Question about offset bias trimpot Forum Vibe

[Michael2]

 Okay, I'm confused...on this page it says I have to place a 250k trimpot to adjust the offset bias: http://www.classicamplification.net/fv/files/fv_mod_02.htm but here it says I have to place a 100k trimpot: http://www.classicamplification.net/fv/files/fv_rh_02.htm . Which layout is correct and what to do with the resistors next to it? I have a 5.0 version and I have no clue. Help would be appreciated.

[Rob Strand]

From what I can see the intent is the same.    The one using the 100k pot has a narrower range of adjustment, which will make it easier to adjust.   The text says

   "(uses 100k trimmer, 4k7 upper limit, and 47k lower limit resistors)"

(Probably not really important but notices 100k + 4.7k + 47k  is in the ball park of 250k.)

[PRR]

> Which layout is correct

Both.

Reading the text, one seems to be an improved version of the other. I'd use RedHouse Bias Offset Mod tweak. That said, I do not think JC's plan (the other) is "wrong".

(Rob's fingers are faster)

[Michael2]

Thanks for the swift replies!

I think I understand but I'm still a noob. I have a 250k trimpot laying around, if I solder it in do I have to do something with the resistors next to it? This is the V5.0 layout that I used:
http://www.classicamplification.net/fv/files/fv5_mod_07.htm

[Rob Strand]

if I solder it in do I have to do something with the resistors next to it?

The 250k version has the shorts/links.

(Rob's fingers are faster)

Don't worry, it's happens to me too. 

[Michael2]

Awesome! Thanks Rob!

[PRR]

Are you now able to trim the lamp brightness (trem depth) to a good setting?

These other mods remind me of lipsticking a pig. A fine pig, and yes the offset is a little fiddly, and yes it could be restricted so the sweet-spot is larger.... but is it a real problem?

This has the schematic and other mods --
http://guitar-gear.ru/forum/index.php?app=core&module=attach&section=attach&attach_id=10247

[Michael2]

@PRR:
I don't know yet, I hope it gives some more depth. For now the wobble is too weak to my taste...

I love the way you paraphrase the mods, and I think too that most of them are hardly making a lot of difference. The unity gain mod was very welcome though. I hope this one too. The rest I leave alone.

[Michael2]

Update: it works great. I have to admit it gives more adjustability but the effect is subtle.

So, I needed more wobble and suddenly realized that the bulb cap Musikding supplied with the kit was a simple wine bottle cap (unfortunately no booze with it!) I put some alu foil in the bottom. And the other day, when I was building the effect I was in doubt how to point the photo cells to the bulb and think I read somewhere that they needed to be placed in an angle (don't ask me where). Now I decided to bent them flat and voila, the sound is intense and deep. I'm very happy with it.