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2nd June 2009, 08:33 PM
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#1 |
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diyAudio Member
Join Date: Nov 2004
Location: Poland
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Renovation of fifty years old tube amplifier
By accident I bought fifty years old german tube amplifier Braun CSV-13. It is 12W EL84 push-pull. All the goodies are closed into metal case, the frontpanel is made of alluminium, the cover is heavy, made of perforated steel. At the rear panel we have archaic terminals in german DIN standard. Even mains terminal is strange and it's impossible to buy suitable plug.
I replaced it first, and connected the amplifier by DIN terminals....and the sound was horrible. Slow, fat bass, no shape, no space, no details, and many distortions at higher sound levels. So I replaced all the tubes. And nothing was better. I started to search schematic, and I found it. After short inspection I decided to bypass preamp and tone control, and... bingo! It plays quite well. But after few days of playing electrolytics started to leak. No way out, there's need to solder. I made new power supply, I replaced old selenium rectifier, and I rebuilt driver section to omit electrolytics in the signal path. In the end I replaced old flimsy plastic rear panel with DIN terminals by new panel made of solid aluminium and equipped with modern Monacor speaker terminals and RCA signal terminals. Unfortunately OPT's haven't ultralinear taps, but the sound is very good anyway.
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2nd June 2009, 08:35 PM
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#2 |
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diyAudio Member
Join Date: Nov 2004
Location: Poland
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Old terminals:
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http://www.audiosurgery.beepworld.pl/dacki.htm |
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2nd June 2009, 08:39 PM
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#3 |
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diyAudio Member
Join Date: Nov 2004
Location: Poland
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Power and driver tubes:
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http://www.audiosurgery.beepworld.pl/dacki.htm |
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2nd June 2009, 08:42 PM
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#4 |
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diyAudio Member
Join Date: Nov 2004
Location: Poland
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New power supply:
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http://www.audiosurgery.beepworld.pl/dacki.htm |
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2nd June 2009, 08:44 PM
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#5 |
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diyAudio Member
Join Date: Nov 2004
Location: Poland
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New rear panel with modern terminals:
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http://www.audiosurgery.beepworld.pl/dacki.htm |
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2nd June 2009, 08:45 PM
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#6 |
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diyAudio Member
Join Date: Nov 2004
Location: Poland
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lowering feedback:
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http://www.audiosurgery.beepworld.pl/dacki.htm |
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2nd June 2009, 08:46 PM
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#7 |
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diyAudio Member
Join Date: Nov 2004
Location: Poland
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Rebuilded driver stage:
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2nd June 2009, 08:48 PM
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#8 |
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diyAudio Member
Join Date: Nov 2004
Location: Poland
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Rear view:
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2nd June 2009, 09:04 PM
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#9 |
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diyAudio Member
Join Date: Sep 2006
Location: Pleasant Hill, CA
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Congratulations!
Everything is fine, except what for did you lower feedback?
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The devil is not so terrible as his mathematical model! Wavebourn: We Create Creativity! |
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2nd June 2009, 09:12 PM
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#10 |
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diyAudio Member
Join Date: Nov 2004
Location: Poland
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It was after Dynaco ST35 schematic, something like that:
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