hi
i am new here, so i'll be Grateful for your patience and your help as well
i am trying to build a power supply for a 12b4 preamp line level to drive my dynaco st70.
i want to use an ez 81 (have some not in use) and a choke
i need some help with the tran and ps specs, there is a local shop that i can give the specs and they can wind a tranformer
i aded a schema for the ps this is from my limited understanding and stuff I picked from the net, i marked ''?'' were i'm not sure....dont know
thank you all
i am new here, so i'll be Grateful for your patience and your help as well
i am trying to build a power supply for a 12b4 preamp line level to drive my dynaco st70.
i want to use an ez 81 (have some not in use) and a choke
i need some help with the tran and ps specs, there is a local shop that i can give the specs and they can wind a tranformer
i aded a schema for the ps this is from my limited understanding and stuff I picked from the net, i marked ''?'' were i'm not sure....dont know
thank you all
Attachments
hi
i am new here, so i'll be Grateful for your patience and your help as well
i am trying to build a power supply for a 12b4 preamp line level to drive my dynaco st70.
i want to use an ez 81 (have some not in use) and a choke
i need some help with the tran and ps specs, there is a local shop that i can give the specs and they can wind a tranformer
i aded a schema for the ps this is from my limited understanding and stuff I picked from the net, i marked ''?'' were i'm not sure....dont know
thank you all
PSUD2
I would order a power trafo with the following specifications:
Primary 1: 300 V - ct - 300 V, 50 mA ( 30 VA)
Primary 2: 6,3 V, 1.5 A for EZ81 (9.5 VA)
Primary 3: 6.3 V with ct, 2A for 12B4s (12.5 VA)
The size of the transformer would be some 60 VA.
The reason I suggested (primary 3) 6,3 V with ct for 12B4s is that there is no reason to have DC-heaters with line level preamp.
But if you want to have DC-heaters, then I suggest to use 12.6 VDC regulated with 7812.
The suitable primary would be some 15 V, 1A.
Primary 1: 300 V - ct - 300 V, 50 mA ( 30 VA)
Primary 2: 6,3 V, 1.5 A for EZ81 (9.5 VA)
Primary 3: 6.3 V with ct, 2A for 12B4s (12.5 VA)
The size of the transformer would be some 60 VA.
The reason I suggested (primary 3) 6,3 V with ct for 12B4s is that there is no reason to have DC-heaters with line level preamp.
But if you want to have DC-heaters, then I suggest to use 12.6 VDC regulated with 7812.
The suitable primary would be some 15 V, 1A.
This would be quite perfect transformer and readily available:
http://www.inmadout.com/download/pdf/TA84M18.pdf
http://www.inmadout.com/download/pdf/TA84M18.pdf
An EZ81 can easily feed a couple of 12B4. As artosalo said, no need for DC heaters - just learn how to do AC heater wiring.
The EZ81 heater winding, like all heater supplies, should have a DC reference. Two options:
1. Put all valves on one heater winding, and ground either one side or the centre-tap.
2. Connect the EZ81 heater winding to the EZ81 cathode.
The EZ81 heater winding, like all heater supplies, should have a DC reference. Two options:
1. Put all valves on one heater winding, and ground either one side or the centre-tap.
2. Connect the EZ81 heater winding to the EZ81 cathode.
Usually you would lift the center tap via a voltage divider. You connect the center tap to the junction between the two resistors in the divider.
http://www.diyaudio.com/forums/tubes-valves/219669-12b4-linestage-woes.html
http://www.diyaudio.com/forums/tubes-valves/219669-12b4-linestage-woes.html
That would be a voltage doubler, reduced current will be available. Nothing wrong with the circuit as drawn.Usually you would lift the center tap via a voltage divider. You connect the center tap to the junction between the two resistors in the divider.
http://www.diyaudio.com/forums/tubes-valves/219669-12b4-linestage-woes.html
...and ground the c tap like this ?
Yes. It will work for sure.
And connect the cathode and heater of the EZ81 together.
Usually you would lift the center tap via a voltage divider...
Maybe sometimes, but in this case when the cathode is at low potential it is not necessay.
I have used solely grounded CT of the heaters in this kind of circuits without a sign of hum problem.
thanksAny value from 330 to 470 uF is ok for the cathode capacitor.
proceeding
hi again
for the cathode capacitor i got a pair of nichicon muse 330 microF \ 25v
and a pair of the same with 470 microF \ 25v ( instead of the 360uf in the schema )
will there be an audible Difference between the pairs?
i am considering using both with a toggle switch for ''live Trial and error'' ...?
meanwhile metal work in progress...
hi again
for the cathode capacitor i got a pair of nichicon muse 330 microF \ 25v
and a pair of the same with 470 microF \ 25v ( instead of the 360uf in the schema )
will there be an audible Difference between the pairs?
i am considering using both with a toggle switch for ''live Trial and error'' ...?
meanwhile metal work in progress...
Attachments
I have seen a 6S4 and EZ81 became unusable because a short circuit between cathode and heater. Since this experience, I like to have the cathode and heater at the same potential, but not directly connected together. How?
Well, wiring a high value resistor between them, and (optionally) decoupling it to ground. Something like this. Yes, I'm still using edit with DOS!, but understandable.
Well, wiring a high value resistor between them, and (optionally) decoupling it to ground. Something like this. Yes, I'm still using edit with DOS!, but understandable.
Attachments
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