In Reply to: Capacitor or transformer coupling? posted by Tube Tourist on January 22, 2012 at 02:57:52:
Direct Coupling: Dangerous cascading failure modes.. The upstream tubes grid bias condition is totally dependent on the downstream tubes plate voltage. That means if the downstream tube is unplugged, or its filament fails to ignite - you run the very likely risk of destroying the upstream tube. Sounds nice, no phase shifts like L or C coupling, but your opening yourself up to higher probabilities of catastrophic failure. Unfit for a commercial product design IMHO.
Capacitor Coupling: A leaking or failing cap can certainly induce failures but does not occur often. Phase shifts introduced by successive cap-coupled stages can setup the conditions for an unstable amplifier.
Tx coupling: Only failure mode is from a primary to secondary winding short. This would be caused by insulation breakdown. Very rarely happens.
An oddity if it does.
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Follow Ups
- Reliability analysis - Jim Doyle 17:41:34 01/25/12 (16)
- Never had any issues with DC - Kloss 12:52:22 01/29/12 (1)
- RE: Never had any issues with DC - Donald North 00:23:48 01/30/12 (0)
- Chicken Little !!! Heres the reality Jim ................ - drlowmu 10:02:22 01/26/12 (12)
- It's very easy to protect against those failures, use fuses /nt - bwb 06:36:46 01/27/12 (6)
- Playing chicken: who will pop first, the fuse or the tube? (nt) - Chris O 08:55:28 01/27/12 (5)
- the fuse - bwb 11:02:40 01/27/12 (4)
- "I have no proof but I am confident " That is the path to happiness, good for you! (nt) - Chris O 06:54:35 01/28/12 (3)
- Despite your sarcasm I am confident in my design. - bwb 08:14:33 01/28/12 (2)
- Slow blow fuses are not fast enough, fast blow sound like poop in the signal path. (nt) - Chris O 16:20:53 01/29/12 (1)
- then you must agree that poop sounds excellent because my system does. /nt - bwb 19:47:59 01/29/12 (0)
- RE: Chicken Little !!! Heres the reality Jim ................ - Frihed89 11:16:28 01/26/12 (4)
- I answered my own question: The new Craig Uthus 2A3 amp is cap coupled nt - Frihed89 00:27:36 01/27/12 (3)
- That a shame ....... - drlowmu 14:04:47 01/27/12 (2)
- They come on the market very rarely nt - Frihed89 15:06:21 01/27/12 (1)
- Your Fi amp is very very similar, DC, two stage, L-W. - drlowmu 20:28:13 01/27/12 (0)
- RE: Reliability analysis........direct coupled - Neff 20:46:18 01/25/12 (0)