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Small SE tube amplifier using 12B4A and ECC802S
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Author:  Bennybuis [ 10 Jan 2010, 16:02 ]
Post subject:  Re: Small SE tube amplifier using 12B4A and ECC802S

Well Magnus, too late, I already stuffed it with components. It is running, no css, but resistor and cap, will change later. 12B4A does sound wonderful, really, and the little amp is quite loud as well, I am happy. :) It is standin on it's place doing good. Tomor.row I will button it up and start something else, who knows. I got more cigar boxes....... :D

Author:  azazello [ 10 Jan 2010, 18:14 ]
Post subject:  Re: Small SE tube amplifier using 12B4A and ECC802S

Ben!
Try to change all cathods caps to Rubycon, Nichicon, Elna the same value but low U, 35 or 50 v !
You will wonder to sound!

Author:  Bennybuis [ 10 Jan 2010, 18:38 ]
Post subject:  Re: Small SE tube amplifier using 12B4A and ECC802S

Hi Nikola,

maybe I will, but I still wanna change to ccs, I just didn't have the LM317 in house and it is Sunday. If I was to keep the current setup, I would add a 0,1 uF cap poly parallel to the 47 uF caps as well. But tomorrow morning I will get some LM317 and the right ccs resistors and change the amp to ccs. That always does imprve sound quality a lot.

Nonetheless, the little amp does sound very very god for what it is, and it didn't cost much, did I get the 12B4Afrom Magnus, same thing applies to the output transformers. Only thing to remember, if you wanna build this good sounding small amplifier, I don't get enough gain out of the EEC 802S, so I rolled tubes for the ECC83 from Magnus, and that fixed the problem entirely. Now I love my little amplifier. The combination wood and gold just does something to me, it gives it the retro thermionic sphere, I am so addicted to. The 12B4A kind of light up bright and really improve the looks of any amplifier.

Author:  Bennybuis [ 11 Jan 2010, 15:30 ]
Post subject:  Re: Small SE tube amplifier using 12B4A and ECC802S

Hallo everybody,

I took my little amp to my friends store and had it on Altec Valencias. Wow, that little amplifier really rocks. My friend asked me to build one for him. Here starts my dilemma. Now I cannot duplicate it, because I don't know what output transformers those really are, they just happen to work good with the 12B4A for whatever reason. And my amplifier is of course NOT FOR SALE :)

Author:  Soundbrigade [ 11 Jan 2010, 16:01 ]
Post subject:  Re: Small SE tube amplifier using 12B4A and ECC802S

If it was the trannies I sent you, I can send you more.

Author:  azazello [ 11 Jan 2010, 17:01 ]
Post subject:  Re: Small SE tube amplifier using 12B4A and ECC802S

BEN! Now You just know what is the really good sound from triode conception!!
Congratulations!!!
/I don't like parallel big and small caps on cathode, this is not good idea...this disturbs voices in music...put
100-1000 uF Black Gate, ELNA, Rubicon, Nichicon, they are fast in HF/.

Author:  Gio [ 11 Jan 2010, 23:32 ]
Post subject:  Re: Small SE tube amplifier using 12B4A and ECC802S

Very nice work Ben! :up: Let us know how you make out with the CCS.
Cheers

Author:  Bennybuis [ 12 Jan 2010, 03:11 ]
Post subject:  Re: Small SE tube amplifier using 12B4A and ECC802S

Thanks Gio,


that little thing is without doubt the best amplifier I build so far. Actually I am listening to your DVD's with my headphones on right now enjoying that little thing.
I am quite pleased with it, also my wiring gets better each time, but I knew that. My first PC-boards were terrible, too, but they did work. Very son I will build your OddWatt kit, just that I will build mine without kit :) . I got a matched quad of KT88 I have been saving for when I am grown up enough to build that amp. I think I can do that now, will order a power transformer today and a nice and big Hammond enclosure. Or I will build my GU 50 amp first, but it will be also the OddWatt design, so no big difference. I will probably do that, so I am perfect in laying out my KT88 amp, having had experience with the GU50 amplifier. I got more amps than speakers already (not true, but I am definitely getting there) :smoking:

Author:  Bennybuis [ 13 Jan 2010, 15:21 ]
Post subject:  Re: Small SE tube amplifier using 12B4A and ECC802S

Hallo everybody,

today I cleaned up my little amp, exchanged the parts that weren't really right, like 200 ohm where it should have been 120 a.s.o. I also removed the cap and resistor from the cathode and replaced that assembly w3ith a LM317 and 50 ohm resistor CCS. Now I have exact 200 mA current at all times and a even better amp. It did loose a bit of the goowee tube sound, that is normal, but the bass response is better, the frequency range never suffers from such a upgrade either. I am totally convinced that that is the way to go. Here are the pics final under the hood. Only thing missing on the picture is the headphone jack I just added. That is also a killer headphone amp, really. That little thing really rocks. Idid all the little improvements, like grounding the filament circuitry with 0,01 uF respectively to ground, that made it even more quiet. Now I think it is as good as it gets, I am very happy, I can only advice everybody to build this little amplifier, it rocks and is quite loud, pure triode sound. Why is the little amp so loud?: No idea. I have no way of measuring power, but it cannot be more than maybe 1 watt or 1,5 watts, if you do the mathematics. It has to do with the damping factor, I suppose, whatever that may be.......

Author:  Bennybuis [ 13 Jan 2010, 16:26 ]
Post subject:  Re: Small SE tube amplifier using 12B4A and ECC802S

Hallo everybody,


well everything back to where it was, LM317 out, cap and resistor back in. And here is why. My home made power supply works perfect, supplying my little amp with a bit more than 200 volt B+. The LM317 use so much current on their own, that my B+ drops to about 105 volts, not enough to make this amp fly. I fed it power from an external source and the LM317 definitely works, good, too. But I don't want to change transformers on that little amp, so I change everything back to0 where it was and close the lid and call it a day. :) Nothing is perfect, and I like it just the way it was with cap and resistor. It should be 820 ohm, was 750 ohm (two 1,5 k resistors parallel, now it is exactly 800 ohm, so good enough for me. I will redraw the schematic just the way I build the amp now and post it with all the little changes, like no NFB at all. But now I have to solder a bit.....

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