Trim pot adjustment

[d1469d]

Can some one please tell me how to adjust the trim pots for gain ? And where they are located? I have the first version. I think they are set a little low. It is very quit and I am thinking they have been turned down from the previous owner. The preamp has JJ ecc83s tubes in it that are newer tubes.  I owned one of these when they first came out. I remember the preamp having a lot more gain. Thanks

[d1469d]

Never mind. I got it figured out.

[rnolan]

Hey d1469d, what was the issue ??

[d1469d]

The trim pots for the gain were turned down. I turned them up a bit. I just got the preamp last week off eBay. It sounded a little week from what I remembered it being. It came with brand new tubes.JJ ec83s I think. I new it had more gain than what I was getting out of it. With a little research and asjusting, I think I have it just where I want it. This thing kicks ass. I am taking it to band rehersal today. We play a bunch of 80's and some funky blues so I am excited about all the different tones I can get.

[rnolan]

Excellent  :thumb-up: , there is a post (here somewhere) from MJMP re setting the trim pots but requires a scope.  Do you have a MP1 or MP2 ?, they both kick ass, enjoy (IMHO the ADA MP1/2 preamps are the best ever made, the tone cloners are getting better but....I'm sorry, real is better).  The JJs are a very good fit for ADA preamps particularly the MP1, I prefer the Mullard re-issues in the MP2

[GuitarBuilder]

A little late, but these might help:

[d1469d]

I have the MP 1. It sounded great at rehearsal cranked. Thanks for the photo. I turned the correct ones. That is a relief. I was just going by what I read and by listening to the preamp. I could not  really see much in other pictures I seen. Do you guys have yours modified? Mine is very quit even with the trim pots turned up and I have lots of gain. I was told from the original owner no mods were done to it. I am running a noise gate off my Rocktron Replifex which helps.

[rnolan]

Cool, glad it's working well (ADA heaven).  Seems the MP1 noise mods are popular, particularly with very high gain players so it depends a bit on how you play, the MDRT transformer upgrade is also a very good idea regardless.

[RandallRG]

Man I just "Tweaked" my T/Pots & HOLY CRAP....What a difference! Especially in my Chorus it sounds I-N-S-A-N-E on the S.S. 

[trader144]

rnolan,

What is the benefit of a MDRT transformer?

Is it worth doing with a stock MP-1?

My sound guys are complaining about noise, so the noise mod is in my near future.

David

[jarrodthebobo]

What exactly does adjusting the OD2 trimpot do? I know the OD1 trimpot adjusts the amount of signal hitting the first gain stage but other than that I was told never to touch any of the other trimpots...Especially OD2

[rnolan]

rnolan,
What is the benefit of a MDRT transformer?
Is it worth doing with a stock MP-1?
My sound guys are complaining about noise, so the noise mod is in my near future.
David

Hey David, check (http://www.marshalljmpmodshop.net/miscellaneous_parts_and_replacement_tubes.htm).  The original transformer was not so great, Machinator designed a new one (well it looks like 2 in one ?) apart from being 240v/115v friendly it helps reduce noise and gives better performance.  It's a very worthwhile mod though not cheap (I assume because they are custom made in small numbers).  If I still had a MP1 I'd do the noise mods and MDRT
Cheers Richard

[rnolan]

What exactly does adjusting the OD2 trimpot do? I know the OD1 trimpot adjusts the amount of signal hitting the first gain stage but other than that I was told never to touch any of the other trimpots...Especially OD2

Hey Jarrod, check other threads here (search on OD2 ?), MJMP posted advice re trim pots in a few places.  IIRC it adjusts the gain in the OD2 circuit.

[El Chiguete]

Man I just "Tweaked" my T/Pots & HOLY CRAP....What a difference! Especially in my Chorus it sounds I-N-S-A-N-E on the S.S. 

Can you please comment more on this?