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Homebrew amp schematics [message #10849] Sun, 12 December 2004 06:58 Go to next message
Wayne Parham is currently online  Wayne Parham
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Here are some schematics for SET amps using 45, 2A3 and 300B tubes:
Here's a push-pull 2A3 amp:

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Re: Homebrew amp schematics [message #10850 is a reply to message #10849] Sun, 12 December 2004 08:07 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
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Bob Daneliek who designed the last 2a3 you named and that is his site also has a really easy and cheap SE pre-amp build write up using 5687 tubes. There are numerous links to his site from builders who have done that pre-amp and many claim it is a giant killer.

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Re: Homebrew amp schematics [message #10851 is a reply to message #10850] Sun, 12 December 2004 11:56 Go to previous messageGo to next message
Thermionic is currently offline  Thermionic
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I haven't seen the schematic you referred to, much less heard it. But, from my own personal piddling around with stuff, I can testify that 5687s sound killer! IMO, they are definitely better than the benchmark 6922.

Thermionic

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Re: Homebrew amp schematics [message #10852 is a reply to message #10850] Sun, 12 December 2004 14:55 Go to previous messageGo to next message
colinhester is currently offline  colinhester
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Got a link to the 5687 pre? Would this be a good first group project?....Colin

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Re: Homebrew amp schematics [message #10853 is a reply to message #10852] Sun, 12 December 2004 15:05 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
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Well it is fairly easy schematic. The pre-amp transformer and the enclosure would be most of the cost. If you are interested then let me know.

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Re: Homebrew amp schematics [message #10854 is a reply to message #10853] Sun, 12 December 2004 15:23 Go to previous messageGo to next message
colinhester is currently offline  colinhester
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Yes, Please post link to the schematic!! As far as cost, let's just assume a fixed cost for enclosure - say, $5. This is low, but the circuit will work even if straped to a 2x4. The transformer is a diiferent concern, especially for tube-based projects.

Let me see the schematic and do a cost estimate on it. If you have time, please do the same, and we'll compare numbers. I was really hoping a tube preamp would be the first project; so, you can imagine I was excited to see your post. Preamps are pretty easy to build, and a circuit analysis should be straight forward (he says that now.)

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Re: Homebrew amp schematics [message #10855 is a reply to message #10854] Sun, 12 December 2004 18:17 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
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The website originates from Bob's site; the last link in Wayne's post. The group of builders is the JELabs site. He also has a nice 2a3 SE amp that uses the cheapo Hammond output transformer. It sells for 30$. Don't tell anyone but I think buying Foreplay boxes is one idea. I think he gets 35$ for them. 5687 tubes are on sale at Angelas for 3$ ea. and the sockets go for 2.50$. The trans should be about 35$ the rest of the parts I guesstimate at 50$ Should put us at about 125$ Oh yeah 2.87$ for the 2x4. Check out JELabs and grab the circuit and let me know. No reason this can't be done with a minimum of fuss. Only thing is, on the JELabs site there are so many pics. it is almost too easy.

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Re: Homebrew amp schematics [message #10856 is a reply to message #10855] Mon, 13 December 2004 11:17 Go to previous messageGo to next message
colinhester is currently offline  colinhester
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Is this it?.....Colin

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Re: Homebrew amp schematics [message #10857 is a reply to message #10856] Mon, 13 December 2004 12:58 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
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The site is DIYParadise.com. Once you get on there look for the 5687 based tube DIY pre-amp. You will see what I mean, they spell it out pretty thoroughly. Actually the 125$ price point; now that I look at it seems a little high. More like 80-90$. There aree many people who have built both the pre-amp and amp. The amp uses the same tube as an output tube and people build it SE or Push-Pull. On the site they compare it to a Foreplay.

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Re: Homebrew amp schematics [message #10858 is a reply to message #10857] Mon, 13 December 2004 14:00 Go to previous messageGo to previous message
colinhester is currently offline  colinhester
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Bingo. Looks like the perfect place to start!!!! We still need to let Wayne know what we're up to, if you have not already done so. When and where (forum?) do you want to do the first post?....Colin

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