Hi guys, I am Ben from Holland and I am totally hooked on tube amps. I have a cheap Chinese amp, the Hlly MK-II which implies the 6N2 as the pre amp for both channels and the 6P1 as output tetrode. It sounds ok, I suppose. I have the DIY-K-16LS from tube depot as well and it sounds so much better. So now I wanna build a real one, probably implying two KT88 in push pull ultralinear. Is it possible to let my kit run ultralinear, just by exchanging the output transformers and connecting the ultra linear tap to the screen grids? Just to let you guys know, I have like zero experience with tubes even though I do electronics as a hobby ll my live. One more question, my kit uses on the power transformers primery about 200 volts. Since I live in Holland, I have 220 volts standard, can't I just rectify the outlet power and use it directly to power the anodes? 220 volt instead of 200? Should work fine, or is there a different reason to keep the anodes away from the outlet current? Does anyone have any experience with this kit? Please let me know before I blow shit up. Greetings, Ben.

Hi Ben,

If you own the 240Volts version you surely can supply it with the 220Volts from your plug. Then the amp only should have less output power. Don't play with rectifiers on the mains voltage. That's not a good idea.

Well considering there are certainly much worse things one could be hooked on!


Using mains power without an isolation transformer is not safe practice and we do not condone unsafe practice.

Take a look at Bruce's conversion of the K-12M Tube Amp Kit to ultra-liner mode.

Cheers and welcome to the forum.

Well guys, to answer my own question, the amp runs fine on rectified outlet power, no change in sound, no hum nothing different, just thatit gives me the opportunity to eliminate the power transformer and use a small transformer just for the heaters. I am not gonna do it, just wanted to know if it works and it does. And in my humble opinion is outlet power, after it's fused, almost as save. Studying Bruce's modifications on his kit, i don't quite understand how he wired the output transformers ultralinear. He said he had to cut the power to the shield grids and reroute the power to the driver tube sections. First of all, (for beginners) which pin on the 6005 is the screen grid. After I know which pin is the screen grid, I can cut the traces close to the tubes and wire the ultralinear tap from the new output transformers directly to the screen grids, I can do that. But to where do I have to connect the trace to the grid I just cut? Reroute the power to the driver tube sections? That I don't know, maybe somebody can help me out. Thanks.

We know it can work - the issue is that it is not safe as the line voltage could appear between the ground and signal source should the hot and neutral be reversed.

I am for safety first, ok. I just saw some amps around without a power transformer and I wondered how it can be, now I know. Plus I am quite used to high voltages building radio transmitters. I just never went into tube amps till resiliently. Now I am sitting at home dieing of AIDS, no joke, building tube amps and trying to distract myself as much as I can. Sorry, that is a bit personal, but because of all of this I am not really afraid of anything anymore, including electric shocks. But thank you for you advice, I am not gonna electrocute myself nor my spouse or my cat, I promise. All I want to do is to learn as much as possible as fast as possible about vacuum tubes because I know my time is short Greetings, Ben.

Hey Ben, I don't have a schematic for the K-16. Any chance you could post it?

My - I would keep the K-16 as is. I don't think the iron is the limitation on this amp. Putting the money into another amp seems to make more sense than replacing the existing iron. That way you will have two amps as opposed to one with no use for the K-16 output transformers. Of course you won't be able to build a new amp for only $150.

BTW - would you happen to have a scope? I'd like to see some waveforms of the K-16. Bruce's measurements of the S-5 Electronics K-8LS Tube Amp were not too positive.

Cheers

Well, I do have a software scope using my laptops sound card and I use a second laptop as signal generator. I did that, I just wasn't smart enough to take screen shots for you guys, but I will repeat all of this and share it. I will do that today since the kit is still absolutely stock, so I have some references once I start changing things around. BTW I believe that on my output tubes the shield grid is internally connected to the cathode, so no way for me to access the shield grid, so no way for me to make that an ultralinear amp. I am really new to all of this and I really, really hope I am wrong. It uses the 6005 as output tubes, I have the pinout, it's french, but the pics are understandable, I suppose. I'll post the pdf, if anyone wants to look at it. Greetings from Holland, Ben.

hi Ben, here is an English datasheet: http://frank.pocnet.net/sheets/093/6/6005.pdf

I'm thinking that ultra-linear operation will not be trivial.

Yeah I was afraid of that. The cathode and the shield screen are internally connected, so no way for me to connect the 40 % ultra linear tap, right? Well, the amp does sound pretty good just the way it is. Cheers