DIYstompboxes.com

(https://farm4.staticflickr.com/3901/14441009432_d14c00c61d_z.jpg)

Occasionally posted about, rarely done, it's the Echomatic, from the Stompbox Cookbook. Well, as is often the case with rare DIY projects, it's not what I imagined, but it IS musical and kind of fascinating. On one hand, my dreams of a homebrew echoplex are somewhat foiled; my marantz deck has pitch control, but annoyingly this is DISABLED when record is activated.  :icon_neutral: Darn. But so, as a 'static' (one repeat speed) delay it has a profound, chorus-y magic that is somewhat akin to a Deluxe Memory Man's space rock wobble, but...even more so. Deep.  :icon_smile:

Observations:
- the settings are touchy between the tape deck's gain and the pedal's repeats (feedback) control. there is one little sweet spot where you can get long feedback, but if either control is too loud you can hear a weird background high frequency, a heterodyning whine not unlike a couple ring modulators making noise together.
- the tape deck seems to greatly influence the sound. I can see obtaining a variety of tape machines from large open reel decks to other cassette machines. the key seems to be to find one that has varispeed while record is activated. also for those who don't know, this project requires a three-head tape deck
- did original circuit, so not true bypass, should mod tihs
- mix control does not allow for 100% wet signal, so this effect would not be so great on the auxiliary send/fx bus of a mixer - bummer. Maybe there is a way to put the dry signal on a switchable lift/kill.
- tape type (metal, type 1, type 2) affects the timbre, and so does the selectable tape type switch on the tape deck
- using one of my home made cassette loops is interesting because there's more wow and flutter- more Memory Man vibes.
- the mojo old "reel style" cassette I dug up from my tape bin unfortunately doesn't sound the best - darn.

No conclusions yet. Possible next steps:
- more tape machines to test with it
- Variable speed mod to tape deck - possible? worth it? Can I hack a pot into the motor control? don't want to ruin a perfectly good marantz deck (this gets much use in field recordings and loop playback, so I'm hesitant to hack it)
- modify for true bypass
- figure out dry signal lift

Project PDF:
(http://web.archive.org/web/20120418024426/http://moosapotamus.net/IDEAS/Echo-Matic_a.gif)
(http://web.archive.org/web/20120418024426/http://moosapotamus.net/IDEAS/Echo-Matic_b.gif)

comments/suggestions/questions welcome!
STRATEGY

not much to add.. but I'm following this with great interest... do you have soundsamples?

I gather the annoying heterodyning sound is from the bias generator, or whatever it's called.  We tend to forget that, while tape recording is magnetic, the tape head itself is an electromagnet - a coil that gets turned on, to impose a magnetic charge onto the tape oxide.  The coil gets turned on at a high frequency (see:  http://electronics.howstuffworks.com/gadgets/audio-music/cassette3.htm ), and conceivably, it is that frequency that is heterodyning with something else.

FUZZZZzzzz, I'll try and grab some quick samples during my lunch break today.

Mark, it's funny about the heterodyning- I mean, I've spent plenty of time trying to get various pedals and synth projects to make this sound on PURPOSE, sometimes with no luck! The high frequency of the tape may be heterodyning with whatever tone the too-loud feedback in the amplification of the circuit is making.

Or maybe the inconsistent speed of the tape drive results in heterodyning of the bias.  You won't hear 100khz on the tape, but if a tape loop is simultaneously recording and playing back, there's a pretty good chance you'll hear the difference signal of 100khz and 98.7khz.  That's only a 1.3% change in speed, but it may be just enough to result in heterodyning.  I'm just speculating here.

Sorry, still no time to pull sound samples yet but will do so asap. This thing is definitely some space/stoner rock magic, even if it doesn't do all I want yet.

Right now I'm trying to sort out the signal blend - dry signal is always present at the output, which sometimes you want 100% wet, so a mod is in order. Maybe someone here would have insights based on the schematic in the pdf above.

IC1-D is the output buffer/mixer. I tried disengaging R14 to see if that would kill the dry signal at the output but leave the delayed signal. This goof gave me just very distorted everything, instead. In my still pretty undeveloped schematic analyzing skills, I am seeing now that this was sort of the right type of thinking, but maybe putting a switch between R12 and C10 might be better - might this allow me to disengage the dry signal from going out to R11, the mix pot? How far off the mark am I?

In the meantime, i started looking at ways to modify the Marantz PD-221 tape deck so that the pitch wheel is not for 'playback' only - and sure enough there is this thread http://www.gearslutz.com/board/geekslutz-forum/926423-small-mod-tape-echo-speed-control.html (http://www.gearslutz.com/board/geekslutz-forum/926423-small-mod-tape-echo-speed-control.html)
.... I am not the only person to a) have this problem with the marantz PMD series decks and b) use this tape deck for homebrew tape delay. Unfortunately the thread is light on details but I see the general principle, e.g., find the switch that tells the pitch pot to deactivate when record is pressed, and disconnect. It also looks plausible to put in a different pot value for greater delay pitch/rate range.

advice greatly appreciated!!!

I think it is a misnomer to call R11 a mix pot. I could be mistaken, but it looks a lot more like a delay level pot to me (one lug goes directly to ground). There does not appear to be any level control for the dry signal.

Instead of simply lifting R14, you could try replacing it with a pot connected to IC1a the same way as R11 is connected to IC1c. No promises, but that might give you an independent dry level control to go along with the independent delay level control (R11).

I think modding it for a single wet/dry control would be a little more involved.

~ Charlie

Quote from: FUZZZZzzzz on June 17, 2014, 06:18:01 AM
not much to add.. but I'm following this with great interest... do you have soundsamples?

Built mine last year - here's a vid :

Quote from: moosapotamus on June 19, 2014, 02:19:59 PM
Instead of simply lifting R14, you could try replacing it with a pot connected to IC1a the same way as R11 is connected to IC1c. No promises, but that might give you an independent dry level control to go along with the independent delay level control (R11).
~ Charlie

Charlie, THANKS! I thought there might be another angle to attack this from!!! I will try your suggestion. As it happens, to get a satisfying delayed level, the overall volume pot has to be turned up quite a bit, but then this means there's a huge volume jump between bypassed and engaged effect signal levels...It would be VERY useful to have dry signal on it's own path in this circuit.

Strategy

danielzink, did you try any mods to your version? I referred to your video a few times in preparing for my build!
Strategy

Quote from: danielzink on June 19, 2014, 02:27:11 PM

Quote from: FUZZZZzzzz on June 17, 2014, 06:18:01 AM
not much to add.. but I'm following this with great interest... do you have soundsamples?

Built mine last year - here's a vid :

Quote from: Strategy on June 19, 2014, 02:49:21 PM
danielzink, did you try any mods to your version? I referred to your video a few times in preparing for my build!
Strategy

Quote from: danielzink on June 19, 2014, 02:27:11 PM

Quote from: FUZZZZzzzz on June 17, 2014, 06:18:01 AM
not much to add.. but I'm following this with great interest... do you have soundsamples?

Built mine last year - here's a vid :

Nope. Built it straight off the schematic you posted from the Boscorelli manual.

Made my own PCB though.


Dan

Dan: did you experience any of the squeaky, heterodyning feedback effects on any settings?
Thanks,
STRATEGY

Progress!

Dry signal kill works by adding a toggle switch at R14. Tried adding a pot in series with R14 but, no luck with attenuating, I think R14 would have to get wholesale replaced by a 25k pot, which I don't have at the moment. will try this soon.

For the tape deck, I did some research and found that others have modded these marantz decks. I have service docs on the way with a goal of:
- tricking the front panel Pitch and EQ controls into being active when record is pressed (rewire switching so that the pots engage during record mode)
- increase range of pitch pot so very slow delays can be achieved

Further experimentation with tape types has revealed that Maxell II-S is far and away the nicest sound quality. Finding some high end mastering cassettes (chrome?) might even be good, though I wouldn't know a current source for these. My loops are imperfect, as splicing 1/8" tape is very difficult, resulting in a weird garbled spot in the delays -- but I think it adds to the magic. I intend to open up the "reel style" tape and replace the crappy tape inside it with a loop of high quality tape instead.

DIY tape delay will be mine before summer's over!!!  :icon_twisted:

Bumping old topic as a few folks were following it. My echomatic + modified Marantz deck project is done.

Finished product:
(https://farm2.staticflickr.com/1553/24421519496_f11dc9a643.jpg)

• "dry signal attenuation" didn't work at all, but a "dry kill" works - to an extent. High frequency transient attack sounds from the i/p leak through. It works well enough as a pedal, but the lack of wet-only signal doesn't make it as useful as a mixer effect
• I was able to squeeze the pcb, jacks, wiring, and switching into the battery compartment, but the spaghetti is pretty unstable. I don't think anything's moving now in there, but no gut shots as I don't want to potentially upset the balance, ha ha. Mostly spaghetti anyhow. Would recommend to others, do yours in a separate enclosure with send/return cables, rather than attempt to squeeze it into a tape deck enclosure

How to mod the internal record switch functions on the Marantz PMD221 so that "pitch" control remains active even if Record and Play are activated:
(https://farm2.staticflickr.com/1594/24447796705_82e5fd26fa.jpg)

Summary: not a Space Echo or Echoplex replacement but a fun, inspiring musical thing. Well worth the effort and expense of obtaining the tape deck!

Quote from: Strategy on January 17, 2016, 07:11:49 PM
Bumping old topic as a few folks were following it. My echomatic + modified Marantz deck project is done.

Any luck tackling the high pitched heterodyning noise?

Kind of. I've observed that if you keep the tape bias setting on 'metal' you can get the longest feedback repeats with the least heterodyning. Using type II tape was a huge improvement over type 1. I still have to find some high-end, studio grade 'metal' cassette tape and try that as well. I just make sure to keep the input level on the tape deck around "8", anything above introduces the heterodyning-- ultimately that sound is kind of in the background and has a spacy quality, I've kind of accepted it as a quirk of this project.

Thanks for the reply. I agree about the "metal" setting producing the least amount of heterodyning. I've also found that adding a 3 band EQ in the feedback loop helps a lot. Cut the hi and lo and boost the mids

I don't have an EQ pedal, I did try a resonant synth filter I built set to bandpass and that didn't produce good results. What's really crazy is put a PT2399 delay with modulation in the return chain - gets pretty bonkers. I'll try the EQ trick may be a good excuse to finally build an EQ pedal of some sort. Not familiar with the DIY options at all.

Quote from: Strategy on March 29, 2016, 12:06:41 PM
I've kind of accepted it as a quirk of this project.

Looks like the "It's not a bug it's a feature" type of problem solving. Haha :icon_biggrin:
Anyway nicely done project. I also have the guts of an old tape recorder with the plans of creating a tape echo/flanger. So i just wanted to store this thread for later references.

Now the trick of finding 'metal' tapes. I used to use those in four tracks in the early 90s to get the best sound. Cannot find them in my local area. I can't even find my other old favorites Maxell II-S. I guess ordering online is probably better for finding cassette stuff.

Just tried a metal cassette and its a noticeably better sound than the XLII I was using before. Picked one up on ebay. They aren't exactly cheap (I paid $10 for 1), but you can find them there.

Yeah I was in my friend's record shop Saturday and they actually had two new old stock metal tapes mixed in with a huge stack of new old stock type I types. It really does sound significantly better.

I bought two, one that I can use to make loop tapes for the delay (I also use loop tapes in my four track to do tape loop ambient music), but another one also for just using as a 'master' for four track recording.

Strategy

Are you able to make a loop without a dead spot on the slice? I haven't been totally happy with any of my loops yet.

I've been doing some fun stuff with cassettes lately:
https://www.instagram.com/p/BDbaaogH0fV/?taken-by=scttcmpbll
https://www.instagram.com/p/BBQanWTn0VZ/?taken-by=scttcmpbll
https://www.instagram.com/p/8d8terH0XH/?taken-by=scttcmpbll

Quote from: camp tapes on April 05, 2016, 01:10:23 AM
Are you able to make a loop without a dead spot on the slice? I haven't been totally happy with any of my loops yet.

Are you using a 45^o splice?

My loops are often erratic but I find it often imparts some interesting wobble/chorusing. I am working now on creating a better loop...each one is different. Use a super, super sharp blade, and try to prevent the tape from flipping around.

Your cassette synth is really interesting to me, have you seen Steven Litt's Crudlab MIDI Cassette synth? I would love to buy one if I could as I think some of the DIY science might be beyond me.

The frippertronics thing is fascinating to me would you be willing to share any documentation on how you did that? (PM me?)

Most of my tape work was documented on this album, http://pitchfork.com/reviews/albums/20550-noise-tape-self/
I use a four track so I can get four loops per tape. I use a four track that has separate outputs per track so I can run each channel through effects. My next experiment will be to find a way to disengage the erase head for sound on sound effects. I'm hesitant to do any permanent hacks on my nice four track as I also use it for conventional multi track recording.

Strategy

Reeaaally like those Strategy tracks you linked. Very beautiful. Have you heard the new Deru record? Not sure if he's using loops or what.

My cassette synths control the walkman motor, just like the crudlab version, only he's using an arduino to control it via midi. He's also got a few other bells and whistles in there. I'm working on a final version of my cassette synth which will incorporate the tunable buttons, as well as a pitch ribbon and a pressure sensitive volume control. The idea is to get the articulation of the Ondes Martenot, usuing the cassette as the sound source. Basically a mono Mellotron + Ondes Martenot + lofi sampler.

Quote from: Strategy on April 05, 2016, 12:55:37 PM
My next experiment will be to find a way to disengage the erase head for sound on sound effects.
Strategy

The erase head should have 8 wires connected to it, 2 for each track. You could either disconnect one of the wires for each track and connect them to 4 external switches, or connect all 4 wires to a 4PST switch to turn off the erase head for all tracks at once.

I'll probably try and pick up a cheaper, smaller four track for the switching experiment! thanks for the tips!

Hi Strategy and congratulation for your work !
Can you please explain a bit more how you modded the PMD 221 ? I've just open my 222 and it seems to be the same pitch circuit but I don't understand what you've done. What do you mean by "Jumper Cut" ?

I will post a magnified image. "Jumper" and "Cut" refer to two different things you must do. One arrow indicates a trace to cut and another arrow indicates two points that need to be jumpered together. What this does is rewires the switching related to "record" so that when you press record, it still allows pitch control to be active. These points are hard to see because it's so small. It's very high resolution so if you follow the image link to flickr you can download the full size version and zoom in a lot of detail. But later this week when i get time I'll also post a close-up here.
Strategy

Oh ok, I get it now. In fact I can't have a bigger size for the integrated picture on the site, but I found the pic on Flickr and it's well more precise now. As soon as I have some time I'll try to do the same.

Did you dig into the increased range of pitch pot to reach very slow delays ? I've read on the gearslutz post that you link that you need to change the resistor in order to do that but it's not really documented.

I just tweaked one of the trimpots to increase pitch range, and its working well. I wish it had a little more range, but I'm taking a break from hacking on this thing more.

@Strategy Can you post a high quality image of the result pcb for getting the pitch to work while recording? I cant seem to find much "visual" reference online about doing this mod.

I'm going out of town but will post larger hi-res graphics of the trace cuts/jumper.
Also due to the almost weekly emails about this project I'll probably assemble an official PDF doc that brings together all of the suggested mods, Echomatic Docs, notes and such into one document. But I won't be able to do any of this for a week or so yet
thanks for your patience
Strategy

Quote from: Strategy on June 06, 2016, 11:58:29 AM
I'm going out of town but will post larger hi-res graphics of the trace cuts/jumper.
Also due to the almost weekly emails about this project I'll probably assemble an official PDF doc that brings together all of the suggested mods, Echomatic Docs, notes and such into one document. But I won't be able to do any of this for a week or so yet
thanks for your patience
Strategy

Thanks Strategy for replying so fast! That would be really really really helpful and much appreciated, ( can I buy you a drink for the trouble?  8) ) It seems that the information for this mod isn't very well presented in terms of steps and execution, those of us who are new/green to this modding biz need a little hand holding until we can get the gist of it.
Thanks again!!

just snagged myself a bust up old 430, v interested in the detail of this mod

I tried finding a higher res link of the photo on flikr but couldn't, could anyone send me a link to a clearer picture of the mod? Also wondering if you ever got around to putting a pdf/guide together.


Matt

Haven't gotten to it yet... Have been in work overdrive since summer (including 5 weeks with basically no days off)
Getting to the end of our rough season and planning lots of time off between next week and the holidays, will make it a priority.
Strategy

Quote from: Strategy on January 17, 2016, 07:11:49 PMHow to mod the internal record switch functions on the Marantz PMD221 so that "pitch" control remains active even if Record and Play are activated:
(https://farm2.staticflickr.com/1594/24447796705_82e5fd26fa.jpg)

I too would love to see a clearer picture of the mod disabling the pitch pot bypass. Between which solder points is the jumper supposed to be?

Want to do it myself, but I'm really new at this and troubleshooting/reading PCB layouts is a thing I'm not that good at yet.

Does this have to be a three-head tape deck? Could I do it with a regular walkman-type deck that has input and output?

It has to be three-head
Sorry I've been lagging on the higher-resolution photos and build doc...
! Strategy

I'm guessing the only cheap sources for a three-head machine are yard sales and cruising thrift stores? I live in a fairly low-income area, so even though there are a lot of old electronics around, none are very high-quality.

Any chance you have a spare PCB for the Echomatic? I think I'm going in on this one (just bought a three head tape deck on ebay). Also some hi-res closeups of the variable pitch mod if you still have the photos.

Thanks for posting all your progress on here!

No spares. I get my PCB's made one at a time courtesy of forum people who assist with this -- I'm not sure who from this forum does that these days, I know that Haberdasher from the Madbean forum provides PCB service and I believe he may have done my Echomatic PCB.

I wish I had seen this thread just before to disarm an old tape radio to use some components.....

Thanks for the tip! I found another guy on the madbean forum willing to etch me a board. I'll definitely post my progress here.

Here's a link to my own progress report for anyone interested.  Some pics and and explanation of the pitch control too

http://guitar-fx-layouts.42897.x6.nabble.com/Boscorelli-Echomatic-DIY-Tape-Delay-Build-Report-td32584.html

Hope it helps

Ciaran

That looks great! I'm still conflicted about whether to build mine into a hammond box with leads to the tape deck (a la Boscarelli) or to build it inside the battery compartment (like yours above or the space case). I'm planning a few mods of my own, like a mix pot that pans between wet and dry (remove R14, jump C10, and put the 1 lug of the mix pot to pin 8 instead of ground), and I may try a big muff tone control on the tape output

Yeah.  We did it as stock.  But I would encourage anyone else to at least add a HPF to the feedback line.  I thought the thing was far too eager to self oscillate with lower frequency content.

A tone control would be a nice addition...just be aware of the low frequencies.

If someone had the complete schematics ready I'd might be able to figure it out myself, as it is now I'm not fully able to trace everything on the PCB.

The complete schematic and layout are on page one of this thread

Oh, I see you're talking about the speed control... This guy has a different way of doing it that may be of interest: http://proto-schlock.blogspot.com/2015/04/echo-matic-diy-tape-delay.html?m=1

I tried asking that guy what he did about the original speed control, but seems he didn't understand my question. I guess he just kept it as it is.

Anyway, my baby brother helped me do the mod today! Now the speed pot isn't bypassed in recording mode. He found another place on the PCB where he did the mod instead, but it was basically the same: soldering one jumper and cutting one track in the pcb.

Care to share how you did the mod?

It was tough doing the battery compartment...I bet someone could create a more compact version of PCB (I don't have skills in this)...remember the layout is maybe from 1980s...PCB styles were bigger back then. If you keep your wiring really organized and maybe take the corners off the pcb it's easier to fit in the compartment. One thing I like about doing the external box is that you can actually put effects in the path between your tape deck's loop output and the 'return' input of Echomatic...so it's like an insert effect!!
Strategy

Quote from: Passaloutre on April 14, 2017, 03:20:53 PM
That looks great! I'm still conflicted about whether to build mine into a hammond box with leads to the tape deck (a la Boscarelli) or to build it inside the battery compartment (like yours above or the space case). I'm planning a few mods of my own, like a mix pot that pans between wet and dry (remove R14, jump C10, and put the 1 lug of the mix pot to pin 8 instead of ground), and I may try a big muff tone control on the tape output

That's a pretty cool idea! If you get tired of the echo, you can always just use the box as a mixable loop for any effects you want. Also, keeping the mixer external allows you to put the tape deck elsewhere, like not on your pedalboard where it's in danger of being stomped.

I'm really tempted to try and redesign the mixer circuit using JFETs instead of opamps to get a more "tubey" sound. I think I'll build it the standard way first before I go off on any tangents though. At the very least, I think I'll put the echoplex preamp in the box with the opamps (perhaps separately switchable).

Putting compressor, phase shifter, other things in the return path with echo activated yielded some pretty good effects
the thing to remember is that cassette tape (1/8" tape) is really low fi so it needs help from additional FX.
This effect is very musical but not a replacement for echoplex or space echo IMO. A different, also useful thing.
It would be cool to find a 3-head open-reel tape recorder, using 1/4" tape, and do something like Frippertronics sounding.
it would not necessarily be portable (though very small open-reel decks do exist) but with 1/4" tape I think the Echomatic would be a beautiful thing.

Yes, lo fi is exactly what I'm looking for. As is, I hope, anyone else foolish enough to try this project ;) Still, the demos I've found of this and the "spacecase echo" (which I suspect is very similar) are pretty impressive.

I don't have an Echoplex to replace! If I wanted something with high fidelity I'd buy a Strymon delay, or at worst, build a PT2399 circuit. Worst case if I don't like it, I can sell my tape deck on ebay for what I put into it. That said, I'm really looking forward to this, just waiting on my tape deck to arrive...

So my tape player arrived today... At first I had to reflow the solder on the DC jack... playback is still very quiet. I have to crank the volume knob to hear even a whisper out if the speaker (or headphones). Monitoring the source is quite loud, so I know it's not the power amp that's the problem; rather something between the playback head and the monitor switch. I'm working on tracing out the signal using the schematic... anyone have any tips for troubleshooting a cassette deck?

I got my EchoMatic up and running today (actually yesterday, but I made the video today). I really like it. Super lofi, ambient delay with a lot of modulation, what's not to like? As others have said, it's no Echoplex replacement, but it's pretty cool. I think with a reel to reel it certainly could rival the EP. Obviously the limitations here aren't Boscarelli's circuit, but your recording medium.

Anyways here's my little demo. Pardon the ums and ahs, and the awful compression from my phone. I'll record a better demo later.

https://youtu.be/2T2QTwdB-PQ

Can't contribute to this at all but thinking this is awesome!

I should mention that I built my mostly according to the original design, with a few of my own tweaks. My mods (referencing Boscorelli's schematic):

"Lo-cut" switch is just a 202 cap in series with C4 going to the tape input. Likewise the "Hi-cut" switch is a 203 cap from that same point to ground. As you can hear in the video the Hi-cut has no effect, so that cap value could probably be increased. I guess you'd have to tune it to R5.

I also changed the "Mix" knob from a "wet level" to a true mix between dry and wet sounds, allowing for 100% wet or 100% dry. I accomplished this by removing R14 (again, referencing the original schematic here: http://imgur.com/a/NHRjW) and connecting the pin 8 of the opamp to the bottom of the "Mix" pot (R11). Of course, I disconnected this pot from ground, so it simply pans between full wet at pin 1 and full dry at pin 8. I used a linear taper pot for this, to achieve a 50/50 mix at halfway.

The speed control was taken directly from this page: http://proto-schlock.blogspot.com/2015/04/echo-matic-diy-tape-delay.html , which seems to be a much easier way than dealing with cutting traces, etc. It's completely reversible, as it just replaces a resistor with a pot.

I recorded some better quality demos tonight. Hopefully these demonstrate some of the breadth of this effect. All were recorded with my Gretsch 6120 into my Silvertone 1484, no other effects. I recommend listening with headphones

https://soundcloud.com/passaloutre/sets/tape-echo

I changed the caps on both switches tonight too. The "LoCut" is now a 103 and "HiCut" is a 105 (still fairly useless).

Edit: guts:

(http://i.imgur.com/y80HHWll.jpg)

Since my idea for a high cut switch didn't turn out to be terribly useful, I'm already starting to wonder what might be a worthwhile feature to put in its place. Most of the really interesting mods would involve changes to the tape player rather than the mixer circuit, so I'm left with the usual candidates of putting clipping dudes in the feedback loop of the first opamp stage (and simultaneously adding gain) or misbiasing the Vref, but I have no idea what that would sound like.

Anybody else have some clever suggestions?

Great work Passaloutre -- I am so glad someone found an easier way to mod tape deck for pitch control!!!
And I also will try your wet/dry mod. I used a toggle switch and get some dry signal leak that's not nice. At this point it might even be easier to build a 2nd echomatic than to modify mine, which already has a lot of hacks and I will probably damage if I try to extract the circuitry from the deck battery compartment. 

I'll post my modified schematic. I think the mix mod and the low cut are very useful. I wouldn't bother with the high cut (maybe it would be useful if you used a reel-to-reel, which actually has some treble content).

Here is mine as-built (minus the high-cut). The nice thing is this requires no changes to the PCB, as all the changes involve off-board wiring (and omitting R14).

(http://imgur.com/NC1DJwC.png)

You don't need a DPDT for the Lo-Cut, but I used one because it gave me somewhere to mount the cap. If you want to try the Hi-Cut, send another (switchable) cap to ground from the left-hand node of that switch. Calculate your cutoff frequency using the value of R5 resistor.

Ok, so I have found a problem. I'm running a Tubescreamer before this circuit, and funding that when I engage the echo I lose quite a bit of the volume boost that the Tubescreamer was giving me. Can anyone tell me, based on the circuit as drawn above, why that might be? Is it possible I'm loading down my dry signal by connecting it to the mix pot that way? Do I need a cap between Pin 8 and the mix pot? That pin wouldn't normally have a DC path to ground, but I see now that it does after my modification. For that matter, wouldn't Pin 1 need a cap somewhere?

Pretty much any time I don't understand what's going on in a circuit, the answer involves the word "impedance".

It looks like putting a cap in series with R9 would decouple both opamps from the ground. Can anybody confirm this is the right thing to do? Would that have anything to do with my volume loss when driving this circuit hard?

Cap at R9 is the right thing to do. It reduces pot scratch. I don't think it has anything to do with your overdrive problem; that first stage may just be too much gain.

Hmm, that sounds reasonable, but I'm not convinced it's a headroom issue--if I crank up the TS all the way I get plenty of volume boost. The volume loss happens if the TS is up less than, say, 3:00, which is still well above unity without the delay. Could that possibly make sense?

I finally got a hold of some Type IV Metal tapes today (Sony XR), and the difference is remarkable. Now I can really hear the effect of my HiCut switch!

Playing around with this circuit again last night, and I was finding that it cuts a lot if the treble out of my dry guitar signal. I notice that it has a very low input impedance, could this be the culprit? I also certainly don't need the factor of 10 gain from the first stage. Would it work to bump up the two resistors on that first opamp to 1M in order to increase the impedance and decrease the gain? Would this have any negative effects like adding noise, etc.?

I wonder how this guy did the mod though makes me inspired to build my own now.

Are there any other mods that haven't been documented?

Does anyone know the link for the veroboard or perfboard for the PCB?

Hello !
First post here
I'm trying this project too :)
Could'nt etch q pcb so i went the veroboard route. It's working :)
Now i have to work on the tape deck. I use a marantz superscope c205 modified to be able to reduce motor speed.
As everybody i get a lot or warble at low speed, and some oscillations, but the c205 already has a hpf so it's quite usefull.
Still work tondo though :)


Envoyé de mon Redmi 4X en utilisant Tapatalk

Sorry, don't know of to delete posts here...

almost done :

Hello All!

I have also been tinkering around with the Boscorelli Echo lately. I have a Marantz PMD222 and have built my echo matic circuit on perf board from scratch referencing the authors schematic. This is my first build project and was quite overwhelmed ordering all the parts etc but I managed to get it all together! i think? Its all transplanted into the Marantz unit and Im quite happy with the overall build only thing is my output level is quite low compared to the bypass guitar level. It noticeably drops in volume and tone when i switch it on.. im using a fresh 9v batt and think i have all the components in the right place but its a little hard to know what to expect on your first build.. Anyone know what my problem could be?
I'll attach some pics and can make a video/audio recording if you need. Thanks in advance you geniuses!   ;D
(https://i.postimg.cc/34c7JSgm/IMG-9713.jpg) (https://postimg.cc/34c7JSgm)

(https://i.postimg.cc/WF3TVLJs/IMG-9718.jpg) (https://postimg.cc/WF3TVLJs)