Memory Man info + question

[ethanw]

I got a recent EH memory man (4xMN3008 w/relay switching) which I like, but any guitar seems to distort the input slightly. Just about any signal overloads the "overload" LED.  If you try to adjust the level to avoid this, the bypassed/unbypassed volumes don't match. Anyone know of a fix for this? 

Howard Davis, designer of the original pedal, says this:
A common problem when the DMM is used with hot pickups, or with another
pedal in front of it, is that it overloads too easily. It was designed to be
driven directly from Strat single-coil pickups many years ago when these
were by far the most common type.

My input impedance increase and hot pickup mods greatly increase the
headroom, usually completely resolving this issue. These mods cost $60 total
for parts and labor, and I also do a trimpot alignment as part of the work.
Return shipping/handling adds $12. If you also want a cosmetic
reconditioning that adds $15, and for another $20 I can extend the maximum
delay time by about 25%.

Below are some links to good MM info, some from our Forum members:

GREAT info from Aron from this Forum:  http://www.diystompboxes.com/pedals/mmmod.html  (I did Aron's TLO72 mod on U1, me like!)

Mod I found online:  http://germaniumsky.com/gsky/ideas2.html

Only schem I could find, it's unclear what version this is: http://www.freeinfosociety.com/electronics/schemview.php?id=381

More Great info from Analog Mike, quoted here from his website, http://www.analogman.com/:

The Japanese Panasonic MN30XX chips are the best ever made, a little better than the more recent (but also discontinued) Japanese MN32XX chips in the DM3, AD9 etc. and much better than the BL32XX Chinese chips. These MN chips are all discontinued, only the BL Chinese chips are still made. Don't know how much longer EH will be able to make the memory man with the good old Japanese chips
3X05 = about 4000 delay stages, 3X08 = 2000 stages, 3X07 = 1000 stages.
In about early 2006 the DMM changed to relay true bypass switching, and four MN3008 chips instead of two MN3005 chips. The new DMM has (4 * 2000 = 8000 stages), The older one had (2 * 4000 = same 8000 stages) for the same delay time.
4000 stages is good for about 300mS at reasonable quality (AD9 etc) or 200mS at high quality (DMM).
1000 stages is more than enough for a chorus (we use new old stock MN3007 chips in our chorus). There were also 512 stage chips used fo chorus and flangers (best for a flanger).

To check if it the new version with the relay, turn it on and play, so you are hearing the delays (effect on). Then unplug the power from the back of the DMM. If it turns off and you hear your normal guitar sound, then it has a relay. If you hear nothing then you don't have the relay. You can also tell as the stomp switch only has two wires on it if you have the relay.

I guess they ran out of the MN3005 chips. Theoretically, the less delay chips you have, each with higher number of memory positions to add up to the same amount of memory, the better the sound. But in reality there is little sound difference between two 3005 chips and four 3008 chips. But there are twice as many calibration points to dial in if you have 4 chips. Some delays have EIGHT CHIPS (ad999?) that must be a nightmare to calibrate...
We can install four MN3005 chips on the newer model Deluxe Memory Man to double the delay time to about 800mS. But it's a VERY expensive mod as the chips are about $100 and about the same for our labor in calibration. And after this mod the pedal can no longer be used as just a chorus as the short delay times are now too long for a normal sounding chorus pedal.

Ethan

[ethanw]

No love for the Memory Man?

[StephenGiles]

It's probably cheaper to turn the volume down on your guitar!

[WelshWonder]

Just saw this post and I'd like to say that I had the exact same problem. Really anoying issue be it a strat or a les paul going through. It's a shame as I wanted this pedal to live up to its reputation. I couldn't find a solution to it so I built the the Tonepad Rebote 2.5 and I'm far happier with the rebote than I am with the DMM. I still have the DMM though so if you do find a cure let me know as I wouldn't mind taming it.

Good Luck

[ethanw]

Thanks for the replies, guys. I got it pretty cheap so i figured I'll work with it a little. Aside from the distortion issue it's damn good sounding. I guess Howard davis's mod is good, but this being a DIY forum, i want to do it myself, of course. I'm actually a New Sensor dealer, I might call'em up and see if I can get a knowledgeable tech on the phone.

[aron]

>My input impedance increase and hot pickup mods greatly increase the
headroom,

I wonder if increasing the 100K series resistor would help things? It's part of a voltage divider at the input. The larger, the more the input signal is reduced.

There's a trimpot 100K on one of the 4558 that could help boost any "loss" of input signal as well.

[puretube]

Only schem I could find, it's unclear what version this is: http://www.freeinfosociety.com/electronics/schemview.php?id=381

it`s the: "never trust a schematic on the web" - version... 

[ethanw]

Aron's idea sound good, I might try a bigger input resistor. It looks like there's 2 trimpots on one of the 4558's, guess I could mark them then crank'em up and see if it helps-

Ethan

[WelshWonder]

Aron's idea sound good, I might try a bigger input resistor. It looks like there's 2 trimpots on one of the 4558's, guess I could mark them then crank'em up and see if it helps-

Ethan

Let me know how you go with these mods as I definately need to do something to mine. Good Luck.

[ethanw]

Aron, any guesses as to a good input resistor value? I was think of trying 150K arbitrarily. I tried looking over the inputs of various delays to try to get an idea of values, haven't figured it out yet though. There was an early echoczar schem posted here but the input on that is 10k, different circuit I guess.

Ethan

[aron]

I would temporarily put a 250K pot - replacing the input resistor and adjust the pot until everything is great. Take the pot out, measure and replace with fixed value.

[WelshWonder]

Simple question but how the hell do you get the knobs off this bad-boy? i'm afraid to use too much force in case i break the unit...

[puretube]

pull!

[WelshWonder]

pull!

Just did! yep the come off alright, I got a rag underneath and yanked the bas*ard out! hahahah

[puretube]

http://acapella.harmony-central.com/forums/showthread.php?t=1613410

[MikeH]

Here's what I'd do (but I'm a fan of external solutions):  You could also build an effects loop- you probably have one around already, but I'd add a couple things.  1. Add a volume control on the send, so you can send the MM a not-so-hot signal, and then: 2. I'd build in a booster on the return side.  Something pretty transparent, mosfet boost maybe?  That way you could keep the signal clean, and build it back up afterward.  Oooh and while your at it, you can add a feedback loop.  Those sound sweet on delays; you can get those trippy, overlapping, echo sounds.

[ethanw]

Thanks for all the replies.  The HC thread is interesting, earlier version than mine w/2xMN3305 + socketed opamps. Think I'm going to replace the jacks and tighten up the wiring when I'm in there, hopefully I have a 250K or so trimpot on hand.

Ethan

[dualaud]

what did you find out in respect to the value for the resistor to raise the input Ω?

thanks,
dual

[ethanw]

I didn't get too far yet. I had a hard time finding the correct resistor as the only schematic around seems to be different that my unit.  I guess I'll try to trace the input circuit out-

[scott_v]

resurrecting an old topic but back in the first post by ethanw, i checked this out:

Mod I found online:  http://germaniumsky.com/gsky/ideas2.html

and only tried the mod for doubling the delay time, super simple mod.  used a submini spdt switch and since my power slider switch broke i instead took the lead from the board and soldered directing to the power jack, removed the power switch and used the space for the submini switch to double delay time. i haven't tested out the mod with my normsl setup and volume but i'm pretty satisified by it... i think the added distortion noted in this mod i will not find to be much of a problem since i do mostly experimental and improv music...

thanks for the link, i'm abit of a newbie here so thats why i just found this...