Seduction regulated heater supply.

Dobs · 7504

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Offline Dobs

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on: May 09, 2011, 09:43:58 AM

I need help to modify my Seduction with an external regulated heater supply.

Details here: http://www.bottlehead.com/smf/index.php/topic,1029.msg13298.html#msg13298

Thanks


Offline Paul Joppa

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Reply #1 on: May 09, 2011, 06:21:50 PM
If you Google "DC regulated tube filament supply circuit" you will get some 750,000 hits (!). The first one (tonight anyhow) is the Pete Millet web site; he is a well-respected and knowledgeable DIYer.

Paul Joppa

Offline Dobs

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Reply #2 on: May 10, 2011, 07:08:45 AM
Ok, thank you Paul this is really appreciated.


Offline Dobs

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Reply #3 on: May 14, 2011, 06:09:10 PM


Offline Grainger49

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Reply #4 on: May 15, 2011, 01:26:46 AM
That is pretty much the circuit I was thinking of.  I just don't have any experience with the three pin regulators.  You will bring the wires from the PT-1 transformer to the input terminals and then bring the wires to the two tubes' heaters to the output terminals.

There is only one question, how much voltage is used in the regulation process by the LM1084?  Probably not much so you will end up with a nice clean regulated supply.  What might happen is as you adjust the voltage up it will reach a point where it will not get any higher.

It will not produce the specified 3A because the transformer in the Seduction doesn't produce 3A.  But you have proven that it can run the 6N1P tube.

With the


Offline Dobs

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Reply #5 on: May 15, 2011, 01:49:57 PM
Actualy i was thinking to use an external power source for the regulator to get at least 1.5amp. Much like the one you suggested to me.


Offline Grainger49

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Reply #6 on: May 15, 2011, 02:22:38 PM
If you keep it away from the Seduction itself that should work.  Since wire is cheap move it three feet away.  The PT-1 was developed because the original transformer was not a quiet as PJ and Doc wanted it to be.


Offline Dobs

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Reply #7 on: May 22, 2011, 05:50:01 PM
Paul Joppa said this in a thread talking about 6n1p: One thing I have not tried with 6N1Ps is to feed AC to the heaters. The new transformer (not the original) can supply enough AC power if the DC filament rectifier is disconnected. I am afraid it will have too much hum, but as I said, I have not tried it. FWIW, the 6DJ8 does seem to need DC filaments.

Well, im interestred to try this before i build a regulated external DC supply. Can i get some information how to do it. Do I just plug the transformer 6.3v AC on tube socket pin 4 and 5?
« Last Edit: May 23, 2011, 10:10:37 AM by Dobs »


Offline Dobs

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Reply #8 on: May 27, 2011, 05:04:18 PM
Quote from: Dobs on May 22, 2011, 05:50:01 PM
Do I just plug the transformer 6.3v AC on tube socket pin 4 and 5?

Anyone?


Offline Paul Joppa

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Reply #9 on: May 27, 2011, 05:48:27 PM
Quote from: Dobs on May 27, 2011, 05:04:18 PM
Quote from: Dobs on May 22, 2011, 05:50:01 PM
Do I just plug the transformer 6.3v AC on tube socket pin 4 and 5?

Anyone?
Yes, it's that easy. Sorry for the late response! If you do it, please post what you hear!

Paul Joppa

Offline Dobs

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Reply #10 on: May 28, 2011, 05:52:58 AM
So i have to remove the 3 1uf cap present on the pin 4 and 5 on each socket?


Offline Paul Joppa

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Reply #11 on: May 28, 2011, 06:06:48 AM
No, leave those 1uF caps - they still serve the purpose of draining RF noise to ground.

Now that I think of it more, I'd ground one side of the filament winding. Any chassis ground will do, it does not have to be signal ground. Even better, use a pair of resistors, for example 100 ohms, one from each side of the 6.3v winging to ground - this makes a sort of center-tapped winding which will probably reduce the hum a bit.

If there is audible hum, that center tap can be connected to a voltage divider on the power supply, to bias the heater power to around +35 volts, which would probably make another improvement. The 35v tap on the divider would have to be bypassed to ground with a capacitor, perhaps 100uF electrolytic. But I'd recommend that you try it the easy way first and see if that's good enough.

Paul Joppa

Offline Dobs

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Reply #12 on: May 28, 2011, 06:15:26 AM
ok,

If im correct, i will install one 100ohm resistor connected to ground at each output of the 6.3v of the transformer and keep the 3 1uf cap present on each socket as a start. If too much noise i can try to bias the heater.

And i read that you suggest to change the 1m resistor to 500k for the 6n1p to keep the RIAA more linear, right?

I will post result tonight because im doing it right now.
« Last Edit: May 28, 2011, 06:26:00 AM by Dobs »


Offline Grainger49

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Reply #13 on: May 28, 2011, 08:43:07 AM
I expect if you bias the heater in the second step you get rid of the two 100 ohm resistors.  Otherwise you get a big loop.


Offline Dobs

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Reply #14 on: May 28, 2011, 09:37:43 AM
I have connected the heater directly on the AC output (no 100ohms resistor installed) and its fairly silent with the 6n1p-EV. I need to reconnect the heater to the DC supply to compare because im really not sure if its noisier than it was before.

I will make more test with other tube like 6922, 7308, 6n23p, 6n23p-EV and 6n1p.



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