Med-high voltage Valvecaster/Tube preamp project

[momo]

Thanks,
OK maybe I was not clear on my setup:
See my regulator, still works although at some point in the beginning, much current went thru it once and it got hot, no smoke, still works.
I get a bit less out, 11.9v max instead of the 12.3v I was getting.
I too think I might of damaged my 120w power supply as it was screaming at some point as I was going to , say, 13-14v out, it's as if it had runaway current and had reached its output limit.
Now that would mean a major short somewhere.
I did check the resistance, no tube, no power, using the dc input wires, it was all over the place, would change conditions on the way, what did work 5 seconds ago, now does not work...ect....!
I use this psu to test, but I also tried the transformer that will be used in the end, a 14vdc, 1A psu.
So the regulator does not have to do much work.
Maybe a 317 current regulator would be better?
I think at these low volumes my setup should be good, filtering seems good compared to potential gain of the VC.

[GibsonGM]

got hot, no smoke, still works.

Are you SURE of that?  Test regulator on its own, NOT connected to the breadboard.  So, with 14VDC supply, the regulator output about 12.3V?   If you put a 680R resistor, or thereabouts, on the output to ground as a load - does the voltage remain constant?  How about if you then try a 330R as a load?
POST VOLTAGES with each test, before and during test.

I too think I might of damaged my 120w power supply as it was screaming at some point as I was going to , say, 13-14v out, it's as if it had runaway current and had reached its output limit.
Now that would mean a major short somewhere.

It means the PSU is being killed, yes.  Measure its voltage output unloaded, and compare it to what it used to output, unloaded (you did measure before, right? lol)

If there is a short on your board, any PS you plug in will likely be damaged in short order...if it all is going thru the regulator, that may well shut down and save the PS. It is hard to tell if PS or reg or both are damaged without consistent measuring and posting of voltages.   Voltages at your board and tube pins should remain constant when power is applied, not jump all over.  That indicates loose connections, shorts, or faulty 'something'.

I recommend a consistent voltage measurement, recording, and posting routine if you'd like help!  After you have ENSURED there are no shorts anywhere in the circuit, that the power supply is in fact working as it should, and that the regulator isn't fried 


Maybe a 317 current regulator would be better?


There is no reason a 317 would work better. LM7812 is made to do this job.  IF your 12V regulator is not damaged, it is fine in this circuit, especially since it is heat-sink mounted, which is good to see.

Debug....check...post voltages.  Clear, concise, methodical....   

[momo]

Thanks for that, yes I realize me just saying what is happening won't help!
OK, well for now, I decided to cleanup my whole lab... :-)
Therapy.
Will do the test soon enough, thanks for the tips.

[momo]

after some research, I decided to try breadboarding the Black Valve schematic, which , from what I read is a more open sounding version on the VC.
Thanks to Uncle Doug ! https://www.youtube.com/watch?v=HrkYUPmEUhk
I found a frequency response calculator based on the cathode bypass caps usage.
See the difference between both schematics.

[GibsonGM]

Ok...and?  For guitar, there is little useful signal below 80Hz...most ppl like to cut higher than that, in fact.  The <1dB difference probably isn't audible, tho maybe it could 'manifest' itself as sounding more clear - maybe it drops some of the 'woolies'.   Decreasing C2 will get you more highs....

This difference seems to be because of the value of R1 (100k vs 1Meg).  If it works and you like it, go for it!

[momo]

Well until I get this thing going, I won't really know the difference.
OK,
debug, I'm using the BlackValve schematic, which is the same layout, different values, mainly on the cathodes.

I am to the point now where I have voltages as far as power is concerned, and
Weird thing is if I send power to pin 4 and ground pin 5 I loose power(short), unplug pin 5 power comes back to pin 1 and 6.
If I send power to pin 5 and ground pin 4, I dont get the short, power is going to pin 1 and 6, I hear a whine from the regulator at the output so audio connections are good.
I changed places on the breadboard thinking it might be it, but no.
Tubes seem fine with continuity test.
Can someone tell me why no short if i power pin 5 , but I short if I power pin 4 ?
The tube holster has no short.

I have 12.1vdc from my 12v regulator.

Pin1: 12.1
Pin 2: 0
pin 3:0
pin 4: 0
Pin 5: 12.1
Pin 6 12.1
Pin 7:0
Pin8:0

Pin 1:

[momo]

O
STop the Presses.....everything works, and would of worked from the start.
OMG
I had the pinout reversed on the ribbon cable.....was sending plate voltage to pin 9......thinking it was pin 1
OH boy
36hrs later
Yay!
Ok now onto the fun stuff..

[momo]

that I can play with it,...

This Blackvalve circuit is very much like the original, I say it depends on the  actual tube. I have this Mullard 12au7, les out put than a RCA red logo I have, but the Mullard is "richer" sounding. I would gladly use the RCA too.

Front end boosters: I tried the AMZ mini booster, the ROG Fetzer valve with tone control(nice) and presence option( opens up a bit).
I still have the AMZ mosfet boost to try.

So far the Fetzer is best as it adds character. The mini boost sound great and full, but also clean @ 12v.
The mosfet boost might change my mind, but I rather get grit early with the fetzer, then fatten that with the second stage.

Last thing to say, my psu transfo is putting out 18v under load, I plugged the plate voltages on that instead of the 12v, more gain of course, but also opens up in high end a bit....
So, now I'm thinking of boosting the plates....hehe

I'm sure lot's of you are smiling, having been there before...
This plate boosting buisiness I think will open the circuit just right in freq response.

[momo]

Here is a nice Vista for you guys to relax a bit..

[GibsonGM]

That work area is NOT messy enough!

[momo]

Jimi is watching close,listening...

[bluebunny]

That work area is NOT messy enough!

You can see the table top for a start!   

[GibsonGM]

...no bits of cut wire, insulation pieces, tangled jumpers, spilled epoxy, loose resistors and caps, coffee rings, 2-legged pots...

[momo]

I do clean up as I go, once the tempest has calmed.
In the groove though, things fly, bounce, ....spark....sometimes.
I prefer a bit of smoke signals first, at least you have time to respond.

[momo]

Quick question,

I'm a bit obsessed with doubling the plate voltages.
All I have to work with is a 555.
I see the 12au7 max plate current @ high voltages is 10.5ma
I would like to run the plates @ 28v
The 555 has a max current of 30ma @ 30v, somewhere around that.
The question is how much current can it pull @ 28 v , will the 555 burn out rather than fade away....?

[GibsonGM]

The 555 is 4.5-15V supply voltage recommended maximum.   I doubt your 12au7 plates are going to draw 10mA!!!  They draw only a few mA per triode at HIGH voltage, and only microamps at these low voltages.  For reference since the design inverts the signal, a triode's current demands won't be simultaneous. 

There are MANY voltage doubler designs using the 555, here is one. I would just try one and see if it gets hot/smokes.  Of course only apply the ~24V to the plates, not the heaters      https://elonics.org/dc-voltage-doubler-circuit-using-555-timer/

[momo]

I just did this one,
With the VC full drive I get 16.9v out of the doubler.
It does make a difference! from the 12v.
quadruple?...
:-)

[GibsonGM]

Because the 555 has to act sort of like a 'bucket brigade', charging the caps in cycles, the voltage can/will sag depending on how great the load is. 

Did you measure its unloaded output?

[GibsonGM]

For more I'd recommend an 18V wall wart  

[momo]

A few things to say, if it can help others in the same situation.

A few days ago, remember I had an issue with my regulator.
Was not getting infinite resistance on the circuit, continuity beeper would just faintly come out randomly.
Had a "complicated circuit"
14vdc in regulator, out to circuit.
The problem was my tube pinout was reversed, so I was sending plate voltage, normally pin 1, to pin 9, heater, connected to ground...
HAHAHA!
Took me 36hrs work , redoing the circuit many times...

Anyhow, SO: I changed the regulator as it was whining around 14v in.
Regulator now clean, I realize the whine might come from my psu that is complaining.
I now realize it has less current output, starts to complain half way.
---------------------------
So when I use the 14vdc wallwart, all is fine now, see post above.
Now I wonder if I can push my luck and quadruple the plate voltage on the 555...