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DIY Stompboxes => Building your own stompbox => Topic started by: FingerBlisters on October 01, 2021, 06:04:07 PM

Title: More drive from a Zendrive?
Post by: FingerBlisters on October 01, 2021, 06:04:07 PM
Here's a schematic: https://www.pedalpcb.com/docs/Mahayana.pdf

I'm not following that entirely due to parts available. I'm using a on/off/on in the feedback loop with red/red LED, OFF, then a 1n34a/4001 pair on the other side.

I really like the pedal but would like to squeeze a bit more from it if poss. Can I change the 1k (r4) to something meatier like a 10k? I don't keep 1m pots on hand and don't want to double the gain that way, just a little bit more would be cool.
Title: Re: More drive from a Zendrive?
Post by: PRR on October 01, 2021, 06:15:42 PM
> change the 1k (r4) to something meatier like a 10k?

Won't change the maximum gain.

Hard to believe a gain of 470 is not enough. Triple-check everything?
Title: Re: More drive from a Zendrive?
Post by: FingerBlisters on October 01, 2021, 06:26:03 PM
Quote from: PRR on October 01, 2021, 06:15:42 PM
> change the 1k (r4) to something meatier like a 10k?

Won't change the maximum gain.

Hard to believe a gain of 470 is not enough. Triple-check everything?

Yeah everything is right and works great, just needs 8% more nuts.

Out if curiosity what is that 1k doing? Sets minimum gain?
Title: Re: More drive from a Zendrive?
Post by: antonis on October 01, 2021, 06:39:16 PM
Quote from: FingerBlisters on October 01, 2021, 06:26:03 PM
Out if curiosity what is that 1k doing? Sets minimum gain?

Yes.. :icon_wink:

For 8% more gain, place a 12k resistor in parallel with R3 (1k) 
Title: Re: More drive from a Zendrive?
Post by: anotherjim on October 02, 2021, 06:26:22 AM
I'm puzzled. Is your clipping switch in the centre off position giving a setting without any kind of diodes in the feedback? Or, is there a set of clippers always in circuit so they are effective with the switch off?
In the off position (no diodes), the output volume would be very high compared to the plain diode selection.
Is this really a question about gain or output volume level?
Title: Re: More drive from a Zendrive?
Post by: antonis on October 02, 2021, 03:13:01 PM
Quote from: anotherjim on October 02, 2021, 06:26:22 AM
Is this really a question about gain or output volume level?

Quite rife puzzlement.. :icon_wink: :icon_wink:
Title: Re: More drive from a Zendrive?
Post by: Fancy Lime on October 02, 2021, 05:26:41 PM
For more nuts, I would suggest a HiFi enthusiast forum or maybe one of the general guitar gear forums :icon_wink:

Seriously though, I am not sure how to convert 8% more nuts to gain factor or decibels. Our ears are very non-linear when it comes to judging volume or distortion level. Generally, twice the gain factor, or 6db more sounds like "just a bit more". It you want it to sound like "twice as much", you'll want 10 times or 20db more gain. So your original post sounds to me like doubling the gain is what you probably want after all. If you don't have a 1M pot, you can also decrease R3 to 470 Ohm and increase C3 to 220nF.

HTH,
Andy
Title: Re: More drive from a Zendrive?
Post by: Rob Strand on October 02, 2021, 07:13:42 PM
QuoteSo your original post sounds to me like doubling the gain is what you probably want after all. If you don't have a 1M pot, you can also decrease R3 to 470 Ohm and increase C3 to 220nF.
Increasing the caps is a good idea since decreasing the resistor won't end-up doing much if the cap is too small.  Who knows maybe increasing the cap alone would do what the OP wants!
Title: Re: More drive from a Zendrive?
Post by: Steben on October 03, 2021, 02:10:31 PM
Ooooooooooooooooooooooooor.......

You want a distortion rather than an overdrive...
Zendrive is a beefed up tube screamer schematic wise. This means it will never get that hard clipped hairy edge a distortion has.

We all know EQ is more important than anything else, but perhaps this is a perfect example of what "transfer curve desire" is.
I can be completely wrong of course, but it is what I thought about when I read "8% nuts"

Why not change the clipping to LED and LED + BAT41. That might give "oomph" already.

Or feed 18V and change to Zener diodes.