Marshall MS-2 as distortion pedal questions.

[Black Mark UK]

Hi guys, this is my first post. A very interesting and informative forum you have here 🙂

I've just bought my first gutar in years (a Les Paul Studio) and as money is tight just now I need to go down the DIY route. I'm familiar with basic electronics so I thought I'd give it a shot.

I currently have a Marshall MS-2R, which I am trying to convert into a fairly basic distortion pedal (my first effects pedal build).

So far I have removed the headphone section and connected a jack to where the speaker was (need to add a couple of resistors to bring it down to line level though). It's working fine as is, however there are a few final things I need to achieve before I can get it working as I would like it to.

I was wondering if anyone with knowledge on this marshall might be able to help me out with the following:-

1. Without the power switched on to the unit, there is no "through" signal. How would I achieve this? Is it simply a case of running a wire from the positive on the input jack to the corresponding output jack terminal?

2. I want to get rid of the clean channel option, is it possible to wire it so that it is switched either off or overdrive? Any suggestions how.


Once it's up and running I'll post a pic or two for anyone else's future reference, thanks in advance, I appreciate any help. 🙂

 

[Black Mark UK]

Ok I've tried experimenting with removing the rotary switch and connecting various points in an attempt to get it to power to overdrive, but all I can come up with is powering the unit, no output distorted or clean.
Here's a link to the schematic found elsewhere on this forum:

MS-2 Schematic

Can anyone understand from that if what I want to do is possible and advise me how to do it?

Otherwise, I'll just have to scrap the project as I don't have the knowledge to do it myself. Thanks in advance.

 

[will_raymo2000]

You need to find where the preamp feeds into the power amp section (I'm guessing the MS2 is a small amp - just looked it up on google.. very small!!)

Have you tried using the headphone out or is that not at the right level?


EDIT: http://www.diyguitarist.com/StompboxStuff.htm <- the top link has a list of pedals with links to schematics/Parts lists. A possibility if you want to go the complete DIY route - Most pedals cost about £2/3 in components from rapidonline.com and ebay

 

[Black Mark UK]

Through some tinkering about about I found where the 2 contacts for clean and overdrive were on the pcb. I've now hardwired it into permanent overdrive and have a SPST wired in to switch the power on and off. So that part at least is now achieved 🙂

The headphone socket has been removed now, I've attached a jack socket to the speaker out, it's a little noisy, but I can bring this down to live level once I get hold of some resistors.

Next step is to experiment with trying to play through it when power is off. I presume this could be achieved by connecting a wire from input jack to output jack? Anyone?

If this works, it'll do my confidence the world of good (not to mention save me a lot of cash on equipment). Happy days 🙂

 

[will_raymo2000]

Possibly wire in a hard switch DPDT maybe so that one side plays with FX and the other side goes straight through to the output jack?

Or move the circuitry into a maplin project box and put a proper stomp pedal switch on it?

 

[Black Mark UK]

Possibly wire in a hard switch DPDT maybe so that one side plays with FX and the other side goes straight through to the output jack?

Or move the circuitry into a maplin project box and put a proper stomp pedal switch on it?

I messed about with it a bit and if I use a SPDT footswitch (or one side of a DPDT) I'll have done what I set out to do.

The plan is to rehouse the circuit in a suitable box.

Should be able to get to Maplin on thursday for bits to complete it.
Hopefully I'll have pictures of the finished article to post up by the weekend.

Thanks for the link btw, some interesting projects on there.

 

[Minion]

If you want to bypass the Headphone section and a get a better signal for Pedal use you can take the Preamp out on the 3rd lug of the Volume pot , that is the output from the preamp which is right before it goes into the power amp ...

It will be a lot quieter than the headphone output ....

Cheers

 

[Black Mark UK]

If you want to bypass the Headphone section and a get a better signal for Pedal use you can take the Preamp out on the 3rd lug of the Volume pot , that is the output from the preamp which is right before it goes into the power amp ...

It will be a lot quieter than the headphone output ....

Cheers

That's handy to know, I'lll bear that in mind, thanks.

I'm currently using the speaker output as the headphone output was too quiet. But I think I know how to sort that and bring it down to line level using a couple of resistors.

I'm taking a couple of days off from the project until I can get to the electronics shop and buy a switch, will post an update then.

 

[Mikestrat6]

If you want to bypass the Headphone section and a get a better signal for Pedal use you can take the Preamp out on the 3rd lug of the Volume pot , that is the output from the preamp which is right before it goes into the power amp ...

It will be a lot quieter than the headphone output ....

Cheers

I realize it's an old thread, but should someone come across it I thought it'd be worth mentioning that (at least theoretically) you might consider cutting the trace to pin 2 and moving the switch to after the decoupling cap in order to protect whatever comes after it from seeing any DC potential. Also, you might want a buffer to drop the output impedance. Lastly, consider tapping the bypass before the input resistor.