Hi all!
I'm moving my first steps into the world of tubes.
I need a preaplifier with phono stage and i'm thinking to build it.
Maybe it's not the project for a beginner, but i already have an amplifier.
I was thinking about some issues:
1) It's worth to design it all DC coupled, skipping the coupling caps? There
is a lot debate about their influence on sound...
2) Since DC coupling drives to growing plate voltage in the following
stages, i was thinking to put in the first stage a tube like E86CC, wich
works at 12 V on plate. I did some calculations and i ended up with an
estimated S/N in the first stage of 72 dB: it seems not a good value, or?
Maybe i can use both sections of the E86CC in parallel to raise the S/N by 3
dB, but what is better: 72 dB or 75 dB using both section, with the supposed
problems with differences between the sections?
I would like to hear your opinions.


V-Twin

V-Twin wrote:

Hi all!
I'm moving my first steps into the world of tubes.
I need a preaplifier with phono stage and i'm thinking to build it.
Maybe it's not the project for a beginner, but i already have an amplifier.
I was thinking about some issues:
1) It's worth to design it all DC coupled, skipping the coupling caps? There
is a lot debate about their influence on sound...

Direct coupling is difficult with tubes, and to do it
means the methods used may be more complex, and sonically
worse than caps and resistors.
Try building a few things to find outabout.


2) Since DC coupling drives to growing plate voltage in the following
stages, i was thinking to put in the first stage a tube like E86CC, wich
works at 12 V on plate. I did some calculations and i ended up with an
estimated S/N in the first stage of 72 dB: it seems not a good value, or?
Maybe i can use both sections of the E86CC in parallel to raise the S/N by 3
dB, but what is better: 72 dB or 75 dB using both section, with the supposed
problems with differences between the sections?
I would like to hear your opinions.

Try it out, and listen, and measure......

Patrick Turner.



V-Twin

See below...

"V-Twin" wrote in message
...
Hi all!
I'm moving my first steps into the world of tubes.
I need a preaplifier with phono stage and i'm thinking to build it.
Maybe it's not the project for a beginner, but i already have an
amplifier.
I was thinking about some issues:
1) It's worth to design it all DC coupled, skipping the coupling
caps? There
is a lot debate about their influence on sound...

It's all bunkum in pre-amps. Design for best performance with RC
coupling. At the impedances you will be using there will be no
problem getting a good response down to below 20 Hz with modest sized
capacitors, as well as a good RIAA curve (bass boost.) You'll need a
rumble filter anyway.

2) Since DC coupling drives to growing plate voltage in the
following
stages, i was thinking to put in the first stage a tube like E86CC,
wich
works at 12 V on plate. I did some calculations and i ended up with
an
estimated S/N in the first stage of 72 dB: it seems not a good
value, or?
Maybe i can use both sections of the E86CC in parallel to raise the
S/N by 3
dB, but what is better: 72 dB or 75 dB using both section, with the
supposed
problems with differences between the sections?
I would like to hear your opinions.

Not worth the design compromises.

V-Twin

Cheers,

Roger
------
Roger Jones, P.Eng.
Thornhill, Ontario,
Canada