Show us your flea-watts amps!

[FlaCharlie]

Here's one I built this past summer. As with several previously posted examples, it's based on the little Magnavox 8300 or 8600 series. Unlike those previously shown, I modified it to be a true SET using the dual triode 12BH7 as outputs. It's a little closer to being a true Magnavox than some designs in that it uses the stock OTs. It sounds great with a surprisingly solid bottom end.




Got lots of great advice from Dave Gillespie on this. Here's the original build thread:
http://www.audiokarma.org/forums/in...0-or-8600-conversion-to-12bh7-outputs.824135/

 

[TubeGator]

appj mini watt filling in while older brother gets fixed up

 

[Mike Stehr]

RH84

 

[Redboy]

Beautiful work, @Mike Stehr!

 

[Redboy]

This one's by far my coolest vintage tube amp...

It's a Signal Corps Dual Channel Amplifier, model AM-43C/FRC ca. 1956. It's "stereo but not stereo", built before the commercial dawn of stereophonic sound!

6SN7 > SE 6V6, and overbuilt to the hilt!

Thread here: http://audiokarma.org/forums/index.php?threads/my-coolest-vintage-tube-amp.752165/

 

[Palustris]

I purchased this little 6V6 amp on the auction site because I liked the tubes on top look. These show up on the site every once in a while and there are two versions; this is a National kit. I never expected the little output transformers to sound good, but bought it anyway because it was cheap. I fully rebuilt the unit with a nice choke in the power supply which also received new high quality caps. I added a three conductor power cord and eliminated the first two stages of bass and treble controls. A simple 12AT7 front end configured as voltage amp/split load phase inverter driving the output tubes through Russian caps is the entire audio circuit. Bass is remarkable on my Zu speakers, considering the size of the output transformers.

 

[BinaryMike]

My homebrew Parsimon amplifier pumps out 5~6W per channel and sounds damn fine on bookshelf speakers, despite being built with the cheapest parts imaginable. Full documentation is published here: http://audiokarma.org/forums/index....-pentode-power-amp.464003/page-2#post-9046145

 

[artdecoradio]

I purchased this little 6V6 amp on the auction site because I liked the tubes on top look. These show up on the site every once in a while and there are two versions; this is a National kit. I never expected the little output transformers to sound good, but bought it anyway because it was cheap. I fully rebuilt the unit with a nice choke in the power supply which also received new high quality caps. I added a three conductor power cord and eliminated the first two stages of bass and treble controls. A simple 12AT7 front end configured as voltage amp/split load phase inverter driving the output tubes through Russian caps is the entire audio circuit. Bass is remarkable on my Zu speakers, considering the size of the output transformers.



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I have the same amp. It really sounds good and has a very cool look to it. Check out this post that I made about it 4 years ago:

http://audiokarma.org/forums/index.php?threads/interesting-tube-amp-found-information.627961/

The amp was evidently made by a company called MERRELL. They were also sold by Radio Shack. Here's an ad for the amp which also appears in the above-listed thread:

 

[FlaCharlie]

Sure. There is an extra choke underneath... 35lbs to get 1-3wpc lol.

Two 6da4 damper diodes
7F8 driver tube
45/2a3 power tube
Two small filament transformers for the 2a3/45
Power transformer is an old freed.
2 Power supply chokes
hammond 126c interstage transfomers
james audio outputs.


It is pretty simple not too many parts.

The hardest part was the metal work.

The mistakes I made on my first build were:
Had the LED's on the 7f8 reversed so no sound came through.
Had the interstage transformer wired wring so the sound was muddy and weird.
After working through those it sounded great.

I'd like to do a Brook 12A with all modern parts next but just because I've always wanted one.

I've been thinking of building something with some 7F8s that I have. Not many people seem to use them. Do you have a schematic you could share or some info on the operating points you used? You mention using LED bias on them. Did you experiment with other methods first or go straight to the LEDs?

Any insights into using these tubes is greatly appreciated.

 

[mashaffer]

Hopefully I didn't post this earlier (pretty old thread)... My SEUL KT88.



Not pretty but sounds nice IMO. when I get my OB table speakers upgrade done I plan to incorporate it into my main system.

 

[Lavane]

Definitely flea power, and my first home-made tube amp:

Still undergoing some development, but it does work.

Thread here:
http://audiokarma.org/forums/index....re-p_p-amp-talk-me-out-of-building-it.847654/

It is intended as a small PC speaker amplifier.

Push-Pull, uses 5902 subminiature tubes. It runs from a 12V power brick.

I'm currently building a Lexan and metal grid cover.

Basic design by Bruce Brown, and published in the April 2011 copy of AudioXpress, but with modern power supplies.

You just jumped right into the deep end, didn't ya?
My first amp build was a 300B using two 6j5's per channel instead one 6sn7. I thought THAT was ambitious.

 

[primosounds]

I purchased this little 6V6 amp on the auction site because I liked the tubes on top look. These show up on the site every once in a while and there are two versions; this is a National kit. I never expected the little output transformers to sound good, but bought it anyway because it was cheap. I fully rebuilt the unit with a nice choke in the power supply which also received new high quality caps. I added a three conductor power cord and eliminated the first two stages of bass and treble controls. A simple 12AT7 front end configured as voltage amp/split load phase inverter driving the output tubes through Russian caps is the entire audio circuit. Bass is remarkable on my Zu speakers, considering the size of the output transformers.



View attachment 1374813

I rebuilt one of those for my kids room. It was hooked up to some vintage Sansui speakers , the kind with the lattice front. It would really pump out the jams and i always had to tell them to "TURN THE STEREO DOWN!" It would rattle the windows in the house. But to be fair, that is a PP 6v6 amp which is around 12 watts per channel power.

 

[Slack73]

Homebuilt 6CY7 amplifier, circuit design by Matt at Cascade Tubes. Around 1.3 watts per channel.

 

[mashaffer]

Homebuilt 6CY7 amplifier, circuit design by Matt at Cascade Tubes. Around 1.3 watts per channel.

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View attachment 1407817

Love that look. Nice work!

 

[FlaCharlie]

Homebuilt 6CY7 amplifier, circuit design by Matt at Cascade Tubes. Around 1.3 watts per channel.

Nice. I'm not familiar with the 6CY7 so I looked it up, a dissimilar triode. I couldn't find any plate load specs for section 2, what OT primary impedance did you use? Do you have a schematic you could post?

 

[Slack73]

Love that look. Nice work!

Thank you!

Nice. I'm not familiar with the 6CY7 so I looked it up, a dissimilar triode. I couldn't find any plate load specs for section 2, what OT primary impedance did you use? Do you have a schematic you could post?

The OT primary on mine is 5.5k.

The schematic and info can be found here:
https://www.cascadetubes.com/the-6cy7-amp/

 

[Nutsfortubes]

 

[rodcad]

Pair of Decware kits bridged into mono. Very temporary home on top of the Cornwall.

 

[dallen9494]

DG-SE1

 

[Lavane]

DG-SE1
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Very nice layout. I have a small spud amp under construction. One tube that can be used puts out 1.2 watts. I'm going for the big 5.5 watt version. That's the nicest DG-1 I've seen yet. Congrats!