Page 1 of 1

How much current does the Poseidon draw?

PostPosted: Sun Oct 07, 2007 2:15 pm
by audiowize
I'm thinking most specifically about Ned's version, but I'd imagine they're both close. I purchased a pair of these from Ned to go into a set of 829B push-pull monoblocks... so it should be interesting.
-Paul

PostPosted: Sun Oct 07, 2007 6:09 pm
by erichayes
Hi Paul,

The maximum plate dissipation of an 829B is 30 watts per section, so you can feel comfortable with around 100 watts consumption, quiescent, kicking up to around 250 watts on peaks. My 60WPC prototypes run at around 180 watts, quiescent, using four 6550s. They blow a 3 amp regular fuse after around 10 seconds at maximum output.

Not quite...

PostPosted: Sun Oct 07, 2007 10:28 pm
by audiowize
I was wondering how much current the poseidon driver boards need? I am planning to run the 829B's at about 85ma per tube. @390v on the plates, 210v on the screen grids.
-Paul

PostPosted: Sun Oct 07, 2007 10:36 pm
by WA4SWJ
Hey Paul,

When you get the amp done I'd love to see some pictures. I built an 832A amp and I've been enjoying it a lot (thumbnail at left). I have a set of 829's lying around too. It will be interesting to see how yours turns out.

PostPosted: Mon Oct 08, 2007 1:56 am
by erichayes
Paul, compared with what the output tubes are going to require, the front-end current needs are negligible--probably only 30mA at most per channel.

It's important to calculate the voltage drops needed for the headwater stages, but in the big scene you really don't have to worry too much about current droop or voltage drop from them if your power supply is stout.

PostPosted: Mon Oct 08, 2007 7:53 am
by Shannon Parks
In either the stock Poseidon board or Ned's version, the 12AX7/5751 is biased at 1mA and the 12AU7/12BH7 is biased at 6.5mA.

Thanks!

PostPosted: Tue Oct 09, 2007 12:29 am
by audiowize
Thanks a bunch! That is a very light current load. I need to model my power supply pretty precisely, as I'll be running ~390v on some power caps rated at 400v.

One more question, the 829B is similar to two 6L6's, and the output impedance on the Poseidon seems high. I was considering removing R12 and R13, and providing individual bias voltages. I would also adjust R14 and R15 (and the adjacent coupling caps) to work better with the paralleled 1/2's. Any ideas?
It would seem that if you have a 500k pot and 1m resistor to ground, but the bias supply has ~30k to ground, why have the 1M25 resistance in the first place? I think I must be missing something.

PostPosted: Tue Oct 09, 2007 5:56 am
by Shannon Parks
This is a bit of a mod, so I can only swag this stuff - so don't hold it as gospel. I would change R12 and R13 to 50k, R15 to 250k and C4 & C5 to .22uF.

Hmm

PostPosted: Sun Oct 14, 2007 3:19 pm
by audiowize
Would you call the grid leak value of the stock Poseidon setup to be around 100k?

Re: Hmm

PostPosted: Mon Oct 15, 2007 5:34 am
by Shannon Parks
audiowize wrote:Would you call the grid leak value of the stock Poseidon setup to be around 100k?


It's around 123k with the bias circuit resistors.

815

PostPosted: Mon Oct 15, 2007 9:48 am
by EWBrown
Another in the 832 / 829B "family" is the 815, another RF (and audio) dual power tube, but with an octal base rather than the big Septar base. The two plate caps are angled off the top of dome, giving it a vaguely "satanic" look... or perhaps Mickey Mouse with trimmed ears Yellow_Light_Colorz_PDT_02

In the 1949 ARRL Handbook, the tube section in the back indicates that this tube can also be used as a class AB2 PP audio power tube, with a fair amount of power capability , so it isn't strictly "Class C RF only" (not that the 832 and 928B can't work on audio, they do so very well, in spite of the original design intentions).

Data Sheet Here:

http://www.mif.pg.gda.pl/homepages/fran ... /8/815.pdf

Go with the "CCS" rationgs, Continuous Commercial Service, that is the more "conservative" ratings and the tube will have a much longer service life.

"ICAS" is Intermittent Commercial and Amateur Service, which is for relatively short duration transmissions (or screamin' guitar licks). :o

I'm not sure of the NOS availability of these, or if The Russians have their own version of this one.

/ed B in NH