shaka tube build problems...

[Paul Marossy]

The tone pot on any of these Shaka HV tone controls should be at about 9'o clock.

That's exactly where I keep mine.  

What I mean about the ceramic caps is that they may be making things sound rougher than if film caps were used throughout. I know that I have said in the past that I can't hear a difference between films and ceramics in the past, but in this case I think I may take an exception. I does seem to make a difference in some circuits, at least when the low voltage types are used. High voltage types do a lot better.

Here's an interesting page about caps: http://members.aol.com/sbench102/caps.html

[petemoore]

I used to type about how I could hear a ceramic cap difference in one position...it's been a while...
 But someone said 'cumulative' effect', so I believe that but still use ceramics for high end rolloff sometimes or in a pinch.
 Speculation only cause I've never raeally done that much testing on it, but people do seem to a preference for non-ceramics in stompbox building, using film caps or even springing for metals in builds.
 I still wonder if the cumulative difference is really much more than just perceptable.

[Paul Marossy]

My intuition tells me that in this particular circuit, cap types could make a noticeable difference in how it sounds. I say that because the preamp tube is already running in starved plate mode and I think that somehow might exaggerate the non-linearity of low voltage ceramic caps in this instance. This would mean thay you have non-linear caps feeding a tube operating in its non-linear region. Things could get a little weird.

Just my theory...  

[george]

at high gain there is lots of noise that comes straight into your head killing your eardrums

sounds like you need this: http://www.generalguitargadgets.com/diagrams/switch_lo_dpdt_input_grd.gif

I had a high pitched squeal on my Shaka Tube at high gains, that could be heard even when pedal in bypass mode - this fixed it

[george]

[quote="Paul Marossy"
As I said before, adding a 0.1uF cap to ground on the output really seems to help it to sound a lot less harsh.[/quote]

Hey Paul.  0.1uF sounds kinda big .... I did something like that as well but I found that it somehow made the tone muddy and harsh.

I found the standard 0.01uF for the tone control didn't do anything - I changed it to 0.022.

The standard 100K tone pot is also very touchy - it's hard to get the setting just right even with a log taper, so I replaced with a 100K resistor and 10K pot.

BTW I also removed the cathode resistor caps on both valve stages 'cos it was pumping bass like anything

I'm still not happy though - I'm toying with putting in separate bass and treble control a la the 4-knob tube driver ...

[Paul Marossy]

george-

0.1uF sounds kinda big .... I did something like that as well but I found that it somehow made the tone muddy and harsh.

Hmm... worked fine for me. I tried a 0.01uF at first, but I couldn't really hear any difference at all until I put a 0.1uF on there. I have that as a bright switch on my Shaka Tube, I can switch the cap in and out of the circuit output.

It's interesting to hear so many varied results with this circuit. I wonder if there is some common thread here - like the type of caps used, the opamp, etc.? I think mine sounds awesome as long as the tone control is around 9-10 o'clock.

[changes]

well paul worked for me too
thanks
the gain is a lot less now
but i still use it 12 o clock max
cause i don´t like the distortion coming out
i like it as a blues machine
i tried a 47n and 100n can´t find which i like best.
with the 100n i have to max the tone cap
with 47n looks fine
but has more gain...
i´ll try another tube in it (12AU7 or 12AT7)
but i think it starts to sound as supposed to be
thanks again paul

[Paul Marossy]

BTW, I have a 12AT7 in mine, and it sounds quite good, IMO.  

[GreenEye]

I must be blind, dumb, or both.  

Where is a good schem of the Shaka Tube, and where is the "demo?"  All I found on the net was a hand sketch that was barely legible.  I'd love to see a nice layout/build instructions for this, not just pictures of the insides of a built one...

[Thomas P.]

I must be blind, dumb, or both.  

Where is a good schem of the Shaka Tube, and where is the "demo?"  All I found on the net was a hand sketch that was barely legible.  I'd love to see a nice layout/build instructions for this, not just pictures of the insides of a built one...

You could look at Pauls or my website.

[Paul Marossy]

I have a PCB layout at this page: http://www.diyguitarist.com/DIYStompboxes/ST1590BB.htm
Look at the links on the bottom.

Aron's original soundclip can be found here: http://www.diystompboxes.com/pedals/sounds/shakaTubeDemo.mp3

This is the only schematic that I know of: http://www.diystompboxes.com/pedals/schems/shakatube.gif