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Chip Amps Amplifiers based on integrated circuits

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Old 19th April 2003, 08:58 PM   #11
Philo is offline Philo  United States
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Here's a quick pick of one of mine going into a boombox upgrade. it cost about $15 total w/ the psu and will have about 30watts/chan.
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Old 19th April 2003, 09:14 PM   #12
elizard is offline elizard  Canada
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well i think you just sold me for a gainclone

any recommendations for a transformer?
where i can get a cheap-er one from canada? specs for the transformer?
I'd stick to 2 monoblocks, each with a separate power supply i suppose (so long as its not twice the cost!)
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Old 19th April 2003, 09:36 PM   #13
Philo is offline Philo  United States
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eLizard,
You should read through the "This is not just another Gainclone" thread. I know it's huge and gets off track once and awhile but has just about all the info you need. Check around with local suppliers for some transformers. I would stick with toroidals as they are more efficient and generally quieter. Victoria Magnetics and Plitron are excellent manufacturers if your surplus search comes up empty. A Google search will find them. Call them up for a quote. Peter Daniel, the forum's Gainclone King, can probably help you with local Canadian sources, as well..
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Old 19th April 2003, 09:49 PM   #14
elizard is offline elizard  Canada
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yeah, i read the first about 200 posts or so .. then my head hurt

but yeah .. i'll keep reading that

thank you all .. and yeah, any specs for the torroids i should look for?
i'm new at all this
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Old 19th April 2003, 09:59 PM   #15
Philo is offline Philo  United States
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Can you live with 38watts per chan? Unless your speakers are less then 86db sensitivity or you play your music really loud, you don't need more IMO. A 180VA toroidal transformer with dual 18 volt secondaries for each monoblock would be perfect. I use even less (120VA-18VAC/chan) for my main amp and it drives my 89dB B&Ws more than loud enough. Pics are @post 81 in the big thread.
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Old 19th April 2003, 10:08 PM   #16
elizard is offline elizard  Canada
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yeah i can live with 38watts

i've 91db crap speakers, and my new set will be 89-90 .. so 38 will be great

gonna price it all .. as long as its under $200 w/o chassis (i can do that myself with some aluminum or wood) its all good
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Old 19th April 2003, 10:15 PM   #17
Philo is offline Philo  United States
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The transformers are your biggest expense and you'll get under $200 easily. Just pay particular attention to the ground paths and keep your signal path as short as physically possible. Those have been most people's biggest headaches.
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Old 19th April 2003, 10:27 PM   #18
elizard is offline elizard  Canada
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thank you, i'll be sure to work out some price tonight

btw, what sort of amp rating should the transformers be rated for?

also, i already have a active preamp, do i just leave out the pot? or do i replace it with a resistor?
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Old 19th April 2003, 10:29 PM   #19
Philo is offline Philo  United States
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A 10 amp (5/winding) 18VAC transformer (10*18=180VA)
A 50k resistor to ground instead of the pot would be the obvious solution but I have had some extra noise in my experiments using that configuration so I just made my amp an integrated version.
Peter, any suggestions?
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Old 19th April 2003, 10:33 PM   #20
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hmm. well i can point out a few suggestions and i'm sure others can shoot them down.

apexjr.com may still have one of those 48Vct -7A transformers (E I core) for $10, and they also have lm3886 chips and heatsinks.

www.goldmine-elec.com has the lm3875t chips for like $4.75 or $5. they also have lm837n opamps 4 for $1 (and they're quads). no resistors or caps to speak of. well, mylar 1uF 5 for $1, but that's not much better than local for me! also they have some 3pdt (actually 4pdt if you look at the diagram...) for 70 cents each, 6v coil thoguh... oh and they have cool magnets which aren't really related but still cool.

www.newark.com always has stuff, and they pack insanely. if you need extra boxes just order 50 each of differenet values of resistors... i now have like 13 small boxes...
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