Guitar Gear Forum

I stumbled in to these on the internet last year. It is such a simple design and I have a big pile of vintage 12AU7 & 12BH7 tubes so I decided to slap one together. This pedal actually runs off of a 9vdc power supply but I use a 12v one I happened to have on hand.



Here a pic of my first. I was too impatient to paint the box before digging in. I made the tube guard out of big washers, stand-offs and screws.



It's basically a clean boost and it has a truckload of kick without all the HISSSSS you normally get from them. It's great for giving a lightly broken up tube amp a huge kick in the pants. I also like to run an OD in front of it to get the Valvecaster itself crunchy. It's loads of fun and about $40 or so to build. I put an amber LED under my tube socket for an indicator light to enhance the glowing tube effect. The filaments in the tube are always lit but the LED makes it look like it only goes on when I step on it. Here is a short video showing that feature.

[video]https://www.youtube.com/watch?v=L_0vt802HYo[/video]

can't watch the video at work - but it looks pretty cool!

Could be kinda of a a primer on how a tube works.
Can you identify the tube pins - and a brief overview of what each component does?

I think I may be able to follow that circuit through and get a better understanding of how preamp tubes work.

It actually is a cool way to learn a little about how preamp tubes work.
Here it the pin-out info:



Here are the parts shown on the tube itself. All 12A_7 tubes are built this way.



I'll look for some detail about the function a little later when I have time to post them.

thanks, but there are some labeling inconsistencies between these two diagrams - I guess the anode is the plate, and the filament is the heater?

I slapped them up so fast I didn't even look at them. Yes, there are a few alternate terms for the components. The video below is very informative and gives you a very detailed look inside a tube, explains what each of their functions are and how a tube works.

[video]https://www.youtube.com/watch?v=WnZRJjmOZb8[/video]

If you want to go old school and feel like you are sitting in a 1940's classroom watch this one. It goes into detail about how tubes are used for military applications they haven't been applied to in 50+ years.

[video]https://www.youtube.com/watch?v=2eDb8ojvreo[/video]

This is a FANTASTIC thread, Riffraff. I was looking into making one of the 9v powered tube boosters last year, but was put off by the sound from the clips I watched. Yours sounds really great! Really enjoyed the Westinghouse video. Funny how many applications there are for tubes that aren't even known much anymore.

to the board!

Thanks for the welcome and definitely try one. It's a fun little build you can do in a few hours. I love it for low volume playing in front of my Tweaker 15. It just makes it sound so much bigger and fuller.

Any chance of a gut shot of the pedal? Recommendations for caps?

HA! I think it's a rat's nest but I'll open it up for a shot. I don't remember what I used for caps but I don't remember being real picky about the components. I ordered everything through Antique Electronic Supply but the tubes and some of the resistors which I already had.


****** UPDATE ******

Here is the rat's nest



....but it works.

I didn't even notice before - but I guess you had to add a switch to the circuit layout?

Do you just switch the power in and out - the LED on and off - and true-bypass the entire circuit with the three different sections of the switch? I really wouldn't even know how to do that...........

It's doable. You just have to look for a diagram with the switch added.



I like this build design. It would be cool to Use IC sockets so you can swap caps & resistors to do gain & tone tweaking.

BTW, Thanks for making me take a gut shot Grimespace. I temporarily retired most of my drive pedals when I stopped using a Tweaker and picked up Delta Blues 115. The Valvecaster was my always on pedal with my Tweaker. I tested some tubes today and picked out three that all tested well above 100, a RCA black plate 12AU7, a RCA clear top 12AU7A with a side getter and a Sylvania 12BH7. The 12BH7 sounds huge but the RCA clear top really works beautifully with my DB115. The VC is definitely going back on my board for that amp.

Hey man - thank *you* for taking the time to do that. Looks good, although I'd be more inclined to go the route of the other one you posted. Doesn't matter much, though - yours sounds killer, and I've already gotten some of the parts needed to make a test unit for myself. Thanks for showing up, and hope you stick around!