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Old 18th August 2004, 07:33 PM   #1
Bifi01 is offline Bifi01  Belgium
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Question RAIL power supply / BI Amping question

Hi All,

I have two questions that have been running around my head during the design of my latest A/B Class Amp.

- I noticed many just use the cap/bridge solution to create the RAIL voltages... Is there any advantage in using a Regulated Power Supply to provide the RAILS in a A/B class AMP?

- My Amp would be a four channel amp driving two bi amp speakers. So one pair of amps driving the right speaker, other the left. Is it advisable to use different power supply circuits for each amp within one pair, resulting in four different supplies? Or will one supply for each pair be sufficient? Since both amps within a pair will be amplifying the same signal I had my doubts about the effectiveness implementing different supplies.

Could you give me some advise ?

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Old 18th August 2004, 08:41 PM   #2
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I am designing a class G, but will eventually be making 4 seperate channels. I have pondered this thought as well. Even though it will take more componants and probably cost more to make, 4 seperate power supplies is better because it reduces the probability of getting ground loops between the channels. This can create some unwanted noise & instability especially if you are bridging channels. Just remember to reference each power supply ground together.

Ground loops are a really annoying problem and difficult to track down. If you can build your circuit any way possible to reduce the likelyhood of ground loops, do so.
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Old 20th August 2004, 04:13 AM   #3
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Default Friends will turn nervous, but i will tell you my strange idea.

I had made, long time ago some tests with regulated, adjustable and stable power supplies, and i could perceive (hearing) that result is worst than simple supplies with not so big condensers....4700 uF each rail to each consumption ampere.

I perceived that the bad work this kind of supply made to me, was very good hearing audio......some non real dinamics... when charged, hi power peaks....when hard driven, the voltage reduced making one "decay"..... the first impact strong, followed with reducing volume.

I made comparisons, those late times i was alone to judge, this way, no good judgement.....had no friends cooperation, different now a days, having a small audioholics club to check all ideas.

Was clear to me, and i made several tests....many days, many musics....and i really prefered the defective sound, resulted of lowering voltage when the amp was hard driven.

Then, i increase condensers, used 20000uF each ampere, and this value for each rail..... sounded worst!

Of course, subjectivism is not something you can believe, better to make your own tests.

Those things, preferences, are a matter of "taste"....as an example; i like very much small woman, 5 foot high, small feet and i prefered the ones do not like to talk too much (because i already talked too much!)... those tall girls, with big feet, are usefull, in my idea, to disturb bad neighboors living under my apartament, making noise when walking... those women are also usefull to change burned lamps....but for other meetings..... those tall girls are awfull ,as the males are ,in my taste!...hohohô.... subjectivism not science, some madness personal variations only.


Sorry, Brazil only to be sold... top secret ultimate schematic, not to share...encapsulated VAS:
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Old 21st August 2004, 12:07 AM   #4
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Default Ps options

1 building a psu for each channel should be a 'first' ('monoblocks' are the way to go in high end audio)

2 regulated or non-regulated is i.m.h.o a commercial factor. Non-regulated is cheaper. Regulated has more components and is less power efficient.

Soundwise I prefer regulated PSU, in the case you have the same rail voltage for all the stages. (the things I've build).

As you are building a 4-way amp you could choose to have two toroids each powering two regulated psu's for 1 of the amps.
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Old 24th August 2004, 06:02 AM   #5
Bifi01 is offline Bifi01  Belgium
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I would be using series feedback on the PSU for regulation.

Do you have any experience what kind of device to use as the pass thrue device? Wether to use transistors, as they allow almost any C to be connected but have a larger dropout (+/- 1.2V), or fets, who have much smaller dropouts (+/- 0.2V) but require specific capacitive loads.

I have read at Analog Devices about the AnyCap topology they use. In this topology they use fets but allow any C load to be connected without the possiblity of instability due to the pole/zero 's. Anyone familiar with this topology and how to use it in more powerfull regulators? (I would need about 7A/40V)

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