I don't recall SB-220s being sold new with 3-400Zs; I thought they were all
shipped with 3-500Zs.
The 3-400Z was really "zero bias," so using a bit of bias as normally used with
3-500Zs, at similar Ep, can result in lower ZSAC.
Also I believe the 3-400Z has not been manufactured since before 1970, so I'd
guess the tubes have to be 38 years old, or older...
(Of course, 3-500Zs could be that old, too, if they're "originals.")
Why not test the amp itself and see how it works?
WB2WIK/6
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]On
Behalf Of WLI
Sent: Sunday, April 26, 2009 1:40 PM
To: amps@contesting.com
Subject: [Amps] SB 220 with 3 400 tubes
I am looking a purchasing an SB220. I have two to choose from. One has a
pair of 3 400 tubes and the other has 3-500's. The one with 3 400's looks
cleaner but I am not sure if the tubes are equal. Can some one tell me if
the amp with the 3 400's is as good or if there are any problems with this
substitution.
Thanks
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