not enough gain, maybe?

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not enough gain, maybe?

Postby jerrodw » 02 Aug 2014, 20:58

Hi everyone.

I have decided to make a go at building effects and so I went with what seems like a good starter kit.

http://www.generalguitargadgets.com/eff ... ass/adamu/

Finished up last night with mostly good results. Everything seems to be working great. No noise and maxed volume seems to offer quite the boost but with the gain dimed I cant get anywhere near the level of distortion in the sound clip linked above. Right now a maxed gain gives me a mildly broken up tube kind of sound. It actually sounds pretty nice but obviously not the level of gain I was hoping for.

Here is a link to the circuit - http://www.generalguitargadgets.com/pdf ... ass_sc.pdf

I put a 47k resistor at R6 for more gain per GGG. Any advice on troubleshooting would be greatly appreciated!!
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Re: not enough gain, maybe?

Postby Nocentelli » 02 Aug 2014, 21:08

And it's definitely 1M in the feedback loop?
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Re: not enough gain, maybe?

Postby jerrodw » 02 Aug 2014, 22:22

Sorry but I'm very new to this and that includes schematic knowledge. I assume you mean R8? If so then yes it is a 1M resistor in there.
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Re: not enough gain, maybe?

Postby Nocentelli » 02 Aug 2014, 22:52

The gain is set by varying the resistance to ground from the cap off the inverting output (-). The samller the reistance, the higher the gain. The gain is determined by the 1 + (1M ÷ (47k + up to 500k from the pot)). As the pot is reduced in size by turning it, the gain goes up from 1M ÷ 547k = gain of roughly x3, to 1 + 1M ÷ (47k + 0k) = gain of x 21 ish - that should be plenty to drive the diodes into clipping, with some of the faux sustain that yields. Check the input resistor (R5) is 10k, not 100k or 1M or 10M - That would bring the gain right down. Is the cap connected to the gain pot definitely 1u? However, with the 4k7 original resistor in place, the max gain is 10x bigger at 1M ÷ 4k7 = 200, maybe reduce the 47k to 22k or 10k, and see if you prefer the higher gain.
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Re: not enough gain, maybe?

Postby DrNomis » 03 Aug 2014, 12:05

To get more gain at maximum gain settings, you can try changing R6 (4k7) to something like 2k2 or maybe 1k5, hope that helps...... :thumbsup


Or maybe change R8 (1M) to something like 1M5 or 2M2...... :thumbsup
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Re: not enough gain, maybe?

Postby jerrodw » 03 Aug 2014, 16:55

Thanks for the help guys! I think I will try swapping R6. Now after my first pedal build I get to do my first pedal disassemble :)
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Re: not enough gain, maybe?

Postby jerrodw » 03 Aug 2014, 19:48

Putting a 47k at R6 did the trick, thanks again fellas!
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Re: not enough gain, maybe?

Postby Nocentelli » 03 Aug 2014, 20:47

jerrodw wrote:I put a 47k resistor at R6 for more gain per GGG. Any advice on troubleshooting would be greatly appreciated!!


jerrodw wrote:Putting a 47k at R6 did the trick, thanks again fellas!


Hang on, I thought it was already 47k? :scratch:

The original DOD 250 R6 is 4k7, which would give more gain at maximum than 47k.
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Re: not enough gain, maybe?

Postby jerrodw » 04 Aug 2014, 05:37

It was, that was a typo :oops:

I meant to say I put in the 4.7k
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