Sevtlana SV811-10

[Donald E. Turner]

I just saw an add for the Svetlana SV811-10 in the back of a
magizine. Interesting, is Svetlana generating a new type?
The transfer curves seem typical for a triode, very linear and
much lower drive requirements in terms of voltage swing
compared with the 845 for instance. Is this the answer to a
better 845 type of tube?

The add had few specifications. Has anyone eperience with this
tube yet? Running two tubes P-P, class A or possibly AB1, what
could one expect in output.

.........Don Turner

[Kurt Strain]

The SV811-10 has the following characteristics, and is another new
type low power transmitter tube (or high power triode, whichever).
It really doesn't replace any tube, it fills a gap by providing some
decent power at less than 1 KV plate voltage.

Filament: Thoriated tungsten, 6.3V+-0.3V, 4A
Max DC plate voltage: 800V
Max signal DC plate current: 160mA
Plate Dissipation: 65W
Amplification factor: 10
Transconductance: 3.8 mA/V
Plate resistance: 2500 ohms
Cgp: 8 pF
Cgk: 7 pF

Typical Operation, Audio Power Amplifier, Class A1 Single Ended:

DC plate voltage: 800V
DC grid voltage: -50V
Peak AF grid voltage: 100V
DC plate current: 80mA
Effective load resistance: 8000 ohms
Power output: 23W

Typical Operation, Audio Power Amplifier, Class A2 Push-Pull, 2 Tubes:

DC Plate voltage: 800V
DC grid voltage: -50V
Peak AF grid-to-grid voltage: 200V
Zero-signal DC plate current (per tube): 80mA
Max signal DC plate current (per tube): 80mA
Effective load resistance (plate-to-plate): 10,000 ohms
Max signal power output: 45W

Price is about $30. The main difficulty with these tubes are high primary
impedances required of the transformer. I know of no quality output
transformer dedicated to this tube yet. Even still, Eric Barbour reports
they sound great even as 300B substitutes in some amps.

Kurt

[sports]

turn...@ccnet.com (Donald E. Turner) wrote:
>I just saw an add for the Svetlana SV811-10 in the back of a
>magizine. Interesting, is Svetlana generating a new type?

It is a modified 811-A, which has been an extremely popular rf tube for
at least 40 years. If you look at the two side by side you will see the
grid on the 811-A has very closely spaced wires, the 811-10 has much
wider spacing. Also the 811-A has a plate cap, on the 811-10 the plate
connection is brought out the bottom. They also make a 811-3 which would
be much closer to the 845.

I live in Huntsville, Alabama, where Svetlana is located, and discussed
this tube with the folks there. The quality of construction is very good,
and it is a nice looking tube with it's ceramic base and classic shape.
It looks real nice in operation too, as the thoriated tungsten filament
lights up bright.

>The add had few specifications. Has anyone eperience with this
>tube yet? Running two tubes P-P, class A or possibly AB1, what
>could one expect in output.

I have used the 811-10 in a SE circut on the bench and the sound is very
good. I plan to build an amp around this tube.

Joe

[D Weill]

>>The add had few specifications. Has anyone eperience with this

>>>could one expect in output.

>I have used the 811-10 in a SE circut on the bench and the sound
>is very
>good. I plan to build an amp around this tube.

I am very interested in this tube either SE or PP and would like
to follow any amp development projects with it. One person that I
respect a lot thinks that it is really excellent. My main
interest is PP Class A no or very low feedback.

ciao

--
dweill

[Eric Barbour]

I second that. It's really good, especially considering the low price
and unusual source (Ryazan tube factory in Russia, derived from the
811A). The -10 version is capable of distortion lower than even the best
300Bs, 2A3s or 45s. (WITHOUT any feedback)......

Please don't listen to the few snobs who are knocking this tube--
they tend to belittle anything that isn't NOS, scarce, expensive,
and sitting in their closets in quantities.
Most of them haven't even built an amp for this type yet.....

[Kurt Strain]

Eric Barbour (ebar...@netcom.com) wrote:
: I second that. It's really good, especially considering the low price

I'm not worried about tube snobbery, but I would like to know what output
transformers can be used with the SV811-3 or -10. And what recommended
operating conditions?

Kurt

[David O'Rourke]

In article D Weill <10056...@CompuServe.COM> says:
>
>I am very interested in this tube either SE or PP and would like
>to follow any amp development projects with it. One person that I
>respect a lot thinks that it is really excellent. My main
>interest is PP Class A no or very low feedback.
>

I've had some experimental experience with the 811A-10. Sound-wise you
can expect a very neutral-to-dry character, similar to a 211. The plate
resistance (Rp) is on the high, 3500-3800 ohms by estimation. For class
A operation a supply of 500-800 volts is preferred so that a reasonable
grid swing can used. A load of 5000-12000 ohms is suggested, use the
higher end of the range if you plain to do a zero feedback amplifier.

Currently I have a test bench amp running push-pull class A2 with a plate
supply of 650 volts and a grid bias of -35 volts. Cathode followers are
used to directly drive the grids of the 811A-10s, allowing positive grid
swings for maximum power (28 watts, Pdt 70 watts, Rl 5000 ohms). The amp
has a very clean sound, with a detailed top-end and dry bottom. Negative
feedback is used but sparingly.

Two cautionary notes, the filaments on these tubes do use alot of power
(4 amps at 6.3 volts) separate transformers for the filaments may be
necessary to avoid cooking your power transformer. The maximum plate
dissipation of 65 watts is rather liberal. The original 811A had two
power ratings 45 watts continueous and 65 watts intermittently (5 minutes
on 10 minutes off, if I remenber correctly).

Hope this information is of use

David O'Rourke

Triode Music