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Old 17th June 2015, 06:01 PM   #131
fmmech_24 is offline fmmech_24  Austria
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Old 19th July 2015, 07:48 PM   #132
Kay Pirinha is offline Kay Pirinha  Germany
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Well, looks fine!

Would you please post the schematics of your amp? Thx in advance!

Best regards!
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Old 29th September 2015, 06:38 PM   #133
fmmech_24 is offline fmmech_24  Austria
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Schematics:
MosFet_TO-3_final.pdf

latest TO-3 based PCB:
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Old 15th October 2015, 05:13 PM   #134
fmmech_24 is offline fmmech_24  Austria
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Old 25th January 2016, 08:38 AM   #135
pserci is offline pserci  Italy
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Hi, how and where can be purchased these PCB? Regards, Paolo
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Old 23rd November 2016, 05:01 PM   #136
Kay Pirinha is offline Kay Pirinha  Germany
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Hi,

please pardon me for reviving this dusty rusty old thread!

As mentioned here, my stereo Crescendo presents some hum, even with no preamp connected to it. Not that much, not disturbing at all, it is audible only if you poke your head into the woofers. But it could do better, couldn't it?

I've shown some images of my build here. You see that I've provided a central ground right between the large electrolytics. Literally everything returns to this, both taps of the power transformers' secondaries, speaker ground (separate for both channels), input gnd (dito), signal gnd (dito), just everything. R10 is present on both PCBs, so no earth loop should be expected. The case is connected to protective earth of the power cord and also loosely connected (via two diodes in antiparrallel and a 0.1 F cap) to the gnd star. Alle jacks are well insulated form the case.

Today I saw HumNSmoke's solution here. Could I really expect to get rid of the hum if I'd provide two separate gnd stars, one for each channel? And why?

Best regards!
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Old 23rd November 2016, 07:25 PM   #137
HumNSmoke is offline HumNSmoke  France
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Hi man
This is how I did. The remaining hum was the mechanical one from the transformers. My concern when I did this was I lowen the peak power from the power supply by a factor 2.
And later I also balanced the inputs, for no worry any more with long wires from the preamp.
Is your hum here from the life begin of the amp, or later ? If later, maybe some recap could help. I'd also take care to provide very good isolation between transformers and case (and between tranfos themselves), because I believe the rubber washers (both top and bottom) are far too thin after all those years: have a look at my HugeMac isolation recipe.
But in fact, I would have never got rid of the hum without the help of guys here.

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Old 2nd September 2017, 10:54 PM   #138
nigelwright7557 is online now nigelwright7557  United Kingdom
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Quote:
Originally Posted by fmmech_24 View Post
Schematics:
MosFet_TO-3_final.pdf

latest TO-3 based PCB:
Why have you left copper on top layer where mosfets go ?
This means you will need to insulate heat sink from pcb.

I usually make a new part with no copper on top layer.
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Old 22nd September 2017, 09:37 AM   #139
overall feedback is offline overall feedback  Croatia
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Update for Elektor Crescendo Power Amplifier 1982
I would like to share some playworks. Close to original, but with additional places for plastic power transistor packages. Also places for compensation caps, as spice shows unconditional stability with few more pickofarads. All there in attachment, if some mistakes please write it here.
This amp is real legend, it deserves more buildings
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File Type: zip Crescendo.zip (691.1 KB, 51 views)
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Old 22nd September 2017, 10:03 AM   #140
Kay Pirinha is offline Kay Pirinha  Germany
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Thanks, very appreciated!

Which plastic FETs do you recommend to replace these 2SK135/2SJ50 originals?

Best regards!
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