Damon
10-13-2006, 01:41 AM
Fell into my lap this week ...
http://www.artifactaudio.com/jennings_organ_amp.JPG
It's an amp from a Jennings Organ, circa 1958. Gorgeous Monstrous Partridge Transformers... it ran 2 EL34s (at 550 to 570 volts on the plates!), 1 6SN7, 1 GZ34, and 1 6X5 (separate rectifier for the screens+preamp). Boy, did they ever like to run their tubes hard. And that big oilcap is 8uF at 1000V!
It's not totally original, the electros are all American, dated early 70's... can't fire it up as is, it was made to be controlled remotely... the power, signal in, and output are all on the same octal plug. Besides, the input sensitivity is too low to just plug a guitar right in.
I could lose the 6X5 and set up a more traditional screen supply... that would free up an octal socket, and I happen to have a bunch of Mullard EF37A's on hand, which are like an ancestor of the EF86... replace all the electrolytics (track down 600V parts), install a volume control, 1/4" I&O jacks, power switch...
Or (way more work) I could take it apart and use the trannies on a new chassis, lay it out like I want, frees me up to use any preamp tubes and a more tradidtional guitar circuit... maybe even switch to a Hammond PT with more sane voltages...
Here's the schem for anyone who's interested: http://www.artifactaudio.com/jennings_schematic.JPG
What's with the neon lamp in the PS? It's inside on the tag board, so it's not an indicator...
http://www.artifactaudio.com/jennings_organ_amp.JPG
It's an amp from a Jennings Organ, circa 1958. Gorgeous Monstrous Partridge Transformers... it ran 2 EL34s (at 550 to 570 volts on the plates!), 1 6SN7, 1 GZ34, and 1 6X5 (separate rectifier for the screens+preamp). Boy, did they ever like to run their tubes hard. And that big oilcap is 8uF at 1000V!
It's not totally original, the electros are all American, dated early 70's... can't fire it up as is, it was made to be controlled remotely... the power, signal in, and output are all on the same octal plug. Besides, the input sensitivity is too low to just plug a guitar right in.
I could lose the 6X5 and set up a more traditional screen supply... that would free up an octal socket, and I happen to have a bunch of Mullard EF37A's on hand, which are like an ancestor of the EF86... replace all the electrolytics (track down 600V parts), install a volume control, 1/4" I&O jacks, power switch...
Or (way more work) I could take it apart and use the trannies on a new chassis, lay it out like I want, frees me up to use any preamp tubes and a more tradidtional guitar circuit... maybe even switch to a Hammond PT with more sane voltages...
Here's the schem for anyone who's interested: http://www.artifactaudio.com/jennings_schematic.JPG
What's with the neon lamp in the PS? It's inside on the tag board, so it's not an indicator...