On 3/12/07, bbluthang put forth:
>There should be many tubes that can be used in this cct.
>I use a 1AG5, changed some resistors, different pinout, maybe it
>doesn't sound the same as Ken's but it certainly works.
That's very interesting, since that tube is listed as a diode pentode.
>Look for pentodes with 1.2V (1.25V ok too!) directly heated cathodes
>and other similar specs on this list -
>http://pw2.netcom.com/~wa2ise/radios/penciltubes.html
Thanks, there is some very useful information there.
I have two concerns with using tubes -- current draw and plate
voltage -- since I would like to run whatever I build off of the
+15/-15 supply used to run my modular.
Some of the tubes listed with 1.25VDC heater voltages draw as much as
300mA of current. However, there are a number of good prospects on
that list. Some list both low heater voltages and very large (5M)
resistors to ground, which strikes me as unusual.
The 6419 is listed as a "power amp pentode" although I'm not sure
what they mean by "power amp" as it says it has a plate resistance
of 2M. Regardless, it says it draws 10ma with a 0.625V heater
voltage, and has a specified plate voltage of 15V. I'm thinking it would
not be suitable for the CGS65, but having such a convenient plate
voltage invites further investigation.
http://www.nj7p.org/Tube4.php?tube=6419
A found a place selling them for $8 USD.
The 6611 "RF pentode" lists 20ma at 1.25V for its heater, and
plate 30v. That looks like it might work in the CGS65 with some
modification.
Also, $8,
http://www.tubedepot.com/tcp26.html
The 5884 (1.25v, 10ma, plate 20v) and 5885 (1.25v, 20ma, plate 13.5v)
twin tetrodes also look potentially useful, despite their lack of a
suppression grid. Who knows, secondary emissions might have an
interesting effect on the sound.
I can't seem to find a suitably low-power triodes or twin triodes for
the power supply I would like to use. Although I'll keep looking, as
I have ideas for triode-based filters, even though they only exist in
my mind and may not actually work in reality.
On 3/13/07,
sasami@... put forth:
> >http://www.russiantubes.com/prop.php?t=12&p=7
>
> >Unfortunately, it doesn't show the pinouts.
>
>Yes it does.
Yes, you are correct. I just didn't know what the dashed line for pin
3 represented.
>>Does anyone know what pin 3 does?? I am unfamiliar with the symbol
>>in the CGS 65 schematic.
>
>Shield.
Thanks :)
