Tube preamplifier with PCC88

[r!sc!]

... second

[Bernt]

Yeah, that would work. The heater voltage is wrong for PCC88 though, changing the value of the 240 ohm resistor to 270 ohm should solve that.

[r!sc!]

I found another circuit with ECC88. Is it good

[fdegrove]

Hi,

It would be fine: it is indeed a mu-follower meaning that Ao is close to the amplifiaction factor (mu) of the single triode.

If you look closely you'll notice a feedback loop from the output of that stage to the input grid to reduce gain, distortion (which should be very low already) and output impedance (ditto).
Moreover, there's also a voltage divider with a 1/1 ratio at the input formed by the 100K pot and the 100K series resistor in oder to cut the level of the input signal in half.

All in all much added complexity where you, strictly spoken, don't need it.

Cheers,

[rickl]

If I wanted to learn to make a preamp, I'd look at this schematic:

http://www.triodedick.com/6072_voorversterker.html

You will need to change the heater voltage but that is pretty easy.

rick

[formula 22]

Originally Posted by Shoog

I built a cascode line preamp using the PCC88. Unity gain. I based it on Joe Rasmussen's Ultra Linear Gainclone valve buffer (the full tube CCS and MosFet CV implementation). It was a matter of trial and error to get it working so I would have difficulty drawing up an accurate schematic. Still sounds excellent. The PCC88 which I used was a Miniwatt and it bettered both the Mullard ECC88 and the Sovteck 6922.
Using this tube in this configeration requires a flatline power supply as "any" noise bleeds into the signal, the power supply was more complicated than the actual buffer.

Shoog

Hi Shoog!
Please your display schematic.
Thank you

[Shoog]

Originally Posted by formula 22

Hi Shoog!
Please your display schematic.
Thank you

This is the schematic


The thread about it is;

My version of the Vacuum State FVP5

I would replace the second stage LED with a resistor (whatever sets current to 10mA) as the LED defeats the object of the bottom triode - we learn by our mistakes. Iw ould also probably replace the R4 with a 100K or even 150K.

Shoog