What kind of tube did I use back then?

sprinter · 5th March 2011, 08:28 PM

Back when I was 18 and going off to school, I decided I would need a little stereo for my dorm room. I built a little stereo amp (and speakers) with just two tubes. They were twin tubes with one half as a preamp driving the other as a power amp. I'm trying to remember what tubes I used for that. I remember that it worked surprisingly well. I think they were small 7-pin jobs, but I'm not certain. The B+ may have been derived from the 120VAC without xfmr. I do know that cost and simplicity were important.

Anybody know what they may have been? I'm thinking that they may have been specifically designed for that purpose in mind. But they may have just been like a 12AX7 or something, then it could have been anything. Do people still do this? Most designs I see now use at least 3 tubes.

I'll expand this question to include any known ultra-simple transformerless designs.

Thanks

Eli Duttman · 5th March 2011, 08:59 PM

The 6BM8 is a Noval (9 pin mini) type suited to a "spud" (1 tuber) circuit. FWIW, I've been involved in such a project. Look here if you're interested.

mashaffer · 5th March 2011, 09:07 PM

6GW8, 6GV8 et.al. also possible.

Ty_Bower · 5th March 2011, 09:39 PM

Quote:

Originally Posted by sprinter

Do people still do this?

Sure. I'm building a 6BM8 amp that I'm gonna finish any day now, I swear...

http://i69.photobucket.com/albums/i4...E/P1140836.jpg

sprinter · 5th March 2011, 10:29 PM

Quote:

Originally Posted by Ty_Bower

Sure. I'm building a 6BM8 amp that I'm gonna finish any day now, I swear...

http://i69.photobucket.com/albums/i4...E/P1140836.jpg

Yeah, yeah, I've heard that before (usually from me to my wife)...

Thanks guys. I'll take a close look at your projects. I imagine there are some spud threads here. I'd be interested to see any such projects. I've heard the term "spud" but didn't know that's what I did (ahem) years ago. Big question is, how do they compare sound-wise to other, more conventional SET designs? I know they'd be flea power but I will have some 94 dB full-rangers to try it on. Maybe I could even find something more sensitive. I like simple. Simple is good.

Boy, that 6GW8 sure sounds familiar, but I'm not sure.

woodturner-fran · 5th March 2011, 10:49 PM

Maybe Ecl82 or ecl86? Can't recall the US numbering........ but very like half 12ax7 and half el84.

sprinter · 11:18 PM

Quote:

Originally Posted by woodturner-fran

Maybe Ecl82 or ecl86? Can't recall the US numbering........ but very like half 12ax7 and half el84.

Yeah, that's the kind of thing I had in mind.

Oh, I just found the ECL82. It's a 6BM8. Sounds like a really nice project tube.

woodturner-fran · 5th March 2011, 11:19 PM

ecl86=6GW8
ecl82=6BM8

There's also PCL86 and 82, exactly the same valve but with 14V heaters I think.

Wavebourn · 5th March 2011, 11:23 PM

6Ф3П (6F3P) is the same, still available.

woodturner-fran · 5th March 2011, 11:26 PM

I just picked up a ECL82 amp the other day and am about to start restoring it....

see: ECL82 mullard 4-7

5th March 2011, 08:28 PM	#1
sprinter diyAudio Member Join Date: Feb 2011 Location: Seattle	What kind of tube did I use back then? Back when I was 18 and going off to school, I decided I would need a little stereo for my dorm room. I built a little stereo amp (and speakers) with just two tubes. They were twin tubes with one half as a preamp driving the other as a power amp. I'm trying to remember what tubes I used for that. I remember that it worked surprisingly well. I think they were small 7-pin jobs, but I'm not certain. The B+ may have been derived from the 120VAC without xfmr. I do know that cost and simplicity were important. Anybody know what they may have been? I'm thinking that they may have been specifically designed for that purpose in mind. But they may have just been like a 12AX7 or something, then it could have been anything. Do people still do this? Most designs I see now use at least 3 tubes. I'll expand this question to include any known ultra-simple transformerless designs. Thanks

5th March 2011, 08:59 PM	#2
Eli Duttman diyAudio Member Join Date: Apr 2004 Location: Plainsboro, NJ	The 6BM8 is a Noval (9 pin mini) type suited to a "spud" (1 tuber) circuit. FWIW, I've been involved in such a project. Look here if you're interested. __________________ Eli D.

5th March 2011, 09:07 PM	#3
mashaffer diyAudio Member Join Date: Jun 2004 Location: Indiana	6GW8, 6GV8 et.al. also possible. __________________ mike - www.keepingsundayspecial.org

5th March 2011, 10:49 PM	#6
woodturner-fran diyAudio Member Join Date: Jan 2006 Location: Ireland	Maybe Ecl82 or ecl86? Can't recall the US numbering........ but very like half 12ax7 and half el84. __________________ Visit www.tirnahifi.org!!

5th March 2011, 11:19 PM	#8
woodturner-fran diyAudio Member Join Date: Jan 2006 Location: Ireland	ecl86=6GW8 ecl82=6BM8 There's also PCL86 and 82, exactly the same valve but with 14V heaters I think. __________________ Visit www.tirnahifi.org!!

5th March 2011, 11:23 PM	#9
Wavebourn diyAudio Member Join Date: Sep 2006 Location: Pleasant Hill, CA	6Ф3П (6F3P) is the same, still available. __________________ The devil is not so terrible as his mathematical model! Wavebourn: We Create Creativity!

5th March 2011, 11:26 PM	#10
woodturner-fran diyAudio Member Join Date: Jan 2006 Location: Ireland	I just picked up a ECL82 amp the other day and am about to start restoring it.... see: ECL82 mullard 4-7 __________________ Visit www.tirnahifi.org!!

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