Power Supply Resevoir Size

[OnAudio]

Another example is with Bryston.
Bryston 14BSST is 600watts at 8ohms using 44.000uf per rail.
Bryston 28BSST is 1,000watts at 8ohms using 80.000uf per rail.
so, as We can see here, Krell likes "overkill" power supplies compared to Bryston amps.But does that mean Krell amps sound better than Bryston amps because krell uses "overkill" power supplies?...I do not think so!!!There is not an exact capacitance for power supply. other way "all" 100 watts or so at 8 ohms amps will have the same capacitance in all power supplies.

For the Bryston 44000/14 = 3142uF per 8 ohm load, quite close to our projected figure of 4000uF for 8 Ohm

 

[MagicBox]

No, Tief, an amp that dances nimbly across the score for a large orchestra.

Some amps are sluggish, leaden, others are nimble, and do not intermodulate at all.

Hugh

I think (apart from enough capacitance to provide the needed oomph) this is characterized mostly by the ammounts of output stage decoupling as discussed in this thread. When few to no local decoupling is used, the PS itself has to do it all and then indeed 'how quick' can the output device get the required current which is litterally translated to how few sagging will there be at the drain/collector terminal when current is drawn. The amount and ease of sagging as a result of powerdraw is what defines the kind of 'speed' you describe.

Therefore I believe if you properly and sufficiently decouple output devices as close as possible to their terminals through a number of staged buffers, it will no longer matter how 'fast' the main supply is as it is no longer used to supply the T=0 current.

It really is no different than the heaps of decoupling you apply in opamp circuits and even in digital circuits where decoupling is even more important due to the huge huge instant current draws occuring during switching in digital logic.

 

[tiefbassuebertr]

I'm honestly not 100% sure on that and haven't done any critical listening comparisons (concerning "Fast rectification"). Many report favourable results though.

(I first encountered what I call "fast rectifiers" way back when I started out as a repair tech and wondered why certain diodes wouldn't work in TV deflection circuits or SMPS's) I can't help but feel that when you have added snubbers across diodes and across secondary windings that things equal out a lot. But I may be wrong

Anywhere here on diyaudio were upload diagrams of extensive measurements concerning a wide range of different rectifier types used in power supplies of typical audio power amplifiers (without serial voltage regulators).
Unfortunately I don't find this thread in the moment.
Perhaps one of the members know this (most likely the starter, unless it has been inserted somewhere in the middle of a totally different topic, such as
http://www.diyaudio.com/forums/anal...ohn-curls-blowtorch-preamplifier-part-ii.html ).
Here it became clear, that more details have a great influence on the result as only "slow" or "fast"

 

[a.wayne]

Another example is with Bryston.
Bryston 14BSST is 600watts at 8ohms using 44.000uf per rail.
Bryston 28BSST is 1,000watts at 8ohms using 80.000uf per rail.
so, as We can see here, Krell likes "overkill" power supplies compared to Bryston amps.But does that mean Krell amps sound better than Bryston amps because krell uses "overkill" power supplies?...I do not think so!!!There is not an exact capacitance for power supply. other way "all" 100 watts or so at 8 ohms amps will have the same capacitance in all power supplies.

IMO Bryston has always under capped their PSU , we always had issues with them ( 4B) due to such and its quite possibly why they have that weak tinny electronic sound .. Also the Brystons you list are really designed for 8 ohm loads, (4 ohm min)if you are going to play 2 ohm and lower , then you have to have way more than that , hence krell and others who build amps able to sink current into 2 ohm loads ..


Krell = Bass
Bryston = Muddy bass


You will not appreciate Krell amplifiers if you have hi -eff , 8 ohm speakers. Get big beastie speakers and you will understand the talk ...

 

[a.wayne]

Yes. I would think less about capacitance in the PSU and maybe think more about getting decoupling capacitances as close as possible to the power output devices.

For speed (and the timing and phase accuracy that give the detailed soundstage image), you would need something like at least 10uF or 20uF per volt of rail voltage, with one inch or less of total connection and lead-spacing length, at each power output device.

Better yet, use multiple smaller caps that add up to that value, in parallel, with star-like connections that don't share conductors, to lower the total inductance (and ESR) below any of their individual inductances (or ESRs).

The total inductance and ESR would each be divided by the number of parallel caps. I would try to use at least three caps in parallel. (Note that the total connection length can be longer, with multiple caps, but I would still try to keep each cap's total connection plus lead-spacing length at one inch or less, if possible, or at least keep the total for all of them at one inch per cap or less.)

Then add more capacitors as close to each device as possible until you get a total of up to about 2200uF per max output amp, for each device. You don't have to go that high but it would improve the bass and mid response. If possible, make all capacitor connections like a star, where none of them share any common conductor. That will lower the total inductance (and ESR), very drastically. Using more smaller capacitors in parallel is better, especially if they can be placed to not share conductors until they get to the power and gnd decoupling points. But obviously there is limited space. So just do it as well as is practical.

Tom,

Have you tried such a setup before and was it worth the effort ..?

 

[jacco vermeulen]

Mr Wayne,

must i remind you again.

 

[tiefbassuebertr]

Mr Wayne,
must i remind you again.

from which unit is the attached file?

 

[tsiros]

Those who have looked at pulse width modulation in class D and also switch mode power supplies will note that for a linear power supply with a recharge rate of 100 or 120 means that we do not need more capacitance to improve bass reponse beyond 5Hz as by this time if we were to play a 5 Hz tone the transformer would be able to sustain it without help from the capacitors.

Thus for an 8 Ohm load @ 5Hz (has nothing to do with wattage) 4000uF will suffice

not sure if this pertains to class D amps or all amps, but i can see - with my oscilloscope - the power supply voltage sag when playing bass heavy music ( examples #1 #2 #3 ) on a 2*40 W amp with 2*4700 μF and the amp outputting ~ 2*10 W (sorry, not trying more, i don't think the 12" AN will like it, they aren't yet broken in, and plus, they are pretty effin' loud!!! ). Now, you might say, an oscilloscope is too sensitive. No, not mine. My oscilloscope is a DSO nano v1, which is a crappy 10 Msps single channel storage oscilloscope. To see sag with that oscilloscope means it is there. Granted, i am not very good at taking measurements and i see ripple even with the amp not outputting anything. Which makes me worried.

 

[jacco vermeulen]

which unit

Omega power amp, Classé.

 

[a.wayne]

Mr Wayne,

must i remind you again.

OK Dutchie , A spliff for you .... Without pulling out electron microscope , is that one cap per output ,or just caps close to outputs? what value, if possible ...

 

[OnAudio]

not sure if this pertains to class D amps or all amps, but i can see - with my oscilloscope - the power supply voltage sag when playing bass heavy music ( examples #1 #2 #3 ) on a 2*40 W amp with 2*4700 μF and the amp outputting ~ 2*10 W (sorry, not trying more, i don't think the 12" AN will like it, they aren't yet broken in, and plus, they are pretty effin' loud!!! ). Now, you might say, an oscilloscope is too sensitive. No, not mine. My oscilloscope is a DSO nano v1, which is a crappy 10 Msps single channel storage oscilloscope. To see sag with that oscilloscope means it is there. Granted, i am not very good at taking measurements and i see ripple even with the amp not outputting anything. Which makes me worried.

Something is wrong with the specs of your caps

Get a big boy with a ripple current of over 18A, get two and thats over 36A

An externally hosted image should be here but it was not working when we last tested it.

B41607A7278M009 EPCOS Inc | 495-3710-ND | DigiKey

 

[jacco vermeulen]

5 x 4700uF per rail (which is 1 of 4 in a bridged amp), for 8 output devices, as well as is practical.

Seen other amps with that many uF's so close to the output device collector pins ?

(stacking smaller lytics has become somewhat of a Dutchy tradition, as in the times of stacking several small cheeses instead of one biggy )

 

[fas42]

Again, there is a very easy, audible way of discerning what the voltage rail is really doing: use a 2nd amp fed with the voltage rail of the 1st being driven hard as input, decoupled obviously with a high quality cap of sufficient voltage rating, and just listen to 2nd amp's speakers. You might get a bit of a shock ...

Frank

 

[jacco vermeulen]

B41607

At $11 each, i'd be dead before the caps are.

 

[OnAudio]

Yes. I would think less about capacitance in the PSU and maybe think more about getting decoupling capacitances as close as possible to the power output devices.

For speed (and the timing and phase accuracy that give the detailed soundstage image), you would need something like at least 10uF or 20uF per volt of rail voltage, with one inch or less of total connection and lead-spacing length, at each power output device.

So I went hunting for possible candidates

Checkout the specs

An externally hosted image should be here but it was not working when we last tested it.

PLV1J470MDL1TD Nichicon | 493-3874-1-ND | DigiKey

An externally hosted image should be here but it was not working when we last tested it.

PLV1J270MDL1TD Nichicon | 493-3873-1-ND | DigiKey

An externally hosted image should be here but it was not working when we last tested it.

B41691A8107Q7 EPCOS Inc | 495-3715-ND | DigiKey

 

[kenpeter]

I regularly test power factor correction evaluation modules that demonstrate
the latest control chips offered for that purpose. I have observed that for PFC:

Regulation must happens in two stages. This is because a conflict of interest
between a sinusoidal current ripple (in phase) desired by the power company,
and the load usually preferring to see a steady voltage without ripple.

You stick a high voltage cap (smoothing roughly 390VDC + intentional ripple)
between these two regulators. Without the second regulator, the cap required
to achive ripple free voltage (in the face of deliberately rippled current) would
be enormous!

But the second regulator means the resivoir cap need only hold enough juice
to ride out deadtime at the wall socket. Relieved of duty to provide the final
smoothing, it can be of a much more reasonable size.

Also because Joules=Volt*Volts*Farads/2, you get square law reduction in
cap Farads for the same stored energy, when you make the voltage higher.
Or square law increase of stored energy for same Farads...

Anyways, I am just saying: in this context, of holding a huge energy and
bucking this down to a lower regulated voltage, such a resivoir at 390VDC
may appear much much larger than Farads (and ESR) conventionally imply.

The cap at the output of the second regulator can be very tiny. Relieved of
duty to get us through deadtime, sag, etc. Very low ESR at high frequency
of replenishment are more important than ultimate capacity. Devices like
the post above...

 

[tsiros]

Something is wrong with the specs of your caps

Get a big boy with a ripple current of over 18A, get two and thats over 36A

B41607A7278M009 EPCOS Inc | 495-3710-ND | DigiKey

that's a 2700 μF 40 V cap

my amp has a 4700 mF 63 V cap

 

[OnAudio]

that's a 2700 μF 40 V cap

my amp has a 4700 mF 63 V cap

How much ripple current can it handle ?

 

[tsiros]

wat

 

[gootee]

I regularly test power factor correction evaluation modules that demonstrate
the latest control chips offered for that purpose. I have observed that for PFC:

Regulation must happens in two stages. This is because a conflict of interest
between a sinusoidal current ripple (in phase) desired by the power company,
and the load usually preferring to see a steady voltage without ripple.

You stick a high voltage cap (smoothing roughly 390VDC + intentional ripple)
between these two regulators. Without the second regulator, the cap required
to achive ripple free voltage (in the face of deliberately rippled current) would
be enormous!

But the second regulator means the resivoir cap need only hold enough juice
to ride out deadtime at the wall socket. Relieved of duty to provide the final
smoothing, it can be of a much more reasonable size.

Also because Joules=Volt*Volts*Farads/2, you get square law reduction in
cap Farads for the same stored energy, when you make the voltage higher.
Or square law increase of stored energy for same Farads...

Anyways, I am just saying: in this context, of holding a huge energy and
bucking this down to a lower regulated voltage, such a resivoir at 390VDC
may appear much much larger than Farads (and ESR) conventionally imply.

The cap at the output of the second regulator can be very tiny. Relieved of
duty to get us through deadtime, sag, etc. Very low ESR at high frequency
of replenishment are more important than ultimate capacity. Devices like
the post above...

That's a great concept. Are you implying a switching regulator?