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Seduction regulated heater supply.
- Thread starter Dobs
- Start date
Paul Joppa
Moderator
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.
Grainger49
New member
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
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
Grainger49
New member
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.
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?
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?
Dobs said:Do I just plug the transformer 6.3v AC on tube socket pin 4 and 5?
Anyone?
Paul Joppa
Moderator
Yes, it's that easy. Sorry for the late response! If you do it, please post what you hear!Dobs said:Dobs said:Do I just plug the transformer 6.3v AC on tube socket pin 4 and 5?
Anyone?
Paul Joppa
Moderator
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.
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.
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.
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.
Grainger49
New member
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.
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.
I will make more test with other tube like 6922, 7308, 6n23p, 6n23p-EV and 6n1p.
Paul Joppa
Moderator
We do make such a transformer; it's called the PT-5 and is used in the Eros. It can supply 1.3 amps of regulated DC current for heaters, and 55mA of plate current at 275 volts, using a voltage doubler as is done in the Eros. The PT-5 runs are very low magnetic induction in order to maintain a low magnetic leakage field, so that it does not need the molyperm shield tape of the PT-1.
The PT-5 is much larger than the PT-1, and requires a large rectangular cutout on the chassis plate - I think it would be impractical to use it on the same chassis plate, which is why I have not suggested it before.
We did look at making a version of the Seduction with this power supply. It's quite attractive, but it would be the same cost as the Eros, which we feel is a bit better sounding circuit.
The PT-5 is much larger than the PT-1, and requires a large rectangular cutout on the chassis plate - I think it would be impractical to use it on the same chassis plate, which is why I have not suggested it before.
We did look at making a version of the Seduction with this power supply. It's quite attractive, but it would be the same cost as the Eros, which we feel is a bit better sounding circuit.
Paul Joppa
Moderator
You are correct, in both cases.Dobs said: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?
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