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So if we're getting 3000 hours

71.186.171.26
Posted on September 6, 2009 at 16:02:23
Frank
 out of our 12AT7s, what can we expect out of our:

1) 12AU7s?
2) 6SN7s in the circlitron stage of the preamps?
3) 6SN7s (12SX7s, 6/12SL7s) in the input/driver/casdcode stage of our amps?

Seems to depend a bit on the tubes-, posted on September 8, 2009 at 13:26:49
Ralph
Manufacturer

Posts: 1156
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since: April 1, 2002
 I've seen NOS 6SN7s go over 50,000 hours! I've also seen some new ones that could not make 2 weeks :( (most of those were Electro Harmonix). !0,000 hours seems to be an easy feat for most of them

12AU7s seem to be good for 10,000 hours pretty easily as well.

So its really the 12AT7s that have the shortest life.

Electro Harmonix, posted on September 22, 2009 at 15:15:15
marc g.
Audiophile

Posts: 2336
Location: New Orleans
Joined: October 14, 1999
Contributor
  Since: July 8, 2000
 My MA1's came with eight Electro Harmonix 6SN7's of which one was found to be bad the day I hooked them up. Bought four more new ones as spares and as of today, I'm down to 6 of them TOTAL!! Note I haven't had the amps but for two months. The amps are at Acres Verde's house at the moment and he's using shorting plugs so the 6 are enough in his application. Granted, I don't know the age/hours on the tubes that came with the amps, but there will be no more EM's coming my way. To think some folks are paying double for the gold plated pin version. Scary!

marc g. - audiophile by day, music lover by night
Are you inverting phase?, posted on September 22, 2009 at 19:26:29
Frank
 If you're removing the cascode tubes and inserting "shorting plugs" I believe the amps will now invert phase. You'll need to correct that somehow.

RE: Are you inverting phase?, posted on September 22, 2009 at 20:40:09
marc g.
Audiophile

Posts: 2336
Location: New Orleans
Joined: October 14, 1999
Contributor
  Since: July 8, 2000
 The friend that has my amps is doing this, as he's done with his Atma M60's since day one - almost ten years. I'm 99.99% sure he places them in the V2 spot. Anyways, my little issue/experience didn't involve the use of shorting plugs.

marc g. - audiophile by day, music lover by night
RE: Are you inverting phase?, posted on September 22, 2009 at 19:39:19
llwhtt
Audiophile

Posts: 26
Location: SOCAL
Joined: October 28, 2008
 The input (cathode) and output (plate) of the top tube in a cascode are in phase, so no change in phase to the CF stage. I'm assuming the jumper is for the upper tube since removing the bottom tube would take more than a jumper to operate.

Craig

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