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Old 5th October 2003, 10:20 PM   #11
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Quote:
Originally posted by Nelson Pass


Jam says he is sending me a Citation 12 to do something with.
I don't think the previous Citation 12 project I did was
particularly popular, but it's hard to resist the lovely little
chassis and supplies the original provides.

On the other hand, I cannot imagine a +/- 90 Volt amplifier
in it.

Well, the charm of the citation 12 goes away when you have to replace the pair of transformers, and all the caps. You'd only be left with a marginal chasis and small heat sinks. So I'd say stick with the 40(ish) volt rails and keep the power supplies in the Citation 12.

I'd love to see a new Citation 12 design. If you design it, I'll build it. I'll even lay out a circuit board to replace that card edge front end board.

Sheldon
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Old 5th October 2003, 10:53 PM   #12
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Quote:
Originally posted by Nelson Pass
On the other hand, I cannot imagine a +/- 90 Volt amplifier
in it.

why not?

I built one years ago on a shoe string budget using the same topology but different devices / resistor values.

I have simulated one with 72v rails. and saw no reason why it wouldn't work on 90v rails.

I am in the process of building one based on your original citation 12. Except that mine will have a pair of drivers to potentially drive multiple pairs of output devices.
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Old 7th October 2003, 03:15 PM   #13
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I Just found hill dx1500 schematic on the web. As you can see it is drown by some service man... I never built amp with a transformer phase-turn ... is it good amp or not...Could this work!?!
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Old 11th October 2003, 03:27 PM   #14
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Default Re: Re: Need Amp For 90-0-90 V DC

Quote:
Originally posted by moamps
(QSC and CROWN)

those got to be two of the most interesting companies in the pro audio business. QSC has done a great job taking up the market consistently, delivering good value at excellent prices. it is the first company I think that used switching mode power supply in its amps without sacrificing quality.

Crown, being part of the Harman family, is more expensive in general but has a proven track record.

Both are great companies making great products. But they took differnt routs to get where they are today.
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Old 12th October 2003, 01:56 PM   #15
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"I Just found hill dx1500 schematic on the web. As you can see it is drown by some service man... I never built amp with a transformer phase-turn ... is it good amp or not...Could this work!?! "

Ben Duncan mentions this amplifier in his book 'High Perfomance Amplifiers', he refers to it as the 'Hill heat generator'.

The bias/dc off-set are inter-related, not a good thing. I would convert to fully complementary output pairs (MJ21193/94) and add a thermistor to regulate the bias. The driver transformer would be wired as a center tap, and the thermistor would go across the bases of both of the output pairs.

Or build a better circuit.

http://users.ece.gatech.edu/~mleach/superamp/

This amplifier has been around long enought to have the bugs worked out, and truely sounds good.

It was also sold comercially by Heathkit as the AA1800, delivered 400W/8R, and features a bias servo and short circuit protection.
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Old 12th October 2003, 09:03 PM   #16
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Default Leach Super Amp

Woow, i must say that i newer built anything this complicated. It loooks like a realy good amplifier...and also one of not much amplifiers working on high voltage rails, so...i will think about building it if i find all those components...
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