i think I read somewhere that maybe removing the jumpers from the spacexpander, I could use the Fisher as a pre...here is a pic of the module...

Kinda makes sense, remove the output tubes, remove the jumpers, run the expander out to the amp of your choice (preferably with volume control).

I'd check to see if your getting AC voltage out (NO DC please) before hooking it up to an amp you like. Should see around 2 volt peaks with a line source if I remember correctly.

cool...I want to be able to use my soon to arrive Allen Ogran amp....now, what is the procedure to measure what you mentioned...I do have a rat Shaq voltmeter..:-)

ps: I was just busting your chops regarding the Tannoy's...I understand your point as I managed to sell all my McIntosh tubage..

I just scanned this out of my 500C manual. Dunno if any help.

Carl

What does that expander do anyway?

space-expander... how Einsteinian!

It was a spring-reverb a la the Pioneer and Sansui reverbs of the 1970's.

The only trick is whether the signal at the jumpers goes through the preamp (i.e., tone controls and volume control/balance) or it's just line-level (unattenuated) like a tape-monitor loop.

As to DC at the jumpers: there are enough coupling caps in a tube amp that I don't think it's likely that there'll be any DC there (unless some of those caps are bad)! You can check for DC by pulling the jumpers, set your DMM to DC Volts, and measure between the center and the shield of the jack(s). The easiest way to do it is probably to connect an open-ended interconnect to the jack you want to test, and put your leads on the pin and shield at the other end of the I/C. Looking for 0 VDC (or just an itty bit). If your intended power amp isn't completely direct coupled/complementary/capacitorless, you really don't have to worry too much about DC there anyway.

The 400's preamp might want to see a high-impedance load, I dunno.

Finally, if you take the output tubes out, the load on the P/S will drop quite a bit, and voltages everywhere may go UP quite a bit. I'd probably leave the tubes in, put dummy loads (noninductive 8-ohm power resistors) across the 8-ohm outputs and/or turn the speakers off (I think the 400's has loads built in for when the headphones are in use?). I always try to be very nice to the output sections of tube and ss amps, whether I am using them or not!

Finally, if you take the output tubes out, the load on the P/S will drop quite a bit, and voltages everywhere may go UP quite a bit. I'd probably leave the tubes in, put dummy loads (noninductive 8-ohm power resistors) across the 8-ohm outputs and/or turn the speakers off (I think the 400's has loads built in for when the headphones are in use?). I always try to be very nice to the output sections of tube and ss amps, whether I am using them or not!

I stand corrected, makes sense to me. be sure to use the dummy load!

i better buy what 8 ohms in resistors?

I stand corrected...
well, not really trying to correct, just amplify (pun intended) on the suggestion. But I, too, certainly like the idea of protecting a quad of 7868's (not to mention a fine pair of OPT's), too... maybe I'd buy a matched quad of the EH 7868's and throw in there for 'storage' :-)

Here is this tidbit I scanned. :)

Carl

If anyone had a schematic of a Fisher 400 they could post up here, then we could tell immediately whether the spacexpander outputs are appropriate (ie, after the volume control). It'd just be a matter of what they're connected between, on the schematic...

Regards,
Gordon.