EH Deluxe Memory Man - True Bypass???

[casey73]

Just got my brand new EH Deluxe Memory Man tonight. After playing with it for a while, I opened it up. The bypass switch is the familiar blue 3PDT I've use so many times in my own DIY pedals. But in the MM, they use only 1/2 of one section, as a simple SPST switch as the bypass. I thought I'd read somewhere that the new MM were wired for true bypass. Anyone familiar with this? Why would they put the 3PDT switch in and not use it?

I appreciate any input. I'm really confused. The pedal sounds great in the little time I've had to play with it, but I don't think it's possible to be true bypass they way it's wired, and suspect it will be tapping off some of my signal.

[Mark Hammer]

The vast majority of commercial pedals that use a time-delayed signal in conjunction with a real-time signal (i.e., all delays, flangers, choruses, etc.) do their "switching" by simply cancelling or blocking the delay signal from the point where wet and dry are mixed together. You can do that by means of a FET, but you can also do it with a physical stompswitch.

Now, while that doesn't bypass the entire circuit, it *does* cancel the effect, and if the circuit is relatively noise-free and has a nice high input impedance, then tone-sucking is a non-issue.

But why NOT use the extra lugs on the switch? Fair question. It's easier and cheaper for E-H to simply buy truckloads of 3PDT switches that provide many choices with respect to how to switch, than it is to maintain separate inventory for SPDT, DPDT, and 3PDT switches that only provide as many lugs as are needed. Simple business decision. On top of that, if the surrounding circuitry has a nice input buffer, and the output is low-impedance, then the player gains some advantages by always having that circuitry in place, as opposed to completely bypassing all of it.

Finally, a number of time-based designs provide varietries of stereo outputs, and physically bypassing all of them is cumbersome. It is simply easier to make the delayed signal disappear via a single contact.

[Steve A.]

True bypass can also have switching noises not present in other designs. The bottom line is whether the pedal affects your guitar sound when switched off.

Speaking of which, I was *sure* that I could hear a difference when my Damage Control Liquid Blues was switched off, although they advertise true bypass. Then I noticed that with the power supply disconnected, you could still hear the guitar signal. Further testing indicated that the alleged difference was all in my mind...

[casey73]

Yup, that makes sense Mark. I have played with it a little more and it doesn't seem to sound different when disengaged. I also did some more lurking around different sites and saw references to an alleged relay switch somewhere on the board the acts as the actual bypass mechanism. Not sure, and I really don't want to tear it appart right now. I got the DMM because I wanted an analog delay and didn't feel like building my own. Picked it up on Ebay. It does what I want, so I'll quit whining about the bypass