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In Reply to: Re: Depends on how they do it..... posted by Ivan303 on January 21, 2007 at 08:27:17:
I'll give them a call tomorrow to see exactly what it is they do. I found the old post which said the transformers would run in a more linear mode making it run cooler. As well the new power output would be 24 watts not 20 as I thought earlier.Out of the methods you mention which one(s) should have a greater bearing on the quality of the sound?
Follow Ups:
DoughterIt would be best if they reduced the operating current
by increasing the bias voltage.
It sounds like that is what they do because
lower current would produce less heat
from the transformer and the 845.
More output in Class A1 at a "normal" operating point
instead of going into Class A2 (grid current)
because A2 has higher distortion.
Sounds like you don't need the extra watts with
100db Bastanis Prometheus speakers.
It almost sounds like they push the amp to 37W for marketing purposes and would be better off at the lower output. It probably would sound better at the lower output.
That sounds encouraging. I have yet to hear the amp but others say it sounds pretty good the way it is. I hope I don't lose anything by going the lower power route so that it deviates from the design goal, say for example in dynamics.
Talked to Matt at Bel Canto today and it turns out the power decrease upgrade was never as low as 24 watts and is more like around 34. So it turns out mine being a newer model already has it.He also mentioned that it is in Class A1 for the most part (not sure if that means it ever goes into a2)and that the high power is arrived at because of his particular circuit design and the use of a strong driver.
Seemed like a great person to talk to and hopefully my experience with the amp will be similar when I get it. Thanks for all the responses.
Then we can provide some real advice. Perhaps even suggest some improvements you could make.FWIW, if its a single tube SE 845 design then it must run into A2 on peaks to provide 37W. However most people gasp at A2 without thinking and interpret A2 the wrong way. I say better to bias for A1 but design to run into A2 on peaks than to have it hard clip at the Max A1 can provide. I also say that properly designed, A2 does not have to appreciably increase distortion (mine doesn't) but in any case it will be a s... load less than the distortion caused by clipping!
That aside, from what you say it seems to me that it's a simple re-bias of an amp that is biased for A1 but runs A2 on peaks (a good thing in my book) but I'd really like to know exactly what they do to reduce power.
Naz, I have yet to receive the unit but hopefully will next week.
Your insight into it going into what you feel is acceptable A2 is encouraging. Given that Matt said this is the latest version I hope to happily live with it the way it is.It seems to get fairly good praise here and elsewhere from those who have owned it so if I get the same results with it plus have the additional power too spare ( for those very loud listening moments) I hopefully will not regret the purchase.
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