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Old 25th April 2007, 08:12 AM   #1541
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Let's see now if I got it right. I used the PCB CAD file that's on that website, but with rectifiers and filter caps offboard so omitting that left section. I actually have CRC before the multiplier, and both the ground from the second pair of these caps, and the output ground, I wired to the two large holes in the middle of the multiplier half's star ground on the PCB drawing.
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Old 25th April 2007, 08:12 AM   #1542
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Old 25th April 2007, 08:21 AM   #1543
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by Crowbar
........If I were to use separate regulation for the rest of the amp (than the output stages), why not go all the way and use a good shunt regulator? Efficiency is really only an issue with the output stage anyway.......
A few transistor shunt regulator on the front end may make an excellent regulator to complement the Krell PSRR. It could even have a lm317 or tl431 current reg upstream to reduce dissipation in the shunt and improve the rejection characteristics.
Even a cascode reg might work (Walt Jung's recent paper posted on the Forum may help)
There are many options when we are dealing with <40mA @ 52Vdc.
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Old 25th April 2007, 08:26 AM   #1544
PWatts is offline PWatts  South Africa
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They were the standard vanilla ones. The reason for low-ESR being undesirable is due to the 317's inductive behavior at higher frequencies. I've looked into that further and found this link: http://www.tnt-audio.com/clinica/reg...edance1_e.html

it explains it rather nicely and was confirmed with my own measurements.
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Old 25th April 2007, 08:31 AM   #1545
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by Crowbar
Let's see now if I got it right. I used the PCB CAD file that's on that website, but with rectifiers and filter caps offboard so omitting that left section. I actually have CRC before the multiplier, and both the ground from the second pair of these caps, and the output ground, I wired to the two large holes in the middle of the multiplier half's star ground on the PCB drawing.

A schematic would help.
the offboard main smoothing can have it's 0V returned direct to the audio ground.
the onboard smoothing has much reduced charging pulses, but they are still there.
I think your description is saying that the CRC 0v are connected to the local reg star ground. I would not do that. The first C should go to remote audio ground the second C could go to either the remote audio ground or to the reg OUTPUT. You should try to ensure that the MEASUREMENTS the regulator is making on the low current sense traces are uncontaminated by high current and/or high pulse power outputs.
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Old 25th April 2007, 08:39 AM   #1546
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by PWatts
They were the standard vanilla ones. The reason for low-ESR being undesirable is due to the 317's inductive behavior at higher frequencies. I've looked into that further and found this link: http://www.tnt-audio.com/clinica/reg...edance1_e.html

it explains it rather nicely and was confirmed with my own measurements.
extracted from TNT
Quote:
But that supply line, and all the others, was controlled by an LM317 loaded with a 1uF low-Z ceramic cap nearby, and a dozen of 100nF caps distributed around the big chip. With about 2uF of low-ESR capacitance it was no wonder at all that this particular regulator was prone to oscillation. And the chip's current draw profile only exacerbated things. Trashing the ceramic cap in favour for a big ugly and cheap 100uF elcap entirely cured the problem and left the supply stable and of relatively low noise.
this is at odds with the National datasheet!
Who do we believe?

Crowbar,
go and look at the good & bad schematics on page one of that tnt link.
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Old 25th April 2007, 08:41 AM   #1547
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The only high current pulses are on the first pair of off-board Cs. There's no pulse on the output since the amplifier has a class A balanced output stage and there's no output current returned to ground. I should have mentioned this before.
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Old 25th April 2007, 08:47 AM   #1548
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Quote:
Originally posted by PWatts
found this link
Pierre,

there's the option of communicating directly with Werner Ogiers, he's also a member of this club, aka Werner.
Born and living in Antwerp, his homepage=> HERE

(opposed to what Werner stated at the Duhh-HiFi forum, the inspiration for Werner's shunt reg did not come out of the van der Sluis sleeve. J van der Sluis knows squat diddly about designing circuits, the bloke just craves to get between the sheets with P. Walker and J. Hiraga types)
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Old 25th April 2007, 08:52 AM   #1549
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Old 25th April 2007, 08:56 AM   #1550
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Yeah, you missed all the fun.
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