6V6 line preamp

[merlin el mago]

Could I add in series to the two 0-250V 0.8A parallel the one secondary 0-48V 0.1A to increase the voltage to 298V 08.A? I have on hand cap 820uF 550V.

 

[Salas]

No. You can only add in series different voltage secondaries. In that case the voltage will be good but the weaker ones are the current limit. I.e. 80mA * 0.63 bridge DC mA derate to 50mA. You could add in series the 48V to already paralleled 250V though. But don't play with transformer without dim bulb tester and disconnected from PSU.

 

[merlin el mago]

No Salas, I want to paral·lel the existing one 0-250V 0.16A and add in series the 0-48V 0.1A one to have 298V máx. 0.1A if 0.1A * 0.63 = 63mA is enough?

 

[merlin el mago]

But there is something not ok with the PSU isn't normal to have only 310V from an input cap with a bridge, 250V x 1.41 = 352V....

 

[merlin el mago]

I'm now listening no any kind of hum.

 

[Salas]

But there is something not ok with the PSU isn't normal to have only 310V from an input cap with a bridge, 250V x 1.41 = 352V....

Its usually less, about x 1.3 with losses from not too stiff a Tx and diodes

 

[merlin el mago]

1x1.25 ufff

 

[merlin el mago]

Better I will order a custom new one, enough 250V 0.2A or may I ask more volts & mA seen what's happening with Lundahl?

 

[Salas]

I have only few times used Lundahl step-ups for MC carts, and OPT for medium power push pull tube amps. I don't know about their power transformers.

 

[Salas]

I'm now listening no any kind of hum.

How you achieved that?

 

[Salas]

1x1.25 ufff

With CCSed reg loading can happen on so so regulation % Tx especially when pushed near max DC mA spec

 

[Salas]

No Salas, I want to paral·lel the existing one 0-250V 0.16A and add in series the 0-48V 0.1A one to have 298V máx. 0.1A if 0.1A * 0.63 = 63mA is enough?

The 0.1A secondary now is the weaker link so 63mA DC after full bridge derate as in their datasheet note.

 

[merlin el mago]

How you achieved that?

Making cables short and tight & grounding the caps at the filaments reg.

 

[merlin el mago]

Will be enough 275V & 0.3A?

 

[Salas]

Should be enough

 

[merlin el mago]

I think so...

 

[merlin el mago]

Just ordered the tx!

What value to use a OPT or anode choke?

 

[Salas]

I don't know a proven value, I haven't made it with such.

 

[Salas]

What Raw DC and B+ you ended up with your now power transformer? What type of new one you ordered? How does it play now that you can listen better without any hum? Picture with final hum-less wiring arrangement would be nice to see.

 

[Bas Horneman]

Hi Salas,

Any 6v6 preamps out there with an output tranformer that you know of?