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Question about tube replacement (Read 3573 times)

pineman Verified Member Online Posts: 19 Pacific Northwest	Question about tube replacement 04/04/21 at 22:54:55 I have been enjoying the ZMA for over six years now and recently replaced all 4 output tubes when one of them began to fail. Is it generally advised to replace the input and regulator tubes at the same time, or do those typically last much longer? Thanks!
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HockessinKid

Seasoned Member

Online

Posts: 1365
Delaware

Re: Question about tube replacement
Reply #1 - 04/04/21 at 23:06:15

You don't need to replace the input tubes if your output (power) tubes are getting noisey. The stock input tubes usually last a long time.

I suggest you get a new matched quad of output tubes. There are several very decent sounding new production tubes - TungSol, Gold Lion (New Sensor), etc. I really like the sound of TungSol 7027a substitute tubes for the KT66 tubes. A matched quartet can be purchased online for ~$120. Easy swap out, I bias these at ~58 mV.

HK

Nottingham Interspace TT > MWI PH9.0XT or MWI modded Cambridge CNXV2 > CSP3-25th pre > STL STR-1002 Super Rectifier > PI Audio UberBUSS > ZMA-25th amp > Two Ecoflow R2 Max's > Caintuck Lii15 speakers > Rythmik F12G sub > SRA & ZenWave cables

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Archie Seasoned Member Offline Posts: 2735	Re: Question about tube replacement Reply #2 - 04/04/21 at 23:32:45 I concur about the Tung Sol 7027As. I bias at 64 to 68mA though. My last quad seemed short lived but I only got 8 to 9 months out of the quad before that. Maybe my high bias is the issue? How long are yours lasting? I pull mine when one or more starts to drift.
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HockessinKid Seasoned Member Online Posts: 1365 Delaware	Re: Question about tube replacement Reply #3 - 04/04/21 at 23:59:48 Archie, I've been getting about 18 months on a quad, guessing 1600-1800 hours. I calculated bias at 58mV using the plate voltage. I think your biasing a bit high which will lead to shorter power tube life. Happy Easter. HK
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Archie Seasoned Member Offline Posts: 2735	Re: Question about tube replacement Reply #4 - 04/05/21 at 00:12:11 I'm in the "Class A" range which is a 90%+ so I think you are right. I think I'll back it off and see (hear) is there is much difference. I didn't realize there might be a 2X effect on tube life.
Back to top	ZLC Technics 1200G TT w/ Ortofon Jubilee MC cart ZMC1 ZP3 (25th A Mods) ZR2 (25th A Mods) CSP3 (25th A mods) ZMA (25th A mods) Homemade Big Betsy Speakers (F15s) Silver Cabling DIY Isolation platforms under amps & TT. IP Logged Share: Likes:

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