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Old 24th June 2007, 09:15 AM   #1
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Default Leach Amp My design

http://rapidshare.com/files/39029692/leach.rar

its wonderfull
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Old 24th June 2007, 09:40 AM   #2
AndrewT is offline AndrewT  Scotland
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access denied,
can you find a sensible way to post your RAR file?
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Old 24th June 2007, 09:51 AM   #3
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schema
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Old 24th June 2007, 09:53 AM   #4
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pcb proteus 7.1
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Old 24th June 2007, 10:01 AM   #5
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Old 24th June 2007, 10:17 AM   #6
AndrewT is offline AndrewT  Scotland
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Hi,
is the output from the regulators running at about 42Vdc?
This will cripple the voltage coming from the early stages of the amplifier (particularly the VAS and pre-driver).
You should aim for the voltage amplifier running at about the same volatge as the drivers+outputs.
Can you feed 60Vdc into the regulators?
Then set them to that same 55Vdc so that both ends of the amp are on similar voltages.
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Old 24th June 2007, 10:34 AM   #7
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Quote:
Originally posted by AndrewT
Hi,
is the output from the regulators running at about 42Vdc?
This will cripple the voltage coming from the early stages of the amplifier (particularly the VAS and pre-driver).
You should aim for the voltage amplifier running at about the same volatge as the drivers+outputs.
Can you feed 60Vdc into the regulators?
Then set them to that same 55Vdc so that both ends of the amp are on similar voltages.

single voltage for low cost

vas stage 42-45 volts

sory bad speak englis
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Old 24th June 2007, 11:08 AM   #8
AndrewT is offline AndrewT  Scotland
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Hi,
buy some enamelled copper wire (about 0.5 or 0.6mm diameter) and add about 15turns twice to your toroid transformer.
Couple up the extra windings to give the higher voltage and then run a small bridge rectifier and smoothing caps across the high voltage low current windings. Reset your regulator to 55Vdc (1k0 & 43k) and go with that.
This will only cost a few $.
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Old 24th June 2007, 12:01 PM   #9
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Quote:
Originally posted by AndrewT
Hi,
is the output from the regulators running at about 42Vdc?
This will cripple the voltage coming from the early stages of the amplifier (particularly the VAS and pre-driver).
You should aim for the voltage amplifier running at about the same volatge as the drivers+outputs.
Can you feed 60Vdc into the regulators?
Then set them to that same 55Vdc so that both ends of the amp are on similar voltages.

Quote:
Originally posted by zerohead_ak47
single voltage for low cost,vas stage 42-45 volts

sorry bad speak english
This should only affect the voltage swing to the output stage and limit the max output. It should still sound good at real world listening levels into reasonable speaker loads.

Good work! I'd try to limit the length of the wiring from the PCB's to the output transistors (also power supply wiring). This could cause stability problems.

Regards, Mike.
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Old 27th June 2007, 04:47 PM   #10
AndrewT is offline AndrewT  Scotland
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Hi,
your 2k7 feeding the cascode Zeners is allowing about 1mA to flow. [43V-40V]/2k7=1.1mA
The cascode and zeners and tail require about 8mA to operate correctly. 1.5mA into each half of the LTP + 3mA into the tail + 2mA into the zeners. Change the resistor from 2k7 to 360r would suit your low rail voltage, or change the zeners to 12V.

I would also suggest adding the extra resistor that Leach missed out to convert the limiting to IV, but that necessitates recalculating all the other protection resistor values.
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