I basically have two questions about the CGS65.
Firstly, while I've heard some very nice demos of its waveshaping
abilities, I am curious how well it performs as a VCA. If the input
signal is kept below the level at which it distorts, how well does it
function as a VCA?? How well does it mute an incoming signal if no
envelope is applied?? Has anyone here used it as a conventional VCA??
Secondly, I am quite confused about the cathode circuitry. I do not
understand the inclusion of either the regular diodes (which are
described as optional) or the LED's (other than their ability to
illuminate the tube). I believe I understand why this circuit uses
the negative rail for the heater voltage instead of the specified
filament voltage of 1.2V -- since it uses a directly heated cathode,
doing so increases the potential between the cathode and plate to 30V.
Looking at this site: http://www.russiantubes.com/prop.php?t=12&p=7
it looks like the recommended heater current is ~13mA, so its
resistance would be ~100 Ohms. V/i=R 15/.011 = 1.4K 15/.015 = 1K
So I'm thinking a resistor between 900 Ohms and 1.3K is all that
would be needed to limit the current within its recommended range,
and the power dissipated by that resistor would be close to a 1/4W.
It says, "These LEDs are using waste power that would otherwise need
to be dissipated in the current-limiting resistors for the heater, so
even if you are hiding the tube, the LEDs must still be included."
I'm sorry, I don't understand that, than other than the change in
voltage due to the diode drop, how the diodes would effect the amount
of current running through the resistors. Could someone please
explain that??
Thanks :)
Firstly, while I've heard some very nice demos of its waveshaping
abilities, I am curious how well it performs as a VCA. If the input
signal is kept below the level at which it distorts, how well does it
function as a VCA?? How well does it mute an incoming signal if no
envelope is applied?? Has anyone here used it as a conventional VCA??
Secondly, I am quite confused about the cathode circuitry. I do not
understand the inclusion of either the regular diodes (which are
described as optional) or the LED's (other than their ability to
illuminate the tube). I believe I understand why this circuit uses
the negative rail for the heater voltage instead of the specified
filament voltage of 1.2V -- since it uses a directly heated cathode,
doing so increases the potential between the cathode and plate to 30V.
Looking at this site: http://www.russiantubes.com/prop.php?t=12&p=7
it looks like the recommended heater current is ~13mA, so its
resistance would be ~100 Ohms. V/i=R 15/.011 = 1.4K 15/.015 = 1K
So I'm thinking a resistor between 900 Ohms and 1.3K is all that
would be needed to limit the current within its recommended range,
and the power dissipated by that resistor would be close to a 1/4W.
It says, "These LEDs are using waste power that would otherwise need
to be dissipated in the current-limiting resistors for the heater, so
even if you are hiding the tube, the LEDs must still be included."
I'm sorry, I don't understand that, than other than the change in
voltage due to the diode drop, how the diodes would effect the amount
of current running through the resistors. Could someone please
explain that??
Thanks :)