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Old 8th May 2003, 02:08 AM   #1
arnoldc is offline arnoldc  Philippines
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Question Any suggestion for cheapest SET amplifier project

I'd like to make an ultimate, el-cheapo single-ended triode power amp that will deliver 2-3W of power.

will use hammond 125ESE as OPT, locally sourced power transformer and choke.

do you think 6B4 as power and 5687 driver is cheap enough?
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Old 8th May 2003, 02:47 AM   #2
Colt45 is offline Colt45  Serbia
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I see our opinion of cheap differs somewhat..


I'd say something like 6BX7, 6S4, blah.. any cheap suitable triode w/ '$10 special' OPTs ;-)
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Old 8th May 2003, 06:11 AM   #3
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Yeah where's Fred Nachbaur when ya need him...

http://www.dogstar.dantimax.dk/tubestuf/miniblok.htm

Can't get much cheaper than him....err I mean that...yea...

Tim
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Old 8th May 2003, 09:22 AM   #4
arnoldc is offline arnoldc  Philippines
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thanks for your suggestion guys.

maybe a 6S4 and 6922 then? if i get get 2+ watts out of that 6S4, i'm a happy man.
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Old 8th May 2003, 09:29 AM   #5
SHiFTY is offline SHiFTY  New Zealand
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I picked up a couple of Sovtek 6B4 (octal 2a3) for $US50 on eBay... They are pretty cheap and there are lots of schematics available. I am currently running mine at about 25W dissipation with 125ESE for about 5W of audio power. (which is surprisingly loud)

I used 3 separate power transformers I had lying around, built the power supply on a separate chassis.

Sounds really good, a little negative feedback helped though.

I have probably spent $US150 on this project total...
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Old 9th May 2003, 12:36 AM   #6
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Default 6B4

I hear that late model 6B4s from Sylvania were rebased 6AV5s with screen tied internally to plate. 6AV5s are about as common as dirt and almost as cheap....

But the 6EM7/6EA7/6DN7/6GL7 or miniature equivalents 6DE7/6DR7/6EW7/6FD7 will make about the cheapest triode amp possible. Only about a watt, though, in class A1.
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Old 9th May 2003, 07:15 AM   #7
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Default 829-B maybe?

In recent ponderings (and having access to four of these) I've done a search and it seems that with the 2 halves of an 829 paralleled up and run in triode mode you can get around 4 or 5 watts of really nice SE from this tube.

Haven't tried it but there was a very short thread on Audioasylum tubediy (do a search on 829) where someone was running one at about 300v with a 2.5k tranny (IIRC)

NOS RCA of these are about 9 dollars.

**Special base required can be got from tubestore.com for around 7 dollars ea.

just a thought

drew
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Old 9th May 2003, 07:22 AM   #8
arnoldc is offline arnoldc  Philippines
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thanks guys. there's more options than i thought! i love DIY
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Old 9th May 2003, 07:32 AM   #9
Morse is offline Morse  United States
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Hi arnoldc;

Don't forget the lowly 6BM8 SET! Run in pentode mode you can get just over 3wrms from this little $8-$10 valve (complete with it's own triode input section!). While it's not as nice sounding as my 2A3 (with pricey iron and some "boutique" parts), it's quite good sounding.

Just do use more substantial PS iron than I did on my little 6BM8 - that 269JX is going to get replaced with a 270DX as soon as it arrives. Even that may be cutting it a little close, so I'll update everyone on my experiences there (hopefully it will run a LOT cooler than the current PS trafo...). The next step up is a 270FX, but I hope that's not necessary.

Pix to follow once a friend emails 'em to me.....

All the best,
Morse
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Old 9th May 2003, 03:26 PM   #10
john is offline john  Philippines
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Hi Arnold,

Try this 4 watter 6AS7 SRPP. This tube is a relative of the 2A3, 6B4G family. It's a twin power triode... Less tube count .

John
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