Tube Amps / Music Electronics
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|4/25/1998 9:55 AM|
I've come across several NOS 807 tubes that look pretty cool. Very curvaceous! They seem to be similar to 6L6's/KT66's in nature except for the funky plate pin on the top. I was wondering if anyone has tried them in a guitar amp? Like maybe a Marshall/Bluebreaker sort of thing?
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|4/27/1998 6:44 AM|
You're right on about the similarities. The 807 has a 5-pin base and a plate cap, but is otherwise electrically the same as a 6L6. The 807 was developed to be used in many applications, including low power radio transmitting. Positioning the plate electrode's connection at the top allowed much higher anode voltages than would be possible (or safe) using closely spaced base pins for all electrodes. These tubes were used routinely in the US version of the famous Williamson amplifier (english) and were developed to be run in triode (screen tied to plate thru 100 ohm resistor) or conventional pentode. The williamson amp ran in triode, BTW.
Put an 807 tube next to your ear, and tap the side of it. Hear everything rattling inside like loose springs? That's why it's not a good idea to use these in combo amps where vibration will interfere with operation of the tubes. They would never hold up in a bluesbreaker combo.
You could build a separate amp (for use out of the soundfield), like for studio use, with 807 outputs. Take any 6L6 circuit, get some obsolete 5-pin sockets and plate cap connectors, and wire it up.
|4/27/1998 12:43 PM|
Thanks for your comments Doc. I only build combo's in the form of Champ/Princeton style amps. Anything larger are seperate heads with speaker cabinets. Do you think a seperate head sitting on top of a speaker cabinet, maybe with shock mounting feet or chassis of some sort, would still be a problem or would the geometry/construction of these tubes dictate a completely seperate rack mount only type amp? Those sockets and caps sure are expensive!
|4/27/1998 2:02 PM|
A separate head with shock mounting feet may be ok. Where did you see prices for sockets & plate caps? Did you check AES, Angela, or Triode Electronics?
|4/27/1998 4:02 PM|
AES has them cheap. Thanks alot!
|4/27/1998 3:03 PM|
I Have a schematic of a GELOSO amp
"head", originally designed for use in small cinemas. The schem is from 1963 !
Two 807 output tubes. The B+ is 690 Volt
Screen gird, about 300 Volts
Output Power: 50 Watt.
Output Impedance: 1,25 - 500 ohms, selected by wireing different screw terminals on the back of the amp. A very special output xfmr.
Input: 2 microphone and one phono.
In the mid 60's it was often used by small pop-groups as PA or organ amplifier. I my self, had it's little brother, 35 watt, wich I used for giutar.
Here i Denmark GELOSO was knows for great stability, good sound, low price and a not so fancy look.
|4/27/1998 4:04 PM|
Would you happen to have a copy of the schematics for those two amps? The 50 watter and the 35 watter. Thanks in advance.
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