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Old 15th December 2008, 04:36 AM   #1
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Default Found An Old Transformer, Now What???

:bawlingsmash:
SAY I FIND AN OLD AUDIO TRANSFORMER ON EBAY, HOW HARD WOULD IT BE TO FIND A SCHEMATIC TO WORK AROUND THE TRANSFORMER?
I KNOW THIS IS A TOTALLY OUT THERE QUESTION, BUT I AM A TOTAL NEWB.

I WANT TO MAKE A SIMPLE BUT DECENT AMP, AND I DONT HAVE A LOT OF CASH.
I AM THINKING IT CANT BE AS SIMPLE AS THAT, BUT I DONT UNDERSTAND THE INS AND OUTS OF AMP DESIGN,

I HAVE NOTICED SOME SIMILARITIES IN HEATER VOLTAGES FROM A FEW DIFFERENT PLANS AND PLATE VOLTAGES ALSO,

SO THERE YA HAVE IT...JUST BE NICE, ITS MY FIRST POST...
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Old 15th December 2008, 04:55 AM   #2
kevinkr is offline kevinkr  United States
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Buy a kit, not some unknown transformer off of eBay.. Here is just one possibility which seems to be quite popular with Newbs here: http://www.s5electronics.com/ltube.html

I would probably go for the smaller stereo amplifier - 8LS http://www.s5electronics.com/l8stereo.html

These kits provide instructions and all of the parts required to build a working amplifier, and it will work when you are done provided you assemble it correctly.

Another excellent option would be tubelabs Simple SE amplifier, widely discussed here, if budget is a concern you can purchase just a few parts at a time easing the financial stress of getting into tube audio. Many rank beginners have completed these successfully. Link here: http://www.tubelab.com/

Lots of people will be willing to help you out if you approach them the right way, be willing to do a lot of up front study.. To that end I recommend you pick up Morgan Jone's: "Valve Amplifiers 3rd Edition" available at Old Colony Books (and Amazon) here: http://www.audioxpress.com/bksprods/products/bkb40.htm

The companion book: "Building Valve Amplifiers" is a worthwhile addition and is available here:
http://www.audioxpress.com/bksprods/products/bkb99.htm

One further note, please do NOT type in ALL CAPS as this is considered SHOUTING on almost all forums currently in existence. Old hands will consider it very rude, newbies do get some slack however...
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Old 15th December 2008, 05:57 AM   #3
chrish is offline chrish  Australia
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For a stereo amp, you are going to need at least 3 transformers. One power transformer that will provide the high voltage and the low voltage for the heaters of the tubes. You need to find a transformer that provides the right high voltage and enough current, and also enough current for the heaters. You will then also need two output transformers. These are either single ended or push-pull (google these terms if you are not sure) and will need to be the right impedance. I would check for a design you are interested in (tubelab Simple SE is a great start) then search for transformers to suit.

Good luck!

Chris
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Old 15th December 2008, 07:46 PM   #4
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Kahuna-
I agree with the advice to buy a kit, mentioned by the wise folks above. Personally, I don't find that building tube gear with printed circuit boards is much fun, but it is generally a good way to get a working amp if you stick to well-tested circuits like the SimpleSE.

Another possibility is to check the local 'free' pages to try to score an older hifi which will often work as-is, or you can scavenge for transformers.

A simple amp like the RH EL84 is not very difficult to build using point-to-point wiring (and terminal strips!- not a jumble of suspended components and hot glue as often seen at diy sites) if you are handy.

I built a very nice-sounding RH using guitar amp output transformers, but you would probably be better off with something from EDCOR or similar.

I watch eBay auctions from time to time and there are few bargains there, especially when you factor in the shipping cost.

Cheers
John
PS- If you actually do have a transformer already, there are safe ways of figuring out what you have and finding out the specs. Ask here before you plug anything in!
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Old 15th December 2008, 08:14 PM   #5
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Also consider getting Bruce Rosenblit's Beginner's Guide to Tube Audio Design. I have no idea if it is still in print, but there is always ebay. I found it to be a straightforward beginner's text, with a very short chapter on each aspect of tube amp design.

I won won this book at the Burning Amp festival raffle and I find that its a little more "beginner" than MJ's books, which I've read roughly 3 times so far.

It would have been nice to read Rosenblit's book, then read MJ's books (as opposed to the other way around), more of MJ's knowledge would probably have sunk in the first or second time around.

Being an Engineer (ME) and a tube newbie, Morgan Jones' Valve Amps" book was comprehensible but for the non-techie it may be a little advanced IMHO. YMMV.

I would also recommend a simple kit or find an old ST-70, etc. and modify/restore for a good first project.

The folks on this site are more than helpful at answering beginner's questions, so don't be bashful.
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Old 15th December 2008, 08:34 PM   #6
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Here's just a couple of sites that publish and/or sell books that are about tube amplifier design.

http://www.tubesandmore.com/

http://www.audioxpress.com/

There are many others, but these two have a lot of good books. And audioxpress even publishes magazines.

Peace,

Dave
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Old 15th December 2008, 10:40 PM   #7
chrish is offline chrish  Australia
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Wrote my reply very quickly yesterday. For a cheap beginners amp, the expensive transformer will probably be the power transformer. Cheap output transformers can be had from Edcor http://www.edcorusa.com/products/class_x.html

I have a pair of the $20 Edcors in my Simple SE and I love them. Check out the Simple SE threads and I think you will find you can get an Allied power transformer to suit for around $60? That should total around $100 for the transformers.

As mentioned above, salvaging an old amp for transformers and tubes is also an option.

Chris
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Old 15th December 2008, 10:54 PM   #8
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wow! thanks for responses! i do have the valve amplifier book ordered and on its way...
and, i have all my friends on "lookout" for an old console stereo as something to check out/experiment with, etc...

the reason, i dont want to take the kit route, is at the moment i have 5 weeks off, (autoworker) and so, with all this time i'd like to take a less easy approach, and try a tried and true model.

The Darling looks good. I am not overly concerned with high fidelity, but, more with the tube feeling i am hearing so much about.

and, the novelty that a simple amp carries with it, is also part of the appeal....

I have to admit it was the Imp amp that inspired me to look into all this, and even if buying it was on option, that would be too easy...(and a lot less fun)....
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Old 15th December 2008, 11:27 PM   #9
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Kahuna-
I've built a bunch of tube guitar amps and a couple of stereo 'hifi' amps.
I think you will be very impressed with the quality of the sound you will get,even from a simple tube project. A tube amp and efficient full-range speakers really changed the quality of my listening experience.
As I mentioned, I've built a RH84 which is a very nice and simple project.
RH website
I've also built one of Poindexter's (that's his diyaudio ID- his name is Eric Kingsbury) 6V6 Music Machines.
Music Machine and more
It's an excellent-sounding amp but the power supply is a bit complicated for a first project.
Eric's ideas on chassis setup are really excellent. They keep the power supply and the amp nicely separated. If you work with wood, they're fairly simple to make and look great to my eyes.

If you email me I can send you a pic of the RH84 and MM I made- apparently I can't post pics here as I'm a newbie as well.

There's an excellent source for 'ordinary'- ie cheap- resistors and capacitors in Canada- great service.
Just Radios in ON

Books are nice, but if you are short on cash, you can find what you need (and more) online. You've definitely found a good starting point right here.

Cheers
John
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Old 16th December 2008, 12:12 AM   #10
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for inspiration -


http://www10.big.or.jp/~dh/


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