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Old 4th November 2007, 03:27 AM   #1
difflvl is offline difflvl  United States
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Default Quick Leach Amp Question

I've searched but didn't find anything about the rails being this high. Maybe I suck at searching.

What changes need to be made to use high voltage rails of 150Volts?

Also does anyone have a Leach superamp design with more output transistors?

Thanks!
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Old 4th November 2007, 10:40 AM   #2
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You wanting B+ 75 volt and B- 75 volt?
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Old 4th November 2007, 11:05 AM   #3
AndrewT is offline AndrewT  Scotland
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there's a superamp thread running but the board design seems to have come to a halt.
Maybe it needs you to gee it up a bit.

A superamp with two quad sets can easily manage +-100V into a high impedance load.
But most folk want to run 8ohm and 4ohm speakers and that may require as much as 3quad sets for 8ohm and 5quad sets for 4ohm.
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Old 4th November 2007, 05:36 PM   #4
taj is offline taj
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Default Re: Quick Leach Amp Question

Quote:
Originally posted by difflvl
I've searched but didn't find anything about the rails being this high. Maybe I suck at searching.

What changes need to be made to use high voltage rails of 150Volts?

Also does anyone have a Leach superamp design with more output transistors?

Thanks!
Assuming you mean +-150v rather than +-75v:

For a Leach Low TIM amp (and aside from the obvious of making sure the components can handle higher voltage)...

you would probably need to provide a separate lower voltage supply to the small signal sections. Moving to higher voltage rated transistors would sacrifice their other specs.

Then you'd need to recalculate the protection network resistors to execute at the appropriate current level.

Then you'd need to win a lottery to afford all the output transistors you'll be buying, and enough heatsink to keep them alive.


..Todd
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Old 4th November 2007, 10:40 PM   #5
djk is offline djk
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"What changes need to be made to use high voltage rails of 150Volts?

Also does anyone have a Leach superamp design with more output transistors?"

Yes, it's called a Crest 8001 (133V) or CA12. The design of both look like the Super Leach with more outputs and or-ing diodes to lower supply rails. They work like the regular Leach up to the lower rail, and then cascode themselves the rest of the way.

The 8001 has 10 pairs of outputs per channel (should make Andrew smile), the CA12 has 12 pairs.

If you want I could sell you a spare CA12 module (needs overhaul, but would be the basis of a nice mono 1.4KW sub amp) for cheap, but you can buy these amps used for reasonable prices.

I have the schematics if you're a glutton for punishment.
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Old 5th November 2007, 02:15 AM   #6
difflvl is offline difflvl  United States
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Thanks for all the responses.

Ill take a look at the crest I found the schematics in another thread.
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Old 5th November 2007, 09:17 AM   #7
djk is offline djk
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The passwords are all expired on my old posts.
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