SQ-RSEout Space Echo Impedance Balanced Output

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Bo Deadly

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This "SQ-RSEout" PCB is available on OSHPark for ~$10 USD:

https://oshpark.com/shared_projects/Rmc0838n

This tiny 1.8"x1.08" PCB replaces the "filter board" and 1/4" TS jack of the "OUTPUT" of a Roland Space Echo like RE-201 or RE-101. So you basically remove the old filter board and old TS 1/4" jack it's soldered to, disconnect various wires, reconnect some, add one new and then mount this new PCB using the new TRS jack soldered to it.

FEATURES:


  • Impedance balanced output accepts a TRS 1/4" plug and greatly reduces ground loop related hum when driving a balanced input but works correctly with an unbalanced input and with a conventional unbalanced cable.

  • The "standard" 100 ohm output with a sturdy op amp like an RC4580 or NE5532 can drive long cables and other gear that requires a low impedance source.

  • The "H M L" slide switch is used to provide +12dB, 0dB and -12dB output. So +12dB of boost is provided in the H position, the M position is what the H position was and the L position actually attenuates.

  • The inductor / capacitor filter replaces twin-t notch filter of orignal "filter board". Can be tuned by adding an extra small cap. Twin-t was set for 72kHz but oscillator schem reads 60kHz and I have measured 62kHz in my RE-101. So adding an extra 820p should make 62kHz for example.
Note: If your RSE ground is not connected to earth ground, the impedance balanced output may not stop noise or may actually increase noise. In this case, you should use an unbalanced instrument cable and connect your RSE to a properly grounded device. For best results, replace your mains plug with one that has a proper earth ground pin.

SCHEMATIC:

SQ-RSEout-0.9.0schem.png


PCB BOARD 1.8" x 1.08":

SQ-RSEout-0.9.0brds.png


MODIFICATIONS:

The following graphic illustrates precisely how to integrate the new board:

SQ-RSEoutWiring090.png


Remove the old "filter board" and all wires from the LMH switch (careful not to apply too much heat to the switch - flux is your friend). Connect the signal wire to JIN, the signal wire ground shield and existing GND wire (will need to redress these wires - more below) together to JGND and then add a completely new wire from solder lug 16 on the Echo Board to JV+ (gently twisting it alongside the exiting GND wire).

To connect the switch wires just run short bits of bus wire (maybe with little bits of insulation). The different poles of each switch position are not used so you can connect them all together (or not).

Here are some example build pictures:

SQ-RSEoutPrep0.png


The first pic shows all wires cleaned up and prepped. Specifically, consider:

1) C72 has been replaced with a piece of bus wire. To get to C72, the main board has been lifted up but it is completely acceptable to just solder a small piece of bus wire across the pads if you can lift the board enough without de-soldering any of the wires (or maybe use a razor blade to cut the leads of C72 from the top of the board and strap a piece of bus wire across the top). Otherwise, it may be necessary to desolder several wires around wire lugs / pads 13, 14 and 15 to lift the board enough to work on the underside. Regardless, it will almost certainly be necessary to remove some wire lacing. Take pictures. I actually I installed a make-shift connector to make lifting this board easy.

2) The blue shielded signal wire, the ground wire and all switch wires have been de-soldered and prepped. Trim unclean ends, strip and tin all wires. Note that the ground wires might not accept solder very well so you might need to apply extra heat and use leaded solder with a lot of flux.

3) An orange V+ wire has been added from lug 17 on the main board and paralleled with the existing ground wire. The existing ground wire is far too large to fit in the JGND wire pad so you can barely see (right next to the end of the orange wire) that I wrapped a piece of bus wire around it to extend it.

The second pic shows the new board mounted. But first solder the V+ wire to JV+ and the aforementioned ground bus wire to JGND. Using the extra bus wire of JGND, make a "solder lug" on the other side for the equally thick and hard to solder shield wire of the blue signal wire. Add 3 pieces of bus wire for the switch and use some insulation to keep them from touching each other. Make sure the board is perfectly aligned with the bottom of the chassis so that it does not get damaged when the chassis is installed / removed during maintenance. After the board is mounted, solder the switch wires.

ERRATA:

Do not use ACJS-MV jacks. They will work but are difficult to mount to the panel. The outer washer is too tight and inner isolator and washer cannot be used (although chassis isolation is only really required for the foot switch jack). ACJS-MN would be easier. Not sure about Switchcraft 113B/114B.

The PCB holes for the 1/4" jack pins are slightly too small. You will need to crush them a little with pliers first.

C3 680n is not necessary and should be jumped with a piece of bus wire. The idea was that with the extra gain, it might be prudent to roll-off the lows to increase headroom in the high gain position but this has proven to be not necessary.
 

mjrippe

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Very nice!  I know a lot of folks who will want this.  You might contact Shane at www.echofix.com and see if he would be interested in producing kits, unless you intend to do so yourself.
 

Bo Deadly

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Thanks. It takes a village  8)

I don't do kits. If someone wants use this somehow to make a kit go right ahead. But if they want to put there own logo on the board or make changes / fixes that would be a problem because I use all custom components in Eagle and I don't want to share my morass of a component library for fear of embarrassing myself. But feel free to copy anything and everything I've done here. Just look at the part numbers and layout and make your own schems.

The board has been "send to fab" now. So I should have it in two weeks more or less. If it works, I'll "share" it and update this page with the link.
 

mjrippe

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squarewave said:
Thanks. It takes a village  8)

I don't do kits. If someone wants use this somehow to make a kit go right ahead. But if they want to put there own logo on the board or make changes / fixes that would be a problem because I use all custom components in Eagle and I don't want to share my morass of a component library for fear of embarrassing myself. But feel free to copy anything and everything I've done here. Just look at the part numbers and layout and make your own schems.

The board has been "send to fab" now. So I should have it in two weeks more or less. If it works, I'll "share" it and update this page with the link.

I absolutely applaud you giving away your design for free.  You could even look into some of the Open Source licenses to protect your IP if you like.  I mentioned Echofix because Shane is an awesome guy who sells everything you need for restoring Space Echoes.  He even came out with his own modern version of the RE-201.  This could be a big seller for him and could make you a few bucks in return.
 

ruffrecords

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mjrippe said:
I absolutely applaud you giving away your design for free.  You could even look into some of the Open Source licenses to protect your IP if you like.  I mentioned Echofix because Shane is an awesome guy who sells everything you need for restoring Space Echoes.  He even came out with his own modern version of the RE-201.  This could be a big seller for him and could make you a few bucks in return.

Seconded. I have open sourced many of my PCBs. It is easy to make them available to home builders free of charge but preclude unauthorised manufacture for sale by using one of the Creative Commons licences. This is the form of words I use:

"This folder contains the Gerber files for the PCB designs I have released as open source. In simple terms you can make these boards using these files for your own personal use only. If you want to sell the boards or use them in a product for sale you must contact me to discuss licensing terms.

For the avoidance of doubt, all these files are released under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International  (CC BY-NC-SA 4.0) license a full copy of which you can find here:

https://creativecommons.org/licenses/by-nc-sa/4.0/

Please read and understand this license before you download any of the files. All the files are in .zip format and contain a complete set of Gerber files necessary to manufacture the boards."

A genuine manufacturer will not mind paying you a dollar royalty per PCB. You won't make a fortune but it goes some way to covering your costs and a little towards your time.

Cheers

IAn
 

Bo Deadly

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There's no IP in the design. It's an LC filter and an op amp. If it was copied exactly right down to the text, that is implicitly a violation of copyright. When I "share" it on OSHPark, I would have to add something like "this is public domain and can be sold without royalty" or some such. But I won't because I don't know what the correct language is and because it would be pointless to sell something that you don't have the source files for. So shane or whoever should just look at the schem and layout and transliterate as necessary using their tool-chain. Then it's clean of any IP issues.

But thanks for the commendations. I just really hope it works now! If there's some goofy problem that will be really embarrassing. I don't think I've ever made a PCB that was perfect the first time. But this one is pretty simple so I'm hopeful.
 

ruffrecords

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squarewave said:
There's no IP in the design. It's an LC filter and an op amp.
There is certainly IP in the PCB layout but if you are happy to share that even to the point of commercial exploitation then that is of course your choice.

Cheers

Ian
 

Bo Deadly

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ruffrecords said:
There is certainly IP in the PCB layout but if you are happy to share that even to the point of commercial exploitation then that is of course your choice.
Has anyone ever actually made any real money selling PCBs? There's only room for one "all-things space echo repair" site (maybe two if they're on different ends of the planet).

With the cost of living what it is in NJ USA, I'm pretty sure I've lost way more money fooling around with electronics than I would trying to sell PCBs. Although I have "saved" a lot of money making and repairing things myself. That is empowering. We need more people with those skills. So to ask people for money for a little PCB vs showing them how to Do-It-Yourself, does not make sense to me.
 

emrr

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I can think of a few people around here who've sold a PCB concept to a manufacturer for $10K, one time payment.  At least one was selling PCB's here, and stopped.  That's probably a lottery fluke.  Several career freelance designers have advocated such sales.  Question is whether there's a similar market. 
 

mjrippe

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squarewave said:
Works perfectly. Link to OSHPark shared project and other stuff updated.

Thank you so much for all your efforts and most importantly for sharing it freely.  I will definitely be purchasing a few PCBs and trying this out.
 

mjrippe

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So Mike (squarewave) was kind enough to send me a spare PCB and I am excited to order the bits and install it in one of the RE-201 units here at the studio.  As a small gesture of gratitude, I turned his first post into a PDF manual for the SQ-RSEout and I am attaching it here.
 

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  • SQ-RSEout.pdf
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mjrippe

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Tomorrow I will be ordering the couple of bits I don't have on hand.  Did you use a ceramic cap for the 1n and 2n2 values or did you use film?
 

Bo Deadly

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Yes, C1, C2 and C7 are all non-audio-frequency parts so they can be ceramic (or film). Use whatever is in your parts bin. If you have a choice, C1 might benefit from being C0G or film or something that won't drift w/ temp changes. But it almost certainly doesn't matter. Hell, the twin-t board this replaces misses the notch by 8kHz! I can only guess they put the boss's kid on that.

One more word of caution, the OSHPark boards are pretty thick. As a result, it is very difficult, if not impossible to remove parts and clear a hole. Solder suckers and braids are ineffective. So don't make any mistakes! Measure twice. Solder once.
 

mjrippe

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Great, thanks!  I have a Pace desoldering station, but I'll try to get it right the first time  ;)
 

craigmorris74

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I'm trying to install my board in my RE-201, but I can't find C72 in the service manual diagram I'm looking at.  You're supposed to remove C72 and replace it with a jumper.
 
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