This is, to all intents and purposes, a Marshall in a box. Quite literally. It's the front end of a JCM800 amp scaled down and stuck in a stomp with the valves running starved plate. Power is from a Schmitt trigger based charge pump getting us up to 60v on the plates for this one.
Works well as a stomp, works incredibly well as a pre-amp plugged straight into the return of effects loops. Which I suppose is exactly what it is.
The Baby Boob Tube (coming soon) works better as a stomp box to be fair. We just wanted to see if we could make a dual tube pedal work right ;)
(http://juansolo.demon.co.uk/stompage/images/stm800-o.jpg)
(http://juansolo.demon.co.uk/stompage/images/stm800-i.jpg)
droooooooooooooooooool
lovely!
Josh
oh man. I think I need a mop.
:o :o :o
You did it! Nice job, looks absolutely sick! 8)
Dang! Thats a friggin great lookin pedal... I want to build a valve preamp myself soon... love to have a peek at your schemo ;)
(http://mhuss.com/MyJCM/JCM800_2204.gif)
Everything from the input to the master volume, excluding the low gain input. Didn't bother scaling any values in the tone stack as it's driven by the cathode follower just like the real thing. The 10K 2W resistors have also been removed the the plate power line.
Through the front of an amp it was a bit too bright, so the Klon buffer has been modded. The 560R resistor is now a 10K with a 2.2nf to ground, then another 10K and 2.2nf. Filters a little of the high end out, but still sounds great through the loop.
I've got an idea for a 2 channel, 2 tube pedal. It's one I've never seen before in a stomp, and much different to the Marshall preamp. I wonder what that can be? Have a guess, and win a prize (or not!) ;)
Just dawned on me that we actually did the schem for this... Would have been handy building it today!
(http://juansolo.demon.co.uk/stompage/schematics/Valve%20Casters/BoobTubeTwin.jpg)
The 10K/2.2nf filters are now on the Klon buffer.
That would have been handy though.
You don't win a prize by guessing the 2 channel pedal.
Quote from: marauder on April 02, 2012, 01:38:23 PM
You don't win a prize by guessing the 2 channel pedal.
Damnit! >:(
Pure madness :o
Because two boobs are ALWAYS better than one! ;) Great job man! I can't wait for some sound clips.
Damn! You made it happen! And what a great result! Well done! I've been following the Boobtube thread all this time, and seen it evolving.. Now the time came for the BIG evolution, and the Boobtube twin! Guess there will be a whole new thread, as popular as the last..
Hector
Still not sure the Twin is as useful a project as the original BT. Still it was fun to do and I'm really curious as to how Cleggy's mystery dual tube pedal will turn out.
However we've just built the Baby BT today and that most certainly is useful, very. Sadly it's in bits again as we need to do the enclosure. But a totally successful test. really liking it. It offers something different to the BT. To the point I might have have to have another crack at Eagle and see if a board can be done for it. It's a simple circuit (ridiculously so when you see it all sat on the back of a tube socket). It's just with the power and buffer requirements also, it'd be nice to have it on a neat/compact pcb.
I'd love to see either the Tweed Bassman or Blackface Princeton end up done like this. I'd use it as a preamp for recording purposes if I had something like that.
Jacob
I know what Mr C is planning for his dual pedal and it's certainly going to be more Fenderish than mine, but not a Fender...
Fantastic!! :o
I'd like to build something like that, and I have some old 12AT7s I'd like to use.
more fenderish...dumble ODS based perhaps?
that would be way cool!
Well I'll put everyone out of their misery. He's going to have a go at stomp boxing this:
(http://img151.imageshack.us/img151/7483/200702201009334380004lq2.png)
Gonna leave out the eq... Saying that, we've got a couple of 5 band sliders kicking about from an old hi-fi that might work... Probably going a little far for a stomp mind you!
How much does the starved plate design affect the tone, and does it affect the operating lifetime of the valve?
(Does the word 'tube' make anyone else think of bicycle and car inner tubes in the tyres?
Definitely effects it as it lowers headroom. Tonally though, plugged into my clean 6v6 amps return (just using the power stage and by-passing the pre), it makes it sound very Marshall. It's actually how it works best. If I didn't already use the loop for some other things, it'd become a permanent fixture there as it's got a handy loop bypass switch on the back. Maybe it's time to make a loop switcher box... *rubs chin*
We're at 60v on the plates vs around 300v in an amp. Heaters are running at the correct voltage so it's tough to say what valve life will be. In theory it should be longer. Who knows though.
The toob thing comes from our friends across the pond calling them vacuum tubes rather than thermionic valves (which sounds far sexier).
This one is absolutely wonderful.
Very inspiring to enter a forum and see things like this!
Cheers!
I take it back about it being better as a pre than a stomp... We found a mistake that we'd made with the power section meaning voltages were seriously down. Fixed it today and bloody hell it's impressive. I mean, without the grunt it was good, now it's properly ticking along with the power it should be, it's awesome. Very happy bunny.
This is something else man.. great build!
So badass! You guys have done so much work on this project its incredible. One day I'd like to build one for myself. ;D
I'd love to give this one a try, but I'm confused on how to wire the heaters. Are both tubes still run at 6v?
Yep, the heaters for both tubes run at 6v. Run the +6v feed from your regulator to pin 9 and run pins 4&5 to ground on each tube.
Quote from: juansolo on April 22, 2012, 12:28:00 PM
I take it back about it being better as a pre than a stomp... We found a mistake that we'd made with the power section meaning voltages were seriously down. Fixed it today and bloody hell it's impressive. I mean, without the grunt it was good, now it's properly ticking along with the power it should be, it's awesome. Very happy bunny.
What a great effort!
Did fixing this error change the schematic in any way?
Nah, it was me trying to tap into the charge pump halfway through using the newer one that doesn't like that at all. Schematic is all as was and I changed the power veros to cover my mistake ;)
I know this one was put to bed long ago, but if I wanted to slip a brightness switch into this, where would be a good place to put it? (I'll muck around with values)
In the amp the presence control in the power section deals with it. We added the two 10ks and 2n2s at the end to tame it a little in ours so you might want to mess with those.
Is it possible to use 12au7 with STM800 (BoobTube Twin)?, Instead of the 12ax7.
Has anyone built this into a larger enclosure with the toobs contained inside rather than sticking out, maybe in a DD? BTW, the build docs make me laugh.
Quote from: jayallen on February 27, 2015, 03:22:48 PM
Is it possible to use 12au7 with STM800 (BoobTube Twin)?, Instead of the 12ax7.
Yes but in this case it doesn't sound as good.
im unable to see all these images. am i the only one?
Quote from: luks999 on March 15, 2015, 04:19:51 PM
im unable to see all these images. am i the only one?
Might be because original post is from 2012? ;D
haha didnt recognized that. still a pity :'(
Quote from: luks999 on March 15, 2015, 04:24:20 PM
haha didnt recognized that. still a pity :'(
John changed his hosting service, kisy remove "demon" from the URL. Here are the fixed photo links.
(http://juansolo.co.uk/stompage/images/stm800-o.jpg)
(http://juansolo.co.uk/stompage/images/stm800-i.jpg)
thanks cody :)
that one looks amazing. this was on vero, now rej has a pcb 8)
Ah, indeed, a lot of posts 2012 or earlier will have the old link.
Looks different to that now also.