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Old 18th August 2014, 07:06 AM   #981
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Alan, please use the values for the MICAs as given in the schematic!

For example:
Read Pavel Macura's (forum's nickname: PMA) observations about the SYMASYM's tendency to oscillate when he uses Toshiba's 2SC5200 / 2SA1943 and a C9 value of 22pF.
(Explendid amplifier designed by Michael Bittner, our MikeB from post #767 on).

Decreasing the value of C9 to 3.3pF remedied his problem!

The values of the MICAs are essential.
In your case (the MJ21196 has a relatively high Cob of 500pF and a slow transistion frequency of 4Mhz) I would use the given 10pF value for C9.


Best regards - Rudi Ratlos
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Old 18th August 2014, 11:24 AM   #982
alibear is offline alibear  United Kingdom
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Hello Rudi, thankyou for the advice, I will use the values you give.
Alan
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Old 26th August 2014, 05:11 PM   #983
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Gentlemen, I have sent you the NJW-SYMASYM's Builder's Manual and associated documents an hour ago and am currently listening to a pair of 10 ebay - speakers connected to it (attached image).

The NJW-SYMASYM sounds beautifully, but I am having troubles (do no hear the slighest tone), when I try to connect it to pair of 1.000 Mission 781 speakers.
My fault - as I suppose!

I will go on with this issue - Rudi_Ratlos
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File Type: jpg SIMSALABIM 011.jpg (218.5 KB, 370 views)
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Old 26th August 2014, 08:19 PM   #984
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I have just received Rudi's documents.

It is not enough to say they are excellent. They are superb.

Rudi , we are in masterful hands , thank you.
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Old 1st September 2014, 11:00 AM   #985
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Hi, Gentlemen,

I have measured and matched the NJW0281G / NJW0302G - output transistors on the last weekend.

The result is amazing:
You all will have pairs of transistors, the Hfe of which is within 1% !
Some of you (like my friend Harry, who did the proofread of the Builder's Manual) will have pairs that are even close to "cross-matched within 1%" (see image below)!

This is why I have chosen the NJW0 - transistors!
It is the best series of output-transistors that I have ever measured and matched!

Regarding my previous post: one of my Mission 781 - speakers is simply "dead".
I have swapped it between several of my amplifiers, but I it will not sing any tone!
I will therefore offer it on ebay as "defect".

Best regards - Rudi_Ratlos
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File Type: png Image3.png (5.1 KB, 288 views)

Last edited by Rudi_Ratlos; 1st September 2014 at 11:05 AM.
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Old 1st September 2014, 08:39 PM   #986
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Hi Rudi,

Thanks for the construction manual which is very helpful for people building the amp who do have an understanding of electronics.

You are doing a pretty good job for the community by organising the group buy etc.

Greets,
TrustinTech
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Old 5th September 2014, 11:14 AM   #987
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Gentlemen, I have received the NJW0-SYMASYM - PCBs a minute ago!

Click the image to open in full size.

http://abload.de/img/snv32518ybs9e.jpg

The PCBs look magncifent - like a work of art!

I will assemble your orders on the weekend and send the letters / small parcels to you ASAP (next Monday).

Best regards - Rudi_Ratlos

P.S.: Those of you who requested the PCB to be cut: it will take some further days.

Last edited by Rudi_Ratlos; 5th September 2014 at 11:19 AM.
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Old 5th September 2014, 01:28 PM   #988
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Hi Rudi,

this is really good news and the PCBs look terrific!
I have changed my mind regarding the cutting. Is it possible to get the boards uncut?

Kind regards,

Michael
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Old 5th September 2014, 01:30 PM   #989
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Of course: I will not cut your PCBs, Michael.

Rudi
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Old 5th September 2014, 01:35 PM   #990
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Thank you very much!!! :-)

I am quite curious how the amps sound - can't wait to start soldering.

Michael
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