OGBip-2 overdrive on 2n5088 bipolar transistor

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Vitallka
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Post by Vitallka »

Hello. It's me again with my guitar pedal ideas. This time it is a pedal on 2n5088 transistors and it is something between distortion and overdrive.

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ogbip-2.GIF

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Lukasen
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Post by Lukasen »

I like your circuit design and how you use Zener diodes to soften the sound. It's quite original.
I think those 2N5088 transistors give it a good spark (I think they have higher beta, min. 300 according to the datasheet).

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Manfred
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Post by Manfred »

Thanks for sharing, I like the sounds. :thumbsup

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mauman
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Post by mauman »

Sounds good! Your bias plan looks interesting with the two 1N4007 diodes. So the bias voltage will be about 1.2 V?

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Vitallka
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Post by Vitallka »

Yes, the bias from two diodes is 1.2V. I tried the bias from the red LED (1.8V) but then the signal starts to lock and the sound is more fuzz than overdrive

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plush
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Post by plush »

I'd bootstrap vt6 to increase it's input impedance.

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Post by mauman »

plush wrote: 10 Feb 2024, 10:31 I'd bootstrap vt6 to increase it's input impedance.
How would you select the value for a bootstrap cap here? Is there a rule of thumb, or a formula, or is it just by ear? I've built circuits that use them, but have never added one.

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Post by plush »

mauman wrote: 10 Feb 2024, 15:08 How would you select the value for a bootstrap cap here?
Consider this cap as a piece of low pass filter together with the resistors forming the bias network. Calculate it's value a bit past desired cutoff frequency. That's all.

Or you could use Pete Cornish buffer instead, where everything is done already.

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Vitallka
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Post by Vitallka »

I don't see the need to increase the input impedance, because the treble level will have to be reduced in the next stage. After all, not the entire range of sound frequencies is pleasant for our ears, especially when the signal is overloaded

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Post by plush »

Vitallka wrote: 10 Feb 2024, 17:22 I don't see the need to increase the input impedance, because the treble level will have to be reduced in the next stage. After all, not the entire range of sound frequencies is pleasant for our ears, especially when the signal is overloaded
True.
But when one starts thinking about his design as of the product, then he may want to keep the signal integrity and filter unneeded on the next stage, so that the product performs the same with pretty much every source impedance.

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Vitallka
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Post by Vitallka »

If we take the active resistance of the pickup as 10K, then the simulator shows the following picture. It seems to me that 5KHz is quite enough to pass the entire spectrum of electric guitar sound.
If someone wishes, he can make changes to the scheme according to his own preferences.
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Post by plush »

Fair enough.

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