GU-72 Snigel ended
Posted: Tue Jul 19, 2016 8:37 pmSnigel in Swedish is Snail in English, so it was a deliberate Freudian wrongwriting ... 
Well, when you want muscles, a PP with KT88 or even 6L6 will fix most problems with low sensivity speakers but if you want to go SE, what to do?
There are tubes like KT120 and 150, you may find the EL156 not to mention 6S33S (or 6C33C as some say). Did I just see a 12E- somting project in here? Yoy could go for 211, VT4C etc .... I won't continue this namesdropping.
Many of us like to play with odd tubes and one of those is the Russian GU72. A typical radio tune with a lot of testosteron to release.
GU72 is a big and heavy tube, it's a indirectly heated tetrode that in audio application likes to be fed some 700V. It is easy to drive and well ... look at some data.. One drawback - anode's on top.
I got two of those tubes from Bulgaria including sockets. Anode connectors are lying around as long copper strips that will be fastened around the top with a wire going down to the circuits. To avoid kids, cats and adults from being electrocuted I will build a cage around the tubes.
I ordered special transformers for the 700V plate voltage the 26V heater and 6.3V for the driver tubes. However I missed a winding for the bias voltage as well as a low voltage ( ) tap for the driver tubes.
Ordered a lower voltage transformer and a bias transformer just to find put that I could arrange things differently. Don't like a lot of iron.
Drivers will be 6SN7 or 6E5P or C3g, haven't decided yet.
Chassis are some slightly larger (two chassis, monoblocks) Hammond chassis 3" high. However I will mont tubes, transformers and connectors on a 1/2" thick composite material. Looks like black marble but the material has a hard and reflecting surface but can be tooled with drills, saws and router. Wanted something different for this one.
Finally, if and when I get things workibg, what will I get? Approximately 25W of single end power. Will get the membranes of my un-ortjodox two-way speakers move a little.
More to come.
Well, when you want muscles, a PP with KT88 or even 6L6 will fix most problems with low sensivity speakers but if you want to go SE, what to do?
There are tubes like KT120 and 150, you may find the EL156 not to mention 6S33S (or 6C33C as some say). Did I just see a 12E- somting project in here? Yoy could go for 211, VT4C etc .... I won't continue this namesdropping.
Many of us like to play with odd tubes and one of those is the Russian GU72. A typical radio tune with a lot of testosteron to release.
GU72 is a big and heavy tube, it's a indirectly heated tetrode that in audio application likes to be fed some 700V. It is easy to drive and well ... look at some data.. One drawback - anode's on top.
I got two of those tubes from Bulgaria including sockets. Anode connectors are lying around as long copper strips that will be fastened around the top with a wire going down to the circuits. To avoid kids, cats and adults from being electrocuted I will build a cage around the tubes.
I ordered special transformers for the 700V plate voltage the 26V heater and 6.3V for the driver tubes. However I missed a winding for the bias voltage as well as a low voltage (
) tap for the driver tubes.Ordered a lower voltage transformer and a bias transformer just to find put that I could arrange things differently. Don't like a lot of iron.
Drivers will be 6SN7 or 6E5P or C3g, haven't decided yet.
Chassis are some slightly larger (two chassis, monoblocks) Hammond chassis 3" high. However I will mont tubes, transformers and connectors on a 1/2" thick composite material. Looks like black marble but the material has a hard and reflecting surface but can be tooled with drills, saws and router. Wanted something different for this one.
Finally, if and when I get things workibg, what will I get? Approximately 25W of single end power. Will get the membranes of my un-ortjodox two-way speakers move a little.
More to come.
)