Marty Marts Tornado built, but has a small problem

[John Lyons]

Good call marty and reiteratione Puretube!
I replaced the Trimmers with FIxed metal films and the Noise is significantly reduced and the static/crackle is gone.
This makes sence because trimmers generally are 20% or maybe 10% tolerance carbon with less than decent specs.
There is a good bit of hiss still but were getting there.

I had the ground issue on my mind as well. I'll have to look at it and try your suggestions. Thanks!

Here's a new clip, a bit with the gain up then no playing,  and then turning the gain all the way down to hear the hiss.

www.mrdwab.com/john/Tornado_fixed_trimmers.mp3

Still a good bit of hiss with the gain down but as long as we are getting postitive results eventually we'll get there.
Don't know why the metal riffs...I guess the high gain brings out the dark side....!

John

[MartyMart]

GREAT ! - getting better
Yes Ton, my 9v enters the board and is imediately reverse protected and filtered ( 100uf/100n ) direct
to ground, with a short jumper.
All other grounds then run the whole length, input->Q1->Q2-> etc to output ground.
This is one continuous "path" with no odd routing of ground nodes.
Worth a shot !
MM.

[gaussmarkov]

i've been working on a tight layout with guard traces, ground fill, linear signal path, +9v close to ground, signal ground distinct from power ground.  here is what i have so far, a 23 x 23 version (2.3" x 2.3").  there's a little more fussing for actual component placement, but i think i am getting close.

green is ground, red is +9v, blue is the basic signal path.  i have kept the feedback loop well guarded by ground traces or ground fill.  because i made it with eagle it is 100% consistent with the latest schematic.

i am unsure about how where to place the ground pad and where to break the ground trace that frames the layout.  the current arrangement is not right, because it leaves the principle supply filtering at the end of the chain--so i'm sure that gap at the bottom should be filled.  where do you think the break should go?

cheers, gm

[MartyMart]

Gauss, that's looking VERY nice indeed - kick me if I'm wrong here but this is what
I've spotted.
Your 9v connection from battery/PSU runs left and right of it's entry, so while it's filtered
one side , on the other it hit's a trimpot directly - very close to the actual physical connection.
My 9v "entry" is at one end of a strip, is filtered and then goes on to the first trim pot.
Does that make any difference at all ?? .... or am i going mad  !!
Perhaps electronicly it's fine that way .....

Peace,
marty.

[mydementia]

I'm with Marty here...
I'd run the +9V and Ground on the left side of the diode and cut the ground trace at C22 and the +9V trace approx where the GND label is (with a pair of pads to the left of the diode).  Then I'd run a trace/jumper from the filtered side to the of the +9V rail to get filtered power to all inputs. 
I'm used to doing layouts linearly, left to right... you guys and your fancy programs...

[puretube]

my comment "right of the diode" was cc that older layout - not: in general.

In general: the most silent point in the circuit is at minuspole of C20
(using Gaussmarkovs numeration in his last layout...);
this is where both the plus and the minus of the battery ought to be soldered;
this is where the single ground connection to the chassis ought to be (later on);
this is where R1 & R3 & R4 ought to "sit", as well as C2 & C3 and gainpot ccw-lug.
(if its not possible to have them all together physically,
connect these 6 parts through one trace, which then goes to C20 without having
anything else hooked to it to it.
(this can be regarded as one ray/branch of a "star-grounding").

The same goals for C22: its groundpoint  ought to be physically close to R8 & R9 & R11
& C8 (that groundplane you got there is fine, but it ought not to return to C20 through the sensitive input circuit`s ground-trace...

Similarly, trim1 cw-lug ought to run directly to C20 pluspole,
withought "picking up" other supply currents ("dirt") along the way.
(I love to use the word: "star-supply")...

[gaussmarkov]

got it!  thanks everyone for helping me.  ton, i don't need to tell you how helpful you have been.  your explanation for this example has taught us a lot.  thank you.  i will revise according to these comments.

gm

[John Lyons]

So like this?
With the exception of the Ground being moved closer to the PSU "big" cap.Thanks Puretube!



Interesting layout Gauss, it wraps around a bit but the output is pretty far from the input all in all.

EDIT

I was just going to post this and Gauss posted. Well maybe this will confirm the revisions at least...?

John

[MartyMart]

Thanks Ton, superb
Gauss - this is pretty close to how my power/ground is connected other than after
filtering, they are almost 4cm apart !!
But the parts Ton has pointed out are connected to power / ground in that same way.
I'm also used to laying out in a "linear" way  
Peace,
Marty.

[puretube]

hope it helps 

[John Lyons]

So is the layout i hacked two posts above about what you were thinking putetube?
I didn't move the ground of the Gain pot closer to the source but...

To make things slightly nore complex:
Pulling the first FET does nothing for background noise. Pulling FET one and two Lowers it to just about the right level (sheesh) .

Sometimes there is a pot betwen the first and second, and the second and third stages in high gain amps.
I wired up a dual gang 500KLog pot with the first side as in the schematic. Then the second half of the pot between the 820K after Q2 then the wiper to the top of the 180K  (Lug one ground, Lug two to the top of 180K, and Lug 3 to the right side of the 820K.

Here what it sounds like.

www.mrdwab.com/john/Tornadodualvolume.mp3

HB Neck pickup for the single note stuff and the bridge for the chordal stuff.
Gets pretty clean and all the way up to meltdown.

There is still a little bit of hiss with the dual 500K volume turned all the way down... Also the tone knob was set almost all the way down on this recording. I'll try so more fitering at the end an re do the tone stack possibly which should take the hiss down as well as alow me to have the tone pot centered more. The amp is pretty mellow sounding so it's not just a bright amp. I used an Electrovoice RE20 as well which is a pretty flat responce mic.

Watta you think?

John

[RDV]

Alright! Looks like we have somefeedback (literally and figuratively)  to work with. I need to check out Gauss's post in detail but I have this clip for comic relief. Marty, seems my built has way more gain than yours. This is with the voltage at 6 volts across the board. I can get singing feedback with out plucking notes...

www.mrdwab.com/john/tornadonoise.mp3 

This is the newest board with the parts spaced out.

Gain full up, humbucker bridge, after I stop playing I turn down the gain all the way and that's the noise I get.The static varies. The underlying rushing noise is consistant with all the 3 builds.

EDIT: Almost forgot that I disconnected the Feedback when the clip was recorded. I couldn't hear much difference and wanted to see it it affected the noise at hand...

I need to go over the posts above with the original layouts. I just wanted to post this so you know i'm not crazy and to let you hear what's going on.
Thanks for the pics marty!. I need to study those now as well. Your clip is much more tame than mine. If I didn't know better I'd say it's not the same circuit!

Marty. No hard feelings obviously. Just strange that we have such different behaving builds. It does sound great. Just need to tame this beast.

John

My Dr. Boogie makes that same noise so I look forward to someone figuring it out(because I've failed too). I almost have to think that this is a downfall of JFet circuits that have many cascaded stages.

RDV

[John Lyons]

Do you get the static as well as the wooshing noise RDV?
Try the trim pot thing by replacing the trimmers with fixed resistors. Worked for me.
My Dr Boog is pretty quiet actually. Maybe I'll replace the trimmers on it and see if it gets even better!

Use shielded wiring (in/out and to the switch and back) keep the wires short and uncrossed and you should be fine.

John

[gaussmarkov]

here's another draft.  C22 has moved so that it has a different ground on the star, per ton's suggestions.
the input section up to and including the gain pot has it's own arm.  and for good measure, i put the "output"
section on it's own star arm as well.  well, except for R22.  any idea how important that is?

i also made sure that all of the components would fit this time and made the gain connections a little more
spaced out.

john commented:

Interesting layout Gauss, it wraps around a bit but the output is pretty far from the input all in all.

i think i know what you mean so let me tell you my thinking and maybe i can get some more feedback.  if you
follow my signal path you will see that no components are next to each other.  in all of our previous layouts,
there are some instances where two components in series are positioned right beside each other in a sort of
doubleback.  i thought of that as not linear.  so i did not do this anywhere.  at worst components in the signal
path are at right angles to each other.  the path goes straight up the left side, stair steps down from the upper
left-hand corner to the lower right-hand corner and then shoots straight up the right side.  my guess was that
this is practically very linear.  and, of course, it enables me to keep the width of the board smaller.

that said, i could easily expand sideways and we would still have enough room to put this into a 1590BB. 

all the best, gm

[John Lyons]

Gauss

That looks good. My only concern is the grounding.
Form how I usnderstand it you want the first stages to have the cleanest ground. Which would be right at the ground point by the 100uf cap.
Then the higher current/gain areas are at the other end...down the line. You can look at it like, the cleanest signal get s the cleanest grounding.

If you cut the connection to the right of the diode and then fill in that plane on the far right (or cut it out making the board a tiny bit smaller then the ground path cleanest to dirtiest. (you need to connect the to left section to the top right as well) The ground path then goes from the bottom up the left side, over the top and then down the right side...clockwise.  Does this make sence? Simple to do with your layout now.

Thanks for working on this more!
Any thoughts on the clip folks. Not my horrid playing but the dual volume idea.

John

[MartyMart]

The clip sounded like mine when I had the 2m2 pot in there, more cleaner tones
but mine was "sucking gain" !
I have it back to "schem" values now and it is a BEAST !
I still dont have that noise though, I think it's all to do with layout, Gauss is onto that now
so let's see if a new version fix's the issue ..... finally 

MM.

[John Lyons]

Marty
Gauss's new layout makes sense to me with the star grounding points.
Not much hum issue with mine but clean grounding can help with a few issues.

Did your noise go up at all with the gain increase? I have mainly hiss now proportionate to the gain level
it seems tolerable, but less noise is always good. If you get a few minutes could you make a maxed gain clip? 

Getting closer...

John

[gaussmarkov]

john got me thinking (again).  one more suggestion-- and even closer to the star ground ideal--how about a jumper direct to C20 for the Q2 ground branch like this:

[John Lyons]

Surprise...it's me...

That looks better gauss. More direct and will clean up the trace going up the side and over the top.
Plus it will make the board a couple millimeters smaller!

John

[Meanderthal]

 I gotta say, I really have to admire your determination and patience with solving this problem!