EM5 Echomachine build

[Ben N]

Nice work. Just curious--why'd you put the pushbutton switch where you did, instead of the location of Q1 in the original? And can you explain the working of the MOS in the original (and what "CP1" is)?

[gcwills]

I placed the on/off switch as close as to the output buffer to eliminate any noise from the M65831.
Not sure what you mean by the MOS - if you are referring to the M65831, it is an echo/karaoke delay IC.
The CP1 test point is to allow for checking the clock signal as previously mentioned.

[Ben N]

I meant the switching IC, but I think I get it.

[digitalunderdog]

To add modulation to the EM5, one option is to use the LFO/clock oscillator circuit from the EH DMM.
As time permits I might breadboard this to see if it is suitable. The "pi" LC network in my EM5 would be removed, and one of the clock outputs from the 4047 used to drive pin 2 of the M65831

Thank you GC, very interesting. By touching a few of the pins on the 74HCU04N I would get modulation by touching and retouching the pin manually. I suppose I could remove the pin from the board and attach some sort of on/off modulation current to the pin. Very confusing indeed! I will check that 4047 schematic, thank you.

[digitalunderdog]

Perhaps of interest as a mod.

I often run my EM-5 on batteries. One day I noticed that the repeats were extra long with very cool warped artifacts. As expected, the battery voltage was rather low.

I figured that I could recreate this great sound with an external sag control I have boxed up. It didn't work. I don't have the schematic handy but if I recall correctly the voltage gets regulated seperately for the ic's. If you 'sag' just the one of them you should be able to get the longer repeats with warped artifacts.

Very interesting and thank you for sharing. A sag control would be an excellent way to have a "tape age" type control on the EM5. Excellent idea Vortex, I'm definitely going to give this a try and try to utilize.

One interesting mod I did was change the vale of R20 from 75k to around 39k, which gives way more control over the volume of delays using the mix knob.

[gcwills]

I meant the switching IC, but I think I get it.

OK, the 74HCU04N is wired as an oscillator for the M65831 clock. It is controlled by the associated transistors to set min and max oscillation frequency.

[pinkjimiphoton]

2399 delays will do that too, it gets to a point tho where the reg will lock 'em up... but as it starts to fail, man, ghostly trails that modulate all over the place!! lol

i'm thinking of building one of these myself, thanks for the info!!!
gonna pull the trigger on a board, there's a few left on ebay and amazon

https://www.amazon.com/Tape-Echo-Machine-delay-pedal/dp/B01CI1H6QE

found the chips on ebay from polida2008, i've had good luck with them as a vendor over the years.

[gcwills]

Due to issues with postimage, the images I posted with my original build thread have disappeared so I have reposted them here.
To view images, just click on them.

Hi all,
For some time I've been aware of the obsolete Ibanez Soundtrack EM5 Echo machine delay. It has garnered a lot of fans for its tone.
So decided to bite the bullet and build one.
The heart of the EM5 is the Matsushita M65831 karaoke echo ic which although obsolete seems to be still available via Ebay and other online sellers.
I simplified the circuit somewhat by eliminating the fet switching and using a TL074 instead of the two dual opamps.
Also, the delay clock was simplified to a simple LC arrangement with a hex BCD switch to set delay time.
Here is the original Ibanez EM5 circuit:

[gcwills]

Below is the circuit of my simplified EM5 Echomachine.

As mentioned, I have removed the FET switching and now the wet signal is switched in and out with a SPST pushbutton.
To simplify the clock generator I used a pi LC network of two 470p capacitors and a 100uH inductor between pins 2 and 3 of the M65831. Delay time is now set with a hex BCD switch to allow 16 increments of delay time from approx 25ms to 400ms.

These simplifications allowed me to build the EM5 on a small perfboard which can fit in a 1590B box.
I am really liking the sound of this delay pedal and can see why it receives such good reviews. Of all of my delay pedals, it sounds closest to a tape delay. Repeats do not get in the way of the dry signal, in spite of being brighter than BBD or PT2399 designs.

To come are some photos of the populated perfboard

[gcwills]

Here is an image of the populated perfboard:



Not much to it apart from the M65831 and TL074. Not shown is the hexadecimal BCD switch and outboard pots etc.
It makes for a fairly small footprint which allows for mounting in a small 1590B diecast box.

[gcwills]

To add modulation to the EM5, one option is to use the LFO/clock oscillator circuit from the EH DMM.
As time permits I might breadboard this to see if it is suitable. The "pi" LC network in my EM5 would be removed, and one of the clock outputs from the 4047 used to drive pin 2 of the M65831

[pinkjimiphoton]

Due to issues with postimage, the images I posted with my original build thread have disappeared so I have reposted them here.
To view images, just click on them.

Hi all,
For some time I've been aware of the obsolete Ibanez Soundtrack EM5 Echo machine delay. It has garnered a lot of fans for its tone.
So decided to bite the bullet and build one.
The heart of the EM5 is the Matsushita M65831 karaoke echo ic which although obsolete seems to be still available via Ebay and other online sellers.
I simplified the circuit somewhat by eliminating the fet switching and using a TL074 instead of the two dual opamps.
Also, the delay clock was simplified to a simple LC arrangement with a hex BCD switch to set delay time.
Here is the original Ibanez EM5 circuit:


[/quote

Grant, you rock dude!
i just recently came across this circuit and bought the chips n stuff... look forward to building it.
this will help a lot, thanks man!
peace!

[gcwills]

Thanks pinkjimiphoton.
Good to hear you are building an EM5 - it certainly is a great sounding delay pedal.

[pinkjimiphoton]

started populating it tonite. unfortunately 3pdt.com is gone or down or something,  can't seem to get the schematic for this particular project anywhere. the build doc will work i guess, i just prefer to have a schematic in case of issue. so this thread is a lifesaver

[reddesert]

I made a vero layout for gcwills's clever simplification of the Ibanez EM5. This layout is unverified because I don't have the chip; but it should be pretty close. You'll need the M65831, a binary coded rotary switch, and a 100uH inductor; all the other parts are pretty standard.

[pinkjimiphoton]

nice!

[pinkjimiphoton]

i did build the board up, and MAN!~

i have two echoplexes, and this sounds really close. very impressed!! i wanna work up a vero, but its above my paygrade... so i think i may try red's.

i ordered another board so i can add a little "gift" to a shipment to a friend

THANKS!!

[pinkjimiphoton]

The CP1 reference on the original circuit is a test point to allow measurement of the clock frequency. The 74HCU04 inverters form an oscillator to generate the clock which is fed into pin 2 of the M65831.
In my circuit, a simple LC pi network is used instead of a crystal as the clock oscillator.

AH! that anwers a big question!!

[reddesert]

I made a vero layout for gcwills's clever simplification of the Ibanez EM5. This layout is unverified because I don't have the chip; but it should be pretty close. You'll need the M65831, a binary coded rotary switch, and a 100uH inductor; all the other parts are pretty standard.

The previous layout had an error - I did not make the M65831 chip wide enough.  I can't edit the previous post, but here is a corrected version of the layout:

[pinkjimiphoton]

hey red,
cool~ i ordered the hex switch to try this and it came in, and i got the night off to get some builds on, so i think i'll give it a shot at verifying it for ya.

stay tuned, and thanks for enabling my abject and utter lazyness!! lol