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Building the Echo-Matic (Marantz tape delay)
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Building the Echo-Matic (Marantz tape delay)
appliancide
I've seen a few threads about this, but none specific to the actual mods. I have a Marantz PMD222 and PMD221 that I am going to attempt these mods on. Most of the information can be found here:
http://proto-schlock.blogspot.co.uk/2015/04/echo-matic-diy-tape-delay. html

I would also like to add simple passive high-pass and low-pass filtering in the feedback loop like Thomas White did here:


I am assuming the best place for the filters would be between C9 and R13. I was planning on using a variation of the "Stupidly Wonderful Tone Control" for the high-pass, and a low-pass like the tone control on a Rat pedal (pretty much the same as the simple, passive lpf on the Doepfer DIY page). I am wondering if Thomas bothered to buffer the feedback path, or if he is just compensating with the variable gain on the feedback opamp. I will probably try the simplest possible way first, and make adjustments if that doesn't work.

I am excited to start on this. I was intimidated at first, but except for the pitch control, none of the extra circuitry has to be invasive, unless you want to cram it all into the battery compartment. I'm still deciding if I want an external box, or a self-contained unit.

Anyone else done this?
Isaiah
If I remember correctly, the PMD-222’s Pitch control is disabled when it is recording.
I was a bit disappointed when I discovered this as I had hoped to use it as a tape echo.
As it is, you can switch between two fixed times using the Speed switch.

Is this also the case with the PMD-221?
largemouthbass
You can enable pitch when recording, just need to cut some traces.. Heres the thread I followed, and i can confirm that it works
https://www.gearslutz.com/board/geekslutz-forum/926423-small-mod-tape- echo-speed-control.html


Isaiah wrote:
If I remember correctly, the PMD-222’s Pitch control is disabled when it is recording.
I was a bit disappointed when I discovered this as I had hoped to use it as a tape echo.
As it is, you can switch between two fixed times using the Speed switch.

Is this also the case with the PMD-221?
appliancide
I don't think that you need to bypass the switch that disables the pitch control, as described on the gs page, if you bypass the speed resistor as detailed on the proto-schlock page. The mod discussed on gs will allow you to use the pitch control on the unit itself during recording, but you would still need to replace the speed control resistor to get the full range of speed control.

I will cut the trace from that resistor to the pot, instead of desoldering one leg and hoping it doesn't short to anything inside the unit. I'll report back if this doesn't work, and the switch bypass mod still needs to be done.
DMR
I have a 221 I've been planning to mod, but haven't done yet.

You're correct that you don't necessarily need to cut the switch trace to get pitch control during recording. The switch just controls the front panel potentiometer, switching it to the pot to the middle of it's range when recording.

But since there is also a fixed resistor in series with that front panel pot, you can replace the series resistor with second pot to get a wider range of pitch control regardless of whether the switch connection was clipped or not. The only downside of this to me is that in playback mode, you would then have two methods of adjusting the playback speed (the original front panel pot, and the new pot), which is a little ugly from UI perspective.

I am hoping to replace the series resistor with a vactrol setup to get both manual and voltage control of the delay time, but haven't gotten around to it yet...
appliancide
I'm ready to start on one of these. I've decided to use the tilt EQ that Tom W uses in his reverb instead of messing around with passive filters. I like the way it works with the reverb, and it should work just as well with echo. If it's too subtle, that's no big deal to me, as I will be using this in an effects send most of the time, so I can always make more drastic changes with the mixer.

Right after the third opamp stage seems like the best place for the EQ, instead of my initial idea of only filtering the repeats.
limpmeat
Subscribing....

I bought an old hostage negotiation recording device that is based around one of these marantz tape recorders. I've been planning to hack it into a delay for a while.
appliancide
I decided to build my first attempt at this circuit as a stompbox running on 9v, and to use as many old/on-hand parts as possible. I've had some old flanger enclosures sitting around for years. They are ugly, beat up, and have wonky holes drilled in them. In other words, perfect for this build.

I built the circuit on perfboard, without doing a layout first. I figured the echo-matic and tilt eq are both simple circuits, so why not? (Because I really need to take a few hours to learn kicad, which I've been putting off for several year now.) I didn't have any through-hole 33 or 100pf caps, so I used smd caps (0805 and 1206 respectively).This most likely saved me from painting myself into a corner, as the perfboard is a pretty small. Smaller electrolytic caps and doing the layout ahead of time probably would have helped a bit there.



By sheer luck, everything fit inside the enclosure. I was so wrapped up in trying to finish this, that I forgot to figure out where the PCB and battery holder were going to be mounted. The above picture shows the lid rotated 180 degrees from where it ended up, as I was just test fitting things. With all of the wires in place, the lid barely fits

The pitch potentiometer is mounted in the box. I used a two piece mta connector, so the box and tape player can be separated and used separately.

Once I started testing, it was not working correctly. The echo was faint, and the repeat knob had little effect. There was oscillation and feedback, especially if the tilt eq was on the high pass end of its rotation. The mixer was also not working as expected. I thought there must have been a problem with the tilt eq circuit, so I went over it several times looking for errors, and found none. I tried bypassing that part of the circuit, and still no joy. I was ready to give up. As a last resort, I decided to try a different tape deck. It worked! No idea what the issue with the first deck is. It plays and records fine, as far as I can tell. Oh well, I have less than $10 in that deck, and it will still be used during my next noise set.

Here's the finished product in all of its ugly, parts bin scavenged glory:



I think I will try to build another one as a module someday, with voltage control of some or all of the parameters. Until then, I am beyond thrilled with this thing!
Rex Coil 7
This looks like fun. Is there any reason one of those home stereo system dual cassette decks couldn't be used? I still have two of those from my "killer" home stereo I had in the 1980s back before making CD copies of your tapes and albums was a ~thing~. I think blank Cds were somewhere around $600.00 back then (that isn't an erroneous extra zero there ... they were six hundred bucks back then ... for ONE blank CD). Of course this was before the 286 CPU was even invented.

Anyhow ... could a dual deck cassette recorder/player be used for this purpose?

cool
appliancide
It has to be a three head unit with the ability to monitor the play head while recording, at least for this circuit. The space between the record and play heads is your delay.

With enough planning and work, I'm sure any collection of cassette parts could eventually get you there, but I'm setting aside that sort of tinkering until I retire.
Rex Coil 7
appliancide wrote:
It has to be a three head unit with the ability to monitor the play head while recording, at least for this circuit. The space between the record and play heads is your delay.

With enough planning and work, I'm sure any collection of cassette parts could eventually get you there, but I'm setting aside that sort of tinkering until I retire.
That makes a lot of sense. Thank you. thumbs up
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