http://www.audiocostruzioni.com/a_d/...d-modifica.htm

On Mon, 04 Apr 2005 08:03:48 +0200, Pippo wrote:

http://www.audiocostruzioni.com/a_d/...d-modifica.htm


is it stereo outputs only in valve or 5.1 outputs in valve?

For non-Italian speaking RATs:

it is a VERY interesting tweak of a SACD, where the operational amplifiers
treating the differential output from the converters and providing the
analog output are replaced with tubes. An ECC82 is used as differential
amplifier and one half of a ECC88, in cathode follower, provides the low
impedance output (per channel). Filaments are run on stabilised DC, B+
comes from a dedicated CLC filter per each channel. It is really
unbelievable how this guy managed to fit all that stuff under the hood of
the original Sony SACD.
There are only 3 tubes therefore I suppose that only plain stereo output has
tweaked, not 5.1 (which is generally not used by RATs and similar).

Ciao

Fabio


ha scritto nel messaggio
...
On Mon, 04 Apr 2005 08:03:48 +0200, Pippo wrote:

http://www.audiocostruzioni.com/a_d/...d-modifica.htm


is it stereo outputs only in valve or 5.1 outputs in valve?

Il Mon, 04 Apr 2005 08:51:16 +0000, Fabio Berutti ha scritto:

For non-Italian speaking RATs:

it is a VERY interesting tweak of a SACD, where the operational amplifiers
treating the differential output from the converters and providing the
analog output are replaced with tubes. An ECC82 is used as differential
amplifier and one half of a ECC88, in cathode follower, provides the low
impedance output (per channel). Filaments are run on stabilised DC, B+
comes from a dedicated CLC filter per each channel. It is really
unbelievable how this guy managed to fit all that stuff under the hood of
the original Sony SACD.
There are only 3 tubes therefore I suppose that only plain stereo output has
tweaked, not 5.1 (which is generally not used by RATs and similar).

Ciao

Fabio


ha scritto nel messaggio
...
On Mon, 04 Apr 2005 08:03:48 +0200, Pippo wrote:

http://www.audiocostruzioni.com/a_d/...d-modifica.htm


is it stereo outputs only in valve or 5.1 outputs in valve?

Only stereo output front.

Fabio Berutti wrote:
For non-Italian speaking RATs:

it is a VERY interesting tweak of a SACD, where the operational amplifiers
treating the differential output from the converters and providing the
analog output are replaced with tubes. An ECC82 is used as differential
amplifier and one half of a ECC88, in cathode follower, provides the low
impedance output (per channel). Filaments are run on stabilised DC, B+
comes from a dedicated CLC filter per each channel. It is really
unbelievable how this guy managed to fit all that stuff under the hood of
the original Sony SACD.

Having the tubes right up against the ribbon cables would
concern me. Usually those ribbon cables have digital signals
on them, and I had noise coupling problems with tubes right near
the digital stuff (microcontroller circuits for sensing button
presses and commands to the CD transport, etc).

Sub-mini tubes, aside from looking "cute", reduces the
space issue. But any tube will produce heat (mostly from the
heater) so one has to select a spot away from digital circuits
and select a spot near everything that won't mind the heat.
Unless you use filament signal tubes, but that limits what
you can do with cathodes.

In fact I'd be concerned, too, but there are only a few volts to be swung:
the tubes can be fed only 80-90V and work at 1/10 of their rated anode
dissipation. I have a tubed phono preamp using EF86s and ECC88s @ about 1/4W
per anode or less: the glass gets barely lukewarm, and the screening metal
can remains as cold as the rest of the unit. I suppose that using a similar
approach (low dissipation + screening cans) there shouldn't be any problem.
By the way: in this case the flat cables convey high frequency signals,
while the tubes handle LF. This probably eases the noise issue, but don't
shoot me, I'm not an electronic professional.

Ciao

Fabio


"robert casey" ha scritto nel messaggio
k.net...
Fabio Berutti wrote:
For non-Italian speaking RATs:

it is a VERY interesting tweak of a SACD, where the operational
amplifiers treating the differential output from the converters and
providing the analog output are replaced with tubes. An ECC82 is used as
differential amplifier and one half of a ECC88, in cathode follower,
provides the low impedance output (per channel). Filaments are run on
stabilised DC, B+ comes from a dedicated CLC filter per each channel. It
is really unbelievable how this guy managed to fit all that stuff under
the hood of the original Sony SACD.

Having the tubes right up against the ribbon cables would
concern me. Usually those ribbon cables have digital signals
on them, and I had noise coupling problems with tubes right near
the digital stuff (microcontroller circuits for sensing button
presses and commands to the CD transport, etc).

Sub-mini tubes, aside from looking "cute", reduces the
space issue. But any tube will produce heat (mostly from the
heater) so one has to select a spot away from digital circuits
and select a spot near everything that won't mind the heat.
Unless you use filament signal tubes, but that limits what
you can do with cathodes.

Fabio Berutti wrote:

In fact I'd be concerned, too, but there are only a few volts to be swung:
the tubes can be fed only 80-90V and work at 1/10 of their rated anode
dissipation. I have a tubed phono preamp using EF86s and ECC88s @ about 1/4W
per anode or less: the glass gets barely lukewarm, and the screening metal
can remains as cold as the rest of the unit. I suppose that using a similar
approach (low dissipation + screening cans) there shouldn't be any problem.
By the way: in this case the flat cables convey high frequency signals,
while the tubes handle LF. This probably eases the noise issue, but don't
shoot me, I'm not an electronic professional.

If the tubes normally have tube shields over them, then the ribbon
cable issue goes away.
Take a look at my web page
http://pw2.netcom.com/~wa2ise/radios/tubedac.htm
where I describe a few tube related mods to CD players.

WOW! This is a contribute! Sub-miniature tubes fit anywhere and are even
easy to find (see Russian 6N16B-V which is +/- a 6211..) If I hadn't done
something similar with an ECC88 I'd clone Your project.

Thanks

Fabio


"robert casey" ha scritto nel messaggio
nk.net...
Fabio Berutti wrote:

In fact I'd be concerned, too, but there are only a few volts to be
swung: the tubes can be fed only 80-90V and work at 1/10 of their rated
anode dissipation. I have a tubed phono preamp using EF86s and ECC88s @
about 1/4W per anode or less: the glass gets barely lukewarm, and the
screening metal can remains as cold as the rest of the unit. I suppose
that using a similar approach (low dissipation + screening cans) there
shouldn't be any problem. By the way: in this case the flat cables convey
high frequency signals, while the tubes handle LF. This probably eases
the noise issue, but don't shoot me, I'm not an electronic professional.

If the tubes normally have tube shields over them, then the ribbon
cable issue goes away.
Take a look at my web page
http://pw2.netcom.com/~wa2ise/radios/tubedac.htm
where I describe a few tube related mods to CD players.

Fabio Berutti wrote:
WOW! This is a contribute! Sub-miniature tubes fit anywhere and are even
easy to find (see Russian 6N16B-V which is +/- a 6211..) If I hadn't done
something similar with an ECC88 I'd clone Your project.


Thanks, happy you like it. A new idea (at least to me, it's
probably been done somewhere) is a differential pair-SRPP
circuit. See at AudioKarma:
http://audiokarma.org/forums/showthread.php?t=36116
http://audiokarma.org/forums/attachm...id=31022&stc=1

If you want differential outputs use a tube and circuit like V6
in place of R10. I've only run simulations, haven't built it yet...