12AB5/12AV6 low cost SE tube integrated amplifier (with pics)

[6942]

Howdy people!

I spent the last couple of days, building a tube stereo integrated amplifier.
I tried to go.....'easy-on-the-bank-account;....on this amplifier build.
The tube line-up consists of C-H-E-A-P NOS vacuum tubes:

A Westinghouse 6AX5GT rectifier tube
A pair of RCA 12AV6 driver tubes
Plus a pair of obscure GE 12AB5 tubes (6V6 tube in a 9 pin bottle).

I used a new $39 Hammond open-frame power transformer (250V CT@130ma/6.3V@2A).
I built a hybrid bridge with the 6AX5 rectifier tube, and hit my target B+ at 250Vdc.
Added a 5H/125ma choke, a 12.6v@1A filament transformer, and a pair of EDCOR GXSE output transformers.
A Cosmos 100K stereo volume pot, and were good-to-go!
I took a couple of pictures of the amp itself, and the last picture is of the amp & the DIY 2-way acoustic suspension speakers.

Enjoy!
Steve

 

[printer2]

Obscure 12AB5's? I probably have 20 of them.


Looks good.

 

[6942]

LOL....well, they sure were obscure to ME??

 

[bblumentritt]

Looks great! Nice work.

How does it sound? Pretty well, I should think.

 

[6942]

Sounds pretty decent in my book.
Especially considering the total build cost was around $250.

Output is only around 4wpc, so relatively efficient speakers are a must.
Those DIY speakers are 89 db/watt efficient; super nice mid-range, nice high end (1970's EPI concave tweeters), but the compromise is the bass response starts to roll off....slowly....below 70hz.

 

[printer2]

LOL....well, they sure were obscure to ME??

Yeah, never would have heard of them if I did not look far alternatives to 6V6's.

 

[6942]

I could have used 12V6GT or 12AQ5 tubes, as I have more of them than the 12AB5 tubes.
Still, it's always fun experimenting with.....like you said.....'alternatives'.

 

[rghill]

I found an old Wollensack reel to reel that has two 12AB5's in it.

Best part of that score was $5 for the Sylvania 12AX7. It also has a 12AU7.

 

[Telenut62]

Nice build, you've definitely been thinking left field there.