Med-high voltage Valvecaster/Tube preamp project

[momo]

For some reason I always stayed away from commercial wall warts and high gain...
For sure that would be more practical if I can get clean DC.
I could do a regulator / filter board just for that..

but then
What will I do with all that extra space?...
:-)

[antonis]

but then
What will I do with all that extra space?...

Better Tonestack, Delay, Reverd, etc..

[momo]

but then
What will I do with all that extra space?...

Better Tonestack, Delay, Reverd, etc..

Well....now I have to ponder other options, what would sound glorious in there added to the VC and AMZ boost....
I have some vibroverb, neovibe, Pez 90....hmmmm!

[GibsonGM]

(this isn't any sort of 'commercial wall wart' required - they're quite common (!), and it's not high voltage (over 30V is usually considered "high voltage")...)   

Most wall wart supplies can be filtered easily with just a couple of R's and C's on the board where the power input is - we do this every day.  Someone else designed it, made it for you, and all you need to do is plug it in. If it dies, you can easily replace it...it's safe, neat, inexpensive, saves time, you can substitute another similar one if you have a problem, it is never possible to have line voltage on the chassis, it's uncomplicated...but that is up to you, I will say no more.   

What to put in there?  First, a working Valvecaster!     Then the next circuit you desire, and then the one after, when each step is working   

That is a nice collection of pedal PCB's, by the way.

[momo]

John Lyon boards...

OK, had a nice long walk and so here I go with the plan:
Yes, a wall wart it is.
I will breadboard everything first, get it all going, no matter how long it takes.
So, VC as the base in the box, AMZ booster and.........how about a Neovibe..!
My Neovibe board is well under way..
Now I thank everyone helping me, I,m going all in for this one.
I will definetly have questions about linking the 3 circuits together as I think nthere will be way too much gain.
Anyhow, today I tape the insides with copper tape.

[GibsonGM]

That sounds reasonable, Mario  

Make VC on BB.  Be sure it works, and sounds the way you like.

Then make VC on a board, and test it with your wall wart.


Then make boost, test boost, solder boost PCB.

Then wire boost and VC together with a bypass switch.  Test again.

When you are done adding everything, and have tested all of this, with their own bypasses, wire the inputs and outputs to the main 3pdt BYPASS SWITCH LAST.  This way you know all the circuits WORKED before you tried to set them up with true bypass.

You see how this works    We say "KISS"....."Keep it simple, stupid"  and that applies to ALL of us. 


You may need this:  http://www.tonepad.com/project.asp?id=35

[momo]

Update, major runaway current issue...

I re-did my breadboard wiring, everything seems legit.
Here are the mods I put up on circuit, the problem is that I get current going way higher than 150ma as I jack up the voltage gradually.
For now, there is no DC regulator circuit, just direct from variable DC source.

I'm going for a cleaner VC :  R2: 100k
                                          R3: 47K
                                          C3: non electro wima cap 0.1uf
                                          No tone circuit.

What can be causing this "semi-short" ?
A lady is either pregnant or not, so I'm not sure I'm semi-shorting....hehe

[antonis]

12AU7 needs about 150mA filament current at 12.6V and 300mA at 6.3V..

[momo]

Thanks,
Yes I know this, right now I am as the original schematic, DCv into pin 5 of tube, that linked to pin 4, that to ground.
I was getting smoke, in a general way, not localized on a particular component.
I re-did the wiring, checked all components.
I realize now, the smoke was coming from those tiny tiny connector wires, the current rush got them got.
So I won't be using those anymore, I have bigger guage connectors, will use that.
I still don't understand how current can go higher that way at small voltages, I started getting into smoke around 10v, that was already around 160ma....
Stopped everything.....slowly stepped away from the rig, a bit like Peter Griffin would do.....walked away..
:-)

[antonis]

That calls for a 60 Ohm "resistance" rated lower than 1.5W..

[momo]

Hang on...
Hmmm,
Ok, so I assumed that the current would self balance to 150mv by the tube demands, you are saying I would need to put a resistor in series on the DC supply, ok I get that, I thought it would limit itself...
Is that it?
My supply can deliver 120w...
As far as I know, a burnt out faulty tube would not have current flow.

[antonis]

you are saying I would need to put a resistor in series on the DC supply,

No...

I'm just guessing the cause for smoke..

There is a low resistance "somewhere" across supply + and -..

With tube out of socket, measure resistance across + Vcc IN and GND..
(power supply disconnected, of course..)

[momo]

A few issues. jeeze, happy to find this out but wow...
I thought maybe the new breadboard was maybe shorting somewhere, but no.
I have 2 meters I use on circuit, one for volts and one for current.
I was getting mega ohms of resistance as per what you mentioned to do, and it would slowly go down.
That cheap meter was causing the problem, if I unplug that meter, infinite resistance between the two dc poles.
So thats good, eliminated one problem.
Still, no sound and lots of whine from my psu.
Voltages:
Sort list, 1 and 5 have 8.92v from a 9v source, nothing on everything else.
Pin 9 not grounded, so logically the heaters should be in series.
I have 4 to ground and 5 to psu.
That 8.9v should be good enough for the tube to start.
I tried 2 tubes that I know work...

[momo]

So I.m back on the voltage regulator, much more quiet.
Still the plate resistors don't seem to be doing the work, both pins are at source Vcc.
Audio connections passes thru as the volume works.
Gain pot does nothing despite rewiring, one extremity is on pin 3, the other end with center to ground.
Audio passes where I hear the psu whine, but tube does not transmit with 9v on heaters....

[momo]

One more info, sorry for flooding...

With voltage regulator, works fine, no heat.
My psu can output 120w @ 24v max, yet, it starts screaming close to 12v, does not want me to push more.
SO
It's either it has come to its limit of current flow, in which case I would get smoke on the circuit, but no, all is calm.
Could it be the other way, where there is a ground missing and I'm pushing thru the regulator with no take from the circuit, this should not stress out the psu. Regulator is fine...

[momo]

Sometimes you never know how deep the iceberg goes.
So I think I had faulty plastic audio jacks, the input was shorting a few electrons I think.
I noticed right away a difference in audio levels which got higher. That is,  no dc present, just circuit bleed.
Anyhow, now I measured current on pin 5 heater, it's a very very efficient heater lets say.
I get 140mA @ 3.5v psu....
No shorts and infinity resistance now when I plug the meter on the dc input without power.

[momo]

I know this is annoying!...sorry everyone.
I have been on this today for 11 hours.
Rewired the whole basic breadboard setup.
I passed the aspirator on that board!

retried plugging everything , nope.

[diydave]

I have been on this today for 11 hours.

It's not an answer or solution at the moment, but often it's better to let it rest for a while. Sometimes the answer is right in front of us, but we don't see it because we're too 'hung up' about it. I've encountered that many times myself. But with a fresh and calm perspective, the solution eventually came. And it was often something very obvious.

[momo]

Thanks, hopefully I won't let it rest like last time, which was a few years!
Ok, no worries, I'm encouraged by the fact that it's not a difficult circuit to build...
I hope it's not my new breadboards, they look cheaper than usual..

[GibsonGM]

Start simple...disconnect regulator from tube. 

Power on.

What is the voltage at the regulator input and output?

With no power, what is the resistance from pin 5 to ground?

To be honest, I suspect your power supply or regulator are defective, or that something is not wired correctly at the heaters (?) although, that should be easy to see.  If the PS cannot source the current for the heaters, it will show that big voltage drop that you report.   Since you report "no heat" at the regulator....which should be dropping what, 12V...I have to say look at the power supply.  Dropping that much voltage SHOULD make it VERY hot - I would think a heat sink would be necessary...