V-Twin wrote:

"Patrick Turner" ha scritto nel messaggio
...
Some folks use a lot of current in the input stage of their phono
amp to allow the chosen triode to work where its Gm is the highest,
and its noise the lowest.
Hence the use of 6C45pi, 417A, and paralleled 6DJ8 tubes, etc,
and this supposedly allows the use of moving coil carts, without a step up
tranny.

Therefore is a good idea, or?

Not necessarily.
Some folks like this way of doing an amp.
Some folks don't, so I suggest you find by using a soldering iron
and your ears, and a CRO.



Once you have got past the first stage, there is no need for high current
following stages,
since the SNR isn't a problem, and a gain stage with 3 mA is ample.

Ok.

The noise of the stage is determined by the grid input noise, the shot
noise,
and the flicker noise of the tube, which is worst at LF,
and spoils many tube phono amps, so tube choice and
careful selection is very important.

I only have very basic knowledge about this, i need to learn more. Any
suggestion (books, web sites...)?

There is a fair bit around the web on phono tube preamps.

The old book like RDH4 don't have 6DJ8 circuits within it, but it does have lots
of applicable theory, which you should know about,
if you want to fiddle around with tubes.

Patrick Turner.