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Old 5th June 2008, 09:33 PM   #1
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Default Need ideas - 6L6GA & 6X5GT

I've come across a couple old (1945 vintage) 6L6GA tubes. They're beautiful with their ST bottles and smoked glass sides. I'd like to build a stereo single ended amp out of them. In the same box came a few 6X5GT rectifiers. I'd like to use them in the power supply. I think I'm going to need a separate 6X5 to feed each 6L6GA?

Any hints, or pointers to a recommended schematic?
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Old 5th June 2008, 10:16 PM   #2
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Default SE 6L6 Schematic

You could adapt Bas' SE EL34 schematic for 6L5 use.
Just change the cathode resistor to 720R.
Yes you will need one 6X5 per channel.

DanL
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Old 5th June 2008, 10:17 PM   #3
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Default I forgot the link - sorry

http://basenjes.de/tubes/jbsel34.htm

DanL
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Old 5th June 2008, 10:24 PM   #4
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One easy choice - use TubeLab's Simple SE circuit. You COULD use the PCB if you use a single rectifier like 5V4G. With the 6X5, yes you'd need two.
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Old 6th June 2008, 02:13 AM   #5
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TubeLab's Simple SE is appealing. I've taken a good look at it. I like building kits where someone else has already done the design and proven the circuit is sound. It doesn't hurt that many others have already built it as well. I'm not completely married to the 6X5, it's just that I happen to have them.

What kind of power transformer would I need to run a pair of 6L6GA in the Simple SE board? George seems to like the Allied 6K7VG, but I'm thinking the B+ would end up too high for the 6L6GA.
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Old 6th June 2008, 03:32 AM   #6
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Quote:
George seems to like the Allied 6K7VG, but I'm thinking the B+ would end up too high for the 6L6GA.
YES, big time! I plugged a pair of crusty old 6L6GA's into one of my amps, and they REALLY didn't like it. They were on the verge of runaway, and would slip into uncontrolled red glow mode whenever they wanted to. The old 6L6 (metal) and the 6L6GA's want about 380 to 390 volts with cathode bias to remain in spec. I have used 400 to 410 without issue, but the Allied 6K7VG can make 440 to 460 with a 5AR4. I have been using some surplus HP power transformers for amps like this, but I don't have any more left. They are 650 VCT.

I have a Hammond 272JX (600VCT) on my bench. Hammonds are known for running high. I will hook it up and try it over the weekend if I can find the time.
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Old 6th June 2008, 02:00 PM   #7
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Guys,

The AnTek AN-3T325.pdf toroidal power trafo should do nicely for this project. Wire the 6X5 heaters in series and connect them to the 12.6 VAC winding.
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Old 6th June 2008, 02:16 PM   #8
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I'm wondering if the AnTek AN-3T275 would be a better fit, and just use a 5AR4 rectifier. My problem with the AnTek transformers is that I never know where to buy them, other than wait for one to show up on eBay. Can I just call the guys and order one? Do they sell direct? I guess I should try sometime...

I'm also looking at the Hammond P-T270HX. AES has them on their website for $63. But, I've read that sometimes the Hammond 200 series have a mechanical hum and that kind of stuff really turns me off.
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Old 6th June 2008, 02:22 PM   #9
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Ty,

Use the 6X5s with the AnTek trafo, as a 5 VAC winding is not present.

You most certainly can order directly from AnTek. Like me, they're in NJ. Look here.
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Old 6th June 2008, 05:12 PM   #10
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Does this look anything close to correct?

Click the image to open in full size.
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