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Old 13th April 2005, 10:29 PM   #1
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Default Definitely NOT a Loftin-White!!

opinions on this circuit please.values etc.I've got a working version of this,just wondering if anyone out there can come up with operating points for it.My High voltage is 404v B+.
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Old 13th April 2005, 10:43 PM   #2
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Um no, not really. I don't know how you expect to get anywhere near full swing from the driver.
Also, I don't know if you intended this to be balanced (PP), if not it'll have a lot of cross-talk at low frequencies, unless you regulate the cathode voltages.

What's the 2A3 plate resistors for?

Oh, and 12AU7 works a bit better than 6N7, though I suppose you have one or two on hand to use up.

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Old 14th April 2005, 12:24 AM   #3
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I'm not clear about what you're trying to achieve. Series amplifiers aren't generally a good idea in power stages. Is it PP?
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Old 14th April 2005, 07:34 AM   #4
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It's single ended and sounds amazing.Here's the schematic again with the values i use.
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Old 14th April 2005, 07:38 AM   #5
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The single 100ohm pot regulates the cathode voltages:1.5 on the 6n7 cathodes,150v on the 2A3 cathodes.2A3'a have 275v across them,Try it and see.
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Old 14th April 2005, 02:59 PM   #6
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Is the diagram missing a connection to the 6SN7G cathodes? There doesn't appear to be a DC path to ground for the input tube cathodes.
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Old 14th April 2005, 05:11 PM   #7
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I think his schematic program neglects junction dots. Looks to me all the current flows through the 100 ohm rheostat.

So just how much power is this capable of, and how much is the 2A3 actually capable of at its operating point? The driver (especially with 4.7k? yeesh) will murder your output.

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Old 14th April 2005, 05:46 PM   #8
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It drives my B&W DM22's pretty loud.Even better with the Lowthers.Any suggestions for improvement would be most welcome.It's not my circuit,it was given to me to try out.
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