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Old 14th November 2018, 02:15 PM   #51
maty tinman is offline maty tinman  Spain
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Default Mundorf MLGO table. Ripple and ESR at 100 Hz.

Quote:
Originally Posted by Mark Johnson View Post
Um, wouldn't Zout be equal to (1/gm) plus (smallterm / Beta_squared) ? So at DC, about 33 milliohms when delivering 800mA?
To compare with the expensive Mundorf MLytic Audio Grade (AG) MLGO:

[PDF] http://www.mundorf.com/english%201.1...eiten/MLGO.pdf

Click the image to open in full size.
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Old 14th November 2018, 02:22 PM   #52
maty tinman is offline maty tinman  Spain
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Mundorf M-Lytic AG Capacitor 63V 22,000μF (ESR = 7 mOhms), the cheapest in EU here:

https://www.audiophonics.fr/en/conde...0f-p-5999.html

32,10 tax incl.

26,75 tax excl.
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Last edited by maty tinman; 14th November 2018 at 02:24 PM.
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Old 14th November 2018, 06:51 PM   #53
xrk971 is online now xrk971  United States
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Hi Maty,

I have used it in CFH9 current feedback Class AB and the cap Mx works well. To get low ESR for cheap, I have used a cap array of 20 x 1000uF 60mOhm caps to get a 3mOhm ESR x 20,000uF equivalent cap after the cap Mx for cheap. These caps are sold in bags of 50 for $7.

Here is CFH9 Class AB amp with MOSFET cap Mx:
Click the image to open in full size.

Here is cap bank being used with a Class A DLH amp:
Click the image to open in full size.

I am pretty sure I used the cap bank with a cap multiplier at some point but can’t remember the exact amp.

If you have more questions about cap Mx, maybe ask in that thread as this is a bit OT with respect to the original title thread.
Thanks,
X
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Old 14th November 2018, 07:23 PM   #54
Mark Johnson is offline Mark Johnson  United States
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Eventually you reach a point where the economic optimum is to build a full fledged voltage regulator with negative feedback. NFB circuits have incredibly low output impedance at (2 x fmains) if that's what gives you the woody, see excerpt from Jack Walton's article in Linear Audio, below. Pink line at 120Hz. Do you see 6 milliohms? Do you see 1 milliohm? Do you see 0.1 milliohms? Do you see 0.02 milliohms? I see them.

I happen to own a class-AB power amp (50 watts/channel into 8R) whose power supply is in fact a voltage regulator with huge amounts of NFB: the Akitika GT-101. Consider it an "existence proof" that NFB voltage regulators can indeed drive the rails of a class AB power amp. Akitika publishes all schematics online, including the schematic of the GT-101's voltage regulator / power supply. Have a look and calculate its Zout at 120 Hz, I expect your estimate will be very darn low.

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Old 14th November 2018, 07:38 PM   #55
maty tinman is offline maty tinman  Spain
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Quote:
Originally Posted by Mark Johnson View Post
Eventually you reach a point where the economic optimum is to build a full fledged voltage regulator with negative feedback..
You are the second person who told me today. The problem is finding one that works for a Class AB amplifier of about 100 watts at 8 Ohms. For DAC and headphones there is no problem.

Years ago I was about to buy the GT-101. I did not see clearly that such a low slew rate was enough to reproduce the transients of an orchestra. And I wanted more power by then. I had even thought about the improvements!

And yes, better in the other thread: Juma's Easy-Peasy Capacitance Multiplier
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Old 14th November 2018, 08:30 PM   #56
Dave S is offline Dave S  United Kingdom
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Quote:
Originally Posted by Mark Johnson View Post

I happen to own a class-AB power amp (50 watts/channel into 8R) whose power supply is in fact a voltage regulator with huge amounts of NFB: the Akitika GT-101. Consider it an "existence proof" that NFB voltage regulators can indeed drive the rails of a class AB power amp. Akitika publishes all schematics online, including the schematic of the GT-101's voltage regulator / power supply. Have a look and calculate its Zout at 120 Hz, I expect your estimate will be very darn low.

_
I also happen to own an Akitika GT-101 and I have performed measurements on the regulated power supply. I measured 17mOhms output impedance @ 1.6A output current.

I also measured >1Mhz ringing on the turn-off edge. Although, this is unlikely to happen in a real amp due to the input bandwidth limiting filter slowing the slew rate compared to my switching load.
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Old Yesterday, 12:16 AM   #57
Mark Johnson is offline Mark Johnson  United States
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Perhaps Bonsai's next amplifier project, in a couple of years, will be a 200 watts/channel class AB amp with regulated supply rails of vanishingly low output impedance. Then when he unveils this amplifier, you can copy his regulator design, without needing to purchase twelve boutique electrolytic capacitors (at 26,75 apiece) to get the output impedance you want.

Or perhaps it won't, who knows. I can't speak for Bonsai but I do know that MY next power amplifier project, will definitely not have voltage regulators on the supply rails.
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Old Yesterday, 08:53 AM   #58
Bonsai is offline Bonsai  Europe
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I used cap multipliers on the e-Amp (180 Watt per channel VFA) for the front end stages up to the VAS. I think there’s about 30 or 40 dB ripple attenuation IIRC.

For class A amps they bring a real benefit - and especially CFA. A good VFA should have very high PSRR.

I agree though that spending a fortune on boutique capacitors is a high road to nowhere - as are commercial products that boast about ‘500 000 uF’ PSU capacitors.

An image of Don Quixote and windmills comes to mind.
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Old Yesterday, 05:46 PM   #59
maty tinman is offline maty tinman  Spain
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Boutique and expensive capacitors but very good caps too.

Two Mundorf MLGO in a DC Blocker or class AB PSU is a very good choice. Verified by me with my first DCB, the prototype.

The same DCB with Mundorf MLytic Audio Grade (AG) MLGO 25VDC / 47000F, 125C vs EPCOS:

* Much better than: EPCOS B41231A7159M000 15000 F, 35 V, 85C (inside the prototype)

* Better than: EPCOS B41505A7189M000 18000 F, 35 V, 105 (out of stock) (inside the others DCB, DCBx2 and DCBx4).

https://www.audiocircle.com/index.ph...381#msg1667381

Quote:
Months ago, my TV system:

DCB (prototype, cheap EPCOS) + DCB + DCBx2

Until a week ago:

DCB (prototype, cheap EPCOS) + DCBx2

Now:

DCB (mundorf) + DCBx2

and just now is Monday night. The TV sound is much better than a week ago and better than months ago! TDT TV with sound from an AV Yamaha.

DCB and DCBx2 with much expensive and better EPCOS capacitors than the original DCB prototype.

In other words:

DCB proto with Mundorf is better than DCB proto + DCB.
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