24 pin to 13 pin internal Buffers

Started by chrish, February 04, 2018, 08:47:12 AM

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chrish

I've been doing some research on buffers and finding some good information on the internet.

I  can't bring myself to install the internal GK 3 kit on my G505 or G 202 because I'd have to carve into the guitar  to install the pickup.  Still trying to figure a way to tap and split the existing hex pickup circuit to feed gk3 preamp board.

The main problem (I think) is the 24 pin preamp board operates on 15 volts DC and the gk3 preamp board operates on 7 DC volts. I believe that mismatch would result in needing a decoupling circuit.

And then there's impedance problems (I think) associated with loading the one hex pick up from two preamps and I believe that's where the hex buffer need to be applied.

Or maybe I can just tap in somewhere, I don't know because I read on the forum somewhere that the gk3 circuits already contain a hex buffer.

https://www.seymourduncan.com/blog/the-tone-garage/buffer-the-weak-tone-slayer

http://www.muzique.com/lab/buffers.htm

https://www.vguitarforums.com/smf/index.php?topic=2279.msg13239#msg13239

jim-analog



Greetings,

Chrish, are you still trying to find a solution to this? There are a few ways to go about it, but I'm not sure if you wanted to maintain the 24 pin full functionality (with hex fuzz output internally generated and multiple CVs and modes available) or ONLY end up with the more minimal 13 pin outputs, with no hex fuzz and fewer CV signals. So, if you do want to continue on, please clarify a bit and I may be able to help out or at least put you on a path.

  To start, both the 24 pin and the 13 pin individual string outputs are amplified/buffered internally, but at different voltage levels out. The 24 pin circuitry uses +/-15VDC, while the 13 pin is +/-7VDC. There are also fewer control voltages to use from the 13 pin, as some from the 24 are not recognized by the newer equipment (frequency, resonance, LFO, etc.) as for hex fuzz, it is not internally generated in any of the 13 pin systems, but may be part of the subsequent processor units (I'm not that familiar with them) or not.

I'm currently working on an outboard adapter system to maintain all the 24 pin functions from my customized 505 guitars and simultaneously add 13 pin out at its specifications. So, that way I can play my 300 box, my 700 box (or both at once) and (as example) a GR-50 (which I wasn't impressed with, but for the future I intend to get a 6 appeal) so hence the need for 13 pin output.

Before moving forward, I'm trying to determine how extensive of a project I want this to be, as there are a bunch of things that would be easy to add once the signal path is broken and inside a single (getting large) box. For example, buffered hex fuzz direct output(s), buffered 6 x string outputs, etc., switching between 2 separate 13 pin outputs, on and on. It's all very simple circuitry (primarily different power supplies and level shifting/buffering), all just duplicated 6 times for each set of outputs needed.

All the info is pretty much in the various schematics and at Dr Joness page (Thank You!), but depending on exactly what you have, what you want to do and how you want to configure it, it may be split across quite a few places. Good luck however you decide to proceed and let me know if you'd like any suggestions.

Regards, Jim

chrish

Quote:"I'm currently working on an outboard adapter system to maintain all the 24 pin functions from my customized 505 guitars and simultaneously add 13 pin out at its specifications. "

This is exactly what I would like to do. One hex pickup driving both the 24 pin PC board and the 13 pin PC board at the same time.

It's my understanding from reading Dr. Joness site and this forum, that both my narrow type stock G505 hex pickup and the GK 3 hex pickup share the same impedance at 80 ohms.

I wouldn't have a clue how to design  the circuit  to accomplish this, but think I could handle soldering something together.




GuitarBuilder

Quote from: jim-analog on March 08, 2019, 05:35:55 PM

Greetings,

Chrish, are you still trying to find a solution to this? There are a few ways to go about it, but I'm not sure if you wanted to maintain the 24 pin full functionality (with hex fuzz output internally generated and multiple CVs and modes available) or ONLY end up with the more minimal 13 pin outputs, with no hex fuzz and fewer CV signals. So, if you do want to continue on, please clarify a bit and I may be able to help out or at least put you on a path.

  To start, both the 24 pin and the 13 pin individual string outputs are amplified/buffered internally, but at different voltage levels out. The 24 pin circuitry uses +/-15VDC, while the 13 pin is +/-7VDC. There are also fewer control voltages to use from the 13 pin, as some from the 24 are not recognized by the newer equipment (frequency, resonance, LFO, etc.) as for hex fuzz, it is not internally generated in any of the 13 pin systems, but may be part of the subsequent processor units (I'm not that familiar with them) or not.

I'm currently working on an outboard adapter system to maintain all the 24 pin functions from my customized 505 guitars and simultaneously add 13 pin out at its specifications. So, that way I can play my 300 box, my 700 box (or both at once) and (as example) a GR-50 (which I wasn't impressed with, but for the future I intend to get a 6 appeal) so hence the need for 13 pin output.

Before moving forward, I'm trying to determine how extensive of a project I want this to be, as there are a bunch of things that would be easy to add once the signal path is broken and inside a single (getting large) box. For example, buffered hex fuzz direct output(s), buffered 6 x string outputs, etc., switching between 2 separate 13 pin outputs, on and on. It's all very simple circuitry (primarily different power supplies and level shifting/buffering), all just duplicated 6 times for each set of outputs needed.

All the info is pretty much in the various schematics and at Dr Joness page (Thank You!), but depending on exactly what you have, what you want to do and how you want to configure it, it may be split across quite a few places. Good luck however you decide to proceed and let me know if you'd like any suggestions.

Regards, Jim

Did you take a look at Wayne Joness' SBC-1324?

https://www.joness.com/gr300/sbc-1324-vintage-roland-24-pin_to_Roland_GK-13_converter.htm
"There's no-one left alive, it must be a draw"  Peter Gabriel 1973

chrish

#4
I hadn't seen that, cool box.

However it looks like it's either a 24 pin or 13 pin output unless I missed something at the end of one of the videos. My desire is to have both available at the same time.



1 hex pickup running a 24 pin PC board with a 24 pin cable out.

And that same hex pick up running a 13 pin PC board with a 13 Pin cable out.

Both cables coming out of the same guitar and going to their respective processor units.

That's basically what I have going now, just with an extra hex pickup mounted on the guitar which I guess isn't really that big a deal.

I did write that guy in France to see if he could modify one of his 24 to 13 pin converters and have a 24 pin through output. Never heard back.

GuitarBuilder

Quote from: chrish on March 11, 2019, 04:40:42 PM
I hadn't seen that, cool box.

However it looks like it's either a 24 pin or 13 pin output unless I missed something at the end of one of the videos. My desire is to have both available at the same time.



1 hex pickup running a 24 pin PC board with a 24 pin cable out.

And that same hex pick up running a 13 pin PC board with a 13 Pin cable out.

Both cables coming out of the same guitar and going to their respective processor units.

That's basically what I have going now, just with an extra hex pickup mounted on the guitar which I guess isn't really that big a deal.

I did write that guy in France to see if he could modify one of his 24 to 13 pin converters and have a 24 pin through output. Never heard back.

That guy in France essentially copied Wayne's circuits......
"There's no-one left alive, it must be a draw"  Peter Gabriel 1973