ruffrecords

Re: Regulated B+ Solutions?
« Reply #60 on: July 25, 2019, 04:24:52 PM »
thanks for the ideas and tips by the way!

My pleasure.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'


5v333

Re: Regulated B+ Solutions?
« Reply #61 on: July 25, 2019, 09:00:30 PM »
oh i almost forgot.

would it be possible to exchange the zener(s) for a string of neonlamps?
not many voltages to choose from but arent thoose good for constant voltage sourcing?

ruffrecords

Re: Regulated B+ Solutions?
« Reply #62 on: July 26, 2019, 04:28:04 AM »
oh i almost forgot.

would it be possible to exchange the zener(s) for a string of neonlamps?
not many voltages to choose from but arent thoose good for constant voltage sourcing?

Yes they are basically the tube equivalent of zeners as used in the REDd 47 design.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

5v333

Re: Regulated B+ Solutions?
« Reply #63 on: July 26, 2019, 10:43:44 AM »
A mosfet regulator with neonlamp reference sounds like a cute circuit!
Hope i get the chance to try it out some day.

I think there was a neon voltage reference in the tube version phillichorda organ.

EmRR

Re: Regulated B+ Solutions?
« Reply #64 on: July 26, 2019, 11:02:29 AM »
A mosfet regulator with neonlamp reference sounds like a cute circuit!
Hope i get the chance to try it out some day.

I think there was a neon voltage reference in the tube version phillichorda organ.

It's surely specific to the circuit at hand, but be aware that neon lamps can become oscillators.   I've seen it numerous times in the PSU regulation of Gates SA-39 limiters, for example. 
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

Re: Regulated B+ Solutions?
« Reply #65 on: July 26, 2019, 12:12:36 PM »
A mosfet regulator with neonlamp reference sounds like a cute circuit!
Hope i get the chance to try it out some day.

I think there was a neon voltage reference in the tube version phillichorda organ.

Careful with putting a capacitor across the gas tube, they're liable to turn into a relaxation oscillator.   
As a shunt reg, the idea is that you feed a current to the tube equal to the load you're regulating, plus enough extra to strike them on.  Up to about a 40mA load I generally source about half as much current again to the neons.  So, 30mA for a 20mA load etc.  But best to check the data sheets for details of maximum/minimum values. 
Again, an active CCS feeding the neon shunt would be good here as it will give you some isolation from the HT. 
Then again, I've had neons be noisy by themselves and some sifting through a batch was required. 



Re: Regulated B+ Solutions?
« Reply #66 on: July 26, 2019, 12:22:08 PM »
I took me peek on line for this,  I built this circuit minus the tube diode rectifiers.  The shunt reg was solid and stable, the circuit sounded good.
But don't dismiss my suggestion to try a CCS feeding a resistor as a reference for a cap multiplier.  Might sound daft but a resistor is quiet, linear, and stable.  Excluding carbon comps of course.
Here:

ruffrecords

Re: Regulated B+ Solutions?
« Reply #67 on: July 26, 2019, 03:41:29 PM »
Resistors may be quiet but semiconductor CCS often are not. Probably not a bad idea to decouple their noise to ground with a cap.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Re: Regulated B+ Solutions?
« Reply #68 on: July 26, 2019, 04:28:00 PM »
Resistors may be quiet but semiconductor CCS often are not. Probably not a bad idea to decouple their noise to ground with a cap.

Cheers

Ian

True enough, you need a good CCS.    There are some good schemes out there though, the example below is an extreme example, has an impedance somewhere around 40G for most of the audio band, and is inky black silent. 
Even a simple cascoded Fet can get you up to around 3G impedance and also not be noisy imho, especially if you're going into the gate/base of a cap multiplier. 
And if you don't like squalid-state, there are 100% valve CCS's of course 😉
« Last Edit: July 26, 2019, 04:32:03 PM by Winston O'Boogie »

 

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