DIY Audio Projects Forum
http://diyaudioprojects.com/Forum/

Newbie checking in, K-12G pics.
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=1546
Page 2 of 8

Author:  Cold Macaroni [ 25 Jun 2010, 23:56 ]
Post subject:  Re: Newbie checking in, K-12G pics.

Cold Macaroni wrote:
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.

I take that back. Now that I've had a little time to think about it, I probably wouldn't replace the output transformers if I did it again. The Edcor units are well made and improved the performance of the amp, however with the music I want to listen to at the volume levels I sometimes enjoy, the amp is less usable now for me. I think if I listened to primarily acoustic or mellower music I would do it the same way, but the truth is that although the bass range is extended (going off of the information posted above), now it's harder to listen to the music I like the way I like to. Some more efficient speakers might help balance everything out for me, but those are a few projects out.

I'm still happy with it, and I like the way it sounds, but I feel like I'm limited. Take it for whats it's worth.

Nigel

Author:  Bennybuis [ 26 Jun 2010, 09:43 ]
Post subject:  Re: Newbie checking in, K-12G pics.

Hi Cold Macaroni,

and welcome to the forum. Great that you found the love for tubes, for me it was the k16 kit, that got me started and now I live in tubes and cables and transformers, haha, so watch out, whatever you just started is very much addictive and expensive. I started about 10 month ago, and now, I must have built more than 20 amplifiers, I am serious. I have the OddWatt amp as well, my primary reference amplifier, this baby is the absolute best, hard to beat. Thanks Bruce for making this possible for all of us. You are going to have a lot of fun. Enjoy the music!

Author:  Gio [ 27 Jun 2010, 08:30 ]
Post subject:  Re: Newbie checking in, K-12G pics.

Very nice looking enclosure work. :up:
Cheers

Author:  mwhouston [ 29 Jun 2010, 04:09 ]
Post subject:  Re: Newbie checking in, K-12G pics.

Cold Macaroni wrote:
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.

Double the PS filtering caps. Worked for me.

By the way, love the chassis paint job. Tell me you did it!!!

Author:  Cold Macaroni [ 29 Jun 2010, 07:03 ]
Post subject:  Re: Newbie checking in, K-12G pics.

mwhouston wrote:
Double the PS filtering caps. Worked for me.

By the way, love the chassis paint job. Tell me you did it!!!

I'll give that a shot this weekend if I can get my hands on the caps this week.

As far as the chassis, no paint, that's acrylic! I wanted to build a chassis for this amp, but I'm in a small apartment and limited on tools. I was cruising through tubelab and saw his lexan work and it got me thinking. I've worked with lexan before, and it doesn't have the characteristics I would like for this (it's a little soft and I would need a saw), but I was pretty sure I could find some plexiglass or acrylic locally (I know a BIG arts and crafts store). At anyrate, I scored and snapped the acrylic to size, used some pieces of L channel pine that I happened to have sitting around as brackets. I picked up a pin vise for cheap and used it to run pilot holes and I hand-turned a step-drill bit to cut them to size.... well, once my hands started getting raw and after counting how many holes I had left, I broke down and bought a power drill (though I still used the pin-vise for the pilot holes, I much prefer at least starting my pilot holes by hand, I find it to be far more accurate). The acrylic was covered on both sides with protective plastic sheeting that turned out to be pretty tough. I wasn't very gentle, but when I finally exposed the acrylic I couldn't find a single scratch. If you were stubborn enough, you could build a case like this using only simple hand tools, but I recommend a power drill for that many holes.

edit: We'll see how the acrylic does with the heat from the transformers and the tubes. I took the amp apart the other day to add a brace in the rear to keep the top piece from sagging under the transformers and I noticed very slight but uniform warping around the tube sockets. Just like with cars, mirror-black might look cool, but it shows off every sin.

Author:  mwhouston [ 29 Jun 2010, 08:54 ]
Post subject:  Re: Newbie checking in, K-12G pics.

It certainly looks shiney.

Author:  cheap-Jack [ 29 Jun 2010, 12:24 ]
Post subject:  Re: Newbie checking in, K-12G pics.

Cold Macaroni wrote:
mwhouston wrote:Double the PS filtering caps.

Hi.

Yes, the weakest part of the whole kit is the PS - sand rectifiers+CRC. For class A is OK, but for class AB PP for the kit where current loads chnanges with the O/P power, the simple basic CRC can't handle the current load fluncation. Aslo please note the screen voltage (Vg2) of the O/P power tube must be kept constant to its cathode voltage at all time. The simple stock CRC filter bank can't handle that neither.

I would spend bucks on the most important upgrade, not on something else less critical, e.g. exotic caps & brandname O/P irons, but to modify the CRC filter bank to CLCRC by adding a fitler choke/input cap. The choke due to its high AC rippling reactance & low DCR, will serve as a sorta voltage stabilzer to smooth out current load fluctuation caused by class AB PP operation as much as possible.

Don't forget to add a sand diode as HV stopper diode to each drive stage & powerstage to help minimize HV voltage changes.

A simple filter choke can save building a more complex active HV regulator, which no newbie wants to touch.

Also, don't forge to add a C/R RFI snubber upstream of the sand bridge rectifier which will emit ringing RF noises into the amp.

c-J

PS: that said, I always install a shunt current HV regulator plus HV stopper diodes for my tube projects, power amps/phonostages

Author:  Cold Macaroni [ 31 Jul 2010, 05:47 ]
Post subject:  Re: Newbie checking in, K-12G pics.

After playing around with PSUD2 I came up with a better power supply that I could put together without too much trouble. I built it on a separate board: 1n4007 diode bridge, 3 330uf caps and two 100R resistors.

I've only been listening to it for about 2 hours now, but I'm much happier. There's far less clipping (though I can still hear some with the volume up on some of the hard rock songs on my playlist). The amp seems to have a better handle on the bass, though it's still a bit flabby in more extreme cases.

I'm very happy with the amp right now. Part of that is the new power supply, but I also rearranged my living room so that I'm actually in front of the speakers for most of my time. Before, my computer desk was off to the side of the speakers (where I spend most of my time), as was the kitchen area (where I sometimes spend a lot of time). Now both are lined up with the speakers. As an extra bonus, my desk is now right under the AC. PLUS I've been stuck listening to my laptop speakers or the TV speakers for the last few days while the amp was down... so I'm pretty happy right now (4-day weekend too, woohoo!!)

I'm still planning on an SE KT120 amp in the nearish future, I'm just waiting on some software that's still in the mail before I pull the trigger on that one.

Author:  mwhouston [ 31 Jul 2010, 05:59 ]
Post subject:  Re: Newbie checking in, K-12G pics.

Cold Macaroni wrote:
After playing around with PSUD2 I came up with a better power supply that I could put together without too much trouble. I built it on a separate board: 1n4007 diode bridge, 3 330uf caps and two 100R resistors.

I've only been listening to it for about 2 hours now, but I'm much happier. There's far less clipping (though I can still hear some with the volume up on some of the hard rock songs on my playlist). The amp seems to have a better handle on the bass, though it's still a bit flabby in more extreme cases.

I'm very happy with the amp right now. Part of that is the new power supply, but I also rearranged my living room so that I'm actually in front of the speakers for most of my time. Before, my computer desk was off to the side of the speakers (where I spend most of my time), as was the kitchen area (where I sometimes spend a lot of time). Now both are lined up with the speakers. As an extra bonus, my desk is now right under the AC. PLUS I've been stuck listening to my laptop speakers or the TV speakers for the last few days while the amp was down... so I'm pretty happy right now (4-day weekend too, woohoo!!)

I'm still planning on an SE KT120 amp in the nearish future, I'm just waiting on some software that's still in the mail before I pull the trigger on that one.

Tubes, software-that does not compute!!

Author:  Cold Macaroni [ 31 Jul 2010, 06:10 ]
Post subject:  Re: Newbie checking in, K-12G pics.

I ordered a copy of SE amp CAD. I thought I'd play with it a little before I started building.

I took some pics of the electronics market I went to for the parts, check it out

Page 2 of 8 All times are UTC - 6 hours [ DST ]
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/