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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 14th January 2018, 03:37 PM   #99251
EUVL is offline EUVL  Europe
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http://www.diyaudio.com/forums/attac...r-ii-sk170-jpg


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Old 14th January 2018, 03:44 PM   #99252
scott wurcer is offline scott wurcer  United States
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Originally Posted by scottjoplin View Post
The rice paper plant Tetrapanax - Wikipedia
I was originally referring to the traditional fine art paper made from mulberry in Anhui province it has gone from $0.35 to $4.00 (or more) a sheet for the best grades in the last decade or so. The actual origin of most of the substitutes are lost in translation and generically "rice".
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Old 14th January 2018, 03:59 PM   #99253
indra1 is online now indra1  Indonesia
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Originally Posted by scott wurcer View Post
I've decapped them and posted a photo here. As I said measure them there are no substitutes to use as fakes for k170 and j74 that have the same beta parameter. There especially are no P channel ones or anyone with a comparable process until Linear Systems tried.
Yes Scott, I remember reading your post with internal photo of the K170. But I found the fakes they sell nowadays are rubbish. I had several BL J74 with 2.1-2.6 mA Idss at Vp ~ -2V and other odd parameters. Other members in Pass forum also have similar experience. So we advice to purchase the K170 and J74 only from known good sources, the Linear System's from Diyaudio store, member LiubinCalvin, Spencer and Alweit.

I advice to simply avoid parts clear enough in my view to be fakes because parts purchase for testing will still pour good money that will encourage growth of the fake industry. I can only give advice to purchase for testing when the parts look genuine enough.

Last edited by indra1; 14th January 2018 at 04:04 PM.
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Old Yesterday, 06:44 AM   #99254
EUVL is offline EUVL  Europe
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John,

I was looking at the JC3 schematics yesterday, which is quite some similarities to the A23.
I wonder what was the reason behind using an inverting feedback configuration for the JC3.
And why you revert back to non-inverting in the A23 ?


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