"Cheap trick" to smooth the tone of a TC electronic Tube Pilot...

[freefrog]

.. the tittle of this thread being an attempt to play with words, although English is not my mother tongue.

I've already posted the explanations below in some long tedious posts or threads in other forums... But it should make more sense here. I'll just keep it relatively short for a first topic.

The Tube Pilot is a cheap tube overdrive, apparently "inspired by" Butler / Chandler / Tube works Tube Drivers.

Problem: the Tube Pilot doesn't host any tone control nor tone correction for the upper part of the spectrum. Its response is flat in the high range, making it harsh through most amps.

My cheap and easy solution: adding a small cap between the center lug of the volume pot and its ground lug... It can be done from the bottom of the PCB, without unscrewing anything else than the housing.

The optimal value depends on other parms: amp used, tube mounted in the TP...

I've got good results with 2,2nF, 3,3 nF or 4,7nF capacitors. A TP with a 12AY7 and a 4.7nF cap has a frequency response and THD close to those of a "real Tube Driver", IME.

I use two TP's modified like that for more than a year now and among other tube pedals, most often much more expensive. IMHO, they're up to the task since I've fitted them with smoothing caps.

FWIW - and shared just for the pleasure to share, whatever it's worth.

[ppluis0]

Hi there,

Someone have schematic of this unit ?



As per voltage reading at tube socket appears to have a voltage multiplicator inside:



Cheers,
Jose

[czech-one-2]

.. the tittle of this thread being an attempt to play with words, although English is not my mother tongue.

I've already posted the explanations below in some long tedious posts or threads in other forums... But it should make more sense here. I'll just keep it relatively short for a first topic.

The Tube Pilot is a cheap tube overdrive, apparently "inspired by" Butler / Chandler / Tube works Tube Drivers.

Problem: the Tube Pilot doesn't host any tone control nor tone correction for the upper part of the spectrum. Its response is flat in the high range, making it harsh through most amps.

My cheap and easy solution: adding a small cap between the center lug of the volume pot and its ground lug... It can be done from the bottom of the PCB, without unscrewing anything else than the housing.

The optimal value depends on other parms: amp used, tube mounted in the TP...

I've got good results with 2,2nF, 3,3 nF or 4,7nF capacitors. A TP with a 12AY7 and a 4.7nF cap has a frequency response and THD close to those of a "real Tube Driver", IME.

I use two TP's modified like that for more than a year now and among other tube pedals, most often much more expensive. IMHO, they're up to the task since I've fitted them with smoothing caps.

FWIW - and shared just for the pleasure to share, whatever it's worth.

Thanks a Million, that works like a charm!

[Evadllew]

Hi,
I'm a new member here.
I have recently got my self a TC Electronic Tube Pilot and I have to say the jury is out on this one.
I just can't get a sound/tone i'm happy with. I was expecting it to be able to deliver some nice edge of breakup overdrive but it's got a splatty fuzz sound to it.
So, for £38 off Amazon I though this is an ideal base pedal to mod to my liking.
My question is, does anyone have a schematic for this?
I've followed the threads on here and have stuck a 3.9nF across the volume pot which is an improvement. I've also twiddled with the trim pot with the pedal hooked up to my scope. All this seems to do is make the output trace bigger or smaller, it doesn't seem to alter the amount or shape of the distortion on the output waveform.
I think someone said they would trace it if they got the time anyone know if they managed?

Any info would be much appreciated.
Cheers
Evadllew

[ppluis0]

Hi Evadllew and welcome to the forum.

Try to replace the present 12AX7 (gain= 100 times) with another tube with same pinout but less gain, as 12AT7 (60), 12AY7 (44), or 12AU7 (17) and see what happens.

Cheers,
Jose

[Evadllew]

Hi,
Thanks for the suggestion, i will definately try that.
However, my cheap pedal is now starting to get more expensive
What i was hoping was that someone would have a schematic so i could change the gain structure and maybe add a tone control.
If the tube is being driven by an opamp then the gain of the opamp can be changed to anything you like with the change of a resistor or two or maybe add a trimmer.
That wss my thinking anyway.
But thanks for the reply
Evadllew

[Evadllew]

I've just ordered a jj12au7 to swap in my tube pilot.
Has anyone figured out how to set the trimmer in this pedal?
I'll post how i get on when fitted but the trimmer has me baffled?
I'll try a combination of listening and scope.
Cheers
Evadllew

[Evadllew]

No the 12au7 from JJ is no better.
I just get a more quiet less ballsy spattery breakup.
Unless that trim pot is really critical this pedal just sounds awful.
Maybe if you are after a kind of raw punk kinda sound it fits but not for me.
Any feedback anyone out there?
This is a bit of a one sided thread

[freefrog]

No the 12au7 from JJ is no better.
I just get a more quiet less ballsy spattery breakup.
Unless that trim pot is really critical this pedal just sounds awful.
Maybe if you are after a kind of raw punk kinda sound it fits but not for me.
Any feedback anyone out there?
This is a bit of a one sided thread

Hypothesis 1: you've got a lemon. Because I've two Tube Pilots and none does what you describe. But both units sound slightly different from each other, even with a same tube. So, I’d expect Tube Pilots to sound differently from pedal to pedal, like many of the tube devices that I’ve owned / modified these last decades.

Hypothesis 2: your TP is not a lemon but your rig doesn't cooperate with this circuit for whatever reason.
NOTE – I’ve got boatloads of pedals that I disliked since 1980. Even famous ones. I’ve also got pedals that I’ve failed to mod to my liking. We can’t always win.

Regarding the schematic: not enough free time for that right now, sorry (I'm just trying to come back to a normal life after covid, among other troubles).

Nevertheless, I share below some screenshots done the past years, showing the frequency response and THD of my two Tube Pilots with different tubes and different trim pot settings (gain and volume settings were different as well).

https://imgur.com/a/PL8aFJM

[Evadllew]

Thanks for the reply.
I guess i'll keep trying,different positions on my board, and trim pot settings etc.
Do you know what the trim pot is actually doing?
Thanks again for the info and i hpoe you get back to normal soon.
Cheers
Evadllew

[freefrog]

Thanks for the reply.
I guess i'll keep trying,different positions on my board, and trim pot settings etc.
Do you know what the trim pot is actually doing?
Thanks again for the info and i hpoe you get back to normal soon.
Cheers
Evadllew

Hi,

Still struggling to come back to normal but thx for the kind words.

Regarding the trim pot, I suppose it's just biasing the tube, like the 10k control in the Tube Driver version 2: http://4.bp.blogspot.com/-RTE14qSrmkQ/T ... atic-1.png

But as said above, the TP has obviously its gain set before the tube : a bias pot is not meant to do much in such cases - albeit I prefer the trim pot CCW, personally. YMMV.

Not enough time to dig further now. More later, maybe...

[Evadllew]

I've just had thought about the poor tone etc of my TP pedal.
Could it be that the current supplied by my pedal board supply is just not up to it??
I'll try it with a more robust supply and let you know.

[Evadllew]

I had better mention that i have been using the 9V/500mA output of my supply but with everything else plugged in it might not be up to it?
Just a thought.

[wildschwein]

I had better mention that i have been using the 9V/500mA output of my supply but with everything else plugged in it might not be up to it?
Just a thought.

If you have delays or mod effects in your chain you will need more juice.

[freefrog]

I had better mention that i have been using the 9V/500mA output of my supply but with everything else plugged in it might not be up to it?
Just a thought.

The only way to know would be to try the pedal with a different power supply... and/or without any other FX from guitar to amp.

[rich2000]

It appears that the pedal draws 400mA. A 500 mA supply for you entire board may be a problem.

[Ben N]

I had better mention that i have been using the 9V/500mA output of my supply but with everything else plugged in it might not be up to it?
Just a thought.

A bit more explanation: Even thought you are using the 500 mA output, which ought to be enough, if the total draw on your supply is too high, it will still be overloaded. So if your supply is 1A, and you're drawing 1.2A total, it doesn't matter that you have the right output selected for this pedal. Try it with a separate supply, 500 mA or better, and see how it does.

[freefrog]

Ain't got the time to trace the schematic of the unit. Anyway, there's a lot of SMD components in it and my eyes are getting old.

But I've added a tone control to both of my TP's.

I've first tried a tone stack like in the Butler Tube Driver. Nice but (as expected) there was too much insertion loss.

So I've tried something simpler, in parallel with the smoothing cap already there (itself reduced @ 1,7nF thx to a 1nF + a 680pF in parallel in this case). Recipe applied:

-center lug of the volume pot to center lug of a LOG 50k pot (I insist on "LOG", not linear);

-ground lug of this tone pot to a cap of a higher value than the smoothing one;

-end of this higher value tone cap to ground lug of the volume pot.

With 47nF or 22nF caps, It works half like the "presence" control of a Hot Cake, half like a "contour" control on old Marshall Valvestate's.... It's not really useable at zero (where it mimics the tone stack of an amp with bass full up and other controls zeroed). Maybe then it would be better to add a resistor to limit the amplitude of the pot but it's a detail...

The tone pot is easy to install on the right side of the pedal, perpendicular to the volume pot and next to its axis, between the back of the PCB tube socket and the input jack...

The bottom housing is made of soft metal and relatively easy to saw: On the top of the right "wall", I made two vertical incisions of 1,5cm with 1 cm between them then worked the small bit of metal with a plier until I could break it. It opened a rectangular windows of 1x1,5cm @ 9cm of the lower bout and 2,9cm of the upper side, giving enough space for the pot. Then a pair of washers and a screw was used to attach the whole thing to the metal housing...

I should have done that before since I'm very pleased by the effect of this added control: without too much volume drop, it gives big bass and scooped mids on request and tames the "raw" upper mids of the TP in a musical way.

EDIT- I've realized that my two TP's didn't react so well to a same tone cap value (which seems understandeable since they never sounded identical, even when they had both the same stock Bugera Tube). My various amps didn't react equally well to the added tone pot either. So one TP has been left with a 47nF tone cap and the other, with a 22nF. A 10nF was expected to work since it's a value often found in pedal tone circuits but in this case, it failed: by diminishing high frequencies without scooping enough the high mids, it was just muddying the sound.

EDIT, bis - Also forgotten to precise that I often use my TP's after a treble booster or pre-drive FX goosing the (high) mids. Hence my move towards a darker high-midrange, as allowed by an added tone control. For those using a TP alone, letting the added tone pot full up or not lower than 6/10 would be logical to avoid a too bassy response...

FWIW.

And, some good (or not so good) pics being better than a long discourse...

[freefrog]

And here is the frequency response produced by one of my modified TP (the model with a 47nF cap) once the tone control @ 1/4, 1/3, noon and full up...

[dorukakkus]

Hello
I recently bought a tube pilot and it is awesome! But as already everyone mentioned it sounds harsh and very trebly. I tried the mods people suggesgted. They worked great but it did not work flawlessly. Around 10 to 4 o clock the pot did nothing. When rolled extremely low it worked but sucked out all the treble and the volume dropped massively. It was hard to dial out. So what i did was add a tone pot in series with the volume. It was not useful for me so what I did was:

First I desoldered the middle pin of the volume pot and lift it out of the hole. And soldered a wire to it

Solder another wire to the hole of the middle pin.

Then i connected the pad and the lug of the pot with a 100k resistor.(I initially tried 470k but 100k was better. Maybe a lower resistsnce would sound better but I don’t know.)

I soldered the wire coming from the lug of the volume pot to the new pots left pin(while looking at it from the back)

Then soldered the other wire to the middle lug of the new pot.

Lastly To the right lug of the pot (while looking at it from the back) soldered one leg of a capacitor(which is 0.047uf) and soldered the other leg to ground. To make the ground connection better i used the pots back and connected a wire to a ground.(I don’t think that this is needed but I did it anyways)

The pot i used is 22k

Keep in mind that I am 17 years old and I lack a lot of knowledge. All of the values are guessed. I am pretty sure that someone will make better suggestions for the values of the parts used. After doing this mod the pedal sounded really good to me. It still drops volume but the harshness is gone and it could be used as stock with this mod if needed. Just turn the tone pot all the way. I hope that this helps someone that really likes this pedal but hates the harshness.

Note: Do not drill the hole where I have drilled it. It turns out that it is a really bad place.