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    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Tube power supply

Hello all,
Gathering parts for my first scratch build. All Emission Labs DHT. EML 20B V4 IT coupled to EML 2A3 V4. Not sure what to do with the PS. I don't have the normal decreasing B+ from the output tube to the driver tube, it's just the opposite. Driver tube @ 420vdc, output tube @ 250 vdc. I've never seen an example of that scenario, and I don't have enough on the ball like you guys to know what issues may arise. I'll be using a star ground and taking great care to make sure the signal grounds don't get corrupted by the power tube grounds. So can I do a normal PS design w/ decreasing B+ after each section, picking off the driver tubes B+ first and then the power tubes last. I realize that the B+ for the driver will have to be super clean as I won't have any help from the power tube filtering. Or would this scenario be better served by two complete power supplies ?

as always, thanks in advance for any help

Cheers, Crazy Bill
 

rayma

Member
2011-04-29 8:37 pm
can I do a normal PS design w/ decreasing B+ after each section, picking off the driver tubes B+ first
and then the power tubes last. I realize that the B+ for the driver will have to be super clean as I won't have
any help from the power tube filtering. Or would this scenario be better served by two complete power supplies ?

Yes, you'll need two separate supplies, one each for the output tube and driver.
Then you can better filter or regulate the driver. Think of all the power that would
be wasted trying to drop the 170VDC.
 
Last edited:

Ketje

Member
2012-12-19 7:24 pm
Flanders
Not sure what to do with the PS. I don't have the normal decreasing B+ from the output tube to the driver tube, it's just the opposite. Driver tube @ 420vdc, output tube @ 250 vdc. I've never seen an example of that scenario
How about like this, gives two voltages and an iron not to expensive.
Mona
 

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Along the same lines, as the scheme Ketje provided, is an idea put forward by Pete Millett. A single CT winding can be configured to yield both a "tall" rail and a short rail. Bridge rectify the end to end voltage with either a 100% SS setup or a hybrid (SS diodes to ground) setup. The O/P of the bridge is the "tall" rail's "raw" DC. Connect the anode of an additional diode to the CT. Take the "short" rail's "raw" DC from the 5th diode's cathode.

Both rails are full wave rectified. The "short" rail is, in fact, a FWCT setup. In theory, the 5th diode can be omitted. Practice is definitely "another kettle of fish". For instance, "short" rail rise could be delayed by using a 5AR4, with its plates tied together, as the 5th diode.