Hi,
I received my gpdi/ir today from Thomann in Europe (it is a B-stock unit). I like the sound but I’m noticing a strange, distorted noise/rumble behind the notes, most noticeable on the clean or lower gain settings. I’ve attached a brief recording from the ir output.
I used new cables and different guitars. I also tested a separate power amp and ir simulator coming from the send fx output and the noise/rumble is still present, so I believe it’s coming from the preamp section. Is this an expected behavior? It seems a bit too much.
On a side note: this thing is great as a bass preamp (apart from the noise), proper John Wetton Crimson-era tones! Also, does the full head works with bass as well?
Hello to both of you and welcome to the forum! In order for us to all be on the same page in this scenario, it’s critical to know every single setting of every control on the GPDI/IR, the approximate output of your guitars pickups, i.e. hot, moderate or low, and what, if any, speaker cabinet you are using? And if not a speaker cab connected to the speaker output, then what speaker system are you monitoring the signal on? All of this will help everyone reading these posts, and myself, to understand the signal path, gain staging and other variables which could have a significant impact on the issue at hand which based on the audio clip you posted, does not come across as a noise/rumble, but instead sounds like some gentle overdrive in the lower mids/bass frequencies. This would be indicative of one of the gain stages in the GPDI/IR beginning to clip slightly, and probably could be avoided by simply lowering one or more of the gain stages and or the master volume. Please let me know about the settings and rig configurations, and I welcome your responses. Cheers! Gil
@Bendedavis you should be able to drag drop images to the post and they automatically upload. Like Gil says knowing your front panel settings would be good
Hi! You are right, I’ll try my best to explain my configuration.
The guitar on the recording is a les paul with relatively low output paf style pickups (bkp mules). I also have a strat copu with very low output pickups and it does the same (albeit a little less).
It goes straight to the gpdi, with no cab connected, and from the gpdi ir output to the mixer (a good quality one, ssl six).
I’m not using any eq or compression on the mixer itself. I monitor through the mixer via headphones and/or monitors (yamaha msp5).
On the gpdi part I also tried: the analog out with cab engaged, the analog out with cab disengaged and an external ir loader, the fx send out with an external poweramp sim+ ir loader. The artifacts I’m hearing are not dependent on these.
On the monitoring part: I tried to skip the mixer and monitor through the daw and again the endresult is the same.
Settings the gpdi: actually any setting in LESS/Deliverance (I have not tried the Pittbull), but they are more apparent on the lower gain settings as the artifacts become more difficult to distinguish if the tone of the guitar is distorted. In the recording I believe the first gain was around 10 o’ clock, the second gain less than that but I don’t remember for sure. Anyway this is not dependent on gain (nor dynamics or volume), it happens even with the second gain at 0. The eq is more or less centered. With the same setting on MORE mode, I can get a clean tone by rolling the guitar volume without this “distortions”.
Forgot to mention, all recordings are through analog out with cab sim disabled and IR added in post in Ableton. There was no clipping anywhere in my recording chain.
The GPDI is a 1W tube guitar amplifier. Output power aside, you are running the power amp pretty much wide open with the master set at noon or above, so you are well into power amp distortion territory just like you would be if you set a 50 or 100 watt amp that way.
You also have the bass up there and the Deep switch on, which will eat up output power and might get a bit flubby at that MV setting.
Turn the master volume down to around 9:00 to 10:00 and then turn up the input level on your interface or mic pre. That’ll clean it up quite a lot. If I am trying to get a pristine clean, I’ll leave Gain II all the way down.
That said, I think all your clips sound really good. It sounds like a real tube amp with some push on it, which it would because it is a a real tube amp with some push on it.
In my case the volume is around 9:00 and the depth can be anywere from 0 to max. But as I said, I also tried the fx send out, so the power amp volume shouldn’t matter.
I’m having mine exchanged at GC. Is it possible this could be a power issue? I use a Furman power conditioner but my power comes in close to 124V all the time.
So far, I am not hearing anything wrong. What I hear in the clips is a nice musical sounding tube amp clean sound.
The GPDI, like a typical tube amplifier, produces harmonic artifacts that are pretty noticeable when playing clean. These are created when you play two or more strings, and are enhanced by the power supply architecture found in pretty much every guitar amp to a lesser or greater degree. This is intended to give the GPDI a familiar feel and sonic signature, and like our big amps, tends to have a lot of dynamic range and detail.
Regarding AC input power, the operating voltage inside the GPDI/IR is extremely stable with respect to external line voltage.. You can run it from 85V to 250V AC and not hear any difference. An external power conditioner will do nothing to improve on that.
It’ll be interesting to hear your reaction when you get the replacement.
I checked out your settings here using Sony MDR 7506 headphones with a Hamer Special
and I did a signal strength test on the bench. Here are my conclusions:
I do hear and see (on the scope) the soft clipping on initial string attack and decay you experienced. This is tube stage clipping in the first two gain stages, putting it before the FX Send as you described.
At the settings you posted, this is normal. For reference, turn the preamp volume of any guitar amp you have up to around 10:00 and you will likely get a similar distortion, especially with humbuckers. On some amps, non-MV amps in particular, the volume will be loud enough that you will be forced to back off on string attack as it will be quite loud and your natural tendency is to avoid pain. With an amp like the GPDI, you have the ability to lay into it without worrying about volume or ear damage. But that will also allow you to hear the subtle distortion artifacts you normally don’t experience at volume.
To reduce this distortion, do the following -
Turn Gain I down to 8:00 to 9:00 max. For reference, most Blackface Fender style amps start distorting at 3 or less on the channel volume, which is equivalent to 8:00 to 9:00 on the clock face.
Set the voicing switch to the Clean setting. The Deliverance and Pittbull voicings will add a little grit to the sound and bump up the mid gain a bit, which is intentional. As Gain 1 increases, we want a gradual onset of overdrive as you roll into higher gain settings. If you want more brightness on the clean sounds, turn up the Treble and back off on the Middle to around 10:00-11:00.
Turn the Master volume up. In my test, I set it as high as 1:00 - just at the threshold of power amp clipping with Gain I at 9:00 (NOTE This clipping threshold goes DOWN as gain goes UP). Getting a little power amp mojo happening will help smooth out distortion artifacts in the clean sound. This is why even though Fender amps are described as “clean” they are also quite distorted if you listen closely when you pass 3. Again, these artifacts get masked out at volume because the power amp and speaker behavior are acting as a filter. Your ears are also trying to filter out distortion at volume, a known phenomenon that doesn’t happen with the GPDI unless your headphones are cranked.
Set the Dynamics control to zero. This will provide maximum plate voltage to the preamp tubes and therefore maximum headroom. On the other hand, the overdrive harmonics will soften at the onset of sag, so increasing the Dynamics setting may also work for you.
Experiment with different IRs. The one selected in your photo above - 3/1 - is the Fane loaded Deliverance 412 cab mic’d with two SM57s. It has a lot of top end detail and is fairly tight on the low end. A better choice would be 1/3, the Sound City 412 with the same speakers but a more open low end and is mic’d with an SM57 and a Royer 121.
