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Old 13th January 2013, 10:45 PM   #1
zilch99 is offline zilch99  United States
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Default first tube amp

since I'm new here i think I will buy a kit rather than build from scratch.
the model 16LS stereo amp kit I see over at tubedepot.com looks like a decent starting point. Anyone have some experience with this amp worth sharing?
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Old 14th January 2013, 04:58 PM   #2
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It looks like cheap fun to me.
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Old 14th January 2013, 07:00 PM   #3
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I'll grind my own axe and suggest an "El Cheapo" be built. Undoubtedly, it's more work than a complete kit, but the finished product is a much better performer.

Parts kits for "El Cheapo" are available from Jim McShane. You add a chassis and magnetics. Plenty of support for a 1st time builder is available from the "crowd", here.
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Old 14th January 2013, 08:00 PM   #4
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OK, I have to thank you Eli!

I built the "El Cheapo" (really just the topology using 5965/6P14P-EV tubes) into the carcass of an old Scott 299B and I just can't get over how great it sounds. Right now I am impatient for the clock to swing around to 6:00 so I can go listen to music. I haven't listened to PP (in my stereo system) in a decade.
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Old 14th January 2013, 08:21 PM   #5
GoatGuy is offline GoatGuy  United States
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All that symmetry leads to nice symmetric "conservation of distortions" ... which in turn keeps the music output harmonious. The amplifier works kind of the opposite of a "compressor", and emphasizes the excursions from zero more than the signals around zero. That emphasis in turn dovetails naturally well into the kind of lower-output-with-higher-amplitude-swing behavior of real-world speaker drivers. All in all? Sweet sounds!

The only thing I might do different would be to remove the high voltage rectifier tube, and replace with a pair of inductors and silicon high-PIV diodes. Somewhat higher voltage drive on the 12AQ5s ... a bit more power overall, and still well within the design point of every component. No need for a heater winding for it either - simplifying the transformer requirement.
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Old 14th January 2013, 08:48 PM   #6
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Quote:
Originally Posted by GoatGuy View Post
All that symmetry leads to nice symmetric "conservation of distortions" ... which in turn keeps the music output harmonious. The amplifier works kind of the opposite of a "compressor", and emphasizes the excursions from zero more than the signals around zero. That emphasis in turn dovetails naturally well into the kind of lower-output-with-higher-amplitude-swing behavior of real-world speaker drivers. All in all? Sweet sounds!

The only thing I might do different would be to remove the high voltage rectifier tube, and replace with a pair of inductors and silicon high-PIV diodes. Somewhat higher voltage drive on the 12AQ5s ... a bit more power overall, and still well within the design point of every component. No need for a heater winding for it either - simplifying the transformer requirement.
Look a bit more closely, please. The vacuum rectifier is in a low current B- supply. The B+ supply is "balls to the wall" and uses Greinacher doubler topology. "El Cheapo" is a low budget, but high performance, project.

The hybrid bridge in the B- supply was chosen as the most cost effective way to soft start that rail. The 'AL5 is "dirt cheap". It is highly undesirable for the 12AT7 grids to become positive with respect to the corresponding cathodes.
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Last edited by Eli Duttman; 14th January 2013 at 08:49 PM. Reason: punctuation
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Old 14th January 2013, 08:49 PM   #7
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Well, again, I used a Scott 299B as the foundation for this amplifier so the power supply is different from the "El Cheapo" and I used slightly different tubes. However, the inspiration for the topology definitely came from the "El Cheapo."
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Old 14th January 2013, 09:13 PM   #8
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Here, I will throw my suggestion into the ring and see what happens... I have my kit thinking cap on, so bear with me.

Might want to take a look at this one. If you are looking for something that sounds pretty darned good, easy to put together, low parts count with easy to get tubes, then the Budgie SE might be for you. It uses relatively cheap EL84 tubes, has a small footprint, a PCB (might be easier than point to point if you are without helping hands or the like) Edcor iron easily found and not that expensive, you can get everything including the Hammond box for the chassis on-line. It isn't a kit, but all the information is there that you can get the PCB, top plate, go to Mouser, tubestore.com (they are a sponsor here), and populate the boards.

It outputs a pretty good 3W of sound in single ended mode (though it sounds more than that when I heard my friend's one), has a headphone jack, volume pot, and has a small footprint. You can order a top plate for it too. diytube.com has pretty good support with it too.

Parks Audio - Budgie SE Amp

Add up all the component cost and see what suits you.


Then the other one that I would recommend is the Bob Latino ST70 kit, but only if you have the extra money to spend on the extra wattage you can get from that kit. It comes well detailed instructions.

tubes4hifi amplifier KITs page

And then there is the KT88 SE by member scott17.

KT88 SE Basic or Master Kit

I see him posting here and there and there has been some pretty good feedback on his builds. Plus check out some of his posts of builds because they look very nice. His is based on the Mikael Abdellah KT88 SE build from what I can gather (can switch between UL and triode mode and use a variety of tubes like the EL34, 6550, KT88, KT77, and I think the KT66 even). And it is also in kit form too.

Now, I will just prepare myself for the slings and arrows... but remember one thing -- enjoy it.
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Old 14th January 2013, 09:16 PM   #9
GoatGuy is offline GoatGuy  United States
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Originally Posted by Eli Duttman View Post
Look a bit more closely, please. ... It is highly undesirable for the 12AT7 grids to become positive with respect to the corresponding cathodes.
Oh well, yes, of course. There's always that slow-start requirement. The vacuum rectifier then, I would leave. The rest is hard to best. Especially the cool cathode-loaded inverter for push-pull operation, and the partially biased output tubes.

GoatGuy
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