madbeanpedals::forum

Projects => VFE Projects => Topic started by: blearyeyes on February 16, 2024, 05:05:50 AM

Title: ALPHA DOG Question. [ANSWERED]
Post by: blearyeyes on February 16, 2024, 05:05:50 AM
Will subbing R2 and R3 with 2M instead of 2.2M create any issue?
I looks like a voltage divider to provide bias to the circuit?

Title: Re: ALPHA DOG Question.
Post by: mauman on February 16, 2024, 10:14:59 AM
No issue at all, just a tiny reduction in input impedance that you won't notice.
Title: Re: ALPHA DOG Question.
Post by: blearyeyes on February 16, 2024, 10:48:45 AM
Ah.. I didn’t think about that. Interesting. Somewhere I heard the input impedance is a conglomerate of sorts so I see how that would affect it. I went ahead and made a couple of teepees. Now the LM308 I have, from who knows where/when, is not acting like the YouTube video resistance test would suggest. I’ll start testing the pedal tomorrow. I ordered a handful of OP07s just in case or for future Rat type things.

Thanks for the information/confirmation..
Title: Re: ALPHA DOG Question. [ANSWERED]
Post by: derevaun on February 16, 2024, 09:14:51 PM
FWIW, I found some variation among legit LM308s WRT resistances between pins, using Chromesphere's test. I think the most important ones are that pin 5 isn't connected, so no resistance with any other pins, and a few megaohms between 1 and 8, although there's a range with mine. Two tests that are more dispositive are that it sounds harsh(er) with the 30pF cap removed, and the chip itself draws below 400 microAmps. In any case, I have a fake one (from Jameco) that is my absolute favorite in a DOD250  :P
Title: Re: ALPHA DOG Question. [ANSWERED]
Post by: blearyeyes on February 17, 2024, 07:18:03 AM
I finished it today and it is working fine and sounds great. I was never much of a Rat lover but the Alpha Dog is a different animal. 😜