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Old 20th January 2009, 03:19 AM   #1101
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Thanks Bob,

sounds good - seems all my pre stuff has a cap on the out.

-for kicks
What are we talking for input impedance of the amp, 22k or so??
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Old 20th January 2009, 11:46 PM   #1102
clm811 is offline clm811  United States
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Quote:
How about some progress pictures folks.
FWIW,

I'm laying out the chassis for my amps -decided to go with a pair of mono amps, using some old "junk" amp chassis I picked here and there.

As soon as the panels and heat sinks are drilled/tapped (and once I get some more power supply caps), I should be ready to assemble.

C'mon, guys- Let's see your images!

-Chas
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Old 21st January 2009, 12:08 AM   #1103
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Chas - where did you get that power supply PCB?

It is looking good...
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Old 21st January 2009, 01:21 AM   #1104
pchw is online now pchw  United States
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Quote:
Originally posted by dudaindc
Chas - where did you get that power supply PCB?

It is looking good...
http://www.chipamp.com/orders.shtml

Scroll to the bottom, they are the Amplifier Power Supply PCB below the Aleph PCB. They are on sale with 20% off now. They make very neat and professional look power supply!!
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Old 21st January 2009, 04:51 AM   #1105
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Quote:
Originally posted by pchw


http://www.chipamp.com/orders.shtml

Scroll to the bottom, they are the Amplifier Power Supply PCB below the Aleph PCB. They are on sale with 20% off now. They make very neat and professional look power supply!!
Thanks Fred.
That is not a bad price for such a nice board.
The link for the board is probably incorrect on the website as it leads to an XLS file (BOM) instead of a picture.

==================================
I found them... http://www.briangt.com/gallery/aleph-pcb
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Old 21st January 2009, 05:06 PM   #1106
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do you have BOM for that pcb
also does the pcb support center tap transformer secondary
chas could you give us more Information about transformer
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Old 21st January 2009, 05:22 PM   #1107
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Zooming in on the picture of the board it looks like it supports 4 MUR type diodes, so center tap transformers should work.

From memory, it also supports CCRC filtering - although with a Leach amp I'd just jumper out the R and use 3 parallel caps per rail.
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Old 21st January 2009, 05:27 PM   #1108
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why Bob you would jumper the resistors
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Old 21st January 2009, 05:36 PM   #1109
AndrewT is offline AndrewT  Scotland
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the Leach has pretty good PSRR and also Jen's version has the facility to power the voltage amp from a separate PSU, regulated or not.

The removal of R allows the whole capacitor bank to deliver transient current.

It may be that the loss of ripple attenuation is more than balanced by the improved peak current delivery.

If the resistor were to be replaced by 100turns of 0.6mm diameter enameled wire, the R value would be low and the ripple and interference suppression would be much improved. This may sound better than either of the other options.

But there's only one way to find out, try them.
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Old 21st January 2009, 07:12 PM   #1110
pooge is offline pooge  United States
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Quote:
Originally posted by AndrewT
the Leach has pretty good PSRR and also Jen's version has the facility to power the voltage amp from a separate PSU, regulated or not.

The removal of R allows the whole capacitor bank to deliver transient current.

It may be that the loss of ripple attenuation is more than balanced by the improved peak current delivery.

If the resistor were to be replaced by 100turns of 0.6mm diameter enameled wire, the R value would be low and the ripple and interference suppression would be much improved. This may sound better than either of the other options.

I doubt the class A input circuitry needs to worry about peak current delivery since it is constant current. Thus, I would assume inclusion of the resistor would be MUCH more advantageous for filtering variations due to the current pulses in the output stage than any possible reduction in peak current delivery, if that is in fact a potential problem.

If the CRC is for the output stage, I do agree that an inductor may be a better choice; especially if it is placed away from the amp circuitry, as such an inductor may radiate into the circuitry. The front end would also be the most intolerant of such radiation.
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