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.
Yes. It will work for sure.
And connect the cathode and heater of the EZ81 together.
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.
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
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.