Simplistic Mosfet HV Shunt Regs - Page 298 - diyAudio
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Old 6th May 2012, 05:10 PM   #2971
AndrewT is offline AndrewT  Scotland
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JLH designed a couple of different shunts.
The cap multiplier is a HUM attenuating shunt.
The hum buster is a hum and noise attenuating shunt. Is that what JLH called it?
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Old 6th May 2012, 05:33 PM   #2972
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That's very interesting Andrew . I used a double stage multiplier recently . It was only 22 mA . Yes now you say it I have seen it with JLH . I as an experiment used a near Victorian version to compare using high voltage and RC filters ( same final voltage ) . It slightly won and was about - 110 dB quiet . Very marginally the 1/f or Johnson noise of BD139/40 was higher than the high voltage version . That surprised me . The PSU had a double BD transistor as CCS to ensure safety and cap protection . Calculated surge current 190 A if not ( never happens in real life I know ) . That was because people do mad things which ends in smoke . This was to adapt a bought in product . We needed lower ripple noise . This is a LM317 pre-regulator . I have found 317/317 together can oscillate and RC is simple . I have a 47 V zener to catch the output when disconnected but still powered . The running output voltage is 22 V .

I think Douglas Adams said " The problem with making foolproof things is people underestimate the ingenuity of fools " . Something like that . Hence CCS .

Anyway that's me done with shunt regulators for now .
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Old 6th May 2012, 08:19 PM   #2973
Salas is offline Salas  Greece
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Noise filtering in parallel or regulation in parallel have a thing common (their being shunt) and two things uncommon. Those are a reg has error amplification and voltage reference. The reg usually achieves lower and flatter output impedance. Combinations of filtering and regulating aren't mutually exclusive though.
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Old 6th May 2012, 08:29 PM   #2974
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Default Talon

Hi Salas . I just accept Shunt Regulators . However the more I think about them the more confused I get .

The Chinese amp was Incatech Talon . Shame they didn't go ahead . I would have bought one myself . I know the designer but won't say who it is . Fantastic power supply . I have the drawings somewhere

Inca Designs Talon vs Incatech Claymore - pink fish media

It was a work of art and designed by a power supply obsessive . The most beautifully textured sound . Like a natural hi end successor to A+R A60 . The one they forgot to make .

Last edited by nigel pearson; 6th May 2012 at 08:43 PM.
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Old 7th May 2012, 09:57 AM   #2975
AndrewT is offline AndrewT  Scotland
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What was I thinking about, the Hum buster is actually named Ripple Eater by JLH.
The cap multiplier is a series not a shunt.
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Old 7th May 2012, 11:10 AM   #2976
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Hi Andrew . I have difficultly with that also . I tried the JLH idea and found Early effect a problem if not using the small bleed resistor to ground to ensure the transistors are not in saturation . I used a divider on mine . Some use a diode forward biased CB to ensure Early effect doesn't happen . Also a back EMF diode to CE and BC reverse biased ( 1N4007 my do everythinng diode ) . They cost 2 pence so why not ?

Do you think MOS FET better than Bipolar in Shunt ? I am trying to shunt 100 MHz . The idea only came to me after your comment . I know you are methodical so trust your advice .

Thanks .
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Old 7th May 2012, 11:27 AM   #2977
AndrewT is offline AndrewT  Scotland
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There are many experts here that confirm each other saying that FETs can operate to higher frequencies than BJTs.

That may be enough to decide to use FETs for 100MHz, but that is a mighty target. I suspect the design has different priorities way up there.
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Old 7th May 2012, 11:33 AM   #2978
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Quote:
Originally Posted by AndrewT View Post
There are many experts here that confirm each other saying that FETs can operate to higher frequencies than BJTs.

That may be enough to decide to use FETs for 100MHz, but that is a mighty target. I suspect the design has different priorities way up there.
Me too and I am loosing the battle . I think a ceramic cap is all I can do ( 1 nF COG )

Nigel
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Old 7th May 2012, 02:19 PM   #2979
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A layout question, as I am designing my own pcb:

To accommodate a large heatsink, would it be possible to mount the IRF on the heatsink, and wire them back to the pcb? Does sensing compensate for this?
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Old 7th May 2012, 03:11 PM   #2980
Salas is offline Salas  Greece
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Don't know about the extra inductance on those wires. Never done it like that, can't comment without experiment. If talking SSHV2 there is 5.5MHz open loop zero gain point extension. Loss of phase margin or interference can happen. It will take trial and measurement so you see if still safe with your total configuration. Sensing compensates to the remote node, does not shorten the local force loop area.
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