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Old 16th June 2008, 06:44 PM   #1
flood is offline flood  India
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Default (INDIA) ECC802S/EL84 build, hardware requirements

Dear all,

I am relatively new to this forum, but do a fair shhare of browsing here, since there is a treasure trove of experience and knowledge available here.

i want to build my first amplifier - i have3 done about 4-5 years of research on tube amplifiers, even collected a number of parts but have procrastinated building one for very long. i have built some stompboxes in the past, but was pretty scared of anything that went up beyond 120V...

i drew inspiration from the fact that it is my fathers 60th birthday this year, and i want to build him something rather special - i found the ultrasimple and widely praised ECC802S SRPP/EL84 P-P project here. the simplicity and credos make it very inviting....

i will be subsitituting the ECC802S for E80CC SQ (unless it will not work as a drop in replacement?) or simply with a good pair of 12AU7s.

the problems that i am facing are mostly of a cosmetic nature - i'd like some help from forum members who know whaere i could get stuff done around bombay.

1. i will be using an aluminum for the top, front, back and bottom plates, about 1.5-2 mm thickness. i would like a brushed finish, and if possible an engraving. does anyone know where i could get that done? how about anodizing or high-gloss polishing, if brushin is not feasible? i would prefer a brushed finish, because it looks simple and yet elegant.

2. the chassis - i have an ambitious plan for this - would be wood. ideally, i'd like an exotic wood with a nice structure. any tiops on where i could buy good looking woods

3. also, i'm looking for suggestions for capacitors, especially electrolytics. since there is only one capacitor in the signal chain, i will possibly use a WIMA metal foil or a simple metal polyester cap there, and upgrade to an auricap later if the amp sounds good. i am lost on electrolytic caps though, and do not particularly wish to use SMPS capacitors.

4. i am totally lost on this one - i have had the trannies (all toroidal) wound to specs by miracel, and have been desperately looking for transformer shells. can anyone point me in the right direction? as a final option, i think i will take aluminum lunch dabbas and have the anodized, and cut the edges on the open side for slot-locking onto the top part of the chassis... the trannies should be with me htis week.

5. a couple of final thoughts.... i'm looking for a circuit that will let me turn on LEDS very slowly - say, so that they reach their maximum brightness after about a minute or two.

i know this is a rather ambitious project for a beginner, but i really want to do a good clean job at it and have a decent gift for m father - i have practically everything i need, i just need the stuff listed above. i would greatly appreciate any help, this means a lot to me. thanks a LOT to all in advance!
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Old 18th June 2008, 08:39 AM   #2
ssmith is offline ssmith  France
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for the chassis parts / alu, there were some threads which mentioned a place in Mumbai that could do custom chassis -- have you searched?
Otherwise, have a hunt around for a good metal workshop, and if you give a clear plan you're sure to sort something out.
A good idea is to design your chassis in a mudlaur fashion, so you get all the sheets and it bolts together. Once that is done you can take it to any finisher for powder coating, anodising, polishing etc.
For capacitors, there's likely to be more choice in Mumbai than in Delhi. My suggestion would be to see what's on the market, buy a few different types at or above the value you need and experiment. And don;t throw a lot of money just yet at boutique caps.
by the way, have you found tubes in Mumbai?
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Old 18th June 2008, 08:40 AM   #3
ssmith is offline ssmith  France
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here is the India parts thread in case you missed it.
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Old 18th June 2008, 08:03 PM   #4
flood is offline flood  India
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i found a few tubes in lamington road, but mainly have a few from my student days in germany.

some lamington road shops still have them, but you need to look hard.

thanks for the tips! i will take a look at some metalworkers. hopefully i can find someone willing to do a one-off.
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Old 18th June 2008, 10:47 PM   #5
gofar99 is offline gofar99  United States
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Hi Flood, I'm glad you find the project interesting. You can substitute 12AU7 tubes in the circuit. My original circuit used them without changes. I have since revamped the design a bit and have a KT77 version (posted on the diyaudioprojects.com site). I have a KT88 version in the works at the present time as well. The biggest difference between the KT77 and KT88 versions from the EL84 is the need for a small amount of negative feedback. Within the limits of the tubes the EL84 version really didn't need NFB. It made only slight improvements and as it reduced the gain a 12AT7 would be a better driver. I use 6SL7s and 12AT7s in the bigger amps. Drop me an email if you want more infomation or just to chat.
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