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Old 30th May 2006, 03:28 PM   #11
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These amplifiers are some of the finest power amplifiers every made.

They ain't cheap and nasty and dirty, you can use paralleled output stages upto around 500 watts.

They sound stunning.
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Old 30th May 2006, 05:06 PM   #12
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Is your transformer dual secondary? If so then it is easy peasy...simply make two, identical and completely separate npn regulated supplies, one from each secondary. Then simply wire them in series (so one's neg is connected to ther other's pos as the gound point).
Trust me, the wee electrons 'll never know the difference.
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Old 30th May 2006, 06:04 PM   #13
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Traderbam, I think i know what you mean.. thats a nice idea this would eliminate the need for an NPN driver for the negative supply regultor.

I have made a diagram of my proposed regulator circuit and have added a diagram of what i thought you were saying in your transformer wiring post.
If you could check it out for me id be grateful as using all NPN's makes it a little simpler to design.

Do my values look correct for the upper transistor regulated circuit?

PS. the pass transistor is a darlington not the single transistor as indicated in my diagram.

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Old 31st May 2006, 10:14 AM   #14
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Will be one very very hot pass transistor.
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Old 31st May 2006, 01:13 PM   #15
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Yes, that is what I meant. I've attached the sort of circuit I had in mind. This is simple, cheap and will behave itself.

The 2N3055s are beefy but slow so the R2-C3 are needed to smooth the output impedance at high frequencies. C3 should be rated at 63V or more. C2 should be reated at 50V or more. Use 1W resistors for R1 and R2 and a 1W zener. I'm not sure what transistors you have so I chose an MJE243 for Q3. Let me know what you'd want to use here.

To get more sophisticated will take more parts and careful design because you'll need a feedback system. I am happy to help if you wish to go this way. I think your Maplin modules will sound fine with this circuit.

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Old 31st May 2006, 03:10 PM   #16
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I really wouldn't go this way. You will have too much heat to deal with from the regulator, especially when you get the volume cranked.

Either get a lower voltage transformer, or build a higher voltage amp.
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Old 31st May 2006, 03:31 PM   #17
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Hot stuff Well the regulator has half the V across it as the amp, but it is constant V, so the regulator will probably end up dissipating about the same power that the amp does in heavy use. I haven't done the maths so that's an educated guess. Provided everything is stuck on a big heatsink it'll be ok. It's a lot less effort to use the right transformer...but costly.
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Old 31st May 2006, 04:50 PM   #18
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I'd say the regulator is MORE costly because you need a bigger heatsink
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Old 31st May 2006, 04:53 PM   #19
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And you have more things to go bang!
Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
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Old 31st May 2006, 05:15 PM   #20
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PM, you don't blow things up? Where's the fun in that?
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