Hi:
I have a hi-fi amp that uses 12AU7 tubes. Currently I am using old
Telefunkens. These have consistently been my favorites. I prefer them
over the clear-top RCAs. I tried the Tesla 12AU7 on suggestion and was
very disappointed. I've had excellent luck with the Sovtek 12AX7LPS but
haven't heard anything about the Electro Harmonix 12AU7. Is there a
current production 12AU7 that any of you could recommend that rivals the
characteristics of the Telefunken 12AU7?
Thanks very much, --MR

Hi:
I have a hi-fi amp that uses 12AU7 tubes. Currently I am using old
Telefunkens. These have consistently been my favorites. I prefer them over
the clear-top RCAs. I tried the Tesla 12AU7 on suggestion and was very
disappointed. I've had excellent luck with the Sovtek 12AX7LPS but haven't
heard anything about the Electro Harmonix 12AU7. Is there a current
production 12AU7 that any of you could recommend that rivals the
characteristics of the Telefunken 12AU7?
Thanks very much, --MR

there is not

but there are some other vintage 12AU7 (ECC82) that do rival it

the first one to try is the Telefunken marked ECC82, rather than 12AU7

also try Mullard, Valvo, and Siemens version of ECC82 (make sure they are
OLD, pre 1964)

also RCA silver top with white writing is very good (black plates)

even better is E82CC from Telefunken, Mullard, etc.

and if cost is no object, then ECC802S from Telefunken (make sure it says
made in Western Germany or Germany and from reputable seller)

nope

Jeff S 386 Fla wrote:

nope


How about the current 6CG7 and 12BH7 tubes made in Eastern Europe? Are
they any good? I have also been impressed with the Russian 6SN7 when run
with dc heaters. Is it possible that the 6CG7 and 12BH7 could be as
good? Does anyone have any experience with them?
Thanks, --MR

"S. Rahaman" wrote:

Jeff S 386 Fla wrote:

nope


How about the current 6CG7 and 12BH7 tubes made in Eastern Europe? Are
they any good? I have also been impressed with the Russian 6SN7 when run
with dc heaters. Is it possible that the 6CG7 and 12BH7 could be as
good? Does anyone have any experience with them?
Thanks, --MR

I was not impressed with EH 6CG7, last year, when 4 of us agreed they gave a
POS sound.

The preamp amp which we tested has been changed to mu follower instead
of plate R loaded plus direct coupled CF.
thd is reduced about 6 dB regardless of what tubes are used, still all 2H as
such low levels.

But at the levels used where we did the listen test, thd was about 0.01% or
less 0.25 vrms output.
With Mu follower, its now 0.005%
Yesterday I tested the mu foll stages with 6H30 instead of the 6CG7, and got

3 dB more thd, same load, same mu-foll circuit.

Therefore the thd would be inaudible imho.
Not only that, but the SE power amps thd and the speaker thd would swamp
whatever the tiny artifacts of the preamp may be.

Yet we are able to hear considerable changes to the sound with different
preamp tube brands,
date of manufacture, and tube type number.

The owner of the preamp is now testing to see if the 6H30 russian tube is as
good as the
favoured Telefunken 6CG7 he has been using.

I am visiting on Friday night to have a listen..

His Vienna Acoustic Motzarts are a little bright sounding, and this
brightness was confirmed
when I measured the speakers. So I have provided the preamp
with a treble cut circuit where the treble response above 1 kHz is shelved
down in 3 x 2 dB steps.
Its not really tone control, which mostly just adds an RC cut off of the HF;

the shelf keeps the crucial balance between the top end and the upper
midrange.
many speakers are bright, and many CDs are bright, and we think the switched
filter will
do magic.
We also hope the subtle approach may have some effect on our assessment
of preamp tube performance.

The outcome cannot be predictable.

Patrick Turner.

The owner of the preamp is now testing to see if the 6H30 russian tube is as
good as the
favoured Telefunken 6CG7 he has been using.


Have you tried Russian 6N6 - same base?

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

Andy Evans wrote:

The owner of the preamp is now testing to see if the 6H30 russian tube is as
good as the
favoured Telefunken 6CG7 he has been using.

Have you tried Russian 6N6 - same base?

No.

We tried the 6H30 tonight against the existing Telfunken 6CG7,
and we both thought the 6H30 held its own with the Telefunken, maybe it
handles women singing opera better, we are not sure, and the preamp owner
will spend more time on his own to make the assessment.

There wasn't much difference in our ho.

Patrick Turner.



=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

I love the treble and bass of the 6N30 - I'm not sure about the mids. All round
I'm happier with the 6SN7/6J5 family (and it's a large one too!).

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

Andy Evans wrote:

I love the treble and bass of the 6N30 - I'm not sure about the mids. All round
I'm happier with the 6SN7/6J5 family (and it's a large one too!).

It probably depends how things are set up; I like the mu follower
arrangement, with 12k between the top and bottom tubes,
rather than the use of a resistance loaded gain tube, and direct coupled CF, also
with
resistance load.

Using the volum pot before the gain stage of a preamp
keeps thd to less than 0.01%, and so distortion spuriae
are not what determines the sound colours, since 0.01% of tube distortions from a
triode
are inaudible.
But with the pot between the gain tube and CF output buffer, the input signal is
raised
say 15 dB befoe being applied to the gain pot.
So the thd in the signal will be 0.1% instead of 0.01%, and this may start to
colour the sound.
I then use a CCS load on the gain tube to keep the R load seen by the gain tube to
a
high value, thus keeping thd to a minimum, and the only real load is the gain pot
itself.

There are other topologies, such as using anode followers, ie, shunt NFB,
and all can sound well I find, but I have no set ideas about what is best.

Patrick Turner.



=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

Using the volum pot before the gain stage of a preamp keeps thd to less than
0.01%,

I can't do this easily - my DAC has a SRPP stage direct coupled to the input
circuit, so the volume pot is after that. By then the amplification is already
quite considerable. In any case you need a cap on the output, so putting this
before the volume pot avoids DC in the pot. I don't want to use more than one
cap in the DAC/preamp stage. So I think I'm stuck with this topology unless you
have bright ideas?

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

Andy Evans wrote:

Using the volum pot before the gain stage of a preamp keeps thd to less than
0.01%,

I can't do this easily - my DAC has a SRPP stage direct coupled to the input
circuit, so the volume pot is after that. By then the amplification is already
quite considerable. In any case you need a cap on the output, so putting this
before the volume pot avoids DC in the pot. I don't want to use more than one
cap in the DAC/preamp stage. So I think I'm stuck with this topology unless you
have bright ideas?

I don't belong to the 'CR-coupling-spoils-the-sound' school of thought.

If you have a dedicated tube circuit for the output from a DAC, I would have
thought the
use of a CF was all one needed, since the DAC has enogh level to start with.

CF are an oten maligned way of connecting up a triode, and really I don't know
what the fuss is about, since my experience is that plain old CF have very little
effct
on the sound; its the gain stages that may offer more flavour/colour, and despite
flawless measurements.

But before I could know what other alternatives you could use, I'd need to see
the complete schematic of your set up since recomending things in isolation
of the totality of the system is usually sub-optimal.

Patrick Turner.



=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

I'm running the Electro Harmonix 12BH7A in my Dynaco Mk IV with Triode
Electronics driver board (12AU7 + 12BH7A) and am quite happy with it's
sound. I prefer it to the EI gold pin 12BH7A which is the only other I have
tried. Also I must comment on the Russian SED EL34 which I'm also running
in the same amp and in a modded Dynaco ST-70. In my opinion they sound
every bit as good as the Mullards I've tried in these amps - very balanced.
Oh yes, the 12AU7, I haven't tried any current production yet. I did note
though that my Mark IV does seem to bring out the differences in a few old
production ones I tried. Not sure if the cascode configuration circuit used
for the 12AU7 is more sensitive to this or not.

Cheers,
Jack

"S. Rahaman" wrote in message
...
Jeff S 386 Fla wrote:

nope


How about the current 6CG7 and 12BH7 tubes made in Eastern Europe? Are
they any good? I have also been impressed with the Russian 6SN7 when run
with dc heaters. Is it possible that the 6CG7 and 12BH7 could be as
good? Does anyone have any experience with them?
Thanks, --MR