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Old 10th July 2013, 05:13 PM   #601
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Did anyone found some newer equivallent transistor versions for the original ones (with max 2pF Cob, low noise and hight gain)? I found that in my country are selled allot of fake 2sa970/2sc2240 so i dont want to purcase this version.
On ebay are some kits for sale with NJW0302G/NJW0281G, are they suitable for this amp?
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Old 10th July 2013, 05:28 PM   #602
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The Class A Amplifier Site is always a good starting point for these projects....The Class-A Amplifier Site - Jean Hiraga Index
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Old 10th July 2013, 05:57 PM   #603
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Quote:
Originally Posted by KatieandDad View Post
The Class A Amplifier Site is always a good starting point for these projects....The Class-A Amplifier Site - Jean Hiraga Index
I have that site on mind but i was asking about suitable newer substitutes for the now obsolete transistors.
Thanks.
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Old 10th July 2013, 06:14 PM   #604
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Or this site...Jean Hiraga's Super Class-A Amplifier

All the transistors 2SA872A, 2SC1775A, 2SA634, 2SC1096, 2SC5200 and 2SA1943 are avaiable from LittleDiode - Electronic Components Supplier

Last edited by KatieandDad; 10th July 2013 at 06:19 PM.
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Old 10th July 2013, 06:24 PM   #605
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Quote:
Originally Posted by KatieandDad View Post
Or this site...Jean Hiraga's Super Class-A Amplifier

All the transistors 2SA872A, 2SC1775A, 2SA634, 2SC1096, 2SC5200 and 2SA1943 are avaiable from LittleDiode - Electronic Components Supplier

Thank you very much.
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Old 10th July 2013, 06:56 PM   #606
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i would not trust them to be genuine. they also sell 2sj74 and they still order them in smal quantities. 99.8% of this transistors are fake. so where do they get them? no other company (other then fet audio that ordered a hell of a load a long time ago) have this in stock. at least not the real deal.
and even worse. the same is for 2sj109 no way they order this genuine j-fets this days. NO WAY there just is not possible for a company to order this fets any more.

Last edited by AudioSan; 10th July 2013 at 07:00 PM.
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Old 15th July 2013, 09:02 AM   #607
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A question:
  • would 2SA992/2SC1845 be good for the input. It does have a high Hfe of almost 500 but Ft might be a bit high with 100 MHz.
I used a pair of BC550/BC449 which is good (must be good because it is even used in 10 MHz scope inputs).
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Old 22nd July 2013, 08:44 PM   #608
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Just stuffed aboard with the Fairchild KSA992 and the KSC1845 for the input, used a set of MJE15028 and 29 for the drivers and a set of 2SA1342/2SJ5199 as outputs, works like a champ. Bias resistors at 27K ohm results in 900mA bias current, will have to adjust that later for more current. R3 and 4 I have at 220 Ohms.
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Old 22nd July 2013, 10:40 PM   #609
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Hello,
Where did you find tha ksa/ksc pair for sale? Are they shipping to Europe?
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Old 22nd July 2013, 10:48 PM   #610
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What is the criteria of selecting the imput trannies for this amp? Do we have to use the devices with maximum gain or with matched close gain? Just asking becuase of the diffrent values of the 200 respectively 300 ohms. I assume that they are there with different values because of this aspect. What do you say?
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