Tim voltage divider

blaise · Post by **blaise** » 09 May 2023, 22:00

Hi,

I still am trying to understand the schematic and layout of the Tim from http://dirtboxlayouts.blogspot.com/2022 ... e-tim.html or http://effectslayouts.com/wp-content/up ... ld-Doc.pdf.

It seems to me that R9-R10 (or in the vero layout H-N14 and K-N7) is a voltage divider providing 4.5V. Since we feed 9V, shouldn't R9 and R10 be equal in order to get 4.5V?

plush · Post by **plush** » 10 May 2023, 05:04

Yes, but tim is not biased to 4.5v.

blaise · Post by **blaise** » 10 May 2023, 12:11

That would make sense, but the schematic on this old thread seems to indicate a 4.5V biais. Any idea which is correct?
viewtopic.php?p=161586#p161586

mauman · Post by **mauman** » 10 May 2023, 14:54

Allowing for different versions across time, the best I can tell, Tim and Timmy were biased slightly differently. The schematic corrected by Paul in the Tim thread you linked shows a 4.5v bias (at least, at that time.) The Timmys I have seen all use a 4.9V bias (8.2k/10k divider pair.) The Tim vero layout you linked is from a schematic "based on the Tim", not a clone, and it has the Timmy (not Tim) voltage divider pair and 4.9V bias. But in the end, there's not a big difference between 4.5 and 4.9V.

blaise · Post by **blaise** » 10 May 2023, 15:45

mauman wrote: ↑10 May 2023, 14:54 Allowing for different versions across time, the best I can tell, Tim and Timmy were biased slightly differently. The schematic corrected by Paul in the Tim thread you linked shows a 4.5v bias (at least, at that time.) The Timmys I have seen all use a 4.9V bias (8.2k/10k divider pair.) The Tim vero layout you linked is from a schematic "based on the Tim", not a clone, and it has the Timmy (not Tim) voltage divider pair and 4.9V bias. But in the end, there's not a big difference between 4.5 and 4.9V.

Time for experimenting with the bias voltage then. I quickly compared the Vero layout and the schematic and they seem identical. I need to double check the part with the clipping diodes.

paulc · Post by **paulc** » 11 May 2023, 03:22

Hi Blaise, That 8k2/10k divider really doesn't matter. That was done to try and eke out some extra headroom out of the 2nd stage when a battery was running low. It's always been there for both Tim & Timmy pedals so the posted schematic is wrong. With a healthy pwr supply you will be hard pressed to hear any difference honestly.

Paul C