Super weird issue with GP-10

[cags12]

Hi folks, forking this thread slightly I hope I could get further help.

I have now acquired a GR-55 and wanted to use the Cycfi installation posted on this thread. However, even though I do get Modeled Guitar sound and normal Guitar sound; neither PCM1 nor PCM2 emit any sound. I am certain this is due to the absence of Pin 8 "Synth Vol".

The way I got around this issue with the GP-10 was to set "GK Connect: ON", however I do not seem to find such setting on the GR-55, does that even exist?. I know the VG-99 does have that setting so I now wonder is this a setting only relevant to processors that also take a 1/4" guitar input?

I tested my GK3 internal kit installation and even though SY_VOL is not in use nor GK_SW I do get PCM sounds so I only assume that there is extra circuitry that is sending the right voltage level to tell the GR-55 that the guitar is connected.

Looking at the schematic - I do not quite understand how it does it. My reading shows that the opamp doe snot receive anything on the + end as those lines are disconnected due the absence of both SY_VOL and GK_SW right? the other bit that I am highlighting I do not quite get either what is the end results of those two diodes and the resistance. Could this be helping sending the right signal?

[Elantric]

You need a Pin 8 GKVOL which represents a DC Voltage connected to pin 8

Most accomplish this by cloning the method Gibson Dark Fire employed with a 2 resistors network to deliver +5VDC to pin 8.  Details here
https://www.vguitarforums.com/smf/index.php?topic=22661.0#msg164834
https://www.vguitarforums.com/smf/index.php?action=downloads;sa=downfile&id=80

[cags12]

You need a Pin 8 GKVOL which represents a DC Voltage connected to pin 8

Most accomplish this by cloning the method Gibson Dark Fire employed with a 2 resistors network to deliver +5VDC to pin 8.  Details here
https://www.vguitarforums.com/smf/index.php?topic=22661.0#msg164834
https://www.vguitarforums.com/smf/index.php?action=downloads;sa=downfile&id=80

Thanks Elantric, I thought so but was hopeful there was another way like using "GK Connect".


You mentioned in your other post that VOL at max level is +6.3 VDC but in above comment you said +5 VDC. If I want to have it ta full volume, what value resistors would you recommend? Do I use a voltage divider calculator?

Also in my installation I use +7VDC to power the Cycfi pickups. The Darkfire wiring only uses the +7VDC to generate the voltage for SY_VOL, how can I make sure I will not affect the voltage that goes to Cycfy. In other words, is there a risk to affect the voltage that goes to the pre-amp by the voltage divider in parallel like so?

[Elantric]

https://ohmslawcalculator.com/voltage-divider-calculator
5v is the target for max vol
Source = 7V
R1=121
R2=243
= 4.63vdc

[cags12]

https://ohmslawcalculator.com/voltage-divider-calculator
5v is the target for max vol
Source = 7V
R1=121
R2=243
= 4.63vdc

Got ya, I only asked because in the other thread you said 6.3VDC. But I'll go with the Darkfire target Voltage and resistors.

Correct  - actually +6.3 VDC on GK 13 pin #8  = GK-VOL @ max level .

BTW, I did a quick test and shunted Pin 8 to Ground, this would be like zero volume but it allows the GR-55 to detect the guitar and as long as I keep Off GK VOL on System or Patch settings, it works. I will do the Darkfire mod anyway but this is another workaround.