1620 is correct. Also the 1600 is listed as an equivalent.
Carroll
"MaxH" wrote in message ...
MaxH wrote:
Fabio Berutti wrote:
Dear RATS,
I just finished a phono preamp using a 6J7 as first amplification
stages,
followed by a passive RIAA, followed by a 6F5 as a second amp stage,
and
finally by a DC coupled 6J5 CF as "output" tube. It sounds great (who
ever
said "my project is bull.."?) but it is noisy, even with DC filaments.
OK,
it has a lot of gain, but something is definitely wrong.
I swapped different pentodes and it seems that most of that noise
depends on
tubes.
If anybody is interested in using these tubes in low noise
application,
here's what I found:
- the less noisy are the metal envelope ones (6J7M, Svetlana)
- a bit worse are the European painted-glass shouldered bulb type
(Brit
military CVsomething, supposedly Brimar)
- the more noisy so far are the the painted-glass, big bulb,
straight-sided
EF36 (US/Canada type)
I suppose I have to work a bit on the "grounding" scheme of my unit,
but the
noise I found is not only 50Hz hum.
Conclusion: 6J7 is surely a great tube in other applications (see Leak
"point one" gain stage) but not in this case. In fact, it was not
described
as a low noise pentode like the EF86.
Suggestion appreciated.
Ciao to all
Fabio
Try the RCA 1620, I believe it is the low noise version of the 6J7, and
is
intended for your application. If I got the 16xx version wrong, someone
please
correct me.
Max
Sorry one more thing... buy lots and sort through these tubes.... the guys
on the
Ampex mailing list ( do a web search and you can find out how to join)
will be
able to provide you with some better suggestions, as some of those old
tape
recorders used this tube.
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