how low can you go.....??

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Posted by vinnie2 (A) on January 1, 2017 at 08:27:21

And I don't mean the limbo mon. I couldn't get JC Morrison's remark in his article in SP magazine about running the 845 "low and hot" (low volts hot current) out of my mind. I mean what works for the 845 might work for an 813 right? I first went to 325 vdc for the plate volts with 65 mA plate current, which I have already reported I liked, but this morning I was in my shop wondering what other tweaks I might try while waiting for the other switching transformers, and I was wondering just how low and hot I could get away with.
I went ahead and changed out the cathode resistors from 360 to about 160 ohms and ended up with about 265vdc plate volts and about 93 mA for the plate current on average. Now according to everything I have read you would not expect the 813 to perform well at those operating points, but it is the best sounding set up I have managed so far. It's like somebody strapped a set of brass cajones on them and sent them to a golds gym for a couple months of hard core body building and steroids! The weight and authority are really good. They are almost palpable. My question is why? Is the current the controlling and most important factor here?
I have attached a copy of the plate curves for the 813 in triode connection mode, and the thing I am wondering is how does it effect things to have the operating point that close to 0 for the bias? I would love to hear any explanations anyone has for why it would sound better this way, because I am really curious. Unfortunately JC never said WHY we should run the 845 low and hot, but it seems to work for the 813 as well. Enjoying the heck out of it so far.

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Topic - how low can you go.....?? - vinnie2 08:27:21 01/01/17 (17)

RE: how low can you go.....?? - morricab 11:39:34 01/04/17 (1)

RE: how low can you go.....?? - vinnie2 14:53:32 01/04/17 (0)

RE: how low can you go.....?? - PakProtector 07:16:49 01/03/17 (1)

RE: how low can you go.....?? - vinnie2 08:43:21 01/03/17 (0)

what a hoot! - vinnie2 06:57:28 01/02/17 (2)

RE: what a hoot! - dave slagle 08:59:23 01/02/17 (1)

RE: what a hoot! - vinnie2 10:55:45 01/02/17 (0)

RE: how low can you go.....?? - Triode_Kingdom 10:49:10 01/01/17 (1)

RE: how low can you go.....?? - vinnie2 11:29:42 01/01/17 (0)

RE: how low can you go.....?? - Chip647 09:09:29 01/01/17 (7)

RE: how low can you go.....?? - vinnie2 10:29:35 01/01/17 (6)

RE: how low can you go.....?? - Tre' 12:36:06 01/01/17 (5)

RE: how low can you go.....?? - vinnie2 12:59:34 01/01/17 (4)

RE: how low can you go.....?? - Tre' 13:16:58 01/01/17 (3)

RE: how low can you go.....?? - vinnie2 13:48:34 01/01/17 (2)

RE: how low can you go.....?? - used-hifi 07:52:44 01/02/17 (1)

RE: how low can you go.....?? - vinnie2 08:55:44 01/02/17 (0)

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