How hard would it be to bypass the buffers in a Boss DM2-W?

H

HamishR

Well-known member
I can't imagine it would be easy. I have a Boss DM2-W which I really like except that whenever I plug it in it really affects my signal. I can hear that the guitar sound I have gone to such lengths to make as good sounding as it can be has lost punch as soon as the DM2-W gets involved. I like some Boss pedals, especially their delays, but the tone-suck is real in my set-up.

I like to be minimal and use very few FX at any one time. My board is tiny compared to a lot I see here! Usually it's four pedals tops with one being a tuner.

If bypassing the buffers is what it takes then I'm happy to rehouse if necessary (not fussed about the Boss "silent switching"). Is it the buffers which are making the difference? Would this be a waste of time? Has anyone tried this?
 
I haven't seen the DM-2W but if it's anything like the other Waza series the easiest thing to do (if you plan to rehouse it) is force the switching transistors on and use some other form of true bypass around the entire circuit.

The ones I have traced use a discrete transistor based flip-flop along with JFET switches in the signal path.

This is from the BD-2W, so don't go hacking away at your pedal using these RefDes... but in this example here's a couple of possible solutions.

Remove D3.
Remove D10.
Remove D11, pull the gate of Q19 low.

This forces the switching transistors into Active mode, regardless of what the state of the flip-flop circuit.

Alternatively you could tackle it from the flip-flop circuit by modifying it to start up in the active state, possibly by jumpering Q21 C-E.
This would also light the onboard LED indicator, where forcing the switching transistors on would not.

You'd need to trace the DM-2W to see exactly what's going on and ensure they're not doing something like killing the BBD clock in bypass or anything funny like that.


Input Buffer
1712927556682.png


Output Buffer
1712927844228.png


Flip-Flop
1712927501075.png
 
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Is the concern just the sound of the buffer in bypass?

If it's just the bypass - Could you throw a foot switch and 4 jacks in a box and make kind of a true bypass effects-loop box?
 
juice886 said:
And I'd add that even the standard boss buffer with an input jfet and output bjt stage is a very decent solution.
Click to expand...
It is! But I'm annoying and pedantic and a little too enthusiastic with looking for the best possible solutions to a problem.
 
juice886 said:
And I'd add that even the standard boss buffer with an input jfet and output bjt stage is a very decent solution.
Click to expand...
Unlike the original Ibanez pedals in the early-mid 80s. Using one bypassed was about the same as moving from the high to low gain input on your amp- you lost gain, and high end.
 
Well I can't say for sure it's the buffers I don't like because I've never heard a DM2-W without them. But simply having the pedal in my very short signal chain affects the dynamics and punch significantly enough to be annoying. Other delays like the TC Flashbacks, anything by UA, Strymon etc don't do this. In fact the inexpensive TCs sound fantastic and may even improve the punch slightly!

All Boss pedals seem to deaden the sound somewhat. I had a DD500 for a while which was a great unit - except it deadened to tone a bit. I like the DM2-W for a few reasons - firstly a DM2 was the first pedal I ever bought. The DM2-W takes that basic sound and offers an improvement as well - I really like the sound of the delays. It's not so much that it's not true bypass as that I just don't like the sound of what I assume is the buffers. And for the way I use pedals they don't need to be there. I know the engineers at Boss know a gazillion times more than I could ever hope to but I don't like what their pedals do to my sound.

As it is it looks like if I tried to change anything in there I'll probably kill the pedal!
 
HamishR said:
It's not so much that it's not true bypass as that I just don't like the sound of what I assume is the buffers.
Click to expand...
Hmmm, that certainly is a bit more complicated. Or a lot more complicated.

In theory you could use a relay bypass module like PedalPCBs own to make a Boss pedal true bypass whilst still using the same foot switch built into the pedal. That's just harder to do on the waza ones because you'll probably have to change a resistor to make the pedal always be on by default with the flip-flop transistor switch and find all the correct points to and from the PCB and output jacks, and schematics for the waza pedals aren't really forthcoming. Hopepfully, in that case, Rob's post up above has the right schematic numbers for the DM-2W. But removing the buffer entirely? That's something you'd have to take up with a new design at this stage - sorry!

What you could do, as Erik suggested, is throw the thing into a true bypass loop and see if that improves the situation enough for you. You'll just have to live with the buffer in the pedal when you are using it, but at least when you're not, it will stay out of your signal chain.
 
A couple of questions:
  1. What do you have immediately upstream and down stream of the DM-2?
  2. Is there any combinations of pedals that is particularly sensitive to the presence of the DM-2 when it's in bypass mode?
The presence of the buffers could alter the interaction of two pedals in the chain by preventing one from loading the other. C5 in the schematic above might load the input a little bit. 150pF is about the same capacitance as a 10ft cable.
 
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I usually have tuner first (Korg Pitchblack or now a Peterson Mini strobe), then an overdrive like a Timbreman, the delay, then a reverb such as a Flint or currently a UA Heavenly. That's it.
 
The tuner is buffered-bypass, yes?

you're saying that with the Timberman engaged, you can tell the difference between the DM-2 in bypass mode and a short cable in place of the DM-2?
 
Not sure about the tuner - they say it's TBP but I suspect it's TBP via a relay because you can switch to an always on mode.

And yes, the difference between having the DM2-W vs a patch cable is noticeable. I have tested it a few times and with various ODs. There are pedals where it's a lot more obvious and I have no doubt that a lot of guys will tell me that I can't hear a difference and that I'm imagining things! Sigh...
 
Joking of course. I considered suggesting some sort of true bypass switcher, but the comment about "four pedals tops" made me think that wasn't an acceptable solution.
 
My thought was we could use the A/B box to establish whether HamishR is really hearing what he thinks he's hearing.

My A/B box has a stomp switch and no indicator, so after a few random pressed it's hard to know which way it's connected.

A-B box 04.jpg
 
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