EHX - Memory Boy

snaredrum · Post by **snaredrum** » 10 Jan 2010, 15:21

hi guys - long time listener, first time caller -

i got a memory boy a few days ago, and it's great, but mine just won't oscillate at higher feedback settings.

has anyone had any success with the internal trimpots yet? i'd like to know which one to fiddle with...

jameswillett · Post by **jameswillett** » 29 Dec 2010, 08:04

SO i just got a memory boy and i was checking out video reviews and came across this one..

at around 7:15 the delay time gets gnarly and super lo-fi. in a later review the dude chalks it up to a "shitty power supply". would there be a way to modify the circuit to do this? Like maybe a starve pot off of the power jack?

DrNomis · Post by **DrNomis** » 29 Dec 2010, 12:41

sabriel9v wrote:I've been doing some research on possible mods that you can do to a Memory Boy.

1) I think I might be able to swap out the BL chip for a V3205. What are the tonal differences between an MN3005, MN3025, and V3205?

2) Can the JRC4558s be swapped out for TL072s on the Memory Boy?

The TLO72 is pin for pin compatible with the JRC4558s,so you should be able to just pull out the JRC4558s and pop in TLO72s,the TLO72 is a low-noise Fet-input dual-opamp....

Hides-His-Eyes · Post by **Hides-His-Eyes** » 29 Dec 2010, 12:48

I've got one of these with a dead switch and I'm having all kinds of fun trying to get it out of the switch pcb. Any advice?

roseblood11 · Post by **roseblood11** » 29 Dec 2010, 13:01

I´m really disappointed about the Memory Boy. It sounds much darker than my old Deluxe Memory Man and it produces much more hiss. Considering the price tag, it´s not a bad offer, but it definitely won´t replace the DMM on my pedalboard.

Any ideas who to pimp-my-boy?

JiM · Post by **JiM** » 31 Dec 2010, 13:14

roseblood11 wrote:Any ideas who to pimp-my-boy?

We need good gutshots of each side of each board, to draw a schematic and then find ways to improve it ...

johnnyg · Post by **johnnyg** » 31 Dec 2010, 14:00

Hides-His-Eyes wrote:I've got one of these with a dead switch and I'm having all kinds of fun trying to get it out of the switch pcb. Any advice?

I had the same problem trying to free a carling footswitch from a red dunlop fuzz face with the pcb soldered directly to the footswitch. It was a pain in the derriere as I wanted the switch alive to use somewhere else and was scared to heat it up too much. Despite lots of solder sucking I pretty much had to destroy the pcb with pliers to get the switch out in the end. I think you might be best just making a new pcb or wiring directly to the new switch

Hides-His-Eyes · Post by **Hides-His-Eyes** » 31 Dec 2010, 14:37

Hmmm, I've had one idea so crazy it just might work

a) open the switch up from the back and remove as much as i can like that until just the lugs are left

or

b) hacksaw through the lugs

anything to let me do them one at a time, really

johnnyg · Post by **johnnyg** » 31 Dec 2010, 16:31

As it's a dead switch Id' say that's a very good idea... just cut the lugs off with a dremel maybe (or smash up it's plastic body up with a hammer... that'd be more fun and poss quicker ). With only the metal lugs are left and you'd get them out no probs at all with a pair of pliers and a third hand to hold the pcb whilst you heat the solder.

johnnyg · Post by **johnnyg** » 31 Dec 2010, 16:33

Hmmm, where's the edit button gone?

I made plenty of stupid mistakes bashing that response out and can't fix it into acceptable English

Scruffie · Post by **Scruffie** » 03 Jan 2011, 18:49

What's all this stuff i've read about having to Physically 'Warm' the new Memory Series up to get the full Delay Range?

roseblood11 · Post by **roseblood11** » 03 Jan 2011, 22:00

Compared to a DMM, it sounds as if it´s sticking in an warm asshole, but...

culturejam · Post by **culturejam** » 17 Mar 2012, 18:21

I just got one of these in a trade. I hated my Deluxe Memory Boy, but I like the regular "Boy" much better.

This one is biased properly, and even at max delay time it still sounds pretty good.

Couple things I noticed:

On the daughter board with the BBDs, there is also a LM13700 and a HCF4011 (quad nand gate). I assume the 4011 is the clock for the BBDs (especially since it says "CLK" right next to it!). So is the 13700 there as the LFO?

culturejam · Post by **culturejam** » 17 Mar 2012, 20:22

Another thing I have noticed after staring at this thing...there are test point pads for each of the BBDs and the clock (and a few more on the main board). That is pretty cool.

madbean · Post by **madbean** » 17 Mar 2012, 20:58

culturejam wrote:I just got one of these in a trade. I hated my Deluxe Memory Boy, but I like the regular "Boy" much better.

This one is biased properly, and even at max delay time it still sounds pretty good.

Couple things I noticed:

On the daughter board with the BBDs, there is also a LM13700 and a HCF4011 (quad nand gate). I assume the 4011 is the clock for the BBDs (especially since it says "CLK" right next to it!). So is the 13700 there as the LFO?

I think so. I have one of these too and that was my guess when I saw it.

culturejam · Post by **culturejam** » 17 Mar 2012, 21:19

I want to mod it so that the modulation isn't so insane. I have to keep the "Depth" pot at almost minimum to make the pedal usable for standard delay sounds. I just don't see any trimmers for the LFO.

madbean · Post by **madbean** » 17 Mar 2012, 22:44

Replace the Depth pot with 500k....?

Peamiller · Post by **Peamiller** » 25 Mar 2012, 06:12

Just today I re-calibrated (sort of) my Memory Boy after having messed it up the day before. A while back I fiddled with the trimpots as I played, but made sure I got delayed sound out of it before trying out another pot. Four are definitely for biasing the input, a fifth one seems to be for the balance of out1 vs out2 on the 4th BBD chip, and there's one that says something about input gain for the 4th BBD. I checked out the gig AD3208 for some notes on how to set the biasing, and also used the MN3208 datasheet. The day before I thought I was doing it right just with the datasheet, but I completely misaligned everything. Now it sounds a little bit clearer than I've had it before.

I used an oscilloscope and signal generator. At first I was trying to input a sine wave (~0.6V pk-pk) right at the BL3208 input pin (7) but then realized there's definitely some biasing of that input, so I just set the delay to somewhere about half, feedback to minimum, depth all the way down, and blend to 100% delayed signal. The 4 test points on the board were useful, I think they basically represent the output of each BBD IC, maybe without filtering or canceling out the clock/switching noise. I saw a lot of spikes on the sine wave corresponding to the clocking. Turning the pot, you can see the voltage at each test point hit a maximum and a minimum. I tried to get the scope to show a sine wave sitting right between the two. Also, if you get #1 right, you'll see a sine wave at #2, and so on; if you got one IC misbiased, the next IC"s output shows nothing. At the end, on IC #4, the balance control (balance between output 1 and output 2 of the IC) was used to get the test point looking as much like a continuous sine wave as possible. I can try to get some screen grabs of the traces soon, it might make it clearer. The lab has some great scopes that let you save pictures right to a USB drive, it's so much better than trying to take a picture of the screen.

I did this process without a way to test it so I was sort of just banking on thinking thru the whole thing, but I tested it and it sounded good. I think while fiddling with the gain to IC#4, I messed with the sensitivity of the feedback control, because now it will barely oscillate if I turn the feedback all the way up towards maximum, and it takes a little longer than it did when I just got it. Also the max delay time seems a tad shorter, maybe 400 ms; no aliased-sounding delays. I recall having this before, after playing with some of the trimpots before, and then setting it to get longer delays but more sensitive feedback, kind of odd if that one input gain pot affects both.

The trimpots could be turned over and over again it seemed, but I think they just kept sweeping thru the same set of values. It seemed like the first half turn was really sensitive and would make me go right past the bias voltage I wanted, then the other half turn swept thru the same voltages but I could find the right biasing without it being as sensitive. Anyone know about a trimpot like this?

Unfortunately, no modulation depth control found. I think they make it super sensitive so that you can get slightly over the top chorus/vibrato sounds with the delay all the way down.

Peamiller · Post by **Peamiller** » 25 Mar 2012, 06:23

Peamiller wrote:At first I was trying to input a sine wave (~0.6V pk-pk) right at the BL3208 input pin (7) but then realized there's definitely some biasing of that input, so I just set the delay to somewhere about half, feedback to minimum, depth all the way down, and blend to 100% delayed signal.

Forgot to say (and couldn't edit): I put the sine wave at the pedal input by connecting the signal generator to a 1/4" plug put into the input jack.