small mods to make an Express pedal friendly

Express, Liverpool, Rocket, Dirty Little Monster, etc.

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johndandry
Posts: 84
Joined: Mon Dec 19, 2011 8:55 pm

small mods to make an Express pedal friendly

Post by johndandry »

Hi, Im in the process of building an Express and I know that these amps are not too pedal friendly due to how much gain they have and are designed to use the volume control on the guitar to go from OD to clean BUT.. i’d like to be able to use OD pedals with it when I just can’t get the volume up with my band.
I also like to have the option to go back to stock. So this is what i was thinking and would like to hear your thoughts. I’d like to put and switch to remove the cathode cap across the 2.7k on V2 and possibly the one on V1. Also putting a pot as a variable resistor where the 150k to ground goes between V2a and V2b. I use to have a Dr. Z Rx head and it had switches for two of the cathode caps and it was very useful. I’d love to hear any thoughts and/ or suggestions. Thanks!
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rooster
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Re: small mods to make an Express pedal friendly

Post by rooster »

The sky is the limit I suppose. But the one thing you haven't mentioned - and something I think is a very good mod - is a 500K volume pot. Experiment, try the 1meg and the 500K (audio taper) pots and see what you think. I know some guys are thinking, 'oh man, I need all of this 1meg load to really appreciate this high-gain Express amp!' I don't think this is true. (You will never play this amp turned all the way up.) There are 3 gain stages, not 2 like you will find in a (Class AB) Fender BF circuit or a stock Marshall Plexi/Bassman 5F6A (cathode followers don't count). A 500K pot drives the Express circuit just fine. In fact, it gives you more control over the front end of the amp, and that will help with your pedals.

Also, if you do run the 500K way, change your bright switch caps to 50pf and 100pf (and place a 10pf cap permanently across the volume pot) . The stock values are maybe good for the 1meg pot but overkill with the 500K. Have fun.
Most people stall out when fixing a mistake that they've made. Why?
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jjman
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Re: small mods to make an Express pedal friendly

Post by jjman »

If you have the amp set low enough to not be clipping, it is already in pedal-friendly mode. The un-friendliness occurs if the preamp is clipping somewhere and certain effects are in the front and not a loop. In this case the loop has to be after the 3rd preamp stage since that clips. The 1st two probably don’t.
If it says "Vintage" on it, -it isn't.
Groove1
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Joined: Sat Dec 05, 2009 12:37 pm
Location: 230V, Germany

Re: small mods to make an Express pedal friendly

Post by Groove1 »

Thanks rooster for this post.
Maybe this is the solution for my problem with a little to much bass gain at the guitar volume pot neck humbucker from 8 to 10. I made a measurement at the bass potentiometer in my Express build and it has 1.117 M Log. I will try to order a new one with more exact values.

Groove1
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M Fowler
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Re: small mods to make an Express pedal friendly

Post by M Fowler »

There are a lot of Express schematics to choose from that have altered the tone stack and other things to get a different flavor or animal out of the Express.

I don't recall any effect pedal problems with my customers only which attenuater to use.

Mark
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