Valve overdrive EF 86 / 2x 12AU7

[JeffdaMaori]

Hi guys,
just finished this tube based overdrive, three stages, first stage (right footswitch, first valve from right) is EF 86 based on Renegadrian's EF 86 ( can be found here http://www.aronnelson.com/gallery/main.php/v/Renegadrian/EF86+Preamp.gif.html) , next a 'splitcaster' (based on the 'Matsumin Valve Caster' and 'Renegadrian's Twincaster') being a two stage 12 AU 7 overdrive.
The only piece of silicon is the 7660 charge pump on a Madbean Roadrage board to supply 24 volts (so far nothing is smoking....).
The pedal itself runs on 12 volt. Enclosure I made myself out of a piece of aluminum profile I found at the local recycling centre. I'm a sucker for polished look, so a few hours and a bit of elbowgrease later, sheets of sandpaper, buffing etc, this is what it looks like. Dimensions are 250mm wide, 100 deep, 30 high.
After initial soundtesting I put an extra master volume after the extra 12AU7 stage as the volume jump was to great from light drive to the extra drive, so that has sorted it well. The extra pot is external accessible beside powerjack.
I haven't done any labelling, not sure what I will do there.
Hope you find this interesting.
Cheers

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[JeffdaMaori]

... and here's the guts: looks a bit more messy than planned as I had to experiment and change a bit around, extra master volume etc, but works sweet now.

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[JeffdaMaori]

... and a closer one with the Roadrage charge pump board. Cheers Madbean!

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[JeffdaMaori]

... and a close up of the "engine room". 

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[sprayfe]

Sweet mercy!! Throw an el84 power section in and sell it to me!!!!!
Amazing work!

[jkokura]

Sweet mercy!! Throw an el84 power section in and sell it to me!!!!!
Amazing work!

Heehee... You need a bit more power for that...

Gobstopper - is this all a starved plate design?

Jacob

[JeffdaMaori]

Cheers for comments! Yep, it's starved plate design as highest voltage is 24 volt inside, external walwart supplies 12V 1.5A.
Andy

[nzCdog]

Love to hear how it sounds, I've been totally GASing for a Effectrode Tube Overdrive
I really like the look, its come together really well... nice job

[jtn191]

+1 How's it sound?!?

[bigmufffuzzwizz]

DUDE 

[mjcyates]

Quite awesome!

[JeffdaMaori]

Thanks for comments, guys!

I'm not a snobby tube purist, I've built some nice silicon based stuff and I'm looking forward tp the next projects, particularly UniVibe, Screwdriver, LesLius.
Anyway, obviously this one is more the non silicon type...

Unfortunately I don't have any decent (or even half decent) way of recording at present, hope to get that sorted at some point.

So I'll try to describe it a bit:
first stage EF86 booster has a nice gritty breakup and I like the balance between warmth and edge. You could say it adds a bit of vox tone to it. At present the tube that I have is only a Russian sort of workalike to EF86, I do hope to find a good specimen of a EF86 with exact specs, will see how that sounds. With this tube it needs to be cranked quite a bit, unity gain is at 3 o'clock, so I have it dimed at this stage to get boost and a bit of grit out of it. Nice as a standalone boost and to kick following stages more.

The following 2x 12AU7 stage: left footswitch is on/bypass, middle footswitch engages/disengages second gainstage tube. Sound with one tube is a bit like a cranked tweed (5E3 or so), light overdrive, nice meaty stuff. Think Keith Richard/early Stones sounds. The second tube engages adds quite a decent amount of gain to that. Not a lot of compression with one tubestage, a bit more with both engaged.
I've tried also a 12 AT 7 but that didn't sound great, likewise the circuit doesn't work for 12 AX 7.
Like I guess some tube circuits the dials/settings have some sweet spots and others that don't really work so well with guitar/amp combination. I still have to experiment a fair bit with that as I only have just finished it and I will try a few different tubes as they are obviously the main driver of sound characteristics.

Cheers

Andy

[sgmezei]

That looks great man. I have been looking at Renegadrians layouts for awhile to do a "valvecaster" type of tube pedal. This is really inspiring!!!

[bigmufffuzzwizz]

I'm guessing you already have experience working with tubes gobstopper?

[JeffdaMaori]

Cheers again!
This low voltage stuff is really not that complicated at all, as long as you put the right connection to the right tube pin etc.

I have been building two 'Matsumin valve caster" before like this: http://www.beavisaudio.com/projects/ValveCaster/ and that's a very straightforward build that sounds nice already, this one runs on 9V draws around 150mA current (battery obviously futile...). A great starting point.
Use a good regulated and filtered powersupply and measure that it's really 9 V that it's pumping out, otherwise it might blow the tube heater that runs on 6.3 V.

Getting a good tube is like in an amp important to get happy with it.

I've also been building some tubeamps/high voltage stuff (photo is a Bassman/JTM 45 cross and tubedriven reverb/vibe on top) before but it's really not necessary to have done that to build this stompbox stuff; no chance of electrocuting yourself in the low voltage stompbox designs .
If you have high voltage on the floor spilling a beer over it wouldn't be such a good idea... every drop is a waste...

Andy





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