PAS phono. (curcio)

GeirW · 15th December 2004, 12:31 PM

Gday.

Just some quick questions regarding this stage.

1. Do anyone of you happen to know, the commponent values?
(they have been kind enough to distribute the moded. schem.
at dynaco doctor, but none values. it can`t be that simple
that they use old pas values. (turned operation point)

2. Is my humble attemt on the schematic right.
Opinions on the usage of 6922 !? ,
most phono stages/preamp`s i seen, uses ECC83/12AX7.
From what i can read about the 6922, it`s a very good performer,
but is it right in here.

SY · 15th December 2004, 12:56 PM

6922-oids are an excellent choice for a phono input. Though their gain is lower than a 12AX7, they have (when run properly) much lower noise and suffer much less from Miller effects. The surrounding component values will be quite a bit different between these tubes (12AX7 usually runs at ca. 1ma, 6922 at ca. 8-10ma, and the plate resistances and transconductances are an order of magnitude different).

In my own phono preamp, I use a high transconductance FET at the bottom of a cascode with a 6922-like tube on top. Works a charm, and I get the best of both worlds- the low noise and low gate current of the FET with the swing, linearity, and overload resistance of the tube.

alejo · 15th December 2004, 01:51 PM

Hello, SY I´n search for Phono preamp, plese atach your schematic to see your desing.

thanks
alejo

jan.didden · 15th December 2004, 05:13 PM

Quote:

Originally posted by GeirW
Gday.

Just some quick questions regarding this stage.

1. Do anyone of you happen to know, the commponent values?
(they have been kind enough to distribute the moded. schem.
at dynaco doctor, but none values. it can`t be that simple
that they use old pas values. (turned operation point)

2. Is my humble attemt on the schematic right.
Opinions on the usage of 6922 !? ,
most phono stages/preamp`s i seen, uses ECC83/12AX7.
From what i can read about the 6922, it`s a very good performer,
but is it right in here.

The Curcio design (copyrighted) is available as a reprint from www.audioXpress.com

Jan Didden

SY · 15th December 2004, 06:24 PM

I haven't posted my full preamp design yet because it uses some tubes and FETs which are no longer commonly available (I built it nearly 20 years ago). But Curcio's design is likely to be quite fine.

GeirW · 15th December 2004, 08:28 PM

Gday.

ouch.

Quote:

The Curcio design (copyrighted)

didn`t notice, that isn`t fair play.

15th December 2004, 12:56 PM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	6922-oids are an excellent choice for a phono input. Though their gain is lower than a 12AX7, they have (when run properly) much lower noise and suffer much less from Miller effects. The surrounding component values will be quite a bit different between these tubes (12AX7 usually runs at ca. 1ma, 6922 at ca. 8-10ma, and the plate resistances and transconductances are an order of magnitude different). In my own phono preamp, I use a high transconductance FET at the bottom of a cascode with a 6922-like tube on top. Works a charm, and I get the best of both worlds- the low noise and low gate current of the FET with the swing, linearity, and overload resistance of the tube. __________________ If there's a sucker born every minute, where do the rest of them come from?

15th December 2004, 01:51 PM	#3
alejo diyAudio Member Join Date: Jun 2004 Location: bs.as.	SY schematic Hello, SY I´n search for Phono preamp, plese atach your schematic to see your desing. thanks alejo

15th December 2004, 06:24 PM	#5
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	I haven't posted my full preamp design yet because it uses some tubes and FETs which are no longer commonly available (I built it nearly 20 years ago). But Curcio's design is likely to be quite fine. __________________ If there's a sucker born every minute, where do the rest of them come from?

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