DIY Audio Projects Forum

K-12G Tube Amp Kit Build Thoughts
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Author:  Gio [ 01 Mar 2009, 12:36 ]
Post subject:  Re: K-12 Tube Amp Build Thoughts

I think it will be tough to get shorter connections than a PCB. But do post some photos as they may give some of use ideas too.

Author:  connemaraguitars [ 14 Mar 2009, 09:27 ]
Post subject:  Re: K-12 Tube Amp Build Thoughts

Hi, all,
Life got busy and I didn't have a lot of time to put into my modified K-12 G project. Yesterday, however, she got finished!

In short, I abandoned the PCB in favor of a turret board. I'd never tried to create a layout before, so my results are, well, clunky. In places, connecting wires are way too long. I originally though I was going to have to start over, but decided instead to move some things around on the existing board. I figured, what the heck...if it sounds ok then at least I know I have the basic wiring right and can re-do the layout. Anyway, I went ahead and bought parts to build a second amp (except for transformers).

This weekend I plan to sit down and re-draw the layout so it's optimized for size and connections.

Amazingly, my wiring was darned close to perfect in the first go...except for one connection I missed. Once this connection was added, and the amp plugged into a dvd player and speakers...


There is no comparison to the K-8 amp I originally build, which has no low end.

My only complaint is with the volume control, which I bought at Radio Shack, which matches to specs on the schematic. I get no output until the volume control is at about 11:00, and then the output rapidly increases with only a slight turn on the volume control.

Any thoughts on what might be causing this? It's an audio taper pot.

I'll post photos when I get home from work today, including the mods and upgrades I chose to go with. It's not a work of art but is sounds great.

Author:  gofar99 [ 14 Mar 2009, 19:12 ]
Post subject:  Re: K-12 Tube Amp Build Thoughts

Hi, I'm glad it made sound. I personally like turret boards, but they are not as simple to use as it would appear. I often go through several parts placements on them before settling on final version. The actual location of the boards is key as well. Another thought is to turn them 90 degrees to the chassis. Often this can give you the posts you need close to where you want them.

K-12s are good little amps. I still have and use mine. It is on my PC at present. K-12s have been known to lead to tube addiction and before you know it everything else in the house sounds bad. Welcome to the tube bunch.

Good listening

Author:  connemaraguitars [ 17 Mar 2009, 18:18 ]
Post subject:  Re: K-12 Tube Amp Build Thoughts

Hello, all. I finally got some pics to share. As mentioned before, I'm not terribly happy with my layout...too many long wires. However, the amp is hum at all.

I'm feeding signal from a Pioneer DVD player that was recently replaced by a BluRay disc player in my home theatre syste, The output goes to a pair of Infinity Primus P162 speakers. I was going to build my own speakers but found that these cost the same as good components and sound excellent.

As Bruce noted, this is an addictive hobby! My next steps will be to 1) clean up the turret board layout (and publish the results here), 2) make a new board (maybe) and 3) go about salvaging the K-8LS tube amp I built. The latter will entail a turret board (rather than PCB) and different pre-amp tubes (probably 12AY7s).

Thanks for all the encouragement and support in this process. I swear it made me feel really stupid at times!

By the way, I did not incorporate all of the modifications suggested by others. Nor did I spend much money on the mods I did make. I'll post this information in the near future.





Best regards,

Author:  billnchristy [ 17 Mar 2009, 19:34 ]
Post subject:  Re: K-12 Tube Amp Build Thoughts

It's very nice.

I wouldn't sweat the wiring so much, I think fretting about short wiring is something to do when you are buying pure silver stuff that is 5 bucks a foot. :mrgreen:

Author:  connemaraguitars [ 17 Mar 2009, 21:11 ]
Post subject:  Re: K-12 Tube Amp Build Thoughts

Thank you, my friend! The cost of the wire was $0.75 a foot. So maybe I could save $2 by vcleaning things up. The lack of hum/noise tells me it's clost to right! Lofton

Author:  Gio [ 17 Mar 2009, 22:16 ]
Post subject:  Re: K-12 Tube Amp Build Thoughts

Great work, that looks great. :up: If you don't have any unwanted noise or hum, there is nothing to fix! Sit back and enjoy!

Do you mind if I add a photo or two of your build to the Photo Gallery?


Author:  connemaraguitars [ 17 Mar 2009, 22:46 ]
Post subject:  Re: K-12 Tube Amp Build Thoughts

Post away, Gio! I'll try to add more information when time permits. As you said, though, the amp is absolutely great as is, long wires and all.

Any residual hum (which was virtually imperceptable in the first place) has disappeared after 10 or so hours of operation.

It's a great little amp!!!!

Author:  Simon Yuen [ 20 Mar 2009, 15:01 ]
Post subject:  Re: K-12G Tube Amp Kit Build Thoughts

Hi all,
After I read the reviews of the K-12 M/G Amp, I want to build one too. However I have a question about ordering the kit:

Each tube cost is $5 from Tube Depot (x4 =$20), and the power transformer around ~$15-20, 4 sockets ~$20, R+C+Connectors ~$30. So, the sub-total is around $90 before these two output transformers. Since the K-12 circuit already posted here, should I order the kit for $190 ?

For these two output transformers, I have no idea about their specification. From tube deport, I found few transformers cost from $60 to $260. If I buy two cheapest output transformers, they cost $120. So, in total, the parts are $210. In this case, it is better to buy a kit. Is this calculation correct?

Why these output transformers are so costly (they are relatively small transformers)? Can I replace them with other output transformer (let say the $150 one)? Any specification for the K-12 output transformers?

Thanks for reply.
Simon (A new DIYer)

Author:  Gio [ 20 Mar 2009, 17:41 ]
Post subject:  Re: K-12G Tube Amp Kit Build Thoughts

Plus the kits comes with a PCB so it is much easier to build compared to building it point to point. You need to pick the right transformer load and all the ones you mentions do not specify the load. The kit is a good value.

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