Simplistic Mosfet HV Shunt Regs - Page 308 - diyAudio
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Old 4th June 2012, 07:38 PM   #3071
JOIMONF is offline JOIMONF  Spain
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This circuit is a cathode follower, in parallel, also known as "buffer". It's a capacitor input not seen on schematic, also 47k gird choke on input and ouput. I do not specify this minor changes as I show the schematic for consumtion puposes. Although is good sounding you are right, I always can do better, and now will check other single stage ciucuits no need for paral.lel. Lucky to find now an standard cathode follower ECC81, (proof engineered) HV 250v, and consumption 4,55mA per channel, so 9-10mA the whole tube (stereo).
Dummy load should be 250/0,01= 25k, 8 or 10watts.
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Old 4th June 2012, 08:53 PM   #3072
Salas is offline Salas  Greece
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Correct dummy, and look for 0.3V at T.P. Good luck to new experiment.
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Old 4th June 2012, 09:13 PM   #3073
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Old 3rd July 2012, 12:31 AM   #3074
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Default SSHV2

Salas,

I have my Version 2 up running and everything looks good. I've been trying to tune the current to about 10mA - 100mv as of the instruction, but stopped at 176mV and couldn't go any lower. I can trim the voltage to 140v as desired. The input voltage is 172v. Boards and parts are from Teabag. Any clue ??

Albert

BTW the dummy load is 15K 10w

Last edited by albertli; 3rd July 2012 at 12:37 AM.
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Old 3rd July 2012, 01:14 AM   #3075
Salas is offline Salas  Greece
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There are two breaks. One for max current which is near DN2540 sample IDSS (Q2 IDSS as close as R5 is allowing), one for minimum, as near to Q2 off as (maxR4//R3)+R5 allow. You may notice a 20-100mA operational region printed on the instructions schematic (about). When you want 10mA for your load, trim for +20mA spare. I.e. 30mA in total or 300mV T.P. reading. That extra 20mA caters for the internal consumption needs of the reg and it ''massages'' the shunt Mosfet enough to keep the output impedance spec respectable. Your test dummy is OK for simulating ~10mA @ 140V load consumption. Some of the rest is gonna burn for internal biasing but mainly on Q3's sink. The spare current thing is also mentioned in the instructions text.
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Old 3rd July 2012, 03:05 AM   #3076
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Sorry my bad not to read it thoroughly. It's too eager for me to hope something back running after the version one down.
Thanks and will report after the music on.
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Old 3rd July 2012, 06:05 AM   #3077
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Salas,

What a good design you have. It's so stable that I don't have to adjust the voltage after 3 hours listening.
I now only have one reg for 2 channels and set the current at 23mA. The bass line is better than the version 1 for a good margin. With version 1, I found the bass thin with my LL1660SE 10mA, the weight of bass is more and solid with the version 2, and more details too.
A little off topic, the wave-form with the 1660 doesn't look too good and sounds compress too. It looks very ugly after 4.5k even with 0.1 & 4.7k across the output. I'd like to try without the opt and see how it sounds like. Can I run the reg direct to the 26 anode from it's output point, or I have to series a load in between ??
Thanks

Albert
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Old 3rd July 2012, 07:04 AM   #3078
vgeorge is offline vgeorge  Greece
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Albert, I would first increase the current of the regulator to 40 mA.
If the amp you drive is more than 50kohm impedance, then you can try take the output from the anode.
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Old 3rd July 2012, 07:18 AM   #3079
Salas is offline Salas  Greece
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What you guys mean direct from the anode without OPT? If the OPT is out it it needs some other form of load to swing voltage across, doesn't it?
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Old 3rd July 2012, 07:40 AM   #3080
vgeorge is offline vgeorge  Greece
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What I meant is use the transformer as a choke and use capacitor output.
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