"High Voltage" Tube pedal project suggestions

[box_maker_1]

Hey folks

I've waded a ankle deep into the murky waters of the "high voltage" vs "starved plate" tube design pond.

Seems like most tube pedals are starved plate, ie Tube Driver clones.  I haven't seen a whole lot about high voltage designs for pedals.  Is this is a thing?  I found the "Real McTube II" project, but that's about it.

I'd be interested in the boards experiences and suggestions with "high voltage" tube pedal projects?

Cheers.

[PRR]

284V:
https://el34world.com/projects/tube_box.htm

[puretube]

284V:
https://el34world.com/projects/tube_box.htm

Above project is proudly based on my E-H tube-series circuit-designs (incl. original box).
Aron had box+toroidal xfrmr for sale in his shop too, backindadays ...

Below: my prototypes of the "Hot Tubes" + "Wiggler" live on stage 11 years ago, after 10 years of use on that pedalboard of a local band. (Still going strong today, as I`ve been told recently ...)

[GibsonGM]

You might do some reading over here:  https://www.diystompboxes.com/smfforum/index.php?topic=93936.msg1119386#msg1119386

The "GTFO" is a Soldano GTO Supercharger-based high gain tube preamp that uses a 'nixie supply' based on a 555 IC to get 200-ish volts for B+.  How "for you" it might be depends on what you hope to get tone-wise from such a preamp, and your level of experience with soldering/assembling.    The power supply isn't very difficult but can intimidate some.  Read thru the pages in that topic if interested; there's a lot there.  Parts are not hard to source.   Post back or PM with questions. I built one a few years ago and use it to record with all the time, great little box, it rocks and has a low noise floor! 

[box_maker_1]

That tube stomp box project looks pretty awesome. The website is rather old and bonkers, I kinda dig it.

Has anyone here built it? What does it sound like?
The website says there are sound examples, but I couldn't find them.

[merlinb]

I haven't seen a whole lot about high voltage designs for pedals.  Is this is a thing? 

A high-voltage tube pedal is basically just a regular tube preamp, except it's in a box on the floor. Just borrow the preamp section out of your favourite tube amp...

[Jarno]

Exactly, this, for instance, is a Fender Blackface preamp:
https://frogpedals.com/index.php/product-tag/f2b-preamp/

Based on a Alembic preamp, which in turn is a Fender preamp.

[box_maker_1]

@GibsonGM: I just had a chance to check out the GTFO preamp. That does look seriously cool.

There's 481 post on that thread... so lots to dig into.  Doesn't look like any kits or pre-printed PCBs are available anymore. Looks like Gabriel Tudoran has been inactive for awhile. Any suggestions about where to start would be appreciated!

And thanks Jarno for the Frog Pedal link - will check that out too. That might be an easier place to start as the PCB is available.

[Jarno]

Must say that I built an Alembic f2b clone myself, as I am a bassplayer, and found the gain to be a bit high with my active basses, should be right on the money with a guitar.

[anotherjim]

I think for the F2B, it's probably worth including Fender style high/low inputs either dual jack or switched to cater for actives. This seems to be omitted from many clones and replaces the single input 68k grid-stopper they have. A final master volume for the output is also useful.
If you have 12v heater power, it's also an idea to include a dual opamp balanced XLR output so you also have a DI preamp assuming you have room for its rectifier supply etc.

[amptramp]

You could make an SRPP amplifier stage using a 6DJ8/ECC88 for high gain and low noise.  Just make sure the upper triode is pins 1, 2 and 3 because it has the higher voltage rating between heater and cathode.  The nominal transconductance of 12250 µmhos means the lower plate to upper cathode resistor should be 82 ohms for equal current change in both tubes.  This stage will run at 15 mA plate current.

[anotherjim]

I keep meaning to try this. I have many of those bottles.

[puretube]

Watch out & calculate!
Cathodefollowers and other "drivey" or "exotic" circuits can easily demand too much HV plate-current for the "backwards"-xfrmr. (Depends on the xfrmrs setup/configuration involved).
In case of the mentioned "kit" in replies #1 & #2, your ceiling is 1.5W of power.
Enough for 4 x 12AX7 in some/many cases, but not all!

[GibsonGM]

For the GTFO, I'd nail down the 'nixie supply' part first.  There is one inductor you need to find, probably Mouser has one. I used a cheap one from a pack I got at Radio Shack like 25 yrs ago ha ha.    The actual circuit is simple; I got a generic turret board (found by search engine, one of the tube amp parts suppliers IIRC) to hold everything.    Made the tube holder out of sheet metal and pop riveted it to a Jameco enclosure.   My power supply ran higher than 12V under load, so I used a dropping resistor on the heaters to get down to 12V...using a 12V supply to feed it all would make that unnecessary...you can see I kept the PS away from the circuit to avoid noise coupling...

You can buy one of the power supplies cheap on Ebay:  https://www.ebay.com/itm/162813722252

Or make your own for the satisfaction of having done it...in case that threat doesn't have the schematic any longer, there are tons of schematics and articles about using a 555 timer IC this way, here is one: https://www.instructables.com/High-Voltage-Power-Supply-for-Nixie-and-Valve-Tube/

[printer2]

Or this. A little bigger, I cut the fins off the heat sink so it does not overhang the board.

https://www.ebay.com/itm/384981437781?hash=item59a2ae8d55:g:QScAAOSwroVhsdRT&amdata=enc%3AAQAHAAAAoF110dfVmAwFsGZkz423hr5HxEuo1ECXrSjHSK9gKLI6LqVQSMt1N310Mf9WqZZtlWSWy3XU6B9NaSnVxoK5M59pyXejtKNLkPW3PISAXhzJZRppAL2p%2B9bkNyKMqHEqDf0Z9zv4sRBT1lMsNVmNhaiAAwqpG%2BkHxOZOhnUPo0verN4QGEEuqHqgHwwHUZMP9Mc22RcElL0oBmpvF2H8nWY%3D%7Ctkp%3ABk9SR4ji9uqJYQ

[anotherjim]

The Bigger Muff (if you can work it out).
https://www.diystompboxes.com/smfforum/index.php?topic=110776.0

[box_maker_1]

@GibsonGM - Thanks for the additional info on the GTFO.  I think I would just buy a Nixie kit (I've got nothing to prove ).

Is there a "final" schematic for that pedal that you would recommend?  I found this one:
https://www.freestompboxes.org/download/file.php?id=16295&sid=9cf6fc8e598de4f29d0c58d4ed8ea3fa

From here:
https://www.freestompboxes.org/viewtopic.php?f=13&t=15954

[GibsonGM]

That schematic should work fine, Box, and the SMPS (switch mode power supply, the 'nixie') is in there if you want to try one later!   I note the power supply connection isn't shown there (between R24 and R25), it's probably on the board they supplied with that PDF.

This, from the forum pages, is the one I used:  https://i.postimg.cc/jdH4PL2H/GTFO.jpg

I did not make the tone stack; I follow mine w/a Boss EQ pedal.

I made the same basic thing, with a few tweaks, like a 'pregain' pot (1Meg after the 1st stage, then a 'gain' 1Meg after the 2nd...I find it helps dial in the dirt a little better).  A smaller coupling cap here or there, things like that.  As you get into tubes, and read books that deal with 'tone', you'll learn a few tricks, too. None of which matter with the basic build for now!     If you look back at the pic of my build, maybe do something like it - keep the SMPS off-board so it doesn't make noise that can couple into the main circuit.

I run mine at about 120V from the SMPS, a little low...you'll learn more about THAT later, too   I didn't want as much headroom.  Try a few "B+" voltages with yours, just don't exceed component ratings.  I believe I sourced 400V caps and 1/2W resistors throughout, and I don't exceed around 220V at any time.  I'd stay under the specified "310" volts...let us know if you have questions as you go!

[box_maker_1]

Ok, I was out of town for a few days, but now I'm back at this.
Thanks to the excellent write up here: https://robrobinette.com/Reading_Tube_Amp_Schematics.htm
I now have a pretty good idea of what most of the components in the GTFO schematic do.

Some (maybe dumb) questions:
On the GTFO Schematic:  https://i.postimg.cc/jdH4PL2H/GTFO.jpg
1 - Should the "Ground" connections all converge to the GND connection on the Power Supply (link at bottom of this message). That is the connection to the left of the 50-390V output.
2 - How do you get the +12V DC to feed the heaters on both tubes (pin-4 in the schematic)?
3 - Speaking of heaters, so +12V to pin4 and then Pin5 to ground. yeah?  Yeah.
4 - Where does the other end of the 8K2 resister that feeds the Blue LED connect to?  Some sort of power I assume... but where?
5 - What is the little red diamond to the right of C6 mean?
6 - Assuming I skip the tone stack, is it ok to run the right side of C6 to the output tip?

Whew, I'm slow but I'm getting there.
BTW: The power supply I'm referencing is this one:
https://www.ebay.com/itm/384981437781?hash=item59a2ae8d55:g:QScAAOSwroVhsdRT&amdata=enc%3AAQAHAAAAoF110dfVmAwFsGZkz423hr5HxEuo1ECXrSjHSK9gKLI6LqVQSMt1N310Mf9WqZZtlWSWy3XU6B9NaSnVxoK5M59pyXejtKNLkPW3PISAXhzJZRppAL2p%2B9bkNyKMqHEqDf0Z9zv4sRBT1lMsNVmNhaiAAwqpG%2BkHxOZOhnUPo0verN4QGEEuqHqgHwwHUZMP9Mc22RcElL0oBmpvF2H8nWY%3D%7Ctkp%3ABk9SR4ji9uqJYQ

[merlinb]

1 - Should the "Ground" connections all converge to the GND connection on the Power Supply (link at bottom of this message).

Yes

2 - How do you get the +12V DC to feed the heaters on both tubes (pin-4 in the schematic)?

It shows it on the schematic. 12V goes to pin-4 on each tube, ground goes to pin-5 on each tube.

3 - Speaking of heaters, so +12V to pin4 and then Pin5 to ground. yeah?  Yeah.

Exactly.

4 - Where does the other end of the 8K2 resister that feeds the Blue LED connect to?  Some sort of power I assume... but where?

12V

5 - What is the little red diamond to the right of C6 mean?

Bottom right of the diagram. It's showing the two alternative tone stacks you could attach at that point.

6 - Assuming I skip the tone stack, is it ok to run the right side of C6 to the output tip?

Yes but you should add a pair of back-to-back Zener diodes (4.7 to 6.8V will do) to protect any following equipment from being hit with excessive voltage.