Maximum Voltage for Mr Black Tiger Boost

[Chris S]

I am looking at integrating a Mr Black Tiger Boost into a stand alone reverb tank as it currently operates below unity gain. The voltages are currently around 100v and I'm wanting to use a zener diode to bring the voltage down to something more pedal friendly. I know the pedal is designed is for 9v and most boosts will run on 18v is there any reason I could not run it on 27v (I believe the opamp can handle that much and the capacitors are all above 50v)

tiger boost schematic


example of zener diode used for a jfet boost.


Thanks

[antonis]

It should work as long as Zener power rating is adequate for the minimum (no load) current consumption..

You see in 2^nd schematic that Zener actually feeds only Grids where in your mod it should feed the whole circuit..
4558 min supply current (no load) typically is 3mA (both amps) plus a negligible 200μA current across R10/R11 voltage divider..

Zener CLR (R5 in 2^nd schematic) should be rated for maximun current consumption..

P.S.
I might confused you, so let's make things more plain..
For 100V supply and 27V Zener stabilized voltage, you need 73V drop across CLR..
The value of CRL can be calculated from 73V drop and total current consumption (with a couple of mA added for Zener working current..) and its power rating from its value and current through it..
For circuits minimum current demand (no load), all the "excessive" current (73/CLR) has to pass through Zener..
So Zener's power rating should be adequate to overcome worst case scenario..

[Chris S]

Thanks for that Antonis... OK so the power supply is 247v the current for the circuit and zener we can call 9mA (7ma for boost 2ma for zener working current). So am I right that R=V/I or 247/9 = 27.4k so a 27k resistor? Thanks!

[antonis]

Not quite..

Current through CLR should be the voltage difference between PS and Zener voltage (247 - 27 = 220V) divided by CRL value..
That calls for 24k4 resistor..
You can safely go for a 22k (3W at least..!!) and let the "extra" 1mA pass through Zener (400mW or bigger)..

P.S.
27k should also be fine but better have a Zener working current closer to specs..)

[Chris S]

Thanks!!!

[antonis]

With all respect to Mr Black (except for his "weird" concept about bypass switching..), I'd wire R6 to GND (instead of Vcc/2)..
(no reason for injecting AC garbage into an, as pure as possible, DC point..)