DIY Audio Projects Forum

Newbie checking in, K-12G pics.
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Author:  Cold Macaroni [ 18 Feb 2010, 06:06 ]
Post subject:  Newbie checking in, K-12G pics.

I recently finished a S-5 Electronics K-12G tube amp kit, and since I spent so much time browsing through the project pages and forum before I bought the kit and while I was building it, I thought I'd better register and say thanks.

I'm no audiophile but I'm pretty happy with the results of the kit. To tell the truth, for me (and some of you I assume), projects are at least as much about the planning and building than the actual result... if not MORE. However, It doesn't hurt when something you built yourself actually works when you're done.

I put the kit together bone stock to start with, but I knew the bug would hit me soon enough, so I preempted it and started looking for some of the stuff I'd need for the upgrades I've read here and on Voltseconds page. I have to tell you, finding Auricaps here in Korea wasn't easy. I did eventually find a small audio shop that helped me out. Getting the rest of the caps etc was a chore. There's an awesome electronic components market here (huge), but I'm not exactly fluent in Korean (I can order food... that's about it), and I barely knew what I was talking about. It was way too much for me to deal with. I had to make more than a few trips back there, knowing slightly more about what I was talking about than the time before.

At anyrate, I put everything back together this evening, and holy-crap it still worked. I was pretty happy with the sound before, but this is definitely clearer. The low end still seems a little imprecise, but man do vocals and acoustic stuff sound GREAT. I pulled most of my harder punk off of my playlist for now in favor of some somewhat softer more melodic stuff. This is my first DIY electronics project and my first tube amp, but I think I'm sold.

Thanks again to everyone here at and VoltSecond for the information.

Enough rambling... on to the pics!!

Author:  Gio [ 18 Feb 2010, 13:47 ]
Post subject:  Re: Newbie checking in, K-12G pics.

Welcome to the forum and thanks for sharing the photos of your build! Glad to hear you are enjoying the amp! It is a fun kit. Most of my projects spend a lot of time in the planning and parts acquisition phase. Yes, get a handle on ordering food and beer first and then move onto parts hunting.
Nice idea with the "pin" file. :idea:

Author:  gofar99 [ 18 Feb 2010, 20:50 ]
Post subject:  Re: Newbie checking in, K-12G pics.

Hi And welcome to the forum. The Auricaps made the most significant improvement in mine followed by the various power supply mods. I used hammond ultra linear transformers and they did make it better, but now I would probably opt for some others by Edcor. The amps are IMHO generally nice sounding, but your thoughts on the bass echo mine. OK, but not as clean or deep as other amps. But then the price is hard to beat.

Good listening

Author:  Cold Macaroni [ 19 Feb 2010, 02:58 ]
Post subject:  Re: Newbie checking in, K-12G pics.

I think my next step will indeed be some new transformers, both power and output. I could probably leave the power transformer alone, except they're on 220 here, and I'd like to be able to plug it into a regular socket instead of the giant converter box under my desk. That means I have to start learning about transformers and their specs. I noticed more than a few places down in that electronics market area that specialized in (probably custom wound) power transformers... which means I'll have to know exactly what I need, and why, when I go down there. Then again the guy I picked up the Auricaps from might have some stuff I can grab too... we'll see.

Bruce, where in AZ are you? I actually grew up in Bisbee, lived in Tucson for a few years (college).


Author:  Cold Macaroni [ 25 Jun 2010, 02:11 ]
Post subject:  Update

My Edcor transformers finally showed up. I'm sure I could have sourced some transformers locally, but I wasn't confident enough to try and get what I needed here. At anyrate, they went in and I decided it was finally time to build a case. A couple trips to the store and one long weekend later...

Author:  rock4016 [ 25 Jun 2010, 10:21 ]
Post subject:  Re: Newbie checking in, K-12G pics.


How does it sound with the new Edcor Iron? Is the bass better??

Inquiring minds want to know!

Author:  Cold Macaroni [ 25 Jun 2010, 10:43 ]
Post subject:  Re: Newbie checking in, K-12G pics.

The bass is improved, however I'm finding that when I try to crank the volume past normal listening levels, the sound starts to distort. First in the low bass and then in punchy mids. I'm pretty new to this whole game, so I don't know the right nomenclature or exactly how to describe things. To use a lawn based simile, it sounds like someone cut the tops off all the high-grass. The simple solution is to just not turn it up that high, and that's how I'll solve it for now. I'm guess those are just the limits of this design. I've made some upgrades to the capacitors (now I've also bipassed the coupling caps and the pot) and I suppose I could have screwed things up somehow, but overall I'm still happy with the amp and my new tang-band speakers.

Author:  rock4016 [ 25 Jun 2010, 11:11 ]
Post subject:  Re: Newbie checking in, K-12G pics.

Yeah, that circuit does not have a lot of clean power... Your description is right on the money! That's compression, it's what tube amps do when they run out of steam, it's much more pleasent sounding than what other designs do on the onset of "clipping"

Essentially the plate of the output tube becomes saturated with electrons and when happens no more can be absorbed (the bucket is full so to speak)then output signal is compressed.

Author:  gofar99 [ 25 Jun 2010, 12:17 ]
Post subject:  Re: Newbie checking in, K-12G pics.

Hi, The effect you noticed is rather common. When you extend the response of an amplifier - particularly in to the bass region it may seem like it has less overall power. Actually it is normally quite the same as before, you are just using some of it in a frequency range that had little or nothing before. The sum is about the same. I am glad to see you found the Auricaps as they made the most improvement in my K-12. A good first time project. Now that the bug has bitten you .... what is next?

Good listening

Author:  Cold Macaroni [ 25 Jun 2010, 18:59 ]
Post subject:  Re: Newbie checking in, K-12G pics.

It's good to know it wasn't user error. The Auricaps definitely made the biggest difference of any changes I made to it (I also did some of voltsecond's mods), and if I did everything over again I would probably only replace the capacitors, and maybe the transformers.

As far as what's next ;) First I need a source selector and volume control. I'm getting tired of changing input cables when I decide to watch a movie, or listen to music, or hook my computer up, or xbox or whatever. I found a DIY Hi-Fi place in Seoul that has a nice looking remote control source selector/volume kit that I'm thinking about modifying for use with a Lighter Note kit, but I'm having trouble sourcing a 3-gang 1K motion-controled pot. I only need a 2-gang pot for the lighter note, but I have some other plans that would make use of the third gang.

After that, I'm looking into scratch-building a set of odd-blocks and trying out the different KT- tubes. I'm going to wait and see what kind of listening impressions the KT-120s give, and what kind of circuit design changes are needed for them. I was thinking really hard about a SE 300B design, but I don't think I'm quite ready to appreciate one of those yet.

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