Viva Shaka Tube!

[Paul Marossy]

I have been using my rebuilt Shaka Tube for a few months now, and I must say that I really like the thing for nice big sounding chords without tons of distortion and nice bluesy leads! Just saying thanks for a nice little circuit.  

[Doug H]

Paul,

Along the same lines I just recently started using my Pentode Driver again and love it. I built it a few years ago, it is based on the BK Butler Tube Driver circuit, similar to the Shaka Tube. Only instead of using a 12ax7, it uses 2 miniature 6ak6 pentodes.  I did a few tweaks to make the pentodes sound really good.

After a while I felt it was kind of fizzy sounding, so I started experimenting with low-pass filtering on the output. It ended up being too dark for my SS amp so I just gave up on it for a while. Then I plugged it into my Octal Fatness a week ago and it was voiced perfectly for this amp. With the LPF set up like this, I guess it is like a TS, nice for a bright sounding amp.

Between the pedal and the amp preamp, all the pentode action gets some incredible compression happening and it sounds really "big". It is definitely a "holy grail" tone for me. It really feels as well as sounds good. Gets pretty chunky and cleans up decently too.

Only drawback is the hum.  At some point I will redesign it for a 30vdc wall-wart and dc heaters. But anyway, no need for any TS-style overdrives for this amp, this baby does it all and more.;-)

Doug

[Paul Marossy]

Doug-

Yeah, I saw that pentode driver at your site. Pretty cool little circuit. I can imagine between that and the octal fatness, that you must have some serious tone going on!  

[petemoore]

Could you help me start my first tube project: Shaka Tube?
 The only resistor that needs to be 1watt is the 10R ?..all the others can be 1/4 watt?
 Tube pins 4 and 5 connect to ground?
 And 12Vdc could be from a battery?
 Is there any reason for 12v supply to be 30?
 Anything else you can think of to help me through this one...?!  
 Thanks for the suggestions !!!

[george]

Could you help me start my first tube project: Shaka Tube?
 The only resistor that needs to be 1watt is the 10R ?..all the others can be 1/4 watt?
 Tube pins 4 and 5 connect to ground?
 And 12Vdc could be from a battery?
 Is there any reason for 12v supply to be 30?
 Anything else you can think of to help me through this one...?!  
 Thanks for the suggestions !!!

Hey Pete

The shaka tube takes a 12VAC input and has it's own power supply section that converts this AC input to approx 30V DC to drive the tube plates.  There's no 12V DC involved.

The 12VAC is also directly connected to pins 4 and 5 which connect to the heater filaments of the tube and make it glow.

What Doug is proposing is to eliminate the Shaka's power supply section and run everything off a 30V DC wallwart because he is getting hum probably from the AC filament supply.

I have built the Shaka Tube and personally I don't have any AC hum problem, maybe because I twisted the leads going to pins 4 and 5 together, (maybe I'm just lucky ...:-)).  Maybe I'm not as sensitive to hum as other people, but I find most of the hum in my setup comes from the pickups on my guitar rather than the Shaka.

you are right about the resistors.

[Lonestarjohnny]

When running 2 or more tube's you should also keep your wireing from tube to tube on the same exact pin's when running your wire's from tube to tube, i Have seen this cause 60 cycle hum in some amps,
and also if your heater supply transformer is not center tapped like the older Fender amps you'll need 100 ohm resistors from each leg to ground.
JD

[petemoore]

I guess I'l need a Wall wart for 20Vac...any recommendations as to Ma?
 Otherwise quite quandried...going to try regrouping

[Paul Marossy]

Here's how I did mine:

12VAC wall wart to isolated power input jack. One side goes to ground, the other to the 10ohm/1watt resistor.

The B in the circle is the cathode bias. Connect all the Bs together.

V+ is the voltage after the voltage doubler circuit. Connect all of these together. Opamp gets connected to V+ as well.

Connect all V- together.

12VAC goes directly to pins 4 & 5 of the preamp tube, before going anywhere else. I have no problems with hum, and I didn't use a center tapped transformer or 100 ohm resistors to ground. I did have a problem with it oscillating when bypassed, but that was solved by using a grounded circuit input switching scheme.

You can see more of mine here:
http://www.diyguitarist.com/DIYStompboxes/Bulldog.htm

[Doug H]

What Doug is proposing is to eliminate the Shaka's power supply section and run everything off a 30V DC wallwart because he is getting hum probably from the AC filament supply.

I have built the Shaka Tube and personally I don't have any AC hum problem, maybe because I twisted the leads going to pins 4 and 5 together, (maybe I'm just lucky ...:-)).  Maybe I'm not as sensitive to hum as other people, but I find most of the hum in my setup comes from the pickups on my guitar rather than the Shaka.

It's possible my hum is from using 2 tubes, the tubes I'm using, running the heaters in series, my layout skills at the time, etc. I'm not claiming the heaters have to be DC to avoid hum, others have had plenty of success with AC heaters. But using 30VDC power and DC heaters not only eliminates the heaters as a hum source, but uncomplicates the power supply. No half-wave rectiification needed and the filtering can be much simpler. Since it wouldn't be bipolar you wouldn't need a -15v rail, etc. All you really need is a filtering cap for  B+ and a divider, cap, and voltage regulator for the heater circuit.



EDIT: Oh, and also a divider/filter for the opamp since it is no longer bipolar, but you knew that...



Doug

[petemoore]

I appreciate the information Paul, Doug...all.
 It seems much much clearer this morning !!!
 I'll give this another go ASAP!!!
 Thank YOU !!!  

[Paul Marossy]

Build it! If you get it right, you won't regret it.  

[petemoore]

But hey, I have all the parts there, and feel like I'm getting alot closer to knowing 'where they go.
 Layout is a little akward, socket attached to perf..., and as a first draft, then second...error marks on the board, it has become increasingly confusing, and a little cramped  :!:
  I get the Vacuum out and did the first floor. This sucked the dirt right up the tube !!! ...lol...
     I'll be Very Happy when I get this...! ..meanwhile enjoying the ride.

[Doug H]

But hey, I have all the parts there, and feel like I'm getting alot closer to knowing 'where they go.
 Layout is a little akward, socket attached to perf..., and as a first draft, then second...error marks on the board, it has become increasingly confusing, and a little cramped  :!:
 

You can always breadboard it first and tweak it to your heart's content. That's  how I did mine. With the low-voltage circuit you can breadboard away no problem....

Doug

[Paul Marossy]

I thought that the hardest part of my Shaka Tube build was the physical layout of everything. It's a bit of a challenge...

[petemoore]

THe Tube lights with 10.86Vac on the heater element.
 I took voltage readings from the tube and the opamp.
 TUBE Voltages [with jfet lead nomenclature].
 Drains were at 14.25Vdc
 Gates we're 13.90
 Sources at 13.86
 If biasing tubes is anything like biasing Jfets, I seem to have a problem.
 Side A Opamp voltages were off...[pin 4 at ground, pin 8 at V+ or 14.25.
 output at 3.25Vdc,
 -in at 2.62, +in real close to that....
 I'll have to get a nice sized board and try this again...
 The side B Opamp pins were left open.