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Let's Get Technical => Schematics & Modifications (mods) => Topic started by: trader144 on December 16, 2014, 06:34:04 AM

Title: Adjusting gain and distortion
Post by: trader144 on December 16, 2014, 06:34:04 AM
This is pretty technical so thought I would open up a seperate discussion.

I have an original MP-1 with noise mod, MDRT and Mullard tubes.

I want to maximize the gain, clarity and 3D from the Mullards on tube distortion while dialing back the distortion so that I hear the complete fullness of the tubes and then inject small amounts of distortion even if I have to buy a distortion pedal.

So I want to push OD1 and OD2 and the master hard to hear the tubes sweating and bringing out their full potential with only a little overdrive even at 8 levels, to the extent possible.

Should I start by replacing T2 and T1 with a larger value?
Or should I put a pot in R26?

Or should I try a less powerful U4 op amp?

David
Title: Re: Adjusting gain and distortion
Post by: trader144 on December 16, 2014, 06:35:45 AM
What exactly does the OD1 and OD2 buttons adjust (what component)?

I checked the schematics but couldn't find what they change.
Title: Re: Adjusting gain and distortion
Post by: rnolan on December 16, 2014, 07:05:13 AM
MJMP has put up a couple of posts re how the OD circuits work and what the OD1/2 settings effect and also the 2 trim pots. also others (IIRC El has a bit to say) re how OD1 and OD2 work together (Els famous OD2 = 0 LOL). My main take on the discussion is OD1 and OD2 do different things (and have different eq etc), so understanding that will help you work out what you want. (hence you question no doubt), so dig around here.
MJMP and others can talk to the components... :wave:
Title: Re: Adjusting gain and distortion
Post by: MarshallJMP on December 16, 2014, 11:20:57 AM
Don't see why you should change the trimpots since you want to lower the OD's?

The master is after the tubes so that won't help much.

Replacing the opamp won't change anything since all opamps work in the same way.There is no lo gain opamp,most opamps have an open gain loop of 100.000 which is reduced by the feedback resistor.

http://en.wikipedia.org/wiki/Operational_amplifier