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Old 19th February 2013, 06:07 PM   #121
tomchr is offline tomchr  United States
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Quote:
Originally Posted by Blitz View Post
Can anyone who actually built it comment on the sound of this ? Maybe compared to shunt-regs or maxed-out passive systems ?
I'm obviously biased, but I've been using the 21st Century Maida Regulator in my 300B amp for over a year now. I'm quite pleased with it. It replaced my older regulator design and the resulting sound quality blew me away.

First off, there's no hum. None. I measure about 200~300 uV RMS (80 kHz bandwidth) of noise/hum/EMI on the output. This with a prototype layout. I expect it to tighten up once I get the amp in a proper enclosure. I've tested the regulator stand-alone with 50 Vpp ripple on the input. The 21st Century Maida reduces this to approx 20 uV RMS noise/residual ripple. If you want ripple rejection, this regulator is where it's at.

Secondly, compared to my previous regulator, I got considerably tighter bass with the 21st Century Maida Regulator. I also noticed that the sound stage seemed to open up and the overall sound quality really benefited from the quiet supply.

I've also tried a regular C-L-C supply. Granted, I didn't go all out on the components - I think I used 470 uF - 2 H - 470 uF, but still... That's 40 dB of ripple attenuation. Still not enough to avoid hum, though. I had about 1 mV of hum on the amp output. I also found the sound kinda fuzzy - perhaps from 60 Hz IMD products.

Shunt regulator in a power amp... Funny. I wouldn't go there personally as it would require vast amounts of power dissipated in the regulator. For a preamp, sure. But not for a power amp. But then, that's my opinion. Yours is free to vary.

I hope this answers some of your questions. The bottom line is that I get the best performance (both subjectively and measured) with a good regulated supply.

~Tom
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Old 5th March 2013, 08:34 PM   #122
tomchr is offline tomchr  United States
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Good news - especially for international customers.

I am now able to offer more cost effective shipping. The shipping charges are calculated by weight, so cost will vary with the number and size of the boards ordered. The shipping rates for my boards start at:

USA: $5
Canada: $9
Rest of the world: $12

I use quality shipping materials. The envelopes I use are sturdy, well padded, and 100 % recyclable.

~Tom
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Old 13th March 2013, 12:09 AM   #123
jgf is offline jgf  United States
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I built several of these regs last year, but didn't get around to installing in anything until just recently. I put one in my tube phono preamp, replacing a simple mosfet follower on a zener stack... nice improvement, bass is more solid, image is more centered, high treble is much cleaner and less 'splashy'. Running about 35ma at 330v.

I didn't notice when I built it the max capacitance following the reg was 47uF, but I've got 100. No problems though, but I could reduce that to 50 easily, would that be more optimal?

Thanks Tomchr for making this available!
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Old 13th March 2013, 02:04 AM   #124
tomchr is offline tomchr  United States
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On the output of the regulator, I'd go as low capacitance as possible. Let the regulator do its job. I usually use a 10 uF electrolytic can where the power goes into the amplifier board. That's the supply bypassing cap and it helps with stability. I'd say 1~10 uF is probably enough supply bypassing.

It's good to know that my regulator can handle 100 uF in your application, though. That's handy for Loftin-White/Ultrapath designs and such.

Thanks for your feedback. I'm glad to hear it turned out well for you.

~Tom
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Old 13th March 2013, 04:40 AM   #125
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Tom,

I'll see what I have in that capacitance range and try that,
thanks,

John
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Old 13th March 2013, 05:55 PM   #126
skal is offline skal  United Kingdom
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Hi Tom,

i am from the uk , and i really want to your 21st Century Maida Regulator but those 1uf caps are expensive like 13 pounds each wow could i use a lower voltage say 400v,and is their any chance you could supply the Surface Mount parts for the regulator.

cheers

ska1
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Old 13th March 2013, 07:06 PM   #127
tomchr is offline tomchr  United States
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If you stay below 500 V, you could use 630 V rated caps. That should cut cost. I recommend using polypropylene caps for the caps on the regulator input and output, C2, and C4. The polypropylene caps aren't cheap ($1~$2.50 as I recall) but they do need to be low ESR and the polypropylene caps fit the bill nicely for that.

Notice the note on the schematic says to populate C1A (expensive polypropylene) for voltages above 400 V and C1B (inexpensive electrolytic) for voltages at or below 400 V.

I can deliver a board with the SMDs populated. I do charge extra for that, though. I'm not clear on which of the SMD parts you want populated. Toss me a PM with the details and we'll work it out.

Thanks,

~Tom
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Old 13th March 2013, 09:03 PM   #128
euro21 is offline euro21  Hungary
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Hi ska1,

Epcos 1uF 875V polypropylene (Mouser Part No: 871-B32674D8105K) only 3.42 USD (about 2.30 GBP) at mouser.

http://uk.mouser.com/ProductDetail/E...sboJXfnA%3d%3d

Last edited by euro21; 13th March 2013 at 09:07 PM.
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Old 14th March 2013, 07:37 PM   #129
jgf is offline jgf  United States
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A note about my application that had 100uF on the output: The power line input on the preamp has a CL-80 to limit inrush, I suppose would help the regulator deal with the large cap on its output.
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Old 14th March 2013, 10:56 PM   #130
tomchr is offline tomchr  United States
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Quite a few of the devices in the regulator are in there to allow the regulator to start up into a capacitive load. The requirement of start-up into at least 47 uF load cap also drove the sizing of some of the resistors as significant power is dissipated during start-up and a low-wattage type would not survive.
Some of the devices in the design are there to protect in case of inductive flyback from poor connections - like a cold solder joint on a tube socket.
I had fun torture testing the regulator, that's for sure....

But having an inrush limiter like the CL-80 in the primary circuit of your power transformer will certainly make it easier on the "survival" devices in the regulator. Inrush limiters are good things...

~Tom
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