Valve Wizard Tube Phono Preamp

[spoontex]

I think that I got it,

I've noticed that I haven't voltage on pin 3 of V2 ( cathode ? ), so I swapped the V2 tube until I've found one with more or less the same readings on pin 3 and 8. And now I've balanced output.

osci — imgbb.com

It's possible that Brand new tubes are faulty?!!??!

Anyway, you can tell me if the other voltages are correct?

Thanks a lot!!

 

[Alan4411]

Yes I've installed the T1-T2 and T3-T4 links. My heater supply is 6.3v. I change V3 for a ECC88.

And this are the new readings of two channels.

There is still some confusion here.

Look at the circuit diagram again, see heater chain, only pins 4 and 5 are used on the board. When using pins 4 and 5 with ECC82 and ECC83s you must use a 12 volt heater supply. Using a 6 volt supply in this configuration only half heats the filaments... and leads to very odd behaviour.

See the valve layout and there are two 6.3 volt filaments in there joined in series at pin 9.

The ECC88 or 6N1P valves have their filaments joined in parallel and they are 6.3 volt valves.

Do Not mix ECC83 family and ECC88 family valves on this board.

 

[spoontex]

What??

I think that I can use:

V1 ecc83
V2 ecc83
V3 ecc88

In paralel with 6.3v supply?

 

[Merlinb]

No, not on this PCB, it is not wired that way!

I suggest you use 6N2P and ECC88 at 6.3V
Or:
ECC83 and ECC82 at 12V.

 

[spoontex]

Okey, what valve for V3 do you recommend me for this board?

For 6.3v in paralel?

 

[Merlinb]

V1 = 6N2P
V2 = 6N2P
V3 = ECC88

or:

V1 = ECC88 (R5/R6 & R25/R26 will need to be adjusted)
V2 = ECC88 (R13 & R213 will need to be adjusted)
V3 = ECC88

 

[spoontex]

Uau... it's time to change everthing.

Thanks and sorry...

 

[Alan4411]

Why not just alter the heater supply for 12.6 volts and use the ECC83, ECC83 and ECC82 configuration as you started with?

 

[spoontex]

Because my tranformer only have 6.3 sec. I need a new teansformer and are expensive. The other way I have a little toroid with 12V 1A. It's enough for heater supply?

 

[Alan4411]

Yes it will be fine.
Remember when in 12 volt configuration each ECC83 and ECC82 valve only draws 0.15A. So three valves will use just 0.45A. Ample...

 

[spoontex]

Okey, I will try, and if I use 6N2P for v1 and v2 a didn't need to change anything?

 

[Merlinb]

Correct. 6N2P is like a 12ax7 but with 6.3V heater.

 

[Alan4411]

spoontex,
Slow down. Just keep it simple please.

You can use ECC83 and ECC82s with that 12 volt transformer.

If you want to use 6.3 volts use ECC88, 6N1P and 6N2P.

Best not to mix 6 volt and 12 volt types as stated.

 

[spoontex]

I think that the simplest way to fix this, are buy two new 6N2P and don't touch any component.

Yes Alan, two 6N2P and one ECC88 runing in parallel with 6.3v

Anyway, I found two little toroid transformers into a box, 230v 12v 1amp.

I can't wire this two Transformers this way?

And of course, use two ECC83 and one ECC82 in paralel with 12v supply.

schematic — imgbb.com

I'm learning, thanks.

 

[Alan4411]

I think that the simplest way to fix this, are buy two new 6N2P and don't touch any component.
Yes Alan, two 6N2P and one ECC88 runing in parallel with 6.3v

I agree!

Anyway, I found two little toroid transformers into a box, 230v 12v 1amp.
Can I wire these two Transformers this way?
I'm learning, thanks.

You can wire them like that,
BUT there will not be enough 'power' to supply both the heaters and the HT supply. Here is why:
The heaters need 5.4 Watts (12v x 0.45A = 5.4 Watts) and the HT needs 7.5 Watts (250v x 30mA = 7.5 Watts) That is 12.9 Watts.
Your transformers are only 12 Watts (12v x 1A =12 Watts or VA.)
Also there are power losses using back to back transformers so say 80%.
You would need 2 Amp transformers (24 Watts or VA) to be safe.

Alan

 

[spoontex]

You are right!!

Anyway, I Will buy two new 6N2P tubes.

Thanks.