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DIY Stompboxes => Building your own stompbox => Topic started by: Joe on June 14, 2015, 10:14:14 PM

Title: gain stage idea
Post by: Joe on June 14, 2015, 10:14:14 PM
Been playing with this on the breadboard, seems to have potential. As shown there can be a diode clamp before the volume control for an overdrive, or leave them out for a booster. (The trimpot is adjusted for 4.5v at Q2's collector.) A resistor can be placed between Q1's emitter and Q2's collector to clean things up if desired. Something fun to mess around with.

(http://joe.csoft.net/keep/gain_stage_idea1.png)
(http://joe.csoft.net/keep/gain_stage_idea2.png)
Title: Re: gain stage idea
Post by: Mark Hammer on June 15, 2015, 09:24:32 AM
Thanks for that, and welcome back, Joe.  We kinda missed you.  :icon_smile:
Title: Re: gain stage idea
Post by: nocentelli on June 16, 2015, 01:47:24 AM
Sounds great, some lovely overdrive at higher gain even without diodes on the output. I've got a fair bit of squealing oscillation at maximum gain (using a BC179C and BC109C) will try a limiting resistor in line with the gain pot tonight. Many thanks!
Title: Re: gain stage idea
Post by: tca on June 16, 2015, 04:20:09 AM
The wave form reminds me of some DC coupled experiments I've done with a bootstrap cap. The way you do it, as an old op-amp with a pair of BJT, can be turned into a simple class A amplifier also.

(http://sound.westhost.com/p36-fig3.gif)

Cheers.
Title: Re: gain stage idea
Post by: DDD on June 16, 2015, 02:37:20 PM
So, what's new/interesting/special in the present schematic (except of DC coupling)?