Input Clipping of Digitech XP-100

[Baran Ismen]

Hello everyone. I have a quick question that I think you people would know.

I recently got an XP100 from Reverb and I saw that the input signal is constantly clipping. After seeing that the input volume knob isn't responsive at all, I measured the pot lugs, and I read a range of 73k to 104k between min to max positions between 1&3 and 2&3 lugs. Lugs of 1&2 gives 0 value.

I sprayed some contact spray inside but didn't help. Is this reading normal, or should it be between 0 to 100k?

Then I tried soldering an external 68k resistor between 2&3 lugs to decrease the gain, yet didn't help. Also tried 220k pot in parallel without removing the current one and values dropped to the 0-to-61k range yet still clipping. On both occasions, the measured value seems to be decreased yet the signal is still too hot. Only decreasing the volume of the guitar sends a normal signal that doesn't clip the pedal and blink the red light. 

I'm connecting this pedal to my audio interface and the signal coming to it does not clip the gain stage of the interface by the way, namely, the clip light is off. That leads me to think that it's already being clipped inside the unit somehow, and clipped sound comes to the interface.

As a side note, I am using active Duncan blackouts which have around 130k of output impedance and the input impedance of this pedal seems 470k, which I think should be ok, right?

All solders, parts, and everything seems intact and the pedal works just as it should be apart from this.

Any help would be most appreciated.

Here are some pics :

https://imgur.com/a/gv3bS88

[GGBB]

I'm connecting this pedal to my audio interface and the signal coming to it does not clip the gain stage of the interface by the way, namely, the clip light is off.

Is this why you think the unit is clipping? What about the clip light in the XP100? Depending on the audio interface, the clip light may only be telling you if the analog input is clipping. It could still clip after that at the AD interface or in the DAW software.

Does turning down the guitar volume knob help?

[FiveseveN]

Does turning down the guitar volume knob help?

Yeah, this is crucial information.
For the record, Blackouts are the highest output level pickups that I've come across and they certainly don't have 130K Z_out. Maybe 130 Ohms.

[digi2t]

Then I tried soldering an external 68k resistor between 2&3 lugs to decrease the gain, yet didn't help. Also tried 220k pot in parallel without removing the current one and values dropped to the 0-to-61k range yet still clipping. On both occasions, the measured value seems to be decreased yet the signal is still too hot. Only decreasing the volume of the guitar sends a normal signal that doesn't clip the pedal and blink the red light. 

Here is picture of the input end of the XP100...


Try a 10k or 20k resistor between pins 1 and 2 of the pot, and see if that brings the gain down. It it does, then the pot is pooched.

[Baran Ismen]

I'm connecting this pedal to my audio interface and the signal coming to it does not clip the gain stage of the interface by the way, namely, the clip light is off.

Is this why you think the unit is clipping? What about the clip light in the XP100? Depending on the audio interface, the clip light may only be telling you if the analog input is clipping. It could still clip after that at the AD interface or in the DAW software.

Does turning down the guitar volume knob help?

No, what I mean by that is the one that's blinking is the xp-100's clip led, not the interface.

And yes, bringing the guitars volume down helps; around %20 of the volume applied from my guitar, xp-100 does not clip, yet as you can imagine, whole tone goes away.

Then I tried soldering an external 68k resistor between 2&3 lugs to decrease the gain, yet didn't help. Also tried 220k pot in parallel without removing the current one and values dropped to the 0-to-61k range yet still clipping. On both occasions, the measured value seems to be decreased yet the signal is still too hot. Only decreasing the volume of the guitar sends a normal signal that doesn't clip the pedal and blink the red light. 

Here is picture of the input end of the XP100...


Try a 10k or 20k resistor between pins 1 and 2 of the pot, and see if that brings the gain down. It it does, then the pot is pooched.

As I mentioned in the PM, I did it with some resistors between 2.2k to 8.2k, and it helped yes, decreased the gain & vastly improved the clipping.

By the way, is it just me or the forum is overall slow? Getting constant errors of page not found and transitions between pages are sooo slow..

[digi2t]

By the way, is it just me or the forum is overall slow? Getting constant errors of page not found and transitions between pages are sooo slow..

Slow. I'm getting the same sluggishness. Also, your PM reply was only my answer quoted.

[ElectricDruid]

By the way, is it just me or the forum is overall slow? Getting constant errors of page not found and transitions between pages are sooo slow..

Yeah, there's been some issues the past few days and the site has been dog slow. Normally it's a *lot* more snappy. Hopefully it can get sorted soon. Aron, hit us up if there's anything we can do!

[Rob Strand]

If you have other problems you should sort those out first.

Here's the correct way to decrease the front-end gain without
affecting the pre-emphasis network's behaviour.



With +/-5V supplies in most cases the x2 gain of the original pedal should be OK.

[Baran Ismen]

If you have other problems you should sort those out first.

Here's the correct way to decrease the front-end gain without
affecting the pre-emphasis network's behaviour.



With +/-5V supplies in most cases the x2 gain of the original pedal should be OK.

Hi Rob, sorry but I couldn't understand what you mean by it.

When I got this pedal first, I didn't know that it needed an AC adapter, so I tried with a regular 9DC one, The unit was opening but was not getting any sound of it. I made a quick research and saw that it's not only me in the world who makes this same mistake. Then I got a 9v/1A AC adapter, and with this one the unit is working just fine, all patches, etc. sound as they should be. Only this gain is a bit problematic.

Yet I didn't understand anything by the +/-5V supply. Should I apply this to anywhere or ? Adapter I got measures around 9.5V AC.

[Rob Strand]

Hi Rob, sorry but I couldn't understand what you mean by it.

When I got this pedal first, I didn't know that it needed an AC adapter, so I tried with a regular 9DC one, The unit was opening but was not getting any sound of it. I made a quick research and saw that it's not only me in the world who makes this same mistake. Then I got a 9v/1A AC adapter, and with this one the unit is working just fine, all patches, etc. sound as they should be. Only this gain is a bit problematic.

Yet I didn't understand anything by the +/-5V supply. Should I apply this to anywhere or ? Adapter I got measures around 9.5V AC.

It's not something to worry about.  The pedal converts the external 9V AC to an internal +/-5V DC.  The +/-5VDC is what is shown on the schematic.   All I was saying that with that +/-5V internal supply and R10 and R11 set at the normal 10K values the opamp should not clip unless you have quite a hot input signal.

[Baran Ismen]

Hi Rob, sorry but I couldn't understand what you mean by it.

When I got this pedal first, I didn't know that it needed an AC adapter, so I tried with a regular 9DC one, The unit was opening but was not getting any sound of it. I made a quick research and saw that it's not only me in the world who makes this same mistake. Then I got a 9v/1A AC adapter, and with this one the unit is working just fine, all patches, etc. sound as they should be. Only this gain is a bit problematic.

Yet I didn't understand anything by the +/-5V supply. Should I apply this to anywhere or ? Adapter I got measures around 9.5V AC.

It's not something to worry about.  The pedal converts the external 9V AC to an internal +/-5V DC.  The +/-5VDC is what is shown on the schematic.   All I was saying that with that +/-5V internal supply and R10 and R11 set at the normal 10K values the opamp should not clip unless you have quite a hot input signal.

I found the schematics also and checked a bit -at least the section until this input pot, but I'm not sure which resistor(s) are working as a limiter so-to-say for input gain, but I can measure them all to see if they are actually working or not, yet I believe it's a faulty pot anyway, because I've just confirmed with another guy from Reverb who's selling the same pedal and he said, minimum value of the pot mutes the signal completely, whereas in my scenario it doesn't even lower the gain.

I think I'll replace it, though there's only one shop here in Turkey who sells such unique parts and its a B tapered 100k chassis type pot, not A. I don'T think it'd be massive problem, though, right? 

However it's a bit pain in the arse to desolder the clamps. I hope I won'T break anything

[Govmnt_Lacky]

I think I'll replace it, though there's only one shop here in Turkey who sells such unique parts and its a B tapered 100k chassis type pot, not A. I don'T think it'd be massive problem, though, right? 

The Input gain pot is actually a W100K. This is an "S" taper. You can install an A or B taper pot and it will "work" but it will not function the exact same way.
You could reach out to Digitech and see if they will send you one. If you try to get an original or a work-a-like, be sure to save the plastic extension button on the pot 

[Baran Ismen]

I think I'll replace it, though there's only one shop here in Turkey who sells such unique parts and its a B tapered 100k chassis type pot, not A. I don'T think it'd be massive problem, though, right? 

The Input gain pot is actually a W100K. This is an "S" taper. You can install an A or B taper pot and it will "work" but it will not function the exact same way.
You could reach out to Digitech and see if they will send you one. If you try to get an original or a work-a-like, be sure to save the plastic extension button on the pot 

Hi;

I did already, yet they told me this, which I'd understand after all these years
Dear valued customer,

We appreciate your loyalty and continued use of our products. As a company, we have produced a wide range of products and models over the years, and while we do have data and related materials on many of them, we regret to inform you that due to the sheer volume of products we've manufactured over many decades, it has not been possible to stock parts for most of those models.

After reviewing your inquiry, we have unfortunately found that we do not have the data or parts available for the specific model you possess. We understand that this news may be disappointing, and we apologize that we are unable to fulfill your request.

We apologize for any inconvenience this may cause and appreciate your understanding.

Best regards,

DigiTech® Support Team

Taper shouldn't matter actually theoretically, because for me at least, it'll be something like set&forget, as I only use a single guitar and this pedal will be first in the chain regardless of what I use afterward.. Am I right?

[Baran Ismen]

I'm adding some photos of the readings.

I wonder if they are visible to you people, but not to me. Used this postimg thing to upload..

Uploaded here just in case : https://imgur.com/a/gv3bS88

[Govmnt_Lacky]

To get accurate readings, you really should measure the Input pot when it is removed from the circuit.

[Baran Ismen]

To get accurate readings, you really should measure the Input pot when it is removed from the circuit.

Ok so assuming that pot reads well once removed, what would be the case then do you think? Input Signal being really high for this unit? I see some people using xp100 with active pickups though.

[Govmnt_Lacky]

Ok so assuming that pot reads well once removed, what would be the case then do you think? Input Signal being really high for this unit? I see some people using xp100 with active pickups though.

I have used HOT pickups with these units many times in the past. My bet is that your Input pot is done for 

[Baran Ismen]

Ok so assuming that pot reads well once removed, what would be the case then do you think? Input Signal being really high for this unit? I see some people using xp100 with active pickups though.

I have used HOT pickups with these units many times in the past. My bet is that your Input pot is done for 

My guess is same also, thus I'll get a new one asap and try. Fingers crossed! I'll inform you about the results.

[digi2t]

Perhaps the best course of action might be to simply remove the offending pot from the board, mount a 9mm panel mount pot in the existing hole, and then wire it to the board. It will make removal easier (clip lugs, and desolder the remnants after), as well as not having to worry about not being able to find an A taper pot.

[Baran Ismen]

Perhaps the best course of action might be to simply remove the offending pot from the board, mount a 9mm panel mount pot in the existing hole, and then wire it to the board. It will make removal easier (clip lugs, and desolder the remnants after), as well as not having to worry about not being able to find an A taper pot.

That's what I'm considering, I'll clip the legs, separate the pot itself and suck the remaining with the pump, and solder a new one.

Just soldering pin to pin would work right, or should I connect the 1-2 lugs (or 2-3, the ones that are shorted) externally?