• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Solid State DC filament supply

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diyAudio Senior Member
Joined 2002
GREAT MINDS...

Hi,

*This is a strange phenomenon I've observed. I think it has someting to do with the instantaneous junction temperature affecting the reverse breakdown on the following half cycle.

Yes it does.

Instead of using a different xformer has anyone considered using a voltage doubler?

Not the best PSU, I know, but once filtered and regulated it should be more than adequate for a heater supply,provided the xformer can deliver the current demands?

Peter,

Once again our findings seem to concur...people are posting circuits every other day but none seem to realise the impact of properly designed PSUs.Sigh...:(


Cheers,;)
 
John, Bruce,

So, just to make sure I got this right - how does this look? Power transformer is a 12.6V@4A.
 

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Well I'd put the 1000uf on the input of the regulator and the 22uf on the output. The bridge is drawn wrong of course, but other than that it looks OK. The 7805s in a 220 case are good for 1.5 amps on a suitable heat sink. If you need more current than that split up the load and use more regulator chips with 22ufs on each output.

Or are you testing us Joel?

Later
Bruce:geezer:
 
diyAudio Senior Member
Joined 2002
CAREFUL.

Hi,

Well I'd put the 1000uf on the input of the regulator and the 22uf on the output.

The first cap should have a 25V or higher rating to be on the safe side,the one after the reg. can be 16V and can have a higher value too.

The 7805 does not present high bandwith though but should be O.K. for the heater supply.

Cheers,;)
 
A can of worms

When you open a can of worms, you need a bigger can to put them back ...

What I have seen done for tubed RIAA amp heaters which should be the most sensitive of all. is to use a 317 as a current source. Just about any 317 datasheet will show how to connect it as such. Could be something to think about, particularly if using one regulator per tube.

Step 1: Estimate the tube heater current desired.
Step 2: Drop 1.2V across a series resistor (a function of the regulator.
Step 3: Add capacitance at output
Step 4: Add further RC stages if you have enough voltage to play with, and feel paranoid.

The beauty of such a circuit is that you can regulate both positive phase and negative return (negative through RC or LC network).

Petter
 
diyAudio Senior Member
Joined 2002
WORMS.

Hi,

What I have seen done for tubed RIAA amp heaters which should be the most sensitive of all. is to use a 317 as a current source.

Current regulating the heaters is better then just voltage regulation.


Could be something to think about, particularly if using one regulator per tube.

A series tube at 12VDC?Such as?ECC86 or 88?Then you need to heat that too?

Haven't seen that done anywhere.:xeye:

Cheers,;)
 
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