Matchless Hotbox-style 6111-based pedal?

[RRJackson]

Has anyone ever tried to pull off something like this? I see a lot of 9-volt builds with submini tubes, but it seems like a Matchless-style high-voltage (well, higher than 9-volts) pedal based on the 6111 would be wonderful. The transformer size could be reduced significantly. Obviously it would reduce the overall footprint of the pedal.

Before fumbling through an attempt to make one happen on my own, I wanted to make sure nobody else had left me some tracks in the snow to follow. 

-Rob

[thomasha]

There was something like this over the free stompboxes forum, but images aren't there anymore...

it was basically a GTFO pedal using 6n17b russian tubes, and the 6n17b has a gain in the range of the 6112. Running at 300V. by Darkrain.

it uses a 555 smps, as the GTFO pedal. I never tried it, or tried to achieve 300V with it, but I mostly build small amps, with higher current (10 to 25mA) than a preamp stage (5mA).

The MAX1771 will be a better( and expensive) choice if you like the SMPS idea. To achieve 300V the mosfet must be at least a irf740 (400V).

Or you could use a 12V AC wall wart and an internal 12v-220v transformer.

[RRJackson]

The 6111 has an, "Absolute Maximum" plate voltage of 165 volts and a recommended plate voltage of 100 volts. That's what had me thinking about small power transformers. Heat one of those up to 115 or so and it might yield something interesting.

-Rob

[tonight, we ride]

One of the Kevin O'Connor books (I think TUT 4 or 5, but can verify when I'm home) has a project that is basically that pedal, but with some minor changes to "improve" the tone. I think the only thing changed was moving the Cathode Follower stage to after the tone stack to help negate output impedance issues at some tone settings.

I didn't look at it that closely when flipping through the book, but seem to recall him describing it as just the preamp from a JCM800 in pedal form. Pretty sure this one runs at normal preamp power, so if you're not using the sub-mini tubes expect to include a power transformer that is going to bring the wall voltage up 250V or so.

I can dig out the TUT book when I'm home and confirm what I'm guessing at here if you're interested.

[RRJackson]

I have a couple of those. I just dug out #3 to see if it might be in there because I remembered the JCM800 section, but it wasn't. That's interesting. If you happen across the project I'd love to see it!

-Rob

[tonight, we ride]

I think it's in TUT#5.

I may not have a chance to check it out tonight, but will have time tomorrow or this weekend, and will confirm/deny what I stated above.

[RRJackson]

Not a problem. I'm in no hurry. I just had an idea and wanted to run it by people who spend time thinking about these things.

-Rob

[Metaldestroyer]

Good info here

http://www.diystompboxes.com/smfforum/index.php?topic=79544.msg942552#msg942552

[RRJackson]

How about a transformer like the Edcor XPWR104? Of course, it's 4.5 pounds of iron... 

[gtudoran]

@thomasha thank you for remembering this project. It was posted around here also, and yes, sounded quite nice when i've design it. Now i'm using subminies for a totally different project.
The GTFO remained in the open-source domain, but i gave it a new look and a new PCB design (hope somewhere this month the fist PCB batch will be ready and available for whom is interested).

Regards,
Gabriel

[george]

The 6111 has an, "Absolute Maximum" plate voltage of 165 volts and a recommended plate voltage of 100 volts. That's what had me thinking about small power transformers. Heat one of those up to 115 or so and it might yield something interesting.

-Rob

If the recommended plate voltage is 100v why not just get one of those smps nixie power supplies you can find on Ebay?   They're small and would take up a lot less room than a power trannie and associated filter caps ...?

[RRJackson]

The 6111 has an, "Absolute Maximum" plate voltage of 165 volts and a recommended plate voltage of 100 volts. That's what had me thinking about small power transformers. Heat one of those up to 115 or so and it might yield something interesting.

-Rob

If the recommended plate voltage is 100v why not just get one of those smps nixie power supplies you can find on Ebay?   They're small and would take up a lot less room than a power trannie and associated filter caps ...?

Geez, man...that is insanely clever!

-Rob

[Luke51411]

I'm following this thread as I'm interested in everything tube related at the moment and hope to build a few tube pedals and/or mini amps in the near future. A nixie supply seems like the way to go. Have you seen GrindCustomsFX tube projects? He has a power supply kit for tube pedals, A little more expensive than the ebay nixie supplies but you know you are getting quality and designed specifically for our purpose. Here's his site http://www.grindcustomsfx.com/
and here is the build doc for the power supply https://dl.dropboxusercontent.com/u/28586266/GCFX%20Build%20Docs/CleggsterPSU.pdf

[george]

There's some nice stuff on that site - thanks!!!  I got a smps from a seller in Hungary, it pumps out 250v from 12v dc input at 5 watts, which is enough to power a 12AX7 HotBox clone I built.   It cost me about 15 bucks.  You do need to be careful with this stuff though.

[Gus]

google etc.
"real mctube"

[amptramp]

You can always run the pedal from a 12 VAC wall wart and use a 120 v to 12 v transformer connected backwards to regenerate 120 VAC isolated for the B+ supply.  I have a power supply with a line cord that does exactly that using two transformers, one to generate filament voltage and the other connected backwards to get a 120 VDC supply.