Dirk_Hendrik wrote:Help?
The MN3102 provides a supply voltage and to antiphase clocksignals to the BBD chip. What exactly would make it quieter??
Weaker clock pulse?

Dirk_Hendrik wrote:Help?
The MN3102 provides a supply voltage and to antiphase clocksignals to the BBD chip. What exactly would make it quieter??
Dirk_Hendrik wrote:Help?
The MN3102 provides a supply voltage and to antiphase clocksignals to the BBD chip. What exactly would make it quieter??
Scruffie wrote:From what i've read i'm led to beleive the 3201s are limited to the amount they can drive, so a 4047 may deliver a stronger output yes... Also the 4047 is cheaper.
Dirk_Hendrik wrote:Help?
The MN3102 provides a supply voltage and to antiphase clocksignals to the BBD chip. What exactly would make it quieter??
rep_techy wrote:Anyone have mods for chorus/vibrato to match DMM, I read somewhere that changing the 4558 ics to TL072 ics produce better tone.
rep_techy wrote:Anyone have mods for chorus/vibrato to match DMM, I read somewhere that changing the 4558 ics to TL072 ics produce better tone.
Memory Man op-amp IC chip upgrades
There are a few web sites and posts about improving the sound of an EH deluxe memory man, by replacing the normal 4558 op amps with some high tech chips. The noise and tone in a memory man comes from the BBD chips, not the op amps. The BBD chips have about 10,000 times more noise, and very low fidelity. That is normal in an analog delay and nothing can be done about that, it's why people love their sounds. So replacing the op amps will have little benefit, or so I thought.
After writing the above I got some new DMM pedals, they are now using ST electronics MC4558CN dual op amp chips. I replaced all five of these chips while I was in there (those knobs are a pain to remove) with new Texas Instruments TL072 chips.
Dry sound when playing clean - it is improved. Put the mix to pure DRY (no echo) and the tone when playing clean is a little purer. I was surprised.
ECHO SOUND: also clearer when you listen to 100% delayed sound, much clearer and closer to a digital delay sort of tone. Seems to be more difference at lower delay times.
When I turn up the MIX for about 50% delay I tested for noise by playing a low string gently. The modified pedal is a bit noisier, may be a unit to unit discrepancy or could be the TL072 chips allow more high end through which contains the noise.
OVERDRIVEN sound : running a good OD pedal into the DMMs, with the gain knob set for unity gain (LED just glowing) the sound of the stock one seems a little warmer to me, both dry and echo sounds. But the modified one is clearer again.
DISTORTION : Running a good distortion pedal into the units, the modified one is clearer, the repeats are almost too clear. The stock one has repeats which are darker and more in the background. At this point in the test I brought out a '59 reissue Les Paul with burstbuckers 1 and 2 and played through the Maxon SD9/808/silver, into the DMM into a '66 blackface Deluxe Reverb plugged into a '73 Marshall 4x12 cabinet and just played for 45 minutes as it was a MAGIC combination! Gilmour, Hackett, Page sounds were flowing... best tones I ever got for leads.
Anyway, the difference with changing the op amps is noticeable. But not sure whether I like it enough to go through the hassle of pulling the board out... depends on what you want, clarity or a warm background echo. Also the new 2006 classic style DMM pedals do not use sockets so the chips need to be desoldered, a lot more work. These are the EC2002_REV_E boards which can use four MN3008 chips or two MN3005 chips, and use a relay to switch the pedal on and off. The new XO memory man uses tiny surface mount op-amp chips, so they are VERY hard to replace.
benqbasic wrote:Hey Would be really interested in those sound clips.
Btw have you modded it to true bypass?
rep_techy wrote:I studied the DMM schematic and the VM1 schematic, then replaced key components in the exact same locations so that the VM1 is basically a DMM with a different clock circuit and small surface mount components(note:the newer DMMs are supposed to have small surface mount components also). Tonally, it sounds pretty close to the DMM now only with a little distortion decay on the trails, which may be due to the lower power supply voltage than that of the DMM. I am also debating about installing a tap tempo circuit.
Great ! Could you please post this comparison schematic (unless it contains copyrighted material from EHX) ?rep_techy wrote:I studied the DMM schematic and the VM1 schematic, then replaced key components in the exact same locations so that the VM1 is basically a DMM with a different clock circuit and small surface mount components
Are all your mods you described above ? I like the sound of my VM-1, but sometimes i'd like the repeats to be less dark.rep_techy wrote:Tonally, it sounds pretty close to the DMM now only with a little distortion decay on the trails, which may be due to the lower power supply voltage than that of the DMM.
Did you modify the zener-based regulator for higher voltage ? If not, boosting power supply voltage won't affect the BBDs ...rep_techy wrote:I use a 12VDC power supply currently and am curious about using a 15VDC power supply.
This looks like a task for a small microcontroller (PIC or AVR) and a digital pot.rep_techy wrote: I am also debating about installing a tap tempo circuit.
Me too ! Right now my old Rocktek is just sitting on top of the VM-1, but maybe a Big Muff copy (VD-1) would be better suited for integration. This would need some switching jacks, so they are chained internally when nothing is plugged in, but still can be wired as independant pedals. Where do you plan to put the footswitch, besides or above the existing one ?rep_techy wrote:Am thinking about installing an overdrive in the same pedal b/c of the extra empty space in the chassis.
Yes, i know. (i did the VM-1 schematic, after all).rep_techy wrote:The schematic can be found on Schematic Heaven website. The VM1 schematic is in prior posts.JiM wrote:Great ! Could you please post this comparison schematic (unless it contains copyrighted material from EHX) ?
BTW, isn't the preamp always on in the DMM ?
As you can see in the schematic, the power supply for the preamp and compander (Vcc) is unregulated, whereas the power supply for the BBD (Vdd) is treated by T5 and D4. Raising the power supply would increase the headroom of the preamp, which could then enlarge the compressed signal, which in turn would come closer to the regulated supply rail of the BBDs. This ends up in less overall headroom !rep_techy wrote:I don't know about the zener diode regulator. I suppose you could raise the zener voltage value to allow higher VDC for the delay circuit, but you would have to check with the chip manufacturer datasheet to see what is safe, also the surrounding SMD may or may not be affected also.
Some distortion is normal with BBD, that's why people love analog delays.rep_techy wrote:Until someone comes up with a quick n dirty fix for the slight distortion on the trails, I am quite satisfied with the sound of the modded pedal.
I'll look at a way to add a proper speed control to the LFO. For example, messing with R43.rep_techy wrote:If you don't like the chorus sound you could try changing the chorus cap to twice larger or smaller the original value and see how it sounds. Very cool circuit to experiment with.
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