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Old 26th April 2010, 07:02 AM   #1
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Default schematic request for transformer with 4k primary and UL taps

I bought several NOS output transformers a few years ago and would like to build some amps. My electronics experience is limited, but I have built several 300b amps and a 6SN7 based preamps.

I need some help locating a reliable (preferably simple), nice sounding schematic/design. Here are the transformer specs:

4000 primary w/ UL taps
70 Watt max
320 ma (assumed since this is a 12lb+ (5.6kg) transformer.

Any help would be greatly appreciated. Thx!
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Old 26th April 2010, 04:42 PM   #2
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Assuming they are PP transformers.......KT88 UL PP

Triode Dick's Bill/Mono Bill/Mono Bill 2

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"Mullard 5-20 KT88 PP blocks!
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Old 26th April 2010, 05:57 PM   #3
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30W 300B PP amp?
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Old 26th April 2010, 05:59 PM   #4
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Thanks boywonder. They are indeed PP transformers. I was considering a Mullard type circuit using KT88's or el34. Would a triode connected push-pull parallel circuit using el34's similar to the Marantz 9 be a good match for this transformer?
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Old 26th April 2010, 06:05 PM   #5
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If your OPTs are PP (i.e. 4K P-2-P) then how about: Le Renard? This design outputs 37W, is a good match for 4K P-2-P, and sounds great, and doesn't require UL to do so.

6BQ6s are like more powerful 6V6s, however, these don't require such high screen voltages, and so aren't really suitable for UL. Forch, they don't require the extra help, and moderate amounts of gNFB are all that's required.
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Old 26th April 2010, 06:06 PM   #6
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Quote:
Originally Posted by kevinkr View Post
30W 300B PP amp?
Hello Kevin. I love 300B's, but they're out of my budget range. Do you have any other suggestions? I'm pretty new to DIY, but familiar with safety and layout. Not so much design at this point.
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Old 26th April 2010, 06:11 PM   #7
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Originally Posted by Miles Prower View Post
If your OPTs are PP (i.e. 4K P-2-P) then how about: Le Renard? This design outputs 37W, is a good match for 4K P-2-P, and sounds great, and doesn't require UL to do so.
Thanks Miles. I've never heard of this design. I'll definitely have to research it. Looks like i'll have to research this. I'd prefer designs that others have repeated with success (documentation).
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Old 26th April 2010, 06:12 PM   #8
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by junklocator View Post
Hello Kevin. I love 300B's, but they're out of my budget range. Do you have any other suggestions? I'm pretty new to DIY, but familiar with safety and layout. Not so much design at this point.
I would say KT88/6550 in that case with the option for triode strapping - would result in about 25Wrms output, and sound quite good.

Send me a PM and I will send you a driver design (not to be shared however) you might find interesting, and is not too complex.
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