"SHAKA TUBE" - almost working ??

[puretube]

and the 2µ2 (schemo, top left), the 0.01µ tone-cap,
and the 4 big electrolytics in the PSU...

[MartyMart]

and the 2µ2 (schemo, top left), the 0.01µ tone-cap,
and the 4 big electrolytics in the PSU...

... yes, yes and yes

Though the third "yes" would seem to still be "floating" apart from hitting
pin 5 on the tube ....
Give me a few minutes, while I warm up the "Iron" ... !!

M

[MartyMart]

**********EUREKA**********  !!

.... almost !!
Well Marks 10k resistor to ground from the power board "does" make the
major problem of "cut outs" and "stutters" go away  !! .... BUT ...
At the "clean" end of the gain pot, I have a good overall "level"
At the "dirty" end of the gain pot, I have a nice crunchy OD tone, but
around half the level .... ! ( there just had to be a down side eh !! )

Ton,
being the "tube meister" that you are .... what could cause this "drop" as
the gain is pushed  ?
Your going to tell me about the voltage at the tube arn't you ??
"I swear by almighty god" that I have 11.7v AC at pin 4  ...: D

I'm almost smiling now ....

EDIT:
Just compared it to my SD-9 clone and there is around "double" the
overall volume from this circuit !

Marty.

[puretube]

I don`t care about the filament-voltage of your tube at all - as long as it is between 9V & 14V...
I`ll gladly send you a NOS original SIEMENS ECC83+ a brandnew Sovtek 12AX7WX
if my measures provingly ruin your tube!
I recommend 12.6V +/- 5%, though.

But your volume drop has nothing to do with that.

I suspect markr04`s 10k resistor is the same as your "skin-connexion",
just smaller, and that it behaves as the ground-return to the xfmr
(I have repeatedly recommended this resistance to be 0.0 Ohm...),
and therefore causing a powersupplyvoltage "sag", when the IC draws more current by being pushed harder, than when at idle.

It`d be nice to see what happens at the IC`s pins 4 & 7, when gain is turned up, and plucking the guitar... (compared to gain turned down with no signal).

[puretube]

be sure to "play" with the bias trimpot!
at some point, the sound will break off...
it should be turned back then, until the sound stays on
even with the loudest signal (highest gain).
turning further, it will get distorted and fart out again.

[MartyMart]

I would gladly except your kind offer  !!
I do have a sovtek 12AX7 and three new Marshall ECC83's
I prefer the "sound" of the marshall's but all of them seem to be working
fine in the circuit .
Here's my findings taking readings whilst "playing" - which involved one
very small "croc clip" !
"Clean gain" setting : Pin 7 11.11 volts no change when played
                              Pin 4 -10.38 volts no change when played

"100% gain" setting : Pin 7 11.12 volts increases to 11.33 when played
                              Pin 4 -10.38 volts increases to -10.67 when played

Should I decrease that 10k resistor to ground, maybe try a 4k7 then 2k2
etc to get the "minimum" before the gating/fart comes back ?

Marty.

[puretube]

yes, and keep adjusting bias-trimpot

[MartyMart]

yes, and keep adjusting bias-trimpot

I'll do that, but to this point, the "bias" pot has made zero difference
either way... its "centered" at the moment.

M

[puretube]

I`m going swimming... see ya  

[MartyMart]

When the 10k resistor to ground between boards is reduced, the overall
level ( which is a problem already ) is also reduced .
I tried several resistors from 10M down to 47k - the higher the value, the
louder the circuit is but the worse the "jumping from rail to rail" becomes.
Even at 47k, there is a slight improvement is overall level, but I get a few
"jumps/cut outs" still.
Looks like 10k - 20k is it !!

I may have to re-make this one some other time, and try a better layout
all i can think of is that somehow my layout is causing this, but it has
"zero" errors, so I'm not sure how to improve on it, other than bigger
vero with more space etc to keep tracks/ + - further apart .....

M.

[Paul Marossy]

Sorry to keep bringing this up, but I just wanted to say that the bias pot should have some effect on the voltages. It sounds like your bias may not be connected properly or something...

[MartyMart]

Sorry to keep bringing this up, but I just wanted to say that the bias pot should have some effect on the voltages. It sounds like your bias may not be connected properly or something...

It is changing voltages, just doesn't seem to change the "sound" any.
I did a "noise set" for it, with the gain flat out and no input lead connected
I adjusted it to give me as much "hiss" as poss = max gain  

I have a problem with the layout ... MUST be so !!
I'll remake another when I get a chance  .... ?

Marty.

[Paul Marossy]

Oh, OK. Yeah, it doesn't seem to have a huge effect on the tone in mine, either.  

[markr04]

I think I just figured out my last problem with this layout: input signal is too strong. But I don't know how to fix it, or why the problem exists.

Here's a recording. The part I'm concerned about is the unpleasant clipping that occurs at and just after the attack. Signal chain: passive humbuckers (neck, full volume and tone)>Shaka>mixer>A/D converter>computer.

I believe the clipping is at the IC. I'll be happy to provide voltages if they will help. Please tell me if you want the voltages with no input or with a hard strum as in the recording... or both.

http://www.siteofmark.com/shaka_trouble01.mp3

[aron]

Classic mis-biased sound. Post voltages of every pin and the plate, grid and cathode pin voltages too.

[markr04]

Thanks for your reply, Aron.

I adjusted the trimpot to the point where my sound was full and loud, just before the screaming sound.

From the power supply board:
V-: -10.9v
Bias: -8.6v
V+: 13.3v

IC (TL071)
1: -10.8
2: 0
3: 0
4: -11.1
5: -10.8
6: 0
7: 13.6
8: 0

12ax7
1: .3
2: -10.3
3: -10.4
4: 14.2VAC
5: ground
6: -4.2
7: -10.1
8: -10.5

[Paul Marossy]

Yep, something isn't biased properly.

EDIT: Oops, I didn't see your reply to Aron's post. Those voltages on the 12AX7 don't look right to me...

[puretube]

are you still having that 10k between the "grounds"?

[EDIT]: ooops I wanted to stay out of this project, until I built one up...  :oops:

[markr04]

Paul: I don't know how to fix the odd voltages at the tube, or what to compare them to. Will you elaborate?

Puretube: I desoldered the ground wire a week ago for some reason, so when I came to record the first sample, I used some clips to connect the grounds. When doing that, I forgot about the 10K and connected the grounds before the 10K. It has a fuller sound and whatever I thought I had fixed by using it isn't an issue any longer. So... no, I'm no longer using it .

For kicks, I connected the grounds to the 10K and recorded this (same chain, vol, tone, etc. as previous):
http://www.siteofmark.com/shaka_10k-between-grounds.mp3

Here's the first sample again for quick comparison - grounds are directly connected:
http://www.siteofmark.com/shaka_trouble01.mp3

[MartyMart]

mark04 - that sounds quite "nasty/bad"  !!
Is the "Fart gate" just from the pedal or from the audio sample overloaded ??
I actually have a fully working "OD" which just doesn't get very
"distorted" nor very loud ... but it sounds quite good !!
I dont have that kind of "hard farty" sound going on .....

There's a "boutique" pedal builder that I know quite well and he took a look at the schem/layout.
He recommended a few things, like .1uf caps to ground  directly off pins
4&7 of the op amp ( v+ and v- ) and possible another trim pot on the
PSU & some 10uf caps between v+/v- and ground on the PSU.
I'm going to give that a go.
He builds fantastic "Tube" pedals, so should know his stuff !!

Marty.