Can someone explain the trimpots purpose ?

[Batsinthebelltower]

Hey guys

I just read a trimpot post in this section and it got me wondering ;

On stock ADA what are the trimpots for ? I notice they are located on the main board ; Some people say "more gain" , by gain do you mean overall unit volume, or more distortion on the OD1 & OD2 settings?  :-\

On the 3tm , i have adjusted the trimpots on the tubeboard ; sat one night with it all taken apart, chugging my favourite distortion patch and minutely adjusting the 2 pots ; from what i could tell they were a bass adjustment and high /highmid adjustment. Got it setup pretty neat , and was reassured when i heard it also improved my other patches aswell. Happy with the settings !  :thumb-up:

PS: Dont lean over your opened ada while wearing a long metal necklace , that part wasnt as fun  :banana-trip:

[rnolan]

Hey Bats, you got a zapp  :nono: thanks for the warning and noted :thumb-up: , there are a few trim pots (see one of sparkers posts ?), obviously the OD1 and OD2 are the hot favs to play with.  I've never tinkered with them (haven't had/felt the need) but others have (for various reasons).  IIRC the OD1 trim pot adjusts the volume prior to V1, and OD2 pot what gets to V2 (there is a post where MJMP clarifies this better however)
There are also a few other posts on the topic and in one MJMP posted a guide (needs a scope) to setting them, try a search on trim pots (or similar).  But hey, if it's sounding good and you're happy....

[MarshallJMP]

T2,if you set it higher you will have more OD1 gain,so more distortion in the tube voicing but also a louder clean volume in the SS voicing.

T1,if you set it higher you will get more OD2 gain,works only in the tube voicing and doesn't affect the SS voicing.

Leave the other 2 pots like they are set at the factory.

[RandallRG]

Marshall (or anyone that knows?) I know there are a few Trimpots close to the Tubes to the right of them & another one by itself just about in the middle of the board. Can you tell me which pot affects what so if I wanted to adjust them I know what Pot does what. I just wanted to see if any of them were "Tweaked" a bit if it would make a difference or not? Thanks!  :metal:.

[MarshallJMP]

there is a post with a pic of all the trimpots.Do a search for it.

[RandallRG]

there is a post with a pic of all the trimpots.Do a search for it.

Found It...Thanks!
Adjusted them... :metal:

[trader144]

When looking at the schematic it seems like the trimpots control the amount of resistance in the signal that is going to the grid of V1a and V2a.

So it seems to me that the trimpots are less of a gain control and more for optimizing the signal to be amplified, which indirectly does affect gain.

If we truly wanted to vary the gain within a tube,
wouldn't we do something with the cathode, filament, or plate voltage?

Just wondering.

[trader144]

Nevermind I get it now.
The trimpots reduce the size of the guitar sine wave signal going into the tube grid so the peaks have less of a chance of getting clipped when amplified inside the tube.

[rnolan]

Hey David, well the guitar signal isn't a sine wave but yes the trim pots allow all or less or nothing of it through (is my understanding), they play a part in how hard the tubes are driven, anything not crystal clean is being clipped in the tube (that's kind of the point/job of MP1/2), they help adjust how much (so I suspect to help adjust for different tube gains).