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Old 25th November 2004, 07:50 PM   #1
macce78 is offline macce78  Finland
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Question amp-schematic questions...

Hi!

I'm finally starting my first valve amp project, and as I Googled around for a nice and simple (read: cheap) SE-design I ran in to this:http://www.lundahl.se/claus_b_se.html. What do you guys think of this one, and is it a suitable project for a noob?

Is it OK to run the amp with a 230V // 280-0-280 0,190A / 6,3V 4A / 5V 2A transformer if I connect the 280 V windings in parallel? That's the closest match I can find here in Finland, and I don't have a credit card wich makes ordering from abroad a bit tricky... (it's actually quite hard to find the right parts to any design, and I'm pretty amazed that only the transformer is missing from this one.)

cheers,

Marcus
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Old 26th November 2004, 12:32 AM   #2
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Hi,

That xformer should be O.K.
You could even arrive at the same voltage values if you could source a 10H 200mA choke with a DCR lower than 200 R.

It could be made as a first DIY amp I suppose but be aware of the high voltages involved.

Just one note: I wish Mr. Byrith would have picked a 6SL7 or 12AT7A (for instance) iso that dreaded 12AX7........
And another one: variable feedback often means that unless you have the necessary mearuring tools you'll never be sure when you have the correct setting.
That's enough to drive alot of people bananas...

Cheers,
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Old 28th November 2004, 07:22 PM   #3
macce78 is offline macce78  Finland
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Do you think a 7 H 250 mA 60 ohm choke would do (Lundahl LL1673 / 7H) if I increase the value of the filter capasitors? That's the only choke I found that can handle 250 mA with current.

I calculated that using a 280 V xformer and this 7 H 60 ohm choke will give me about 5 Volts more compared to the original setup. This won't do any harm, will it?
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Old 28th November 2004, 11:30 PM   #4
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Hi,

Quote:
Do you think a 7 H 250 mA 60 ohm choke would do (Lundahl LL1673 / 7H) if I increase the value of the filter capasitors?
Sure.

Quote:
I calculated that using a 280 V xformer and this 7 H 60 ohm choke will give me about 5 Volts more compared to the original setup. This won't do any harm, will it?
That's absolutely neglible. You may even find it to deviate to either end of the scale but better to have a little too much voltage to start with than not enough.

Cheers,
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Old 29th November 2004, 06:56 AM   #5
macce78 is offline macce78  Finland
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OK, thanks Frank
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