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Old 12th August 2002, 05:07 PM   #1
Ralph is offline Ralph  Netherlands
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Default SE with the KR300BXL from KR Enterprice

Hi all,

I'm looking for a SE 300B design that delivers just a little more power that a normal 300B. I guess 15 Watt will do the job but like to stick to SE.

I found this design, using a KR300BXL from KR Enterprice that is said to deliver > 15 Watt operating at 514V @ 135mA. What do you think about this design?

amp http://www.triodedick.com/big_c/big_c%20copy.gif
PSU http://www.triodedick.com/big_c/big_c_v%20copy.gif

Thanks, Ralph
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Old 12th August 2002, 07:03 PM   #2
dice45 is offline dice45  Germany
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Ralph,
the KR300BXL is the best 300B avaiable IMO. It rather sonds like 45 than like a 300B while having much power.

The amp schematics look reasonable to me. Just one objection: this is a single ended amp which is no constant load for its PS.
A CLCLC filter for B+ certainly has a good static filter effect but on load changes it shows a step response taking eternally for coming to rest.

Suggestion: download PSUD II and simulate your power supply. You will see that a simple LC or CLC filter responds much friendler on load changes.
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Bernhard
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Old 13th August 2002, 05:44 PM   #3
Ralph is offline Ralph  Netherlands
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Hi Bernhard,

Thanks for your comments. I'm aware of the fact that the PSU has some problems, I've simulated it in PSU designer. I was in the first place very interessted in the comments about the amplifier schematic itself. Seems a bit complicated, and I've found another schematic today http://www.audiodesignguide.com/my/300blxs_amp_sch2.gif

What do you think?

Ralph
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Old 13th August 2002, 09:07 PM   #4
dice45 is offline dice45  Germany
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Ralph,
this second one would rather be my choice. Although methinks with a 6SL7 a SS constant current source will work better than a plate choke. The 6SL7 has a plate resistance too high; the choke's inductivity might be too low to give you a proper lower bandwidth limit.

I would replace the Jensen coupling caps by SiemensEpcos MKV 25839. By any means! And for the 6SL7, i would try to get my hands on a vintage redbase RCA 5691 or vintage metal base Sylvania 6SL7.
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Bernhard
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Old 15th August 2002, 01:03 PM   #5
jim is offline jim  Belgium
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check this site in The Netherlands for a complete transformerset for the amp at Triodedick's site (kr300xls included)
http://www.ae-europe.nl/trafosets.htm
jim
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