Here's an uncommon one. The TubeWorks Pure Tube TW303 SMOOTH overdrive pedal. It's one of the B.K. Butler designed Tube Driver derivates from the mid-late-90's. I had this unit in for repair and I took the time to trace out the schematic to share here. Inspection of the circuit board revealed that it is the same board as was used in the Real Tube RT-901 and Blue Tube RT-903 5-knob Tube Drivers, so this schematic should give us at least the same topology as used in those pedals if not the same values. I know at least one person has asked about the RT-901 here before, so this should be some help.
Thanks Martin - similar to my Real Tube Overdrive project - but not
I notice the 22uf and 2k2 on the cathodes - BK Butler sometimes used a variable pot in parallel with this to adjust the tube bias point - I prefer the sound when this is shorted - ie: cathodes to negative 12v directly.
cheers
bajaman
This mmeans that the thing is completely identical to the Chinese Kampo Tube overdrive sold here. Schematic is on AG's page. That was a 60 euro (right now, some 90 USD) overdrive (new).
It seems to be a tube based (starved bias) clean boost/od. I was wondering if anyone has actually used this pedal much and how it shakes out? Got it pretty cheap on a lark.....kinda hoping for a pleasant surprise...
I only got to play with the one in my article for a couple days, but it sounded nice enough to feel like it was worth it to write about the circuit. The tone controls are maybe a little iffy, but not bad. The character of the overdrive is interesting; very different than the usual tube screamer thing, but it doesn't sound unfamiliar either. I'd say the best way to sum it up would be to describe it as an exaggerated "warm" sound; thick and woolly - though the top end can get kinda shrill if the treble is maxed out. It's a pedal that sounds kinda strange at first, but you get used to it quickly. I'm pretty sure it's not too far off tone-wise from the other B.K. Butler tube pedals.
"Analog electronics in music is dead. Analog effects pedal design is a dead art." - Fran
I should have this pedal in a few days....I will be running it straight into a DRRI ( or maybe a vintage Fender Vibrochamp- Bronco) that I have been driving with a Zoom G7 modeler( i know). I am trying to get away from the zoom and move to pedals, but I don't know that much about them. I do have an electronics background(bseet) and am thinking about some DIY stuff.....
I will let you know how this pedal works out for me.....I am curious what tube is in it and if possible tube changes are in order......
Tube Works 303 smooth tube boost/od showed up earlier this week......took me a couple of days to figure it out ....I LIKE it a lot.
Now, I have never used pedals, so it took me awhile to set it up and dial it in......but this thing sings. 3 tone controls labeled ice, neutral, and warm are VERY interactive with the volume and push controls ...... this is what messed with me. If you dial all 3 tonecontrols to 0 you get noting out at all no matter the volume and gain settings. I thought that was kinda odd. This pedal likes extreme settings also.....such as dialing the bass all the way up with treble and mid to 0 with gain 3/4 to max and volume set up appropriately....this gives a real nice warm biting woman sound with my LP.
It's got a 12ax7 tube inside and xformer....no batteries(love this!). 3 prong outlet. It is a great boost and light to medium od.
VERY quiet...I have noticed NO noise at all...even while turning knobs and such...this is a biggy! I used it with my DRRI and with a Princeton 112 plus. The DRRI loved it and I gotta say it made me love the SS Princeton 112 plus again. If I would have had this pedal before, I might not have bought the DRRI! I used it 2 different ways with the Princeton. 1st I set it up driven hard into the clean channel and it worked great. Then I set it up just boosted clean to warm up the ss and used the amp to switch back and forth between clean and drive channels....this is a winner! Actually beats the DRRI for flexibility due to the 2 channel aspect.
One niggle....the bypass switch seems to be some kinda momentary switch and didn't always pull in on first stomp till I got used to the feel of it. I sure wish this was a solid click type switch.
Other than that I gotta say this beast is a complete winner in every way. I can't wait to try it into my Traynor YCV20WR and the little vintage Fender Bronco(vibrochamp)....aught to be esp. sweet with the Bronco. A few more pedals and I will be ditching the Zoom G7.
8^)
Wade
ps. Any comments, hints or tips are welcome.......I am wondering if the 12ax7 can be swapped with 12au7 or others and what results might be.....any other easy circuit mods possible.....etc. Also, I assume this is a buffered bypass not true bypass?
You can swap in a 12AT7, 12AU7, 12AY7, 5751, etc... all the usual 12AX7 type substitutes. Each will get different amounts of gain and have a different tone. Different brands of 12AX7 should sound different as well. That's one of the fun things with tubes; you can swap tubes all day long and get very different tones without having to modify anything.
Yes, the bypass is a buffered bypass circuit that uses FETs for switching; similar to Boss, DOD, Ibanez, etc... It wouldn't be hard to modify it to be True Bypass if you wanted. I've noticed that the stock bypass switch can be pretty touchy too - maybe it would be good to give it the true bypass treatment just to have more reliable switching.
"Analog electronics in music is dead. Analog effects pedal design is a dead art." - Fran
soulsonic wrote:You can swap in a 12AT7, 12AU7, 12AY7, 5751, etc... all the usual 12AX7 type substitutes. Each will get different amounts of gain and have a different tone. Different brands of 12AX7 should sound different as well. That's one of the fun things with tubes; you can swap tubes all day long and get very different tones without having to modify anything.
Yes, the bypass is a buffered bypass circuit that uses FETs for switching; similar to Boss, DOD, Ibanez, etc... It wouldn't be hard to modify it to be True Bypass if you wanted. I've noticed that the stock bypass switch can be pretty touchy too - maybe it would be good to give it the true bypass treatment just to have more reliable switching.
that was my only real complaint......that switching isn't real positive...touchy like you say.....I don't know if I'd want true bypass....I've heard that buffered can be better in a lot of situations, I just want it to switch more reliably.
