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Old 17th October 2005, 05:44 PM   #1
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Default 42 single ended

Does anyone know where I can get a schematic for the use of a 42 power pentode (from a 30's radio reciever) as a single ended amp?

I also have a 12AT7 I can use for a preamp, along with a slew of 12au6's , 12be6's, etc etc... yes I got them out of an old radio. I also got a nice usable 35c5 out of the small radio.
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Old 17th October 2005, 07:17 PM   #2
edl is offline edl  Hungary
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Dear ThSpeakerDude88,

Check out this page for 42's datasheet.
http://frank.pocnet.net
With the datas included in the datasheet you will be able to design a simple class-A SE amp with that nice tube.

Regards,
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Old 17th October 2005, 10:17 PM   #3
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alright, thanks! I see that this tube is the same as a 6F6 (correct me if I'm wrong )

I guess 3 watts would be really great , but it looks like thats at a considerable amount of distortion. Maybe a push-pull AB2 setup would be best? Another thing to consider, If I'm going to use a class A/B setup, would different tubes be better?

I'd just like to order some extras to have around from ebay
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Old 17th October 2005, 10:54 PM   #4
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Quote:
I guess 3 watts would be really great , but it looks like thats at a considerable amount of distortion. Maybe a push-pull AB2 setup would be best? Another thing to consider, If I'm going to use a class A/B setup, would different tubes be better?
I dropped the 42/6F6 from my "short list" quite some time ago due to the distortion problem. It may not be that big of a deal for a radio, but unacceptable for high end audio. You'd do much better with the 6V6. Similar power output, working voltages, and gain, but with a good deal less distortion. You could run the 6V6's as a class AB1, as pentodes with NFB. Or run them as triodes without NFB.

Either way, they'll sound a whole lot better.
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Old 18th October 2005, 09:28 PM   #5
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ooo triode w/o nfb would be nice, although I would not have much power. I think I'll go with a 6L6 pp combo for 40 watts or a se for 10. What I'm really aiming at is a nice sounding 20 watt duL mono block setup. 20 watts would be easy in pp ab1 mode, but a class A SE 20 watt monoblock would requier a lot of power to run wouldnt it, not to mention be expensive?
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Old 19th October 2005, 12:57 AM   #6
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A 20 watt SE triode amplifier built according to current audiophile criteria (2 X 300B per channel) would definitely be expensive, and would dissipate 80 to 150 watts per channel.

It would be possible to build a 20 WPC SE amplifier for much less money if you use parts that are less "in vogue". 3 X KT88 (triode wired) per channel would be cheaper, or 3 X TV sweep tubes, find cheap ones with sufficient screen grid ratings for triode operation.

I am partial to surplus transmitter tubes myself, or new Chinese 845's, 40 watts per channel, serious bass, the only drawback is the need for 1100 volts!

Diagram on my web site: http://www.tubelab.com/845SE.htm
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Old 19th October 2005, 01:33 AM   #7
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I recently heard a 40W SE with 2 6C33 in parallel. Sounded great with plenty of power. The builder custom made the iron with bifilur primarys. One for each tube.
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Old 19th October 2005, 11:14 PM   #8
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ok... I have been sucsessfully scared away from a high powered SE setup because of prices and insanly high voltages needed

LOL

I think for my first design, I will try a typical push pull setup. I want something that will be relativly cheap to build, have a very good snr ratio , and obviously sound pretty nice. I may consider a much lower powered SE setup later, unless I can find a cheap tube that will do what I want it to do.

hmm...

how hard would 10 watts be? maybe 5 if that requiers too high of a plate voltage or is too 'spensive. I'm really just designing my first tube amp.. so I want something thats not gonna be expensive, but I dont want it to sound like total crud either!
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Old 20th October 2005, 01:38 AM   #9
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For a 15 Watt push pull amp it would be hard to beat a pair of 6BQ5's/EL84 tubes. This is probably the most common P-P amp design around, and plenty of schematics are on the web. For slightly more power there is the 6V6 P-P amp, also common and good sounding. Either of these would be relatively cheap to build.

If 5 watts is enough, a SE amp could be built with 6L6's, EL34's or KT-88's, one tube per channel. Simpler circuit than P-P, and no crazy voltages required. For a budget SE amp the Hammond 125CSE output transformer is hard to beat at $30.
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Old 20th October 2005, 05:33 PM   #10
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sweet! just what my budjet wanted to hear

I think a single 6L6 or kt88 would be nice, I haven't seen an el34 I don't think.. will look up!

would a pp pair of 6L6 monoblocks sound good?

I know the 6V6's in pp make 19 watts, I believe the 6L6's can produce 40 watts, so 20 watts would be at considerably low distortion.

By the way, I have never heard a 'proper' tube amp, just the old radios that I mess with. How does their SNR compare to transistor amps? The chipamp I built has a SNR around 110 db, its dead silent when turned on, even at full volume , signal or no signal

can a tube amp come close to that, and if properly designed , will there be any hum?
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