• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Tube Amp Kit Suggestions

I am thinking of buying a cheap kit to start with for practice on leaning more about how these what I consider wonderful sounding amps are built. Any suggestions on cheap beginner kits would be much appreciated. I can read all day but need to solder and conect to learn, at least that is my therory.
thanks in advance JOHN
 

tinitus

diyAudio Moderator R.I.P.
2005-11-24 1:47 am
This one looks nice too, but only max 4watt...I dont think it has been around long enough to have any rewievs here, assembled and tested board

http://www.engineeringvista.com/audio/AudioKits/Model-1/pictures_m1.htm

Maybe a bit more difficult, cant say but I think it looks nice, complete kit

http://gabevee.tripod.com/cgv0606.html

And the obvious choice, but no kit

http://www.tubelab.com/SimpleSE.htm

And this sweet thing, seems to be a complete kit

http://www.hawthorneaudio.com/spud_kit.htm

http://pages.prodigy.net/jimmcshane/citpage.htm#parts.htm
http://pages.prodigy.net/jimmcshane/elcheapo.htm
 
Hi John, There is another similar thread on this subject in this section. The K-12 is a good performer for the price. As a first time kit it is pretty easy to build a working amp. As was noted, it is without a case and depending on your situation this is a potentially serious problem. Hot tubes and exposed voltages are not kid or spouse friendly (could be a problem for house pets too). Welcome to the tube family.
Bruce
 
Amps

Thanks Bruce and everyone for the leads on some projects to look into. I have a few tube amps that I am currently using, and some that need work. Have a pair of Bogen 110's that are hooked to a pair of KLHs that sound so sweet it is unreal.
I have a larger setup consisting of pair of Dynaco MK IVs driving Bozak symps B-4000s. And I just love lps, the blues grew up with the blues playin listening just enjoyin.
BUT.... i have no working knowledge of amps dont do my own repairs and have yet to find a decent small scale repair person who I can use, so I feel it is time to learn. Start slow see how it goes. Anyone want to kick around some ideas feel free, I cant use private messaging yet because I am new to group so cant get into any detail questions yet.
Enjoy, JOHN
 
Hi All, I routinely use wood and plexiglas for chassis and have no problems. I generally use a heavy gage central ground buss wire to avoid problems. I keep connections to it as short and direct as possible. I have tried two methods of connecting the buss. One at the input side of the amp and alternatively at the the main power supply ground. Both have worked well for me. None of my current amps including the present P-P KT77, has over 1 millivolt of hum or noise at the speaker outputs.

I have discovered a problem with non-metal chassis in the past. You can not place them near something that generates EMI. I had one on a top shelf (near the ceiling) and it picked up the noise and hum from the heat tapes ( I have radiant heat). Also they will pick up TV generated interference if too close to a TV.

I find it a bigger problem with ground loops in metal chassis. Even with care they can crop up. I isolate my audio circuity from the case if it is metal for just such a reason.
 
Hi, My K-12 is in a metal case (actually one from S-5). I did have some hum issues at first with it, but after isolating everything but the power transformer from the case, they went away. Since then all my amps are in wood cases. Plus I personally think that wood visually matches the warm sound of the amps.

If you run out of ideas on where to get chassis and such, check out the kitchen sections of most big department stores. I regularly use "kitchen" organizers and have some copper rectangular baskets that with a bit of trimming make great tube covers. I tried to paste an image of the early chassis of my newest project, but it doesn't seem to load properly. You can see it on another forum (diyaudioprojects.com) if you want.

Good luck with your project
 
Hi all,

IMHO the hum issues are not caused primarily by lack of shielding.
The main source is the PSU, which needs to be modified. Shottky diodes and a choke or a CRC network will do the trick. I think most of the hum is caused by ripple current. Keep in mind that the PP output stage is not completely symmetrical since the tubes share a common cathode resistor and there is no way to set the idle current through each tube individually. Elevating the heater ground may help, too. I got my AES kit very quiet this way (there is a very low hum present when pushing your ear right into the speaker).
I do not see a problem with a hardwood case, since my modified kit was already very quiet without any case at all.
Although there is definitely a lot of room for improvement those kits already sound very nice in the stock configuration. And once its working it is a lot of fun to tweak.
Even if I ended up spending quite some money for modifications - the learning experience was definitely worth it.

Martin
 
bayermar said:
Hi all,

IMHO the hum issues are not caused primarily by lack of shielding.
The main source is the PSU, which needs to be modified. Shottky diodes and a choke or a CRC network will do the trick. I think most of the hum is caused by ripple current. Keep in mind that the PP output stage is not completely symmetrical since the tubes share a common cathode resistor and there is no way to set the idle current through each tube individually. Elevating the heater ground may help, too. I got my AES kit very quiet this way (there is a very low hum present when pushing your ear right into the speaker).
I do not see a problem with a hardwood case, since my modified kit was already very quiet without any case at all.
Although there is definitely a lot of room for improvement those kits already sound very nice in the stock configuration. And once its working it is a lot of fun to tweak.
Even if I ended up spending quite some money for modifications - the learning experience was definitely worth it.

Martin


I always us PI filters in my valve pre amps.

One unexpected source of HF noise in my tweeters was the 1N5408 switching pulse. I had to put a 100nf across the transformer to kill this.