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Old 28th September 2011, 04:09 PM   #1
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Question Class A tube amplifier Kit

I want to assemble a kit of Class A tube amplifier push pull or single end (dont know wich is best) , something complete i dont want to be outhere looking for transformers and other parts .I want to use it as a a tweeter amplifier , something with 12-20wrms is enough (tweeters are 20wrms max , 4 - 8ohm tweeters) . Something i can have shipped to Europe . budget is 500$ , should be enough for a good amp.

Last edited by lduarte1973; 28th September 2011 at 04:12 PM.
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Old 28th September 2011, 08:49 PM   #2
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This one is worth considering sb343971 - Kit Amplifier Earle winds his own high quality transformers and provides a guide on the web page to help with the build
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Last edited by data; 28th September 2011 at 08:59 PM.
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Old 28th September 2011, 08:52 PM   #3
ChrisA is offline ChrisA  United States
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Quote:
Originally Posted by lduarte1973 View Post
I want to assemble a kit of Class A tube amplifier push pull or single end (dont know wich is best) , something complete i dont want to be outhere looking for transformers and other parts .I want to use it as a a tweeter amplifier , something with 12-20wrms is enough (tweeters are 20wrms max , 4 - 8ohm tweeters) . Something i can have shipped to Europe . budget is 500$ , should be enough for a good amp.
It will be single ended. Any kit will be designed for the full audio range. If you are only driving tweeters then you could use much smaller output transformers and have better performance at lower cost. Also 12-20W is a higher then average pwer from a sinfle ended class A amp so the big market is not there for the kit sellers. If you could do with less power or class-B push pull then it would be easy to find something.

For this application a custom design would be best. You can build a better amp for a given budget if you know it does not have to supply any bass or anything at all below about 2KHz.
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Old 28th September 2011, 09:02 PM   #4
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Sorry I skimmed the OP, Chris has a point.

I really have no idea what would be needed if only tweeters are being powered
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Old 28th September 2011, 09:27 PM   #5
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something like this ?

http://www.ebay.com/itm/Meixing-Ming...item3eed7cb182

http://www.ebay.com/itm/DYUNAUDIO-EL...item336b874e22

http://www.ebay.com/itm/Music-Angel-...item27ba97e3f5

http://www.ebay.com/itm/Meixing-Ming...item3eed7cb182

Last edited by lduarte1973; 28th September 2011 at 09:32 PM.
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Old 29th September 2011, 02:39 PM   #6
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Lduarte: What is the sensitivity of your tweeters? Reasonably priced SE amps using IDHT's are going to produce 2-8 watts or so. To get 12-20W SE, you are looking at high voltage, somewhat exotic tubes that will certainly bust your budget. These high voltage projects are not recommended for a first build either....

As mentioned, if the amp is strictly for tweeter use, you can get away with smaller output transformers and coupling caps since you don't need any LF signal.

I know that you are looking for a full kit, but have you considered the Tubelab Simple Single ended amp? Tubelab George sells PCBs and there is tons of info and support here for building that amp. Spec'ing smaller output transformers will help the budget and it's a very straightforward build. Tubelab George also has a website with loads of info for that amp. You can use 6L6GC's, EL34's, 6V6's, KT88's, etc in that amp easily. I would consider trioded EL34's or 6V6's (depending on your tweeter sensivity) for tweeter duty. Edcor electronics sells both power and output transformers suitable for the Simple Single Ended at several price points.

Tubelab Home

EDCOR Electronics Corporation
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Old 29th September 2011, 02:49 PM   #7
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Consider boywonder's advice.

But regarding those 4 amps you linked on ebay, Earle's kit amp would have much higher quality transformers than those amps come with. Only thing is you would need to ask if he can wind a power transformer specific to your mains if it is not 240v.
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Old 29th September 2011, 03:11 PM   #8
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where are Earle's kit ?

The tweeters are 4 Peerless 810921 , in paralel to make 4 ohm load , 91 db

810921 - Peerless 1″ tweeter - Europe Audio

Last edited by lduarte1973; 29th September 2011 at 03:38 PM.
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Old 29th September 2011, 03:57 PM   #9
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Lduarte: A few things.....If you are planning on running two tweeters in parallel for each channel, your combined sensitivity will be +3db (so 94db) and the combined impedance will be 4 ohm nominal; you will need an output transformer with 4 ohm speaker taps. If your are looking at the Chinese stuff, make sure that they have 4 ohm taps, or you will be loading the amp incorrectly.

Also, you want a relatively flat impedance curve.....

94db sensitivity will blast you out of the room at 12-20W unless you are into head-banging metal; 5-8W SE power should be plenty of volume, which is good news if you want a budget SE amp.

Are you planning on active crossover? That will make the apparent power delivered to the tweeters appear greater, since the amp does not have to use power to amplify LF energy that the tweeters can't use. If you are not planning on using an active crossover, then choice of coupling cap values in the amp can accomplish a similar goal. (they will filter out LF easing the burden on the amp). If you later decide to use the amp for full range service, you can just replace the coupling caps for that use.
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Old 29th September 2011, 04:15 PM   #10
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Quote:
Originally Posted by lduarte1973 View Post
where are Earle's kit ?

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Australia, his amps are thought of very highly down here.

I'm not sure what taps the kits transformers have, but considering that he winds them himself I guess that's not really an issue. You would just need to talk to him about your situation.

Edit:Only problem is you may have a wait as he always has back orders due to demand, last time mentioned I think the wait for one of his non-kit amps was 3 or 4 months.

Last edited by data; 29th September 2011 at 04:28 PM.
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