Shaka tube - You have to try this

[Mick Bailey]

My Shaka Tube build was great, but I wanted a little more control over the tone, particularly as it sounded a little harsh with my junk (but fantastic) Strat copy in the bridge position. I ran up a few ideas on Pspice and ended up with the same tone control as I have on my New Clipper - basically a Big Muff tone control with the following values;

100k Lin pot
.022u cap to ground
22k resistor to ground
33k resistor/4.7n cap connected to input.

To get the best bass response the level pot needs to be changed to 100k (I used a linear and the range seems spot-on).

Other slight changes are;

The .01u cap from pin 6 on the tube socket to tone input replaced with 4.7u electrolytic 

250pf cap on IC1 replaced with 470p

BTW, I used an LF356 for IC1 - won't work as a direct replacement for a TL072 as its a single op-amp. Couldn't tell the difference from a TL071 though.

Don't know how this will work for anyone else, but the tonal changes are staggering from my point-of-view. This is a superb design to begin with, but for me the sound is now exactly what I've been looking for. I've got a few valve amps and the Shaka tube through a tranny Peavey Backstage 110 easily competes on response, sound quality and dynamics. I've tried a wide range of guitars and it's easy to get inspirational sounds with strat-copy single-coils, EMGs, Seymour Duncan humbuckers & SCs, and Gretsch TV-Jones pickups.

Another Idea I picked up (not mine) was to put the valve on the outside of the enclosure. Makes it easy to 'audition' different types.

[aron]

Don't know how this will work for anyone else, but the tonal changes are staggering from my point-of-view. This is a superb design to begin with, but for me the sound is now exactly what I've been looking for.

OOH THANK YOU!

I gotta dig up my unit. I just saw it the other day!!!!!

[aron]

My unit has a socket on the top, so the tube sticks straight out. I use the tube shield as protection (I know, not that good).

[Mick Bailey]

Just a further point - you can switch a larger cap across the 4.7n cap for a mid boost. It seems extreme, but I use a .022u in my New Clipper and it gives a very open, mid-rangey sound that is good on low gain settings. Might be a bit too much on the Shaka Tube - perhaps some experimentation here.

[Mick Bailey]

The .022u switched across the 4.7n  works really well and I've just permanently incorporated into the pedal. This levels out the mid-dip of the circuit and extends the versatility of the design. Sort of a vintage/modern switch.

The other thing to be aware of is that when you change to this tone circuit the centre position of the tone control is the home position and anticlockwise is bass boost/treble cut, with clockwise from centre being bass cut/treble boost. Actually, because its passive its all cut, but it sounds like cut/boost.

How can a mere pedal make me so happy? Now it looks like I'll be back to playing the guitar (for a while) rather than messing around with pedals.........   

[beatnik]

I want to try this different tone stack for my shaka tube, but i don't know what components need to be replaced. Can you help me?

[Mick Bailey]

What I've done replaces the treble roll-off circuit and volume control pot. These are the components hanging off the .01uf capacitor connected to Pin 6 of the tube, as well as the capacitor itself which gets replaced with a 4.7uf electrolytic, positive connected to pin 6.  You need to look at the Big Muff tone circuit http://www.muzique.com/lab/tone3.htm to get the idea of what you need to replace the original circuit with.

You will also need to replace the 10k volume pot with a 100k pot and use the values I've given rather than the Big Muff values. Also, the switched mid boost cap should be included as it makes a real difference within the usable range of the tone pot.  I don't know how to insert an image with this post, otherwise a diagram would be helpful.  I'll mail you a schematic.

Mick

[aron]

Mick, send it to me too and I will post it. I want to try this too.... just working on 2 pedals and my Maestro Boomerang right now.

[aron]

Here it is!

Thanks Mick!

[beatnik]

many thanks mick!
i will try this for sure

[aron]

I just found my Shaka Tube again, so hopefully I can mount this off the pot and check it out.

[Mick Bailey]

If you find the mids are cut too much for the first half of the control's rotation you can decrease the value of the .022uf connected to ground. I played around with quite a few values but kept coming back to .022uf as I liked the extreme range of control. Don't forget to change the level pot to 100k!

[george]

Hey Mick
Is the 100K pot a linear like the tone controls on Jack's page?

Thanks George

[Mick Bailey]

Yes, the tone control needs to be linear, otherwise  you'll find that either the bass or treble range is bunched up towards one end the control's rotation and 12 o'clock will not be the centre position. I also used linear for the level pot, though ideally this ought to be log to match our hearing response. 

[george]

thanks!