GR-55- Creating an external effects loop for the modeling tones

Started by justinmorell, April 30, 2011, 11:26:45 PM

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Elantric


glennfin

#51
Quote from: Elantric on March 31, 2014, 10:26:26 AM
If you insert a 1/4" plug into the VG-99 Guitar Input jack, the VG-99 Guitar Output Jack is disabled.

Not according to the block diagram. If you insert a 1/4" plug into the VG99 guitar input jack, the 13 pin guitar signal is disabled. The guitar input jack signal is routed directly to the guitar out jack, and the switch block.

Elantric

QuoteIf you insert a 1/4" plug into the VG99 guitar input jack, the 13 pin guitar signal is disabled. The guitar input jack signal is routed directly to the guitar out jack, and the switch block.
correct

glennfin

By the way, thank's for the link to the schematics!.... I really appreciate that............  and I see from looking at the schematic that the VG99 guitar input is buffered internally before it goes anywhere else.... ..  (the light bulb is on)  8)  ...

I was wondering about the mod to the GR55 to install a guitar input jack, like on the VG99 so the GR55 could be used as just a normal effects processor with a regular guitar but as I can see now, (and have seen in the other thread about the mod) a buffer would need to be added, like the buffer in the VG99.
That would be easy to do...... A switching jack and a simple op-amp buffer circuit.... or just add the boss tuner like you suggested since you lose the tuner function in the 55 when you do this mod and use the new guitar input jack. the wheels are turning!.  ;D



Quote from: Elantric on March 31, 2014, 12:03:24 PM
correct


Elantric


glennfin

Any idea where I could get a copy of that service manual? The resolution on the one posted is not good enough to read the component details/values. I think I'd like to replicate that same buffer circuit inside the GR55...


Quote from: Elantric on March 31, 2014, 12:32:33 PM
Glad to set your "wheels in motion"

Elantric

#56
Its a terrible copy - but it is all we have -  Roland no longer sells these.

Review this thread on implementing a VG-99 Effects Loop for Normal Guitar signal path - much as folks did with VG-88


https://www.vguitarforums.com/smf/index.php?topic=474.msg1874#msg1874


https://www.vguitarforums.com/smf/index.php?action=dlattach;topic=474.0;attach=420


After the VG-99 Mag PU "FX Insert" mod - you will now be able to connect your GK-3A equipped guitar to the VG-99 using the typical 13 pin cable, then when you select the "Normal Guitar" position on the GK-3A's "Guitar/ mix/ Synth" switch -  you may employ third party guitar stomp boxes on the Mag PU signal path - after the mod you will use the VG-99 "Guitar Out" jack as an FX Send - to feed the Mag P.U. signal ( which connects to the VG-99 via the the 13 pin cable) to your assortment of guitar stomp boxes (Keely Compresser, Fultone OCD,E-H Memory man, Line6 M13, etc.)  then the last stomp box the chain can now be routed back into the VG-99's 1/4" "Guitar Input" jack - - which after the modification to the internal VG-99 routing,  is now an "FX Return  for further VG-99 processing like COSM Amp sims and delays and reverbs and EQ.

To see the signal flow:

Here's the stock VG-99 Signal Flow:




Here's the modified VG-99 Signal Flow after the "FX Insert" mod:





Its a simple mod - move 2 internal connections ( cut & jumper) on a PC board.

The Caveat - the external FX can not be used on the hexaphonic signals ( COSM Guitar)

They only function on the standard Magnetic Pickup's signal path prior to hitting the VG-99's COSM Amp Sims.

glennfin

WOW!... thank you so much for that!.. I was trying to figure a way to use only my VG99 at a live gig as just an FX processor but with my Triaxis tube preamp in the mag pickup chain,,,,, This will do just that. I'm going to make the mod this week sometime!.  Awesome!  :) :) :) and it looks like I can use a regular non-gk guitar plugged into the FX return!....... sweet!


Quote from: Elantric on March 31, 2014, 12:41:11 PM
Its a terrible copy - but it is all we have -  Roland no longer sells these.

Review this thread on implementing a VG-99 Effects Loop for Normal Guitar signal path - much as folks did with VG-88


https://www.vguitarforums.com/smf/index.php?topic=474.msg1874#msg1874


https://www.vguitarforums.com/smf/index.php?action=dlattach;topic=474.0;attach=420


After the VG-99 Mag PU "FX Insert" mod - you will now be able to connect your GK-3A equipped guitar to the VG-99 using the typical 13 pin cable, then when you select the "Normal Guitar" position on the GK-3A's "Guitar/ mix/ Synth" switch -  you may employ third party guitar stomp boxes on the Mag PU signal path - after the mod you will use the VG-99 "Guitar Out" jack as an FX Send - to feed the Mag P.U. signal ( which connects to the VG-99 via the the 13 pin cable) to your assortment of guitar stomp boxes (Keely Compresser, Fultone OCD,E-H Memory man, Line6 M13, etc.)  then the last stomp box the chain can now be routed back into the VG-99's 1/4" "Guitar Input" jack - - which after the modification to the internal VG-99 routing,  is now an "FX Return  for further VG-99 processing like COSM Amp sims and delays and reverbs and EQ.

To see the signal flow:

Here's the stock VG-99 Signal Flow:




Here's the modified VG-99 Signal Flow after the "FX Insert" mod:





Its a simple mod - move 2 internal connections ( cut & jumper) on a PC board.

The Caveat - the external FX can not be used on the hexaphonic signals ( COSM Guitar)

They only function on the standard Magnetic Pickup's signal path prior to hitting the VG-99's COSM Amp Sims.


glennfin

#58
There's no specific instructions regarding the 99, so I'll have to open up the VG99 and take a look inside... think twice, cut once  ???
Shouldn't be to difficult at all for an electronics guy like me....  ;D

After the mod, I can take the MIDI out from the VG99 into MIDI in on the Triaxis so they switch patches together..... however... there is no bypass on the Triaxis, so it will always be inline when using the Mag output.

At the moment, I'm trying to figure out what the purpose is for that return line coming back from the CN16 connector to the guitar input jack.  ???

glennfin

#59
Oh, wait, I think that's the 13 pin signal...... got it!

I'll continue this over in the VG99 forum....  ;)

greekjgg

Ok, I'm trying to reread this thread. I can't tell if the goal has taken on a different path or it was resolved easily and I missed it and the kinks are being worked out on an additional mod?

I ordered some inputs so I can perform the mod for the mag pu using either regular guitar input or external effects for the mag pu in the other thread.

If I'm reading correctly that doesn't allow for external effects of the GK pickup, so I would still need to perform a mod of some sort to get the same functionality from the GK Pickup?
Setup:
Homemade EVH Frankenstrat with built in GK3
GR55
Rocktron Talkbox
TC Helicon Voicetone C1
Tech 21 Power Engine 60

Elantric

#61
You can only add a mono "FX Loop" for your normal guitar signal path - and yes this allows one Gk-13 pin cable between guitar and GR-55.

In regards to using this mod to add FX to the COSM Modeled guitar tones,  I have heard of other users who have made experiments using the GR-55 Guitar Out assigned strictly to output COSM model tones only, and feed an external FX pedal and then feed the FX return into new modified "Guitar In" jack on the GR-55.

Get a pencil and draw the possible signal path diagrams - just be careful to avoid potential signal paths of outputs feeding back into its own input - else high pitch full output feedback will instantly occur  -that could harm your speakers and ears!