Greetings! I recently received my new GPDI/IR from Zzounds, and was using it for silent recording via the IR out for the last couple of weeks. Suddenly, my levels on the IR out were extremely low. So low that I had to max the master volume and line out volume just to get any signal at all.
To troubleshoot, I connected the speaker out to a 1x12 cab. Same situation here–with the master maxed, I can just barely hear some output through the 1x12. It is quieter than the acoustic volume of the guitar strings.
Since the IR out uses a tap off the reactive load, this seems like it is a power stage issue. As a final step, I connected some headphones to the FX send. Plenty of output coming through the send, so the preamp seems fine.
Aside from swapping in another 12DW7, is there anything else I can do to troubleshoot before sending this in?
Hello and welcome to the Fryette Forum! Based on the information you’ve provided, it does appear that the power output section of your GPDI/IR is malfunctioning. It is probable that its the V4 12DW7 tube that is the cause, but not a certainty. You can try installing a 12AX7 in its place just long enough to test the output to see if it changes to expected output volume. If it does, then the 12DW7 will need to be replaced. If you don’t mind, please remove the top cover and send us a clear picture of the inside of the chassis. Please let me know the date of purchase and include the serial number as well. Thanks! Gil
I tried a Chinese 12AX7 in V4 and the behavior was nearly identical. It may have been just a hair louder, but still not as loud as the guitar acoustically.
Order details
Ordered: February 15th 2025 (backordered)
Shipped: April 12th 2025
Serial Number: GPXL240078
Can you try swapping the output from the unbalanced lines (analog and IR) as well as the FX send and run that into your DAW. I just want to make sure that the levels are indeed low from the perspective of the DAW. I don’t think the headphones will give a good indication of the relative signal level.
Oh and, just checking – it did indeed ship with a 12DW7 (ECC832)?
It sure would be nice to both own and know how to use an oscilloscope right now
The v4 tube is indeed a 12DW7 (ECC832).
As for testing levels, I did my best to cobble something together in Logic Pro and my Apollo Twin interface (a bit beyond my skill to be honest). I ran both pink noise and a 1k tone from an output back into the input of the Apollo to grab a baseline in the multimeter plugin, then I routed the tones and pink noise through the input of the GPDI/IR and out of the various outputs back into the Apollo.
Attached you will find screenshots for all the various combinations. I can only attach one image per post, so you will soon see many messages from me.
Pink noise baseline on the Apollo without the GPDI/IR in the chain
As you can see in the meter, there is some noise going on with how I have this setup, but the overall levels did not seem to be affected (only some extra freqs when using the 1k sine wave).
I also turned the line level knob and master volume for each of these and I can indeed see the meter drop to nearly zero when master or line level is at zero, then see it climb again as I max them out.
This is thorough, but I just wanted to confirm that when you use the effects send as a line out it has a normal output level, but when you change using the unbalanced line out from IR or analog the level is low.
What’s the peak 1k signal level you get from FX send vs line outs?
Good morning, Dan. Apologies, I had to create an alt account as I have hit some sort of 24 hour posting limit. I cannot reply in the other account for 8 more hours. Feel free to delete or archive this user when we have this sorted.
To confirm, the analog and IR outs are significantly lower than the FX send. So low that they are nearly inaudible. Both the line outs are roughly -40 dB peak while the FX send is near 0 dB and even clips the meter in one case. Even with the input gain maxed out on the Apollo, the signal is still -35dB or so.
For comparison, the line out and FX send of my Synergy SYN-1 with volume maxed is roughly -7.5 dB when using the same test setup.
GPDI/IR
IR out and analog out: ~ -40dB
FX Send: ~ 0dB
Synergy SYN-1 (for comparison)
Main line out: ~ -7.5dB
FX send: ~ -7.5dB
Thank you, Dan! I would like to hang onto my original R590 account please. As for the unit, is my next course of action a regular support email to arrange for service?
Some final things: number one does the ground lift switch? And does have the speaker connected/unconnected make a difference. I’m just trying to remove to possibly of a bizarre ground loop issue or some peculiar happening with whatever the output is connected to.
I can think of anything else. @Gil will decide what to do he might want to run it by Dave.
The GPDI/IR is still connected to the interface via the IR out
Volume and line level are maxed
GPDI/IR is connected to a 16 ohm 4x12
The levels in the daw are still incredibly low
I can hear the faintest of volume from the 4x12. I put a decibel meter in front of the cab right on the grill cloth. Roughly 48 dB which is only a couple dB above idle noise in this room
The ground lift does not have any effect on the IR out or speaker out
