GU-50 (LS50) - One other tube that can be add to the "Usable Tubes" list ?

[kagliostro]

I was looking around and find some news about some military specs russian tubes, one was the GU-50 (the "copy" of the Telefunken LS50 tube)

I've find news about the use in DIY HiFI amps

Is this a tube that can be add to the list of usable final tubes for guitar amps with good results ??

http://www.mif.pg.gda.pl/homepages/frank/sheets/018/g/GU50.pdf

http://www.jogis-roehrenbude.de/Russian/GU50.htm

http://wavebourn.com/pyramid-8/GU-50.jpg


The GU-at the moment can be find not very expensive and also special sockets can be find

Kagliostro

[kagliostro]

There is something I don't understand

the reason because the GU-50 isn't used in commercial & DIY guitar amps

. was build also for audio use
. has a good 40W plate dissipation level
. is extremely mechanically strong as was build for aircraft apparatus, so perfect for amplifiers on the move
. use a socket that is perfect to avoid moving problems
. is disposable cheap and in large quantities

But only some HiFi guys go the way to use this strong tube, yes, 6550 has near the same dissipation for plate, but is extremely more expensive

can you say a particular reason for this misuse ?

Kagliostro

[spacelabstudio]

There is something I don't understand

the reason because the GU-50 isn't used in commercial & DIY guitar amps

. was build also for audio use
. has a good 40W plate dissipation level
. is extremely mechanically strong as was build for aircraft apparatus, so perfect for amplifiers on the move
. use a socket that is perfect to avoid moving problems
. is disposable cheap and in large quantities

But only some HiFi guys go the way to use this strong tube, yes, 6550 has near the same dissipation for plate, but is extremely more expensive

can you say a particular reason for this misuse ?

Kagliostro

Most practice is cultural.  Sometimes nobody uses it just because nobody uses it.  Or there might be a good reason not to use it.  But I wouldn't know what it is.  If you tried it, I bet folks here would be interested in the result.

Chris

[FYL]

can you say a particular reason for this misuse ?

I can see a few : non standard and very expensive base, not end-user friendly, two sources only (Russia and China, mostly from NOS), spotty availability...

But it's a great tube : the soviets have copied the LS50, one of Telefunken's best power tubes, which had originally been designed in the late '30s for German military applications !

[spacelabstudio]

Just doing some Googling on 'gu50' tube has turned up info mostly on diy hifi forums.  Seems that when they're good, they're very linear compared to more traditional guitar output valves.  Not everyone likes very linear for guitar.  Also noticed that the screen needs a significantly lower voltage than the plate, making the PSU design a little more complicated.

None of those are reasons not to build a guitar amp with a couple of 'em if you're just curious.

[FYL]

Also noticed that the screen needs a significantly lower voltage than the plate, making the PSU design a little more complicated.

Pretty easy to deal with, just have a look at some amps using broadly similar transmitter tubes. Ampeg anyone?

[kagliostro]

Pretty easy to deal with, just have a look at some amps using broadly similar transmitter tubes.

something like this ?

http://www.el34world.com/charts/Schematics/files/ampeg/Ampeg_SVT_Model_6146B.pdf

about sockets there are 3 different versions available (may be more)

one is similar to a standard socket (see the image at right)

Kagliostro

[FYL]

something like this ?

Yep. See how Ampeg gets 600 and 300V from the same xformer tap.

about sockets there are 3 different versions available (may be more)

Standard GU-50 socket:

one is similar to a standard socket (see the image at right)

The bottom section is superficially similar but you need the bracket around the tube and the lid if you don't want to break the glass at the pins! Oh, and the Soviet version has no keypin but uses a ridged glass envelope, so if you don't use the bracket as a guide you can insert it the wrong way.

[DummyLoad]

found this a while back... looked at the GU50s - they seemed OK but the sockets are kind of hokey. east german RFT made the best ones from what i gather.  

another variant is the EL152.

http://tubedata.milbert.com/sheets/118/e/EL152.pdf

page 9 of datasheets is of most interest and presents class AB1 conditions for AF amp with 600Va/300Vg2 that makes 90W. also presented is an 18W class A1 single tube and a class A1 P-P that makes 28W with two tubes running @ 250Va.

my german is weak but the curves tell a story in any language - it does seem to be a very linear pentode.

seems like a fun group hack might be the 28W P-P A1 or the A1 single tube w/ 18W.

--DL

[kagliostro]

Hi FYL

Yep. See how Ampeg gets 600 and 300V from the same xformer tap

with a sequence of dropping resistors ?

The bottom section is superficially similar but you need the bracket around the tube and the lid if you don't want to break the glass at the pins! Oh, and the Soviet version has no keypin but uses a ridged glass envelope, so if you don't use the bracket as a guide you can insert it the wrong way.

That is right, I've seen, in one web site, the user of those socket mark it to know the right way to insert the tubes - that isn't a foolproof solution

Hi DummyLoad

Many thanks for the schematic you posted I'll consider it as a birthday gift (today is mine)

(have you also a link to the Power Supply ?)

another variant is the EL152

Yes also that is a very nice tube but isn't so easy to get

my german is weak

mine absent  

very interesting page nine of the EL 152 datasheet

It will be nice to know the OT primary impedances for the different voltage of use indicated on that page

Thanks friends

Franco

[DummyLoad]

It will be nice to know the OT primary impedances for the different voltage of use indicated on that page

OT impedance  is given - 6th row, labeled AuBenwiderstand

happy birthday. buon compleanno.

--DL

[kagliostro]

Hi DummyLoad

vielen Dank für die Informationen

AuBenwiderstand ................. 1) Von Anode zu Anode

and many thanks for the birthday greetings

Grazie

Franco

[FYL]

Yep. See how Ampeg gets 600 and 300V from the same xformer tap

with a sequence of dropping resistors ?

Big bad 15 W WWs.

Now what about using a CT with a bridge, big Marshall style? You can get B+ and 1/2 B+ w/ any dropping resistors.

[kagliostro]

Now what about using a CT with a bridge, big Marshall style? You can get B+ and 1/2 B+ w/ any dropping resistors.

that's one way, other may be an enough big, lower (1/2) voltage, PT without CT, using a voltage doubler

Franco

[FYL]

Marshall uses a full-wave variant of the Delon voltage doubler.

[kagliostro]

Sorry FYL I misunderstand you

were you thinking of a particular model ?

Franco

[FYL]

It was used on 100-watt amps such as the JCM800.

Check the Q&D schemo below. B+ is 1.414 x sec voltage (minus losses). With a 350V PT you get around 490V B+ and 245V for screens.
As it's a bridge doubler max current isn't halved.

[kagliostro]

Thanks FYL

Franco

[kagliostro]

I got my first NOS GU-50

Strangely, I found it by a neighbor at about twenty meters from where I live, the world is small .............

At the moment I find also were to buy on the cheap those only ceramic sockets (that has the key problem)

About the kind of schematic to GU-50ize, thinking that is a tube with very linear response, which can be a good candidate schematic, looking also to the data on page 9 of the el152 (very similar to GU-50) datasheet ?

For a big PP amp I think a good schematic candidate may be the 200W Hiwatt, what do you think about ?

which may be other schematisc candidate to GU-50izing process, also for an SE amp ?

Kagliostro

[kagliostro]

At least two GU-50 guitar amps were build

http://www.vegalab.ru/forum/showthread.php/19412-Усилитель-для-бас-гитары-на-ГУ50

гитарный ламповый усилитель на лампах ГУ-50.avi

May be the guitarist isn't Jimi Hendrix however ........................

it can be done (Young Frankenstein - 1974)

Kagliostro