TO-3 SYMASYM - Page 65

Grobalt · 15th January 2013, 10:21 AM

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

Grobalt · 15th January 2013, 11:11 AM

I have some MKT 372 100nF 100V left. Can i use them as "Zobel" C15 ?

abc4230 · 16th January 2013, 08:24 PM

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

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

tinitus · 16th January 2013, 08:27 PM

post in english please

moderation

julius20 · 16th January 2013, 09:02 PM

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

Rudi_Ratlos · 16th January 2013, 09:52 PM

@Grobalt: you can use the MKT372 as Zobel caps of course.

Best regards - Rudi

Rudi_Ratlos · 18th January 2013, 08:04 AM

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

atupi · 18th January 2013, 08:11 AM

Very kind Rudi,
Danke !

jprco · 18th January 2013, 12:25 PM

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.

Junie · 18th January 2013, 02:09 PM

Hi,

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

BR,
Junie

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15th January 2013, 10:21 AM	#641
Grobalt diyAudio Member Join Date: Mar 2012 Location: Renningen	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

15th January 2013, 11:11 AM	#642
Grobalt diyAudio Member Join Date: Mar 2012 Location: Renningen	I have some MKT 372 100nF 100V left. Can i use them as "Zobel" C15 ?

16th January 2013, 08:27 PM	#644
tinitus diyAudio Moderator Join Date: Nov 2005	*post in english please* moderation

16th January 2013, 09:02 PM	#645
julius20 diyAudio Member Join Date: Feb 2004 Location: Geilenkirchen, Germany	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

16th January 2013, 09:52 PM	#646
Rudi_Ratlos diyAudio Member Join Date: Jun 2009 Location: Hamburg / Germany	@Grobalt: you can use the MKT372 as Zobel caps of course. Best regards - Rudi

18th January 2013, 08:11 AM	#648
atupi diyAudio Member Join Date: Oct 2010 Location: Bucharest	Very kind Rudi, Danke !

18th January 2013, 12:25 PM	#649
jprco diyAudio Member Join Date: Jan 2009	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.

18th January 2013, 02:09 PM	#650
Junie diyAudio Member Join Date: Sep 2010 Location: Dubai, UAE	Hi, You can use 2SK170 but you need to increased R19 and R20 from 22R to 47R, BR, Junie