Power Tubes for the Fisher 400

Vote for your tube

  • new EH 7868 quad

    Votes: 12 100.0%
  • Brimar EL506 quad

    Votes: 0 0.0%
  • Use adaptors and get JJ 7591 quad

    Votes: 0 0.0%

  • Total voters
    12

tapeworm

New Member
Hey folks my power tubes on my 400 are near the end of the road. Here are my options:

- the new EH 7868s

-BRIMAR BVA Valve England EL506 NOS NIB Quad
a guy has a huge surplus online, I'm still looking into if they are actually matched and tested.

- Get 7868/7591 adapters and put a new JJ 7591 quad in.

What do you think? The 400 is connected to a pair of Ohm Walsh 2's that are 4 ohms.
 
Of those choices I'd go for the EH. They're good tubes and rock solid holding bias really well, sound good too. Get them matched from a trusted seller like Jim McShane. The jury's still out on the Brimars and the JJs with adapters are a real crap-shoot, poor quality control.
 
2nd the EH's unequivocably!! If you should ever decide to go 7591's with it, (which incidentally won't give you many choices either) please, PLEASE, CHANGE the sockets and use Tung-Sol Re-Issue 7591's.
 
2nd the EH's unequivocably!! If you should ever decide to go 7591's with it, (which incidentally won't give you many choices either) please, PLEASE, CHANGE the sockets and use Tung-Sol Re-Issue 7591's.

Hey Larry - I remember when the Tung-Sol 7591's came out, Dave was checking them out, and it would seem that the consensus by your comment here, is that they are better than the EH's. I tried some EH's against the Sylvanias I have in my 800B, and felt the Sylvania's were clearer and had more character than the EH's. May I ask briefly, although it may have been discussed before, what do you like specifically about the Tung-Sol 7591's over the EH's? Thanks.
 
Original sized package and they sound pretty much the same as any 7591 I've heard. After 40 years of sirens in my ears (Fire and police), I can't tell difference between one tube or the other, other than they work or not. I've got both EH's and Tung-Sols in my 800-C's and Sansui 1000A. The Tung-Sols have more grunt across the board, and they tend to start out biased colder (voltage wise) to meet the same current draw. In other words My EH's run about -19v to make 75% of max dissipation and the T-S's need about -21 to -22V to produce the same.

Original sized packaging allows more rigs to use it, and the ones that can use the EH, the T-S has more room for cooling. I noticed a direct cooling effect in my Sansui 1000A when I put the T-S's in it. Transformer temps dropped by 20-25*F with nothing more than ambient convective air movement.

Although Dave hasn't done any recent testing of the T-S against originals (see this article.... http://www.tronola.com/html/7591a_tubes.html) I would be of the mind that they would do better than the EH's.

The only down side to them is their cost. about 1/2 again of the EH's.
 
Original sized package and they sound pretty much the same as any 7591 I've heard. After 40 years of sirens in my ears (Fire and police), I can't tell difference between one tube or the other, other than they work or not. I've got both EH's and Tung-Sols in my 800-C's and Sansui 1000A. The Tung-Sols have more grunt across the board, and they tend to start out biased colder (voltage wise) to meet the same current draw. In other words My EH's run about -19v to make 75% of max dissipation and the T-S's need about -21 to -22V to produce the same.

Original sized packaging allows more rigs to use it, and the ones that can use the EH, the T-S has more room for cooling. I noticed a direct cooling effect in my Sansui 1000A when I put the T-S's in it. Transformer temps dropped by 20-25*F with nothing more than ambient convective air movement.

Although Dave hasn't done any recent testing of the T-S against originals (see this article.... http://www.tronola.com/html/7591a_tubes.html) I would be of the mind that they would do better than the EH's.

The only down side to them is their cost. about 1/2 again of the EH's.


Thanks Larry. Yeah, I worry about my Sylvania's (Fisher branded) running out one day. The Tung-Sol's make sense. Thanks again.
 
If you have them throttled back to about 75% of max dissipation thru use of an I.B.A.M. board or an I.B.B.A. board (Individual Bias Adjustment Mod) &/or (Individual Balance Bias Adjustment) they'll last a lot longer.
 
I have a set of EH 7868's in a Sherwood and have no complaints. They are fatter pins tho, so be aware that once you go EH you're not going back without a socket change. The Brimar tubes are supposed to be the same situation. There is also a Soviet tube, 6P41S or something that is supposed to be compatible, again with the fatter pins. I saw a set of 10 listed on the auction site for 60 bucks from Eastern Europe. I see a lot of those Brimar tubes show up in Europe for small money too. I'm tempted since I have an amp with the big pin sockets already.

That said, if you keep your eyes open you can occasionally turn up old stock tubes for small coin. I was able to pick up a set of 4 Sylvania for what new EH tubes would cost. Only trouble is they aren't remotely close to being a matched set.

I have a sneaky suspicion that a T-S 7591 and an EH 7868 are the same working guts. Might be wrong on that, but they come from the same factory, and it would make sense to use an existing set of guts rather than completely re-tool. My guess is they took the EH 7868 guts and stuck them in an existing GT size bottle and called it a day.
 
EH 7868 and call it a day.

But if you have a long day, consider the DIY adapter route sans the JJ's.

I built some adapters to use 7868 tubes where 7591's are called for. Worked perfectly except for the added height issue. I backed off the idea of hoarding vintage 7868's because of the entry of the new Tung Sols.

7868 to 7591 AND 7591 to 7868 adapters are now available at auction. I always thought it was a pretty slick idea...
 
Hey folks,

Jim McShane sent me the EH quad. I popped them in after spraying some deoxit on the pins without too much trouble. They sound good! The bass initially was flubbing out with the old tubes and now it is strong and clear with the EHs.
 
Quick question. How much surgery is involved to solder the leading going to the face plate tuner dial lamps? The lamp on the left keeps flickering on and off. There is a green wire going into the back of the front panel, right by the treble pot. Its driving me crazy.
 
You might try cleaning the contacts on the bulbs and where they rest on the unit with DeOxit or some contact cleaner. Carefully tension the copper strip that the bulb makes contact with. I'd try that before soldering anything.
 
I fixed the bulbs! What had happened was that the metal cap contacts had corroded and the only thing keeping them on was gravity. I filled the caps up with solder and inserted the bulb while heating the cap, and now the bulbs are as good as new. The EH power tubes are still going very strong.
 
Also I just found a harman kardon fa3 tube receiver in my moms attic the day before she sold her house....Knew there was a reason to look in there! It looks pretty intact, how does the fa3 compare to the fisher 400? worth fixing?
 
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