Author Topic: GK Schematics  (Read 23134 times)

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Offline bea

Re: GK Schematics
« Reply #25 on: July 06, 2016, 03:09:46 PM »
Which means that a 3rd party GK selector should better provide its own power supply which should be able to deliver the power for all attachable GK guitars?

Background of my question is that i would like to have an external power supply feeding a future (planned, JFet) buffer for the internal LoZ pickup. But maybe it is better in the sense or more practicable to use some kind of phantom power through a stereo jack in the guitar.

Offline Elantric

Re: GK Schematics
« Reply #26 on: July 06, 2016, 03:20:34 PM »
Quote
Which means that a 3rd party GK selector should better provide its own power supply which should be able to deliver the power for all attachable GK guitars?

Know that most GK-13 accessories do not provide their own DC power.

Adding yet Another DC power source typically yields Ground Loop Noise 

Most follow what the Roland US-20 Box does , use the "Unit A" connected Gk 13 pin processor to source the +7VDC and -7VDC   
« Last Edit: July 06, 2016, 03:22:57 PM by Elantric »

Offline Elantric

Re: GK Schematics
« Reply #27 on: March 29, 2017, 10:37:28 AM »
All Roland Ready Strats operate identically to the Roland /Fender GC-1 -



GK-3 schematic (above) is 99% similar to the GK-KIT-GT3 Internal kit.

 
the only issue with a standard GK-KIT-GT3 installation on your guitar , the mag PU's become  "loaded down" and dull sounding due to the additional input impedance of the parallel Mag PU connection on the internal GK Preamp board (see connector CN5 below)  and your 1/4" output jack feeding your separate FX/Amp for the mag PU's  = dull sound for the mag PU's even when used with only a 1/4 cable after a standard  GK-KIT-GT3 installation





That is one aspect where on the Fender "Roland Ready" / GC-1 Strat, (see schematic above) Fender deviated from the official Roland GK-KIT-GT3 installation method, by adding that special 1/4" switching output jack with the normally closed switch that feeds the GK preamp board. when you insert a 1/4" plug into the normal Mag PU Output jack, this switch opens, and you disconnect the Mag PU feed to the GK preamp board = better sounding mag PU's on your 1/4 output jack feed. 
« Last Edit: August 23, 2017, 11:42:19 AM by Elantric »

Offline dead3t3rn1ty

Re: GK Schematics
« Reply #28 on: March 30, 2017, 03:48:14 AM »
That's interesting: I noticed something strange when using the regular output jack on my Strat (not the GC-1, an American Standard with gk-kit installed).

A Switchcraft 112AX should do the trick, I need to replace a pot, I will try the new output jack as well.

Online admsustainiac

Re: GK Schematics
« Reply #29 on: March 30, 2017, 08:38:53 AM »
Quote
A Switchcraft 112AX should do the trick,

Fender GC-1 uses the same Switchcraft 12A jack used as input jack on a 1966 Fender Twin Reverb




http://www.markertek.com/product/sw12a/switchcraft-12a-1-4-inch-2-conductor-jack-w-nut-washer-single-closed-circuit?utm_medium=shoppingengine&utm_source=googlebase&gclid=CPX-m7W7_tICFc63wAodZYwMYw


JACK, 1/4", MONO, CLOSED CIRCUIT (SHORTING), WIRED, Switchcraft® 12A
Found in vintage Fender® (and other) amps as the input jack.   Also used in the Hot Rod Deluxe/Deville, Blues Deluxe/Deville as the main speaker out jack.  Includes nut and washer.    Fender® part number 0021550000 (originally 021550).



or

Neutrik NYS229S 6.35 1/4" Phone Jack Mono
http://www.ebay.com/itm/6pc-Neutrik-NYS229S-6-35-1-4-034-Phone-Jack-Mono-Guitar-Effect-Pedal-Bass-Audio-Amp-/142341162360?
« Last Edit: August 23, 2017, 11:43:20 AM by Elantric »

Offline GuitarBuilder

Re: GK Schematics
« Reply #30 on: March 30, 2017, 08:54:35 AM »
Is that a burn mark on your GC-1?

Offline chrish

Re: GK Schematics
« Reply #31 on: October 18, 2017, 12:16:28 AM »


 
the only issue with a standard GK-KIT-GT3 installation on your guitar , the mag PU's become  "loaded down" and dull sounding due to the additional input impedance of the parallel Mag PU connection on the internal GK Preamp board (see connector CN5 below)  and your 1/4" output jack feeding your separate FX/Amp for the mag PU's  = dull sound for the mag PU's even when used with only a 1/4 cable after a standard  GK-KIT-GT3 installation




is it correct then that if you don't use the 1/4" magnetic pickup output, and only use the 13 Pin cable to supply the magnetic pickup signal, that the dull mag pup sound will not be a factor since there would not be a parallel connection load?
« Last Edit: October 18, 2017, 12:18:46 AM by chrish »

Offline gumtown

Re: GK Schematics
« Reply #32 on: October 18, 2017, 02:23:53 AM »
Any type of passive "double termination" will load the pickups down, and start acting more like a low pass inductor, loosing that top-end sparkle.
If a signal requires splitting, it might be better to wire the guitar out jack to connect after the GK active buffer.

Or maybe modify the GK input circuit buffer for the Normal pickup to a raised impedance from 500K ohm to around 2 Meg Ohms.
Free "GR-55 FloorBoard" editor software from http://sourceforge.net/projects/grfloorboard/

Online snhirsch

Re: GK Schematics
« Reply #33 on: October 18, 2017, 05:55:32 AM »
Any type of passive "double termination" will load the pickups down, and start acting more like a low pass inductor, loosing that top-end sparkle.
If a signal requires splitting, it might be better to wire the guitar out jack to connect after the GK active buffer.

Or maybe modify the GK input circuit buffer for the Normal pickup to a raised impedance from 500K ohm to around 2 Meg Ohms.

One of these would be good for the second solution:

http://www.muzique.com/schem/buffmod1.htm

Offline chrish

Re: GK Schematics
« Reply #34 on: October 18, 2017, 12:51:29 PM »
Any type of passive "double termination" will load the pickups down, and start acting more like a low pass inductor, loosing that top-end sparkle.
If a signal requires splitting, it might be better to wire the guitar out jack to connect after the GK active buffer.

Or maybe modify the GK input circuit buffer for the Normal pickup to a raised impedance from 500K ohm to around 2 Meg Ohms.
thanks for that explanation. There is very little information that I found on the internet about splitting magnetic pickup signals.

 I did find this however.

https://arstechnica.com/civis/viewtopic.php?f=6&t=505119

"Here's how this works electrically: A line level output is no more than 600 ohms impedance; in consumer gear it may be much lower. A line level input will be at least 10K ohms.

Let's suppose our output is delivering one volt, and we have the standard values of 600 ohms output impedance, 10K ohms input. Then the input will see about 0.94 volts - the rest being dropped across the source impedance.

Now let's use a Y-adapter to connect another input in parallel. You now have a 600 ohm source driving a 5K load. Each of the inputs will see about 0.92 volts.

This is a drop of about 0.2 dB. I doubt you'll be able to hear it.

If the output impedance of the source is lower, as is common, the situation is better.

There isn't any problem with current, either. Even with the splitter the output is only being asked to supply 0.18 milliamps. If your output can't provide that you have far, far worse problems than will be caused by the splitter.

Where you CAN get into trouble is if you try to drive both a line-level input and headphones the headphones need a lot more current, and as far as the line-level input is concerned, will look like a near short, thereby drastically cutting the volume to the line-level input.

Another way to cause problems is to try to use a Y-adapter to combine two *outputs* to drive a single input, instead of using a mixer. Each output then presents an excessive load to the other and there's not enough current available (not even 0.18 ma) to drive the input. This is where you will commonly get drastic reductions in volume, distortion, etc.

All of the above applies to line-level sources and loads, either consumer or pro. It doesn't apply to mics or guitar pickups. These emit low voltages (extremely low, in the case of a microphone) at a higher impedance (around 1000 ohms), and they have very little current available. They therefore can't be split with any success. The only thing to do with a mic or guitar output is to connect it to a preamp. The preamp output then gives you line level, which can be split as described above."

One of these would be good for the second solution:

http://www.muzique.com/schem/buffmod1.htm

I noticed that that buffer runs on 9 volts DC. So if the buffer was  inserted  between the  GK board and the guitars 1/4"output, would a coupling capacitor be required in order to avoid interaction between the 9 volt battery and the 7.5 volt GK circuit?

Not that I know what I'm talking about. :)

The reason I'm asking all these questions is because I'm trying to determine if it's feasible to install the GK internal kit into my Roland G505 and run both off the stock hex pickup.

 I believe the stock pickup is 600 ohms and the GK 3 pickup is 500 ohms so both pre-amp boards are similar in that regard (input impedance?). However the preamp  operating voltages I believe are different.

Also I was looking getting rid of the stock 1/4" guitar out, enlarging the hole to 5/8 of an inch, and placing the GK13 pin Jack there.

And to complicate matters I was going to plug those magnetic pick up leads that were on the stock 1/4" Jack and plug it into the internal GK3 board to send that magnetic signal down the 13 Pin cable.

The result would be a mag pup signal going down the 24 pin cable and the 13 pin cable. .

Quite a scheme but I'm treading water here.After reading the Forum I now know it may not be feasible without knowledge of coupling capacitor circuits and buffer circuits.

I'm also trying to follow this wise advice I found on the forum.

Quote
"If you are not sure of what you are doing in electronics, be prepared for damage or smoke." :)
« Last Edit: October 18, 2017, 01:01:10 PM by chrish »

Offline chrish

Re: GK Schematics
« Reply #35 on: January 02, 2018, 04:08:24 PM »
 so I've decided, partly because of my lack of knowledge on how to overcome the voltage differentials between the two preamp circuit boards as described in above post, and because I don't know how to overcome the signal impedance problems associated with the splitting of the hex signal, I've decided that I'll just install my GK 3 internal kit, separate from the 24 pin signal path.

So that means just using two hex pickups, one for the 13 pin and one for the 24 pin circuits.

I do have some questions.

Would it be acceptable to use silicone caulk to attach the gk3 preamp on top of the 24 pin circuit board?


The circuit boards would be placed back to back with a non component sides facing with the silicone caulk in between.

Any concerns with this method of attachment?

And I was wondering if there's some secret magic plastic conditioner spray that I could apply to  the ribbon cables for the old 24 pin connections?

My understanding is that those are fragile because of age and could crack.

Offline gumtown

Re: GK Schematics
« Reply #36 on: January 02, 2018, 04:51:55 PM »
I have found the white or black silicone works fine,
 avoid the acid based clear stuff, it will eat the circuit board copper.
Free "GR-55 FloorBoard" editor software from http://sourceforge.net/projects/grfloorboard/

Offline chrish

Re: GK Schematics
« Reply #37 on: January 03, 2018, 09:48:45 PM »
I have found the white or black silicone works fine,
 avoid the acid based clear stuff, it will eat the circuit board copper.
thanks. That's Good information.

Now just need the super majic ribbon cable rejuvenation spray, seems like that cable is vinyl (pvc).

 

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