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Wow! Inexpensive tube amp kit for newbies

post #1 of 217
Thread Starter 
I just ran across this very inexpensive tube integrated amp kit. Looks almost like the perfect kit for people wanting to take baby steps into tube DIY (almost like a tube version of the CMOY)... everything's included and there's a PCB so very little point-to-point wiring is needed:
http://www.web-tronics.com/sterintubamk.html

Plus more info here:
http://s5electronics.com/gpage1.html

8 watts for only $139, and you also get a free multimeter, so the cost is probably really only around $100. Not bad. I'm sure it doesn't sound incredibly wonderful, but I'm going to try it out just for fun, and I'll let you guys know how it sounds with both speakers and headphones.
post #2 of 217
That's pretty cool. I'm interested in a report. The kit looks pretty easy to follow.
post #3 of 217
8 watts? Sounds like a candidate for the K1000s. Anyone care to give it a shot?
post #4 of 217
It looks nice, but a beginner's kit without a case? Tubes run on dangerous voltages and I don't think it's a good idea to have everything out in the open like that, PCB or not. The instructions available for download don't have much in the way of warnings.

The tube used is "11MS8". It isn't one I know and there is no mention of it in usenet archives except in "for sale" listings.
It's not a lot of money to waste if it turns out to be junk, but I wouldn't be hoping for any miracles.

A better picture with more specs is here:

http://www.tubeaudio.com/page23.html

Oh yeah, and it's push-pull. That means you need carefully matched tubes to minimize crossover distortion - I bet you don't get matched tubes for $139.
post #5 of 217
Thread Starter 
Yeah, I'm not expecting miracles, or anything much really. But I haven't built anything electronic for about 10 years now, and for around $100 (I don't have a multimeter, so I like that aspect too) it seems like a neat baby steps project, and if I make mistakes or fry it by replacing the bridge rectifier with four FREDs I really won't mind. It's sort of like the CMOY/META42 thing. Everyone recommends starting with a CMOY with cheap parts before attempting a META.

As for the 11MS8, you might be surprised. Unpopular tubes are very easy and cheap to buy NOS and closely matched. I've bought a bunch of replacement pairs of 12SN7's for my Mapletree Line2m and the whole slew of them haven't cost me more than $25 total.

And with push-pull you tend to get better bass stability than some of the cheaper single-ended designs.

I love how the web page Aeberbach mentioned has a quote that says "Good bye Krell, hello S-5". Laughed out loud at that
post #6 of 217
Looks like a good canidate for tweeking.
post #7 of 217

comparison?

i don't know what i'm talking about, but perhaps someone here can point out the difference.

the foreplay preamp is an audiophile quality kit for only $10 more.

http://www.bottlehead.com/et/adobesp..._stage_kit.htm

i realize that's not quite the same thing, but i'm wondering if the foreplay could be easily modified into a good starter tube headphone amp, rather than trying to upgrade the web-tronics.

just a thought.
post #8 of 217
Thread Starter 
I think the Foreplay primarily does voltage gain; it probably doesn't produce enough current to power any headphones. Everyone says it's a good preamp though, especially with all the upgrades. I think the best deal for a DIY tube headphone amp is probably the Mapletree Ear at $275, plus it apparently drives Grados really well, and has a preamp out to boot.
post #9 of 217
(it's worth the extra $50 to get the Mapletree Ear+)
post #10 of 217
Hmmm, anyone want to take the plunge?
post #11 of 217
Thread Starter 
Quote:
Originally posted by andrzejpw
Hmmm, anyone want to take the plunge?
I just ordered a kit today. Might have time to assemble it by the middle of next week, hopefully. They not only threw in the digital multimeter, but also a free set of screwdrivers. Don't know why, it didn't say anything about the screwdrivers on the website.
post #12 of 217
Check out the thread at Headwize about this amp. PRR mentioned that you can "simply break the traces to Pins 7 and strap 7 to 6. Instant Triode." You will be down to 3-4 Watts, but everyone likes triodes, right .
post #13 of 217
Thread Starter 
The nice UPS lady delivered the kit to my door earlier today. It looks great for something so inexpensive. The parts don't seem to be chintzy -- the power transformers weigh about 15 lbs, the caps are by Samsung, and the RCA jacks are gold plated.

The tubes are NOS Japan, and the base is 3/4 inch solid wood. The kit also came with a free multimeter, with batteries included -- nice touch. The guys at Web-tronics also threw in a set of free screwdrivers.

Here's a picture of the kit contents, in case anyone's interested:
post #14 of 217
Thread Starter 
Finished building the kit! Total construction time was just under six hours. The PCB makes it very easy for a beginner.

Looks absolutely gorgeous in the dark:
post #15 of 217
So, how does it sound?
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