Total Recall Mods/"upgrades"

[claytushaywood]

I'm about to order parts for a total recall build and I had a few opinions to seek.  I remember back in the day a dude that used to work for EHX was offering repairs and modding of old EHX pedals.  IIRC Part of his mod was replacing the 4558 opamps in the deluxe memory man pedals with something lower noise.  I'm about to order parts for the total recall and was wondering if anyone had an opinion on replacing the relatively noisey opamps in the circuit for some higher grade lower noise stuff?  maybe replacing some of the ceramics with films or polystyrene where important?   going into a build like this, id like to make it as good as absolutely possible.  I might be a fan of quality opamps after using so many of the tayda TL072's and thinking i had found gold when I plugged in something more expensive i had gotten from small bear (those tayda TL072's were garbage for a while, ya know the ones with the almost impossible to read letters on the top?)

thanks1

[gül]

I'm about to order parts for a total recall build and I had a few opinions to seek.  I remember back in the day a dude that used to work for EHX was offering repairs and modding of old EHX pedals.  IIRC Part of his mod was replacing the 4558 opamps in the deluxe memory man pedals with something lower noise.  I'm about to order parts for the total recall and was wondering if anyone had an opinion on replacing the relatively noisey opamps in the circuit for some higher grade lower noise stuff?  maybe replacing some of the ceramics with films or polystyrene where important?   going into a build like this, id like to make it as good as absolutely possible.  I might be a fan of quality opamps after using so many of the tayda TL072's and thinking i had found gold when I plugged in something more expensive i had gotten from small bear (those tayda TL072's were garbage for a while, ya know the ones with the almost impossible to read letters on the top?)

thanks1

Howard "Mick" Davis is the guy you're talking about. He's fixed up two of my vintage DMMs for me so far and I can honestly say he's awesome. I used to live near him in Brooklyn. The first time I had him do a repair, I ended up hanging out with him at his apartment for quite a while... We were geeking out on his amazing custom-built hifi system.

I haven't tried different op amps on my Total Recall build. It sounds great as is, IMO. Maybe just go for those Small Bear TL072s. 

[claytushaywood]

What did he do to your vintage dmms?  Did he not swap any opamps?  Thought he did that but. Might be mistaking him for someone else

[madbean]

I'm pretty sure one of the upgrades is swapping the input resistor of IC1 to 220k from 100k. This raises the input impedance and can be useful for humbuckers. On the TR, it's R2.

Swapping the 4558s out may improve S/N slightly although I don't think it'll be that noticeable. The DMM is basically a dirty-a$$ analog delay. But, it's easy enough to try and see if you like. Maybe leave IC1 as 4558 for the grit on the Level knob.

I don't know if there are any other circuit changes he does. I know some of it is cosmetic on the enclosures.

[claytushaywood]

Is there any downside to raising the input impedance?  Now that I'm thinking about it, I'm kinda scared to change anything.  ive had two of the big box reissues over the years one was mn3005 and one was mn3008 one with the power cord built in one with the wall wart.  I actually seem to remember liking the wall wart one better and i think it was the one with mn3008's.  They were magical though.  I've had DM-2's, modded ad9's, vintage ce-2's, the strymon timeline, the damage control timeline, ive had just about every famous delay and none of them came close to the big box DMM (not even the sad1024 vintage units).  They arent just maybe magical, they are completely magical.  The delay sits in the pocket so perfectly.  no other delay repeats quite work like the DMM.  I mean it never gets in the way, it always finds a way to sit perfectly with whatever youre playing. 

anyways- i'm kinda scared to change up anything.  I remember when they rereleased the DMM's with tap tempo and everything- and even the ones claiming to be exactly like the vintage units.  They sounded nothing alike to me.  I mean not even close.  But ehx claimed they were exactly the same circuit.  I think ive brought this up before, but did anyone ever really know if that claim from EHX about the XO series DMM's being exactly the same was true?  I'm kinda scared to use metal film resistors if so...

on to the point of this post- i remember analogman or someone was modding these to have expression pedal inputs.  I saw a band where a dude had two exp pedals plugged up to his big box DMM and it was just killer.  Would adding expression pedals be as simple as installing the switching TRS jack process?

[Jebus]

Would adding expression pedals be as simple as installing the switching TRS jack process?

Yeah, that's how easy it is. Just make sure you install the jack so it disconnects the potentiometer, not the PCB.

[gül]

What did he do to your vintage dmms?  Did he not swap any opamps?  Thought he did that but. Might be mistaking him for someone else

Both of my DMMs took quite a beating during my gigging days. I just had him return them to perfect working order, and now that I think about it, he did do the impedance mod to the newer one while he was repairing it.

[madbean]

Is there any downside to raising the input impedance?

In this specific case, I don't think so. It will lower the maximum gain you can get with the Level control but it will still break up quite a bit. Series resistance can increase the noise floor so increasing the input resistor from 100k to 220k might have a very slight effect, but I bet it's well under the total noise floor of the entire pedal so it won't matter. It's easy enough to socket and A/B the two values with a humbucker guitar and see if it makes any difference for you. More to the point - your options for cleaning up the DMM are pretty limited. It's dirty, dirty, dirty and that is part of the charm. I guess you could go with some hi-grade low noise op-amps. Never tried anything beyond 4558 and TL072 so I'd be interested to hear your results.

[bbd]

Any suggestions for changes to make it more synth friendly?

[madbean]

Well, I don't know what that means exactly. I do know people to use synths/keyboards with EHX Memory Man (seen it plenty of times) so I'd need a little more clarity in what you are after.

[selfdestroyer]

I currently use my DMM on my Juno-60 and love it. Once i get my Total Recall boxed up I will give it a go also. I don't see why I would have any issues.

Cody

[LaceSensor]

made a boo boo today

for all other DMM builds ive made with panasonic chips its needed some form of charge pump and LM7815 (+ve 15v reg)
So I used that reg type. Doh. Realised my error when I tried to verify the power section - same problem on 2 builds
thatll learn me to read the manual.

Luckily it was just putting out 10v, and i didnt have the valuable chips socketed in regardless but still...
pays to check the parts list twice.

Ive also put 1M trimmers into R2 if I recall correctly as I like that impedance mod on my real memory man

[bbd]

How deep should the 1590bb box be?  And has anyone used a 15-19VDC plug vs the 24VDC?  Is there a reason to bring 24vdc down to 15vdc?  Seems like a large loss. Thanks,

[stecykmi]

How deep should the 1590bb box be?  And has anyone used a 15-19VDC plug vs the 24VDC?  Is there a reason to bring 24vdc down to 15vdc?  Seems like a large loss. Thanks,

i believe the 1590bb tall is about 2". you should be able to use a power supply with a lower voltage but the 7915 needs something like at least 17V to work properly. probably you should also use a good quality since a poorly regulated one could bleed noise into the power supply.

[bbd]

Thank you, Where are people getting a 'tall' box?