Med-high voltage Valvecaster/Tube preamp project

[GibsonGM]

You can try....   They don't do so well as you try to make them give out more and more voltage. But worth playing with.

[momo]

Well that was a great workout and learned much.

I tried to quadruple the voltage, was maxing out @ 15. ish volts and the regulator, which was not connected to the doubler circuit, but sharing the main psu was getting hot.

I bypassed the double circuit and I get 17.5 volts raw off the psu...!

I think it will workout fine this way, but only because I'm not stressing the 14vdc 1A psu with much load.
I have not put the Fetzer valve circuit on there, but it should not change much.
The Black Valve circuit has some power conditioning caps on the line which helps for the "raw" 17v I get from wallwart.


This is getting closer to the end of the mods and tweaking, I think with the Fetzer in front, it will be great. I biased the Fetzer kind of clean but with good assimetrical chime....

[GibsonGM]

Placing a 100R resistor with a cap to ground after, say 100u, 470u...may be enough to condition the wallwart supply so that it doesn't make noise with the VC...the Fetzer is a good idea before it.

[momo]

Getting closer,

I gutted one of those small Marshall amps, I just had to have that cute little 3 position rotary switch and the knobs!
Made my input "tonestack", the important part is how nice it looks.
I don't care really for the cap values, as long as they bling.
I got lucky and got .022, .047, .01...!

See the nice jewel that was just made to go on top , there is a tube, it has to have a jewel pilot light.
Output volume on top and the rest of the controls on the plate.

Whoohoo!

[momo]

Placing a 100R resistor with a cap to ground after, say 100u, 470u...may be enough to condition the wallwart supply so that it doesn't make noise with the VC...the Fetzer is a good idea before it.

I'm using this calculator to figure out the numbers, I don't like the voltage drop...
https://www.ampbooks.com/mobile/amplifier-calculators/RC-ripple-filter/calculator/
For the current draw , I figure 150mA for the heaters and then say another 40mA to drive the Supreaux Deux and the rest of the Black Valve/Valvecaster.
I'm trying to preserve as much voltage I can from the wallwart to feed the VC circuit with max voltage.

[momo]

Progress!

I made this baby turret board for the VC components......little one
Populated my plate, will now start wiring.

[GibsonGM]

150mA for the heaters, like 10mA for the rest (that is being very generous, too; it's more like 6mA). Measure current draw directly if in doubt.

My assumption is that you would feed the heaters ENTIRELY on their own - they are then not part of that filter (!!!!). Heaters are always treated separately if need be, and are a 'separate topic'.   

So you filter ONLY the power going to the Supreaux and VC with the 100R/330u or 470u what have you.  Make cap smaller if you like. Give the audio sections 10mA.  Voltage drop will be negligible, about a volt (likely less since these circuits are NOT drawing big current at all).   This is how it's done. 

If you dialed down your supply voltage by 1 volt while playing, I guarantee you won't hear a difference.  This is NOT a critical circuit...or, live w/the noise, or get a well-filtered wall wart that gives the rated voltage instead of trying to 'quad' it and so on, which is likely causing noise....

[momo]

OK well it will work out,
I'm using a psu that puts out 18vdc unloaded @ 1A.
The whole box as you mention will pull maybe 170mA max, so the psu drops maybe 500mv loaded....or at least less than 1v.

Originally, I was going strait from the dc jack to the 12v regulator.
We were talking about a choke and you mentioned the rc filter circuit so I thought it would not hurt to add it on the dc jack directly.
As for heaters, from what I read, ac is more complicated, twist wires, manage wire pathway, while regulated dc is kind of worryless.
So extra filtering on the dc jack, apart from the voltage drop , what can be detrimental to the heaters?
I'm managing grounding well, lifting where I should, no loops, as I want this thing extra quiet...

[GibsonGM]

Well...for one, extra filtering on the heaters will either benefit the noise level a bit, or do nothing (since you're running on DC, there should be very minimal heater noise at all anyway). 

I 'forgot' that you are using a 12V regulator.  If you've set it up correctly (with the in/out caps per the data sheet), then the 100R/cap to ground is not necessary. The regulator should do the job.  But the RC filter coming into the box will not HURT anything as long as the R is rated for the total current you are using throughout, keeping in mind everything that's being run through it.  See if it gets warm

[momo]

Thanks, I might not use it, keep it simple.

[GibsonGM]

Thanks, I might not use it, keep it simple.

Yes!

[momo]

I went for a walk after some delicate soldering.
Then a thought came over....oh no.!..
So I installed a DPDT switch to be able to use both circuits together, or just the VC without the Supreaux.
I realized as I was walking that I could of just just switch power on and of on the Supreaux, all signals hardwired.
I went the other way, I'm switching the input signal path, in series together the Sup and VC, or just to the VC.
In other words, If I switch to just the VC, the Sup is still powered but receives no input signal.
The unused other side lugs on the switch are grounded.

Otherwise, I'm happy with my nano turret board!....coming along nice.

[GibsonGM]

Looks good! When it's done you should post a sound clip...

[merlinb]

Someone posted this old wacky circuit to facebook recently so I thought I'd toss it into the forum for reference. It was called the 'Tubester' 

[PRR]

Someone posted this old wacky circuit...

2002 is not old.

For the curious:

5k input impedance?

It is a 3-page article.  Whole issue, 6MB PDF:
https://worldradiohistory.com/Archive-Poptronics/00s/02/PP-2002-07.pdf

The "filament" should be called heater and is really 300mA, not 150mA.

That octal socket diagram is wrong, and awful. Ignore the center tab and go look-up a proper octal diagram.

[Colman]

an option:


https://experimentalistsanonymous.com/diy/Schematics/Distortion%20Boost%20and%20Overdrive/Ron%20Black%20Tube%20Distortion.pdf

Way back I built it and sounded better than the valve caster as far as I can remember.


Aharon

[momo]

Thanks so much.
I am still evaluating all options and trying them before I commit, so this is great to have, thanks.