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Old 19th May 2011, 12:03 AM   #1
Jeb-D. is offline Jeb-D.  United States
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Default Suggestions for 5k5 40W iron?

I recently obtained some output iron from a sansui 100A. Some say it is 6k, but it measures 5k5 plate-to-plate. Not sure what to do with them. It has no UL taps and I'm looking to build something efficient with aprox 40W output and of course good sounding. I am having trouble deciding, but am thinking something along the lines of:

Class AB1 7591 tetrode (like in the reciever which they were pulled from). $80+ on a quad of tubes is a little (lot) pricier that I'm hoping to spend. But it's high screen rating would allow me to keep it in AB1.

Class AB2 807 or 829B tetrode = Both are cheap and plentiful, but with the screen voltage limitation, I'd probably have to run it in AB2 to achive the desired output with this transformer.

Class AB1 6BG6 tetrode = Should be able to obtain output power without going into AB2. Availability seems kind of scarce. The resonably priced ones are typically singles. Most quads that show up are priced high.

Any input or other suggestions?

Last edited by Jeb-D.; 19th May 2011 at 12:06 AM.
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Old 19th May 2011, 12:05 AM   #2
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307A
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Old 19th May 2011, 12:51 AM   #3
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The Soviet surplus 6П3С-Е (6p3s-e) is a "meaty" member of the 6L6 clan. They are good sounding and not especially expensive. Jim McShane has properly culled and matched stock.
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Old 19th May 2011, 02:05 AM   #4
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Petes magic red board with any cheap sweep tube that will fit the board and 400 to 450 volts of B+. Plenty of power and great sound. I run mine at 600 volts and 3300 ohms for 125 WPC and I have seen 250 WPC on 650 volts and 250 ohms, so ignore the 18 WPC claims.

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Old 19th May 2011, 03:14 AM   #5
Jeb-D. is offline Jeb-D.  United States
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Thanks for the suggestions.
Quote:
Originally Posted by Eli Duttman View Post
The Soviet surplus 6П3С-Е (6p3s-e) is a "meaty" member of the 6L6 clan. They are good sounding and not especially expensive. Jim McShane has properly culled and matched stock.
I was initially considering those. The price is right, but their Vg2 and Vp ratings seem more restrictive than the 807/G-807. Though I know people are using the 6p3s-e's beyond their rating with success.

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307A
I'll check it out.

Quote:
with any cheap sweep tube that will fit the board and 400 to 450 volts of B+
Got any sweep tube suggestions? I'd like to keep it AB1 if possible.
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Old 19th May 2011, 03:20 AM   #6
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Quote:
Originally Posted by Jeb-D. View Post

I was initially considering those. The price is right, but their Vg2 and Vp ratings seem more restrictive than the 807/G-807. Though I know people are using the 6p3s-e's beyond their rating with success.
If to use them within ratings they would not sing. But in order to get good sound from them they need such regime that not even electrodes, but the glass bulb would melt down.

See their more complete curves than you see usually, to get better picture:
Attached Images
File Type: jpg 807triode.jpg (192.9 KB, 309 views)
File Type: jpg 807vah.jpg (193.0 KB, 307 views)
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Old 19th May 2011, 07:57 AM   #7
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Quote:
Originally Posted by Jeb-D. View Post
Quote:
Originally Posted by dsavitsk View Post
307A
I'll check it out.
A bit of a half serious suggestion. Triode curves look a lot like 6L6's, some people swear by them as about the best tube they've ever used, and they used to be easy to find for about $10 each. Unfortunately, the price has gone up, and supply is low, though lots of people seem to have a dozen of them sitting around waiting for a project. There was a thread a while back: Where are the 307A / VT225 amps?
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Old 19th May 2011, 04:22 PM   #8
Jeb-D. is offline Jeb-D.  United States
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Quote:
If to use them within ratings they would not sing. But in order to get good sound from them they need such regime that not even electrodes, but the glass bulb would melt down.
So in otherwords, your saying don't waste my time with them?

Quote:
A bit of a half serious suggestion. Triode curves look a lot like 6L6's, some people swear by them as about the best tube they've ever used, and they used to be easy to find for about $10 each. Unfortunately, the price has gone up, and supply is low, though lots of people seem to have a dozen of them sitting around waiting for a project. There was a thread a while back: http://www.diyaudio.com/forums/tubes...t225-amps.html
Yeah, way too rare. Coming up with a quad for a PP amp would be next to impossible.
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Old 19th May 2011, 05:07 PM   #9
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maybe he meant what he said...run the 6p3s HOT... they sound best that way...as seen on the curves. does not matter as these tubes are cheap.
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Old 19th May 2011, 05:21 PM   #10
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Right. They don't have optimal regime, because optimal regime for sound quality for them means overheating and death, so compromise is needed between better sound quality and longer life. Or, to use paralleled tubes with lowered G2 voltage, like I did the last time I used them (7 years ago).
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