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Old 15th January 2013, 10:21 AM   #641
Grobalt is offline Grobalt  Germany
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Thanks Rudi, i looked into the linked topic of the Lightspeed Attenuator - but your development looks that great, i will wait for it
Today i will start building the second TO3 with MJ Transistors
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Old 15th January 2013, 11:11 AM   #642
Grobalt is offline Grobalt  Germany
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I have some MKT 372 100nF 100V left. Can i use them as "Zobel" C15 ?
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Old 16th January 2013, 08:24 PM   #643
abc4230 is offline abc4230  Germany
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Hallo !

Dann könnte man Fc-100 sammelbestlellung starten.wäre mit alles drumm und dran dabei mit einem stereo set.

Quote:
Originally Posted by Rudi_Ratlos View Post
Jean,

... but be aware of the breakdown voltage of the input differential transistor pair.
For example: VGDS of 2SK170 is −40 V! So: you will be "on the edge".

And yes: the TO3 version is the best sounding version of the SYMASYM in my ears as well, but cannot compete with the FC-100 in my ears.

Best regards - Rudi
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Old 16th January 2013, 08:27 PM   #644
tinitus is offline tinitus  Europe
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post in english please


moderation
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Old 16th January 2013, 09:02 PM   #645
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Hi abc4230,

some time ago Rudi said, that he doesn`t want to do a new run on the FC-100,
because some parts of this amp are really hard to get and it is hard work to provide a complete Gb of pcbs and parts. But you can try it and ask Rudi or even diy
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Old 16th January 2013, 09:52 PM   #646
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@Grobalt: you can use the MKT372 as Zobel caps of course.

Best regards - Rudi
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Old 18th January 2013, 08:04 AM   #647
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If somebody wants to etch the TO3-SYMASYM - PCB by himself: feel free and use the attached layout.
Four tracks have to be wired manually.
The size of the PCB is 140 x 112mm.

Best regards - Rudi_Ratlos
Attached Files
File Type: pdf TO_3_Symasym_V3._BRD.pdf (91.0 KB, 319 views)
File Type: pdf TO_3_Symasym_V3_SOL.pdf (36.1 KB, 261 views)
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Old 18th January 2013, 08:11 AM   #648
atupi is offline atupi  Romania
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Very kind Rudi,
Danke !
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Old 18th January 2013, 12:25 PM   #649
jprco is offline jprco  Canada
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Opinions?
Okay so I've raised the rail voltage to 40V and to follow Rudi's advice, tried different JFET's with higher breakdown voltage than the SK170's (50V or more rather than 40V). I've tried the following matched pairs, bias tuned to 13mA per R22 and my old ears can't tell the difference! (Value of Idss - don't know if value of 9mA is as important as for FC100)
1- Matched 2SK117's (6mA)
2- Matched 2N4393 (20mA) ie 1/2 of 2N5565
3- Single 2N5565 (10mA)
All require some pin re-adjustments. So before the final soldering touches, any opinions on which to go with? Should I measure something else?
Thanks.
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Old 18th January 2013, 02:09 PM   #650
Junie is offline Junie  Philippines
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Hi,

You can use 2SK170 but you need to increased R19 and R20 from 22R to 47R,

BR,
Junie
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