Deluxe Memory Man mods?

[Mark Abbott]

Though I probably should be working hard on my Compressor. I've decided to enquire about some of the mods people have done to the DDM reissues.

I've read the mods in the schemes page. These are 100% bypass, and changing the 4558 IC's over to TLO72's.


As many people are quite impressed with the Burr Brown chip, would this be a better IC than the TLO72?

Basically, I'm curious what can be done to these pedals to make a good thing better.

Yours Sincerely

Mark Abbott

[Mark Hammer]

You need to think in the big picture.  E.g., if the op-amps contribute 15% of the noise and the BBD the remaining 85%, switching to fabulous op-amps that cut the op-amp-derived hiss by 50% doesn't accomplish that much in the way of noise reduction.

My favourite mods to analog delays involve altering the feedback path and reducing the bandwidth, either by trimming treble or bass, or both.  If you roll off treble in the feedback path, it:
a) stops the regen signal from getting too grungy at long delays
b) more naturally mimics what happens to echoes in the real world
c) is capable of getting closer to reverb at shorter delays than delay pedals usually get.

[aaronkessman]

can this be done on a regular stereo memory man by adjusting one of the trimpots?

[analogmike]

You need to think in the big picture.  E.g., if the op-amps contribute 15% of the noise and the BBD the remaining 85%, switching to fabulous op-amps that cut the op-amp-derived hiss by 50% doesn't accomplish that much in the way of noise reduction.

Bingo! Actually it's more like 98% BBD and 2% IC chip noise.

I get a lot of customers who want me to do that mod based on some website they saw, I have to explain this a lot. The pissing in the ocean analogy is often used  :wink:

[Mark Hammer]

can this be done on a regular stereo memory man by adjusting one of the trimpots?

No.  The trimpots are for other things.  The easiest, cheapest, least invasive way to insert a treble cut is to locate the input and ground lugs on the Feedback/Regeneration pot, and solder a cap between them.  A 0.1uf cap is probably a reasonable place to start, but there is no special magic value to aim for, other then something which produces enough of a treble cut that you can detect the occurrence of even less treble on each repeat.  Bigger values for more treble cut, smaller for less.  Indeed, you may be able to leave the pedal plugged in, take out an assortment of caps with long enough leads, touch them to the pot lugs and select a suitable value by ear.

If you want to cut the bass increasingly with each repeat (great for dub music and all Augustus Pablo fans), identify the cap in series with the regen path, just before where it gets mixed back in to be shipped to the BBD again, and reduce its value.  It will probably be set for maximum bandwidth (we'll say that's 20hz rolloff just off the top of my head) so you will want to cut it by about 80% for starters to raise the low-end rolloff by 2 octaves or so.  If, hypothetically, it were 0.1uf, resulting in a 20hz rolloff, you would probably want to replace it with .018uf to raise that rolloff up to around 110hz, or .012uf to raise it to 167hz.

Mike,

Yup, it's easy to get too focussed on specific components, all the while neglecting the many many things that produce a sound, whether desirable or undesirable.

Having said that, there ARE many circumstances in which the number of factors contributing to hiss are few, and replacement of a few select components (an op-amp, or a transistor, or a few input resistors, etc.) will noticeably improve matters.  The question to ask oneself is "How many things are going on here, and how much of a difference could X make in light of that?".  X could be a pricey op-amp, or a certain kind of capacitor, or some pricey wire, or solder, or "the same output transformer SRV used", or any of a variety of things.  If the effect/change sought is multi-determined, you may have to do an awful lot to insure you can produce it.

[aron]

I've read the mods in the schemes page. These are 100% bypass, and changing the 4558 IC's over to TLO72's.

As the originator of some of these published mods, the reason for switching over to the TL072 is NOT for hiss reduction.

I think I explained it in this document:

http://www.diystompboxes.com/pedals/mmmod.html

The mod is totally worthwhile. Anyone that puts a distortion before a reissue memory man can hear the difference.

For me it's the difference between liking it and not liking it on the gig.

[analogmike]

As the originator of some of these published mods, the reason for switching over to the TL072 is NOT for hiss reduction.

I think I explained it in this document:

http://www.diystompboxes.com/pedals/mmmod.html

The mod is totally worthwhile. Anyone that puts a distortion before a reissue memory man can hear the difference.

For me it's the difference between liking it and not liking it on the gig.

I see! I will have to try it then, customers who asked for it said it was to reduce noise. I still doubt it and I have several in stock so I can mod one and use my double blind dual loop box to see if I can hear a difference.

I have some new DMM pedals I just got in this month, 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 modiefed 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 more than I thought it would be. 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. Most people will prefer the upgraded op amps I think.

Hope this helps and feel free to put this info on your site if you'd like.

p.s. I send about 5 people a day to this web site.

[aron]

I just change the input op amp and to me it makes my distortion pedals sound like they should.

The change in timbre is that the "edge"/midrange is altered with the stock memory man deluxe. It's very apparent to me since I know my own pedal like no one else. hehehehe

The modified DMM will not have that nasty edge.

My friend just got a DMM and he was complaining about the distortion timbre change before I even mentioned my simple mod. hehehehe

I told him to check out the mod on the website.  

Ain't I a good friend? :roll:

[Mark Abbott]

Thanks for all the input to my question.

What I was after from my question, was if anyone had done any more work on modding the  Memory Man.

I wasn't thinking of noise reduction when I mentioned the Burr Brown IC, I simply thought they may have sounded better.

I have experimented with the  Memory Man from time to time. When using it I'll be playing some acoustic type of thing on my guitar and try and use the Memory Man to fill it out a bit.
I end up getting delays that I'm happy with and after a little while I realise that I prefer the sound of the guitar going straight into the amp. I've never thought too hard about it, but perhaps it is the fact that it is a little too muddy.

I really only have one more question regarding the Memory Man, what are your favorite settings with the  Memory Man?

I tend to like varing slap back-ish echoes to fill out the sound of the guitar. Usually the longer the echo is, the quieter I have it in the mix.

I have been able to get good chorus sounds from the  Memory Man, but at the expense of the echo. I find its either one or the other. I don't tend to use the vibrato thing much.

I haven't ever plugged into a distortion pedal and then into the Memory Man.

I have it set up this way. I would plug into a five watt amp, and take a line out from that to my Memory Man, I would set the mix control to full (echoes) and taken the output of the Memory Man to my 50 watt amp. I found I had the pure sound from the guitar amp and I could change the tone and levels of the echoes with the larger guitar amp. Of course this was a home practise set up.

Yours Sincerely

Mark Abbott

[Mark Hammer]

If it's an input-matching or input-stage thing, then it makes perfect sense.  Big differences in signal handling and impedance between the TL072 and stock chip.

To those whose notions about the "magic" quality of op-amps may be a little over-imaginative, one of the things you need to keep in mind is that companies prefer to keep larger inventory of a narrow range of parts over shallow inventory in a broader range of parts.  Part of that is that you don't get stuck with inventory of a product line falters (you can use those parts in something else) and part of it is also the volume discounts you get when buying components.

The result is often that the same generic component will often find its way throughout an entire product, even though a different one may optimize functioning in one particular part of the circuit.  If the "generic" part is a decent compromise, that's fine, but occasionally the generic one falls a little short of what is truly possible with a simple component change.  In this instance, swapping chips or transistors or even cap types may provide benefit.

I see a lot of circuits that spread 4558's around the way my kids use ketchup - stick it on everything.  In other cases, you'll see low-power op-amps like TL022's used if the circuit tends to be a current sucker, and the intent is to bring current demands down in service of increasing marketability by having decent battery life.

In other cases, though, the design ends up using an even number of op-amps, and everything except for one single op-amp is perfectly suited to what the circuit needs it to do.  Sometimes the company uses a special one and forfeits the convenience of using the same duals everywhere, but most of the time they just bite their lip and use the same device throughout.  Again, you need to bear in mind they make many different products, and if they can buy those not-perfect-but-still-pretty-good op-amps in high volumes at pennies-per-chip, it keeps product cost down.

[Mark Abbott]

Dear Mark

Thanks for the reply. The IC thing I think will always be an area where the "Mojo" factor is high.

Personally, I don't claim to know everything about IC's characteristics, so I'd rather admit my ignorance and ask the questions.

Yours Sincerely

Mark Abbott.

[aron]

but perhaps it is the fact that it is a little too muddy.

Well it is analog  

I have something I always say, if I want the delay to sound the same, I will play the note twice.    Just a joke!

[filterazonatie]

I know there have been mods for the EH DMM discussed regarding IC chips and opamp chips for a "warmer" sound, etc.

Anyone have ideas on how to get more headroom out of it? I run mine after distortion, boost, etc at the end of signal chain, and the input light is going freakin nuts when I'm hammering it with a boosted signal.

Can't put it first, hate the beating sound of delay before distortion.

Is it moddable?

[StephenGiles]

A gentleman of professorship proportions over at Group diy (PRR) put up an interesting post on this subject of upgrading opamps, I'll get the link.
Stephen

[aron]

All I can say is I can totally tell the difference between the TL072 mod on mine and a stock DMM and I thought I made it clear that the mod was not for noise purposes.

I'm not sure how it turned into a "noise" discussion.

[Primus]

I am thinking of replacing the 4558s with the TL072s. I kind of like the distorted analog sound of my memory man on the repeats, but I want the dry signal to be as clear as when bypassed. Can anyone who has done this explain a little more the sound of the change? What about just replacing the 4558 in the signal path with a TL072 and leaving the regen ones as 4558s?