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AJT 15th July 2012 09:34 AM

My Russian SET
 
Hi, now it can be told.... ;D

the inspiration for building this amp came from this page: 6C33C-B SE Verstaerker von Juergen Buschmann

as i am one who is not a true copycat in the strictest sense, i made some deviations from the original design, first, i will use fixed biasing, fuses are installed to limit current should the 6C33 tubes decide to run-away, i am confident it will not happen, i did a prior burnin-in of the tubes as per recommendations of the fellows at diy-audio....second is the use of diodes for biasing the cathodes of the 6P15P voltage amp tube, my experience with Broskie's CCDA preamps using diode biasing has been very encouraging that i only use resistor/capacitor cathode bias combo in my guitar amps exclusively....and i am not turning back on that....


so, this is to document construction of the Russian 6C33C SET amp.

It starts with building a set of power traffos and common mode chokes and a pair of OPT's or output transformers capable of about 10watts into 8ohm loads....
i chose a core with center leg of 1.5 inches stacked to 2 inches, the traffo is butt joint with a suitable gapping material of about 0.5mm. the mass of the traffo core was chosen so that core saturation at low frequencies are mitigated. Turns ratio of the OPT is 10, with an rp of 150 ohms, our plate load needs to be 300ohms for maximum power output, but since i am not after maximum power output, i opted for a 600:6ohm OPT, so that with an 8 ohm speaker, the reflected load is 800ohms, very easy for the 6C33 plate, a 4ohm speaker otoh reflects a 400 ohms load to the plate of the 6C33 so that is still greater than 300ohms...

Aanyway real speakers are not constant 8ohms no matter how the manufacter tell us it is so...so it is easy for you to guess why the choice of the 6C33, simply put, design and building of output traffo is easy, the low rp of the 6C33 does not require a high inductance primary, leakage is no problem, inter-leaving is easy, you can opt not to have it...... it's an easy choice if you ask me.....

.....

SET tube amps demand a lot of power for a measly power output, here i am making a power traffo of with a core rating of about about 390watts,if you ask me, i wished this traffo could have been bigger, it will supply a continuos power of a little over 220 watts regardless of whether the amp is playing music or not.....if we were building a classAB amp instead, we could be idling at less than this.

http://i5.photobucket.com/albums/y15...T/IMG_2273.jpg

for the power traffo, i used a bobbin for 1.5 inch and 2 3/8 inch stack:

http://i5.photobucket.com/albums/y15...T/IMG_2274.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2275.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2276.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2278.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2281.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2283.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2284.jpg


filament winding terminations:
http://i5.photobucket.com/albums/y15...T/IMG_2286.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2285.jpg

built-up traffo:
http://i5.photobucket.com/albums/y15...T/IMG_2287.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2288.jpg

bamboo pegs at the 4 mounting holes, this lets the varnish go in between laminates.
here the traffo is hung out to dry for a day or so....
http://i5.photobucket.com/albums/y15...T/IMG_2289.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2290.jpg



these are the output traffos, core is 1.5 x 2 inches, impedance ratio is 600:6 ohms, so that turns ratio is 10..........

building a pair side by side, one section by one section at a time until the whole buld is completed, ensured that the pair built are identical......

http://i5.photobucket.com/albums/y15...T/IMG_2291.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2292.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2295.jpg

dipping in varnish:
http://i5.photobucket.com/albums/y15...T/IMG_2296.jpg

hung out to dry under the sun after dipping in varnish....
http://i5.photobucket.com/albums/y15...T/IMG_2298.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2297.jpg

temporary brackets installed on the 2 opts to keep the E's and I's together since they are butt joint with a gapping paper sandwiched in between them...
http://i5.photobucket.com/albums/y15...T/IMG_2300.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2302.jpg

with endbells installed after painting:
http://i5.photobucket.com/albums/y15...T/IMG_2325.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2376.jpg

AJT 15th July 2012 09:37 AM

2nd installment: chassis preparation;

aluminum gage 14 was used, 0.075inch thick for both box and bottom plate, wooden sidings used to cover the sides...aluminum is very easy to work with, a joy to drill and quick to file out and polish....i used a half round file to make straight cut-outs....:D

after drilling and punching holes, ready for powder coating......

http://i5.photobucket.com/albums/y15...T/IMG_2374.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2373.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2375.jpg

bottom plate:
http://i5.photobucket.com/albums/y15...T/IMG_2395.jpg

after powder coating.....
http://i5.photobucket.com/albums/y15...T/IMG_2408.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2411.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2412.jpg

AJT 15th July 2012 10:51 AM

3rd installment: mounting of traffos, filter caps and sockets......

http://i5.photobucket.com/albums/y15...T/IMG_2417.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2418.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2419.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2420.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2421.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2422.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2423.jpg

stainless steel allen key type bolts used, guaranteed rust free for the life of the amp....
http://i5.photobucket.com/albums/y15...T/IMG_2424.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2425.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2426.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2427.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2428.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2431.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2432.jpg

tubes fitted...
http://i5.photobucket.com/albums/y15...T/IMG_2472.jpg

Alexontherocks 15th July 2012 11:35 AM

excellent work, impressive build quality!

I believe he 6c33c is a beautiful tube. i plan on using it to drive a gu81m based set amp (still have two big bottles left)

http://www.moehrenbude.de/Moehre/ima...33C_simpel.pdf

output transformer is tricky...260mA 5k primary. Still haven't found an exact match in commercially available (and affordable) products.

anyways...great work and I like the white bells!

AJT 15th July 2012 12:17 PM

Quote:

Originally Posted by Alexontherocks (Post 3092846)
excellent work, impressive build quality!

I believe he 6c33c is a beautiful tube. i plan on using it to drive a gu81m based set amp (still have two big bottles left)

http://www.moehrenbude.de/Moehre/ima...33C_simpel.pdf

output transformer is tricky...260mA 5k primary. Still haven't found an exact match in commercially available (and affordable) products.

anyways...great work and I like the white bells!


thanks Alex, i built all the irons in this amp......there are no commercially available traffos that i know of......

indeed the 6C33 is a beautiful tube.....

AJT 15th July 2012 12:22 PM

wiring completion;

at the start......
http://i5.photobucket.com/albums/y15...T/IMG_2682.jpg

bias and high voltage dc psu board installed......
http://i5.photobucket.com/albums/y15...T/IMG_2683.jpg

high current main B+ rectifier installed in pcb at the left, the 2 filter caps are for the 400volt dc supply to the 6P15P voltage amplifier stage....
http://i5.photobucket.com/albums/y15...T/IMG_2690.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2692.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2693.jpg

central grounding bus installed.....
http://i5.photobucket.com/albums/y15...T/IMG_2694.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2695.jpg


front-end wiring complete....
http://i5.photobucket.com/albums/y15...T/IMG_2711.jpg

input tube 6P15P cathode bias uses diode string in a pcb.....
http://i5.photobucket.com/albums/y15...T/IMG_2713.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2714.jpg

6C33 grid bias pots installed....
http://i5.photobucket.com/albums/y15...T/IMG_2712.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2719.jpg


almost there......
http://i5.photobucket.com/albums/y15...T/IMG_2735.jpg

i wanted a time delay for the 6C33plates to give enough time for the filaments to get warmed up prior to application of B+ so i designed and built a 3 minute delay timer with a soft starting resistor of 12k/5watts in series with main B+ ac supply to the bridge rectifier....there is a 2 color panel led that blinks red about once each second and turns green at the end of the timing period...the 12k resistor is shorted out at this time.....

http://i5.photobucket.com/albums/y15.../IMG_2730a.jpg
http://i5.photobucket.com/albums/y15...T/IMG_2739.jpg

underside of the amp completed.....
http://i5.photobucket.com/albums/y15.../IMG_2748a.jpg


the bottom plate is fitted with 2 x 12volt ball bearing fans, so mitigate potential noise, these fans are powered by 6 volt dc supplies, they move air to go past the 6C33 sockets to somehow cool them down....
http://i5.photobucket.com/albums/y15...T/IMG_2746.jpg

rajucc 15th July 2012 12:24 PM

Great Work

Alexontherocks 15th July 2012 01:44 PM

Wel done Sir!

You must be proud. Completing a project without commercially available products is real DIY.

Could you please take some measurements when you are finished? :)

Best

MelB 15th July 2012 02:09 PM

Bravo. Most excellent work. Love the pics on the transformer winding. In fact, I love all the pictures! Thanks for sharing.

AVWERK 15th July 2012 02:21 PM

2 big thumbs up!


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