Marshall MS-2 into a boost/overdrive pedal! HELP!

[Kinkless Tetrode 66]

This is my first stompbox build!  I have worked with tube amps before, but never built one of those floor boxes!  I would like to know wheter you guys think it would be a good idea to use the speaker leads as the "output" or just to use the headphone out?  I am also looking for a way rewire the 3 position potentiometer (off/clean/od) into a 2 way switch which would eliminate the off, leave me with a clean/od toggle.  Next question would be how would I wire this pedal- I have a DPTP switch and plan to use the MS-2's light.  Could someone give me some advice on the project or show me a diagram of how to get this wired up?  Thanks.

[Kinkless Tetrode 66]

Any ideas on how to get that 3 position potentiometer (off/clean/od) turned into a 2 way toggle switch (clean/od)?  What is a "normal" line level, how much resistance do you think I need to add for the "speaker output" idea?  Thanks! 

[Mike Burgundy]

Slow down, take a breath. I applaud your enthusiasm, but think for a moment about how you want to extract information from others - you need to feed them some (and clearl info, too) first.
You'll get more answers if people don't have to dig around for what an MS2 is, and a schematic would help.
Speaker outs, headphone outs, line outs and guitar-level outs are all very different things. Different impedances, different levels. Sometimes you can cheat with that, sometimes you can't.
A potentiometer is also totally different from a switch - I reckon you have a 3-position rotary switch, not a potentiometer in there. Schematic, again.

[Kinkless Tetrode 66]

An MS2 is a 1 watt micro solid state amp, built by Marshall, using only a volume, tone and a 3 position rotary switch running on a 9V battery.  I also has a headphone output, and a 0.8w speaker.  Here is a picture and schematic:


What I would like to know is, how to rewire the 3 position rotary switch into a 2 way toggle switch (clean/od)?  And how could I wire this true bypass using a DPTP switch, using the amp's led light.  I would also like to know whether I should use the headphone out, or the speaker out.  Thanks.

[Mike Burgundy]

switch: replace the 3-pos rotary (two switches in one) with a regular SPDT (Single Pole Double Throw - one switch with two possible options or "trows") for the *upper* half of the switch, connect one outer pole to the OD connection, the other outer pole to the ON connection, and the center to the junction of the following 180k resitor and 0.01uF cap. That's a clean/od switch.
Hardwire the power for always ON (so remove and ignore the lower switch) or replace the switch with an SPST to switch power off when not in use. Make sure the circuit is powered when in use, even in bypass. Switching power on and off in conjuction with bypass will yield undesirable results.
Disconnect the LED/resistor combo, you'll need that for bypass switching.
Looking at the schematic, the speaker out and headphone out are *the same thing* - have a look. No other circuitry involved, the jack and speaker are parallel - it is a switching jack (the little arrow thingy indicates that) so plugging in a headphone disconnects the speaker. You can simply use that jack.
I'd include an output control of some sort - say a 100k pot. No idea how well this chip copes with higher impedances, or how loud it's gonna be. Trial and error time.
Bypass switching is now the regular scheme, such as : https://www.generalguitargadgets.com/tech-pages/51-switching-and-wiring/33-many-bypass-switching-options

[Kinkless Tetrode 66]

Thanks for your reply!  I have to be honest, I still do not fully understand of how to go about how to go about with the clean/od switch and power on hardwire...  Otherwise, I have disconnected the LED (jumper wire is now in place) and have added a 100k output pot control.  Thank you for the help, also was just wondering, what would could happen to the chip at higher impedances?

[bluebunny]

Looking at the schematic, the speaker out and headphone out are *the same thing* - have a look.

I built this little amp from this schematic.  It has a mistake in it.    The speaker output should come before the 510K resistor.  (Only the headphone output should be after it.)  And I built mine with two switches: one for power and one for OD on/off.

[bluebunny]

Hmmm... is there an echo in here??

This thread is posted twice.  And I answered it twice...

I'm sure that's a sign of, um, something...