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Old 27th March 2014, 11:25 PM   #1611
bcmbob is offline bcmbob  United States
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Thanks Evan. Need any aluminum dust ??
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Old 29th March 2014, 02:25 PM   #1612
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Quote:
Originally Posted by giuliodido View Post
Thank you Jim!

Regarding JFETs matching: sorry for my poor English. I'm able to measure Idss (actually I use a regulated 10V psu), but in my stock I can't find matching 2SJ74 and 2SK170.
What I might find (I don't have them at hand right now) are 2SK170 and 2SJ74 with different Idss that are suitable for "EUVL's degeneration trick" ( http://www.diyaudio.rs/index.php?app...ttach_id=13749 ), obviously using Idss (2SJ74) = Id * (1 + Rs*Yfs). I was wondering if this approach could be used here too. In this way I will be able to use every piece of my stock.
I hope it's clearer now

The Singapore temperature thing: if I measure Idss of my JFETs with the same condition in which Spencer measures his (room temperature and 10Vdc), and then I order from him JFET with matching values, maybe I can hope to come up with actually matched pairs. I hope this is clearer too, sorry again for my English (and for my ideas :P)
Ok, I managed to find matching 2SK170 and 2SJ74 below 0.7% at 10Vdc. The first couple is at 11mA, the other one around 9mA. I don't think there will be problems in having different front end channels.
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Old 3rd April 2014, 03:48 PM   #1613
bcmbob is offline bcmbob  United States
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This build has been running without a C9 cap (ghosted blue). Instead of just asking where to place it (them), I drew out the circuit so any additional suggestion could be added. The CL-60s run very hot which I believe is normal, but not sure they are in the best location.

So how many C9s and where?
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File Type: jpg 20140403_112805.jpg (104.6 KB, 216 views)
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Old 3rd April 2014, 04:31 PM   #1614
Zen Mod is offline Zen Mod  Serbia
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NTC needs to be hot , to drop resistance

greenhorn alert !: pull off mains cord!! , then touch NTC !

that way you'll burn just finger , not brain

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Old 3rd April 2014, 05:02 PM   #1615
AndrewT is offline AndrewT  Scotland
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Fitting bypass relay contacts will get the temperatures down.
And prepare the NTCs for the next occasion they are required.
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Old 3rd April 2014, 07:32 PM   #1616
bcmbob is offline bcmbob  United States
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My fingers are just fine - thank you! As for the brain part, remember I lived through the "60s" so I'm working mostly with cinders there.

My thought was the CL-60s should cool somewhat after the resistance falls, but they stay right up there. I won't fret about it.

Andrew - your idea sounds slick, but I believe would require an additional power source - correct?

No mention of the C9 filtering. Does that imply it may be considered optional and required on noisy mains only? I see there are two in the BA-1 PS schematic:


"Capacitors C1 and C2 are line-rated types only, as they will be filtering AC line voltages."
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Old 3rd April 2014, 08:21 PM   #1617
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Quote:
Originally Posted by bcmbob View Post
Andrew - your idea sounds slick, but I believe would require an additional power source - correct?
Not if you use an AC relay. Look at the attached soft-start circuits.
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File Type: gif softstart w ac relay.gif (88.7 KB, 150 views)
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Old 3rd April 2014, 08:45 PM   #1618
Zen Mod is offline Zen Mod  Serbia
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same talk - last few posts :

Aleph J illustrated build guide
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Old 3rd April 2014, 09:03 PM   #1619
bcmbob is offline bcmbob  United States
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Some clever ideas. I'll take a shot at incorporating something similar in the upcoming complementary (& hopefully balanced) build.

Thanks
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Old 13th April 2014, 01:32 PM   #1620
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Default BA-3 3-Deep Turbo?

How about a BA-3 3-deep Turbo? With 32V rails and 1A bias per device what would we get for output power? Would the big chassis heat sinks be big enough? Would I need a fire extinguisher? What would it take to get to 50 watts?
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