit like that.

 

[dudiluty]

Ok thanks for the reply.

One other question..

I made a drawing of a wiring scheme (9v battery)..

https://www.dropbox.com/s/ro1d2qx5h04n5dv/20210121_212308.jpg?dl=0


Should this work like the original? And will it bypass properly with the switch? How about the grounding ?

 

[ErikH]

Well, the original worked with an an on/off switch rather than a stomp switch so totally different. The way you have it now, the battery will always be on and it will drain even when not plugged in. What you need is a TRS jack at the input. Hot to tip, ground to sleeve and the battery negative to the ring. This way when you plug in a mono plug to the jack, the ring and sleeve will connect, completing the circuit and engaging the battery.

There are a few different ways to wire up a bypass switch. That should work? Another option is this way: https://www.diystompboxes.com/pedals/DPDT.gif

 

[dudiluty]

Ok but did the original also bypass? Or just killed the sound when in off position?

And for the battery.. i can use this?..
https://www.tdpri.com/attachments/tr...up-jpg.675244/


The rest of the scheme looks fine ?

I edited my wiring https://www.dropbox.com/s/nw6yzw8wr7lg02t/20210122_051537.jpg?dl=0

 

[ErikH]

The original had bypass, because of the on/off, but true bypass was not a thing then.

Yes, that battery hookup diagram is fine. Just follow that regardless of your diagram.

 

[Artie]

It works and sound good but when i'm using it and use the volume pot of my guitar it starts to crackle(sounds like a dirty pot). But when i switch the TB off or get it out of the chain it stops. I have read that it has something to do with the DC that is going through the pot...

I would be very concerned about this. If I understand you correctly, there's a good possibility that your pedal is sending DC up into your guitar. This is not good for the pickups. (Or anything else, for that matter.) If you have a meter, measure across the tip and sleeve of the pedal "input" jack while the guitar is plugged in. If you're seeing any DC, I'd put a cap in series with the input line going into the pedal. Something large, like maybe 1 - 10 uf should work fine without blocking any signal that you want. You may need to experiment with that value, but you definitely want to block that DC from feeding back up into the guitar.

And, as a side note, that will probably also stop the "crackle."

 

[dudiluty]

Thanks for the replies ! I look into it