[John L Stewart]

Originally Posted by John Byrns

In article , wrote:

John Stewart wrote:

I take from your comments that you would like to run the E182CC at 35 ma
plate current, each side. Max plate dissipation is 4 watts per side.
That results in a max plate voltage of 114 volts.

Looking at the plate family of curves I estimate by eyeball Rp to be
about 2.5K. Calculation at the spec sheet operating point of mu equal to
24 & G being 15 ma/v gives Rp to be 1.6K. But of real concern is the
very short grid base at these conditions while Eb is 114 volts & grid
bias is -ve 2 volts to set that Q point!

In a general sense, the higher the mu of a triode while used as a power
amp then the supply volts needs to be increased in order to develop any
reasonable output power. By eyeball I would think you would need to run
a plate supply of something like 150-160 volts & increase the grid bias
so that Pd of 4 watts is not exceeded.

In any case, it looks like the resulting Rp would be about 3K. In a PP
amp the source then becomes 6K, working into whatever OPT you select.

The 15K/135K interstage transformer I referred to as used by Lloyd
Peppard is a Hammond 124E, the same as you had referred to. Not sure if
you had the Hammond in mind. I have one here that I use now & then in
experimental circuits. But others make something similar, I guess.

When I referred to boutique parts I had in mind your reference to the
HA-106 at $360.00. Fairly obvious to anyone, Hammond is anything but
boutique.


Hi John,

I designed the amplifier using the simplified Class A Triode design
guidelines that Patrick posted in rec.audio.tubes a month or two back. I
am going from memory without looking it up, but that gave me a plate
voltage of 162 volts and a total current of 40 mA per channel, 20 mA in
each of the two push pull triode sections used in each channel. I
followed Patrick's recommended plate dissipation of 80% of the rated plate
dissipation, which gave me 3.2 Watts per triode section.

I have decided to initially build only one channel on a chassis sized to
accommodate two channels for stereo. This will allow me to sample the
amplifier with my existing Hammond output transformer, and then if I like
it I can purchase two of the new Hammond 1609 transformers. This assumes
that my existing transformer, once I am able to locate it, is the same
size as the current Hammond 1609 Transformers. If the new 1609 won't
easily fit the same chassis mounting holes, then I will have to rethink
this plan, and either start with a throwaway mono block, which I don't
want to do, or just spring for the two 1609s.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

Hey John Byrnes, did you ever build that Potato Amp?