7868 novar

Andy Le Blanc · Post by **Andy Le Blanc** » Wed Jan 02, 2008 9:09 pm

An Ampeg Gemini G-12 went across the bench today....#050218... it needed a fuse holder and had a broken ground wire on a filter cap.... apparently it was found at a yard sale some years back and bought off an old friend.... It came to me with the original tubes..... and instead of 7591s... which I was expecting and not wanting to track down ..... 7868 had been installed and over stamped on the tube compliment sticker at the factory....GE.... and still very nice sounding cranked... I'm very impressed ..... even at the end of their service life they are very pleasant......yet another tube to yearn for... any thoughts..

philmanatee · Post by **philmanatee** » Wed Jan 02, 2008 11:46 pm

My favorite magnatone 260R runs 7868's, I love them! Phil

dartanion · Post by **dartanion** » Thu Jan 03, 2008 12:21 am

New Sensor makes new prod of both these tubes, with the 7591As actually sounding quite comparable to NOS. Haven't tried their 7868 yet.

Andy Le Blanc · Post by **Andy Le Blanc** » Thu Jan 03, 2008 1:51 am

its good to see favorable reports about a tube....... ive used several sovtek tube types .... theyer everywhere..... most amps I see are 6v6 or 6l6.....and then every now and again something differnt pops up.... very nice.... the amp was beat to peeling.... bird poo..... and great to play....

tictac · Post by **tictac** » Fri Jan 04, 2008 2:11 am

They are the same tube just different pinout

TT

Andy Le Blanc · Post by **Andy Le Blanc** » Fri Jan 04, 2008 3:45 am

yes they are......RC-28 has them together..... RC-21 only has the 7868..... what are the benifits of the novar base?....... there must have been a justifaction in the consumer market place..... where does one find a history?

CaseyJones · Post by **CaseyJones** » Fri Jan 04, 2008 6:08 pm

Andy Le Blanc wrote:yes they are......RC-28 has them together..... RC-21 only has the 7868..... what are the benifits of the novar base?....... there must have been a justifaction in the consumer market place..... where does one find a history?

There are no benefits to the novar base. Octal bases are stronger and they're self indexing. I have pin straighteners for 7 pin mini and 9 pin mini, when's the last time you've seen a pin straightener for 7868s? I've had 7868s go gassy when they cracked at the base around the pins.

IF they were a good idea to begin with we would have seen numerous late '60s amps designed to accept 7868s. There are a few amps like Ampeg, Magnatone, Alamo and Bogen that used 7868s. Perhaps it was a good idea at the wrong time, tubes were obsolete right around when 7868s were introduced. We still dig 'em, right?

I'd rather punch a chassis for readily available octals that have to track down goofy sockets. Yes I have sockets for them, yes I still think they're goofy.

skyboltone · Post by **skyboltone** » Fri Jan 04, 2008 7:03 pm

I do like goofing with different tubes. 7551s for instance were a designed for mobile AM communications use and should work fine on 12.6V filament voltage. They were used as both transmitting and modulator tubes which means they will work fine in the audio range. They have a CCS power output of 20 watts in a pushpull pair and fairly low load impedence. Best part is they are about $5 each. I don't know the brands avaiable but suspect a BUNCH of Jan types. FAA, the military, and a very brief commercial career in AM two way radio.

A little later down the road.......I got too many projects now.

Dan

Andy Le Blanc · Post by **Andy Le Blanc** » Fri Jan 04, 2008 9:10 pm

its a sign of the inner geek... some things that look like a good idea turn out to be not so good... the triode is only a hundred years old and assumptions of a purpose are easy after the fact... there'll be someone trying desperately to exactly recreate that amp eventually.... that 7551 looks usable... now I'm not a HAM guy... just what are the requirements of Continuous Commercial Service ?....

skyboltone · Post by **skyboltone** » Fri Jan 04, 2008 11:31 pm

Andy Le Blanc wrote:its a sign of the inner geek... some things that look like a good idea turn out to be not so good... the triode is only a hundred years old and assumptions of a purpose are easy after the fact... there'll be someone trying desperately to exactly recreate that amp eventually.... that 7551 looks usable... now I'm not a HAM guy... just what are the requirements of Continuous Commercial Service ?....

Basically something like an old marine or air service radio direction finder transmitter. Turn the sucker on and let the tubes operate at full power for 8 to 10 thousand hours, then change them whether working or not. Also Air to Air and Air to Ground comms with FAA have always been AM. The reason given is that FM has a threshold for tripping the detector stage. With Amplitude Modulation you'll always hear something just above the noise level but still usable in a pinch. This tube was designed for mobile service. Nominal 12 volt mobile service. Kinda leaves out airline or big military air or even probably tanks and stuff. Smaller military vehicles like trucks, jeeps, heavy equipment, mobile communication centers and the aformentioned navaids.

ICAS is the non-commercial designation. Notice that the 7551 doesn't give you a higher plate voltage for ICAS. Don't you believe it. They'll take more.

Andy Le Blanc · Post by **Andy Le Blanc** » Sat Jan 05, 2008 3:47 am

Jeezzzz..... you learn something every day.... I got to met the fellow that designed and built the transmitters for the local public radio (fm).... the ratings for those are unbelieveable..... he comes across as a real braggart.... but the amps are real and the stations that use them sound good.... very technical field but in the end still running tube amps....

Tube Amp Archive

7868 novar

7868 novar

Re: 7868 novar

Re: 7868 novar

quite comparable

Re: 7868 novar

They are the same tube just different

Re: They are the same tube just different

Re: 7868 novar

I'd rather punch a chassis

Re: I'd rather punch a chassis

full power for 8 to 10 thousand hours