Mpp

[Salas]

Originally Posted by Joachim Gerhard

I bought my tube collection around 20 years ago when they where really cheap after consulting with a friend of mine that designed the Intonation preamp. Well, not all of them. The Philips E88CC SQ already costed 130,- DM a pair back then.

In the phono there will be surprises maybe. Some famous types in line level or amps can have inadequate hum to cathode from the heaters, out of spec en, many things. Different from sample to sample. Takes luck. Down to what theoretical Rn the 6C45Π can take the noise spec of the head amp? 1nVrtHz?

edit: I found some analytical spec. Seems like Rn=300R (en=2.2nVrtHz) if run at 10mA so not to create other noises. 2nVrtHz for 20mA, same 50V Va. I hope it will not need a grid stopper due to high gm, that would add up. Do ferrite beads work on tube base pins well?

http://www.triodeel.com/6h30.html

[Salas]

Doh! That was a 6H30 page. 6C45 would be 1nVrtHz.

[loek]

Originally Posted by Audiofanatic

Joachim,

First of all, it was a pleasure meeting you at the X-fi in Utrecht.
Tjuus,


Audiofanatic

José

Me too Joachim.
Grusse, Loek

[Joachim Gerhard]

I do not intend to use the 6C45pi directly connected to the MC cartridge. I will use a Lundahl transformer before it. I plan to run the 6C45pi on 15mA with Led bias.
The first version will have a simple Anode resistor but i may try Anode chokes or constant current sources later.
Hi Loek, nice to meet you too.
The 6C45pi can stand more current so a Fet-Tube casode could be build like in the Athur Loesch circuit. I could then use 4 x 2SK369 on 40mA total. That whold be very low noise too. The Gm of that stage would be a massive 160mS.

[Salas]

That's cheating. Jfet head amp phono in disguise.

[Joachim Gerhard]

I know, lets see what works best.

[Salas]

I saw it in a dream already...

[Joachim Gerhard]

If they have some swarm intelligence they will assemble themselves.

[Salas]

[Joachim Gerhard]

I build a Stereo Anti RIAA. Again i use a slightly modified Lipshitz Legacy network. This time i have optimised the final voltage divider for 300 Ohm loading. I use now 300 Ohm most of the time as input impedance of my MC stages. This Anti RIAA can also be put behind a CD or better SACD player with sufficiently low output impedance and then the player can drive the phonostage. I do not say that this is a fidelity test of any kind but a sraight wire bypass could be quite telling at least about the tonal balance.