Hi guys,

so here are some test results on the K-16LS kit amplifier. First of all, I don't have a real scope, I only have a software scope which utilizes the sound card with all it's limitations. The same softwarescope I run from a second laptop as signal generator, which isn't perfect either, but nothing really is. Anyway, that is the best I can do right now. Any suggestions are very welcome, I try to learn something new every day.

The amp has been great so far. It is definitive my best sounding amp. I really love it. I attach some pics of my setup and the screen shots.

some more pics

Here come the square wave test results. I hope that helps. Kind regards, Ben.

I hope that helps. I will repeat those test and maybe some more and better ones on my cheap chinese of the shelf amp very soon, but for now my spouse has reclaimed her laptop, so no more testing for me tonight. It's 10pm where I life.

BTW I conducted experiments with a light bulb for cars with 2 glow wires which of one has to be broken. That gives you a home made vacuum tube diode that actually works. If anybody is interested, I will post the pics of the setup. You can listen to your local AM station using such a device as a rectifier. Cheers, Ben

Hey Ben - what are the green and red traces on the plots? Also, did you put a load on the amp?

Hallo, the red trace is the left channel and the other color is the right channel. And of course I put a 8 Ohm load on it, don,t have no 4 ohm speakers. Greetings from Holland.

Hey Ben, just work with one side of the amp at a time. Use one channel of your scope to monitor the input from the signal generator and the other channel of the scope to monitor the output from the amp. That way you can compare the input wave to the output. It could be that the input singal from the generator is not good to begin with. Don't be surprised if the sound card produces poor low and high frequency waves.
Cheers

Hallo everybody,

sorry guys, that all is pretty new to me, I should have posted the source wave form as well. My sound card doe an excellent job till about 4,5 kHz. I tried to use jst one computer channel for channel, somehow that doesn't work for me, maybe I do something wrong, but the setup with two computers works pretty good. I will post screen shots of the source waveform, just not now, because it's like 2 AM where I live.
The amp is standing on my desk, driving 2 Bose 201 series III speakers just fine. Those Bose speakers aren't really loud, I don't know how many DB 1 watt 1 meter, but the amp has sufficient power to really piss of the neighbors.

Now I have to wait a couple of weeks, (funds are an issue) then I will order from Edcor the CXPP25-MS-8K output transformer and exchange all the caps ( I don't know which ones to use, yet, please guys, help me out) and wire my amp ultralinear, put it into a nice enclosure and move on to the next tube amp project. I'm hooked now, haha, my spouse already hates tubes, I don't blame her.

Hallo everybody,

now it's time to take a more critical look at my amp. Here are some things about it I don't like. The anode voltage on my pre amp tubes 5670 is on my left channel 14 volts higher than on my right channel, which is probably just the tolerance from the resistors, but I will fix that, of course.

The potentiometer for the volume control is pretty shitty, too, since when you try to listen really quiet, the left channel starts ca. 1 mm before the right channel. I will fix that, too.

Since I have 8 power tubes and a friend with a tube tester, I will try to match my tubes a bit so they work good in pairs. Worth a try.

The only modification so far is that I painted the bread board flat black with school board paint (black board paint). Looks good. Not my idea, got that from Bruce. (Will post a picture)

Guys, what capacitors should I use and where can I get those? Remember, I live in Holland.

Anyway, the amp has been great so far, I would definitely purchase it again. Now I wanna wait how it sounds ultralinear with new output transformers and then I will duplicate it, but without PC board, just point to point.

Hi, Just my 2 cents here. I have had excellent results with ALPs Blue variable resistors and would recommend them to anyone. Second the caps, this is always a matter of personal choice. Sort of like ice cream, do you prefer vanilla or chocolate? My personal favorites are Auricaps, Russian K40Y9, and Jantzen Standard Z caps. They are widely available. Good modest priced alternatives are WIMA, Sprague (now CDE corp), Parts Express own brand of audio caps, and Solen. You can spend more and get others, but it is probably not cost effective on the K-16. I only use the first three types in signal paths in my designs. The others I often use in power supply applications. Hope this helps.

Good listening
Bruce