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Old 3rd October 2012, 09:12 PM   #521
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Default Can I still purchase PCB's?

If it's still possible to obtain PCB's, this is what I would like:

4 AMP PCB
2 SKPR-PCB
2 PSU-PCB

Please let me know. Take care.
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Old 3rd October 2012, 10:00 PM   #522
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Sorry Michael,

I do not have a single PCB left.

Best regards - Rudi_Ratlos
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Old 4th October 2012, 03:26 PM   #523
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Default Put me down for the NEXT round of PCB's

Put me first in the next round of PCB's. Thanks for letting me know. Take care.
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Old 4th October 2012, 04:51 PM   #524
brianco is offline brianco  Ireland
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@Rudi

Is there any possibility for a group buy for matched devices as in your other version?

Many thanks

B
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Old 4th October 2012, 05:29 PM   #525
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Brian,

I didn't offer matched devices (transistors) for the SYMASYM in the past.

What I offered was "hard-to-get" parts, like my favourite DC-blocking capacitor on the input, Vishay's MKT1822 / 10F, or MPC74 0R22 / 5W resistors.

If you talk about matching the SYMASYM transistors: it is not as essential as you think.
I have once compared my own, highly-matched TO3-SYMASYM to a totally unmatched SYMASYM and could hardly hear any difference.

If you want to match transistors: go and use BJTs for the input differntial pair (f.e. MPSA18, if you do not use a Pre-AMP, or 2N5551, if you use a Pre-AMP)
and match them with your DMM.

Talking about the output-transistors: I recommend you to use NJW0281 / NJW0302.
The OnSemi NJW0 have a very small COB, and - this may answer your question: they have a very small Hfe deviation, when you buy them (from MOUSER for example).
I bought a bulk of 75 pcs. of each several months ago and matched them for some German DIY- friends.
The max. deviation within this bulk has been < 5%!

Best regards - Rudi_Ratlos

P.S. Have a look at my current SYMASYM-build (Post #515). I am using BJTs for the differential input pair.
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Old 4th October 2012, 06:47 PM   #526
brianco is offline brianco  Ireland
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Thanks Rudi...

Certainly makes life simpler!
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Old 6th October 2012, 06:52 PM   #527
evette is offline evette  Canada
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Yes Mr. Rudi,, I,ve made a number of changes to the circuit..First change r20=22ohm +r19=22ohms change to 47 ohms. this change is good to 45vdc.above this voltage you should put a power diode in series with the resistor. Across the drivers a 100pf cap from base to collector gets rid of any nasty rf garbage. Sit back listen,,check your bias I set mine at about 60ma and adjust to find the sweet spot..ENJOY Regards Evette
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Old 6th October 2012, 06:57 PM   #528
evette is offline evette  Canada
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Sorry rudi My input trannies are mps8099 Regards Evette
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Old 6th October 2012, 07:39 PM   #529
cjkpkg is offline cjkpkg  United States
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Do the mje15030/31 need to be fully insulated from the heat sink/chassis or is it OK for the tab to be connected to earth ground via the hold down screw?

Need to determine if I need shoulder washers for these or not.
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Old 6th October 2012, 08:36 PM   #530
evette is offline evette  Canada
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Yes they do. Evette
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