A possibly useful mod for the TC electronic "Tube Pilot" overdrive.

freefrog

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This cheap tube pedal has no tone control so...

For anyone wanting a warmer tone from it : just solder a small capacitor between the center lug and "ground lug" of the volume pot.

2,2nF is a good value with a dark amp for the stock 12AX7.

If you swap the inner tube for a lower gain 12AY7, there will be less bass / more high range so a 4,7nF cap might be necessary (and with a 12AY7, it will give a frequency response + THD largely similar to those of a Butler Tube Driver; at least thar's what my frequency analyzer says).

It can be done easily on the pcb side, just by opening the pedal.

HTH.


Footnote: this topic "recycles" a thread that I had posted to joke but apparently it wasn't necessarily a good idea. So I post something else instead... ;-)
 
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èfdejonck

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Hello Freefrog,

I've sawn your post about the TC tube pilot on different forums and tried it yesterday with a 4.7nf and a 12AU7 and it works great! Although I would like to tame a bit more the high ends (or enhance the low ones), I'll try out your recommendation of a 14Kohms resistor in parallel of the 4.7nf cap but I wonder if you know how I could add a tone pot on this pedal? where should I sick it? instead of the 14k resistor? I search a lot for the TC tube pilot diagram but had no chance finding it...

Thanks a lot for your help on the first small mod, it makes a lovely creamy boost pedal and the gain knob is now usable all the way!
 

freefrog

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Hello Freefrog,

I've sawn your post about the TC tube pilot on different forums and tried it yesterday with a 4.7nf and a 12AU7 and it works great! Although I would like to tame a bit more the high ends (or enhance the low ones), I'll try out your recommendation of a 14Kohms resistor in parallel of the 4.7nf cap but I wonder if you know how I could add a tone pot on this pedal? where should I sick it? instead of the 14k resistor? I search a lot for the TC tube pilot diagram but had no chance finding it...

Thanks a lot for your help on the first small mod, it makes a lovely creamy boost pedal and the gain knob is now usable all the way!
Hello,
Glad if my humble contribution has been helpful.
To be honest, I've still not traced the schematic of the Tube Pilot so, I don't see (yet) how a tone pot could be added to the circuit. I'll give it a glance ASAP. For the moment, I'm way too busy: COVID crisis = tons of unexpected work here. :-/
Thx for your understanding.
But stay tuned: I'll try to come back later with the beginning of an answer. :)
 

èfdejonck

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Many thanks for fast reply! There is no need to hurry, I'll try to understand the pcb as well but I'm kind of a rookie on that subject. I'll definitely try the 14k in parallel tonight and let people here know how it affects the sound.
 

freefrog

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Many thanks for fast reply! There is no need to hurry, I'll try to understand the pcb as well but I'm kind of a rookie on that subject. I'll definitely try the 14k in parallel tonight and let people here know how it affects the sound.
Hello,
Still not found the time to dig the Tube Pilot question but I suddenly realize that posting on a hurry made me commit a mistake or, at least, a confusing statement: the 14k has not to be in parallel with a 47nF cap. It has to be in SERIES with the 47hF (or 22nF, or 10nF) cap AND this series of two components has to be in parallel with the resistive track of the volume pot - IOW: between its center and ground lugs.
Replacing the 14k resistor with a pot in order to obtain a variable low pass filter should make sense (without necessarily ditching the 2,2nF or 4,7nF cap between output and ground).
More later about optimal values for these components. I just need life to lend me a bit more free time. ;-/


EDIT - I share below two pics until now buried in my archiives and showing...

-where to put the "smoothing cap" in the "easy mod" way. There's enough room and it takes hardly a few minutes to do;

-how the frequency response changes with a smoothing cap (in this case, a very low 680pF one, light green line) VS with a 14k resistor in series on a 47nF cap, the whole being in the same physicail position than the smoothing cap (purple line).

Tube Pilot Easy Mod.jpg


Tube Pilot Frequency response with various tone shaping caps.jpg
 
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dj335

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Hello FreeFrog.
This cheap tube pedal has no tone control so...

For anyone wanting a warmer tone from it : just solder a small capacitor between the center lug and "ground lug" of the volume pot.

2,2nF is a good value with a dark amp for the stock 12AX7.

If you swap the inner tube for a lower gain 12AY7, there will be less bass / more high range so a 4,7nF cap might be necessary (and with a 12AY7, it will give a frequency response + THD largely similar to those of a Butler Tube Driver; at least thar's what my frequency analyzer says).

It can be done easily on the pcb side, just by opening the pedal.

HTH.


Footnote: this topic "recycles" a thread that I had posted to joke but apparently it wasn't necessarily a good idea. So I post something else instead... ;-)
This cheap tube pedal has no tone control so...

For anyone wanting a warmer tone from it : just solder a small capacitor between the center lug and "ground lug" of the volume pot.

2,2nF is a good value with a dark amp for the stock 12AX7.

If you swap the inner tube for a lower gain 12AY7, there will be less bass / more high range so a 4,7nF cap might be necessary (and with a 12AY7, it will give a frequency response + THD largely similar to those of a Butler Tube Driver; at least thar's what my frequency analyzer says).

It can be done easily on the pcb side, just by opening the pedal.

HTH.


Footnote: this topic "recycles" a thread that I had posted to joke but apparently it wasn't necessarily a good idea. So I post something else instead... ;-)

Hello, Freefrog.

I just found this message you posted back in February regarding the tone mod you suggested for the TC Electronic Tube Pilot. I would like to try the mod you are suggesting, and wanted to ask if I could clarify the value of the capacitor.

In your first post dated Jan 5, 2021, you say to use a 4,7nF cap if you are using a 12AY7 tube. To clarify, is that a 4.7nF cap? In other words, a 4700 pF cap?

Also, in your post dated April 10, 2021 where you are replying to "efdejonck", you state the cap value as 47uF, then as 47hF. Those look like typo's, and that you meant to write "4.7nF"

Please reply to me when you get this/see this. I would like to get the right value cap and do this mod.

For those who might be interested in what I'm doing, I bought the Tube Pilot so I could put it at the front end of my pedal board. I have been missing having my guitar connect first to a vacuum tube, instead of to the electronic circuitry of the compressor pedal that was in first position. I wanted to restore the response and feel of driving a vacuum tube first, and not an IC chip. I also didn't want any added distortion. I wanted the Tube Pilot to be a unity gain buffer. No breakup, and have the output level be the same when the pedal was on as when it was off in bypass mode.

However, I could not set the Tube Pilot's "Tube Drive" level control low enough to avoid any tube breakup with the stock 12AX7A. Also, with the "Out Drive" all the way up, the output signal was still much lower when on than in bypass. So it wasn't working as a unity gain/no distortion buffer.

So I installed a NOS RCA 12AY7 tube, and now I can set the "Tube Drive' low around 8 o'clock, and the "Out Drive" at full, and it's become a unity gain buffer with no noticeable break up. Yes!

However, it's also now brighter on the top end, with a mild loss of low bass. Sounds like your cap mod would restore the tone I'm looking for. So I'm anxious to try the mod, but want to use the right value capacitor.

Regards,
DJ335
 
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freefrog

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Hello FreeFrog.




Hello, Freefrog.

I just found this message you posted back in February regarding the tone mod you suggested for the TC Electronic Tube Pilot. I would like to try the mod you are suggesting, and wanted to ask if I could clarify the value of the capacitor.

In your first post dated Jan 5, 2021, you say to use a 4,7nF cap if you are using a 12AY7 tube. To clarify, is that a 4.7nF cap? In other words, a 4700 pF cap?

Also, in your post dated April 10, 2021 where you are replying to "efdejonck", you state the cap value as 47uF, then as 47hF. Those look like typo's, and that you meant to write "4.7nF"

Please reply to me when you get this/see this. I would like to get the right value cap and do this mod.

For those who might be interested in what I'm doing, I bought the Tube Pilot so I could put it at the front end of my pedal board. I have been missing having my guitar connect first to a vacuum tube, instead of to the electronic circuitry of the compressor pedal that was in first position. I wanted to restore the response and feel of driving a vacuum tube first, and not an IC chip. I also didn't want any added distortion. I wanted the Tube Pilot to be a unity gain buffer. No breakup, and have the output level be the same when the pedal was on as when it was off in bypass mode.

However, I could not set the Tube Pilot's "Tube Drive" level control low enough to avoid any tube breakup with the stock 12AX7A. Also, with the "Out Drive" all the way up, the output signal was still much lower when on than in bypass. So it wasn't working as a unity gain/no distortion buffer.

So I installed a NOS RCA 12AY7 tube, and now I can set the "Tube Drive' low around 8 o'clock, and the "Out Drive" at full, and it's become a unity gain buffer with no noticeable break up. Yes!

However, it's also now brighter on the top end, with a mild loss of low bass. Sounds like your cap mod would restore the tone I'm looking for. So I'm anxious to try the mod, but want to use the right value capacitor.

Regards,
DJ335
Hello,

èfdejonck was refering to a message that I've posted on another forum (the gear page). In this message elsewhere, I had shared another recipe to soften / darken the sound of the Tube Pilot.

This 'other recipe' was to use a 14k resistor in series with a 47nF cap (= 47 nF a.k.a NANOfarad = 47000 pF a.k.a picofarad) then to put this series of two components between the middle lug and ground of the volume pot.

It's not the same than my first recipe, consisting to put a simple capacitor (without series resistor) between the mid and ground lug of the volume pot. in this case, the capacitor can be a 4.7 NANOfarad (=4700pF) for a 12AY7 tube or a 2.2 NANOfarad (=2200 pF) for a 12AX7. At least, that's what worked for me.

So and just to be clear, I've not talked about MICROfarad (whose symbol is µF). But if I had to do that, I'd mention a 0.047µF cap for the "other recipe" (with a series resistor) while my first recipe (without series resistor) would refer to 0.0047µF or 0.0022µF caps... knowing that 1µF = 1000nF = 1000 000 pF. :)

HTH. English is not my mother tongue and life is often busy here, so, sorry if ever my answers seem difficult to decipher.
 

dj335

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Hello,

èfdejonck was refering to a message that I've posted on another forum (the gear page). In this message elsewhere, I had shared another recipe to soften / darken the sound of the Tube Pilot.

This 'other recipe' was to use a 14k resistor in series with a 47nF cap (= 47 nF a.k.a NANOfarad = 47000 pF a.k.a picofarad) then to put this series of two components between the middle lug and ground of the volume pot.

It's not the same than my first recipe, consisting to put a simple capacitor (without series resistor) between the mid and ground lug of the volume pot. in this case, the capacitor can be a 4.7 NANOfarad (=4700pF) for a 12AY7 tube or a 2.2 NANOfarad (=2200 pF) for a 12AX7. At least, that's what worked for me.

So and just to be clear, I've not talked about MICROfarad (whose symbol is µF). But if I had to do that, I'd mention a 0.047µF cap for the "other recipe" (with a series resistor) while my first recipe (without series resistor) would refer to 0.0047µF or 0.0022µF caps... knowing that 1µF = 1000nF = 1000 000 pF. :)

HTH. English is not my mother tongue and life is often busy here, so, sorry if ever my answers seem difficult to decipher.

Freefrog,

I got your reply. I really appreciate you clarifying that I am to use a 4.7 nanofarad cap for this mod. I am looking forward to adding the cap, and see if it brings back the bass and reduces the highs, per the frequency graph you showed.

I also appreciate that you said that the 14 k ohm resistor in series with a cap you were telling efdejonck was for another mod.

By the way, I contacted TC Electronic's technical support team about if I could use a lower gain tube to move the breakup higher up in the volume setting, so I could turn my Tube Pilot into a unity gain buffer with no noticeable breakup.

They replied that they cannot give me any technical help with modding my pedal. Also, any mod that I did to it would void the warranty. I would argue that just changing out the tube to a different type is not a warranty voiding modification!

Worthless technical support team.....

Finally, your English is very good. I just wanted to clarify that you were saying a 4.7 nF (nanofarad) cap (4700 picofarad).

Thank you much!!

DJ335
 

freefrog

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Freefrog,

I got your reply. I really appreciate you clarifying that I am to use a 4.7 nanofarad cap for this mod. I am looking forward to adding the cap, and see if it brings back the bass and reduces the highs, per the frequency graph you showed.

I also appreciate that you said that the 14 k ohm resistor in series with a cap you were telling efdejonck was for another mod.

By the way, I contacted TC Electronic's technical support team about if I could use a lower gain tube to move the breakup higher up in the volume setting, so I could turn my Tube Pilot into a unity gain buffer with no noticeable breakup.

They replied that they cannot give me any technical help with modding my pedal. Also, any mod that I did to it would void the warranty. I would argue that just changing out the tube to a different type is not a warranty voiding modification!

Worthless technical support team.....

Finally, your English is very good. I just wanted to clarify that you were saying a 4.7 nF (nanofarad) cap (4700 picofarad).

Thank you much!!

DJ335
You're welcome.

For the record, my screenshot in the post 6 shows what happens with each of my "recipes":

-the "first recipe" with a single capacitor on the volume pot just trims the highrange, without affecting other frequencies. It's shown by the yellow / light green line, even if in this case, the cap had a much lower value than 2.2nF or 4.7nF;

-the "other recipe" with 47nF + series resistor lowers all frequencies except the bass and is therefore the solution to apply for more bass;

-on this basis, it must be possible to try a "third recipe" involving 47nF in series with 14k and these two components in parallel with a 2.2nF or 4.7nF cap... It would form a "stepped" filter, like those that I've already mounted as "cathode caps" in tubes amps.

Please, note that I consider such recipes as "subject to change without notice" and as modifiable if needed: The reason being that IME, Tube Pilots are inconsistent. I've two of these pedals and they don't sound the same, even when they host the same tubes and are set in the same way. If I wanted them to sound identically, I would have to try different filters, paradoxically.

So, let us know the results of your experiments. Good luck in your attempts!
 


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