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-   -   Ultimate PSU for power amps? (http://www.diyaudio.com/forums/power-supplies/51749-ultimate-psu-power-amps.html)

The golden mean 16th February 2005 11:30 PM

Ultimate PSU for power amps?
 
Well, noting is ideal in the electronic world, but what sort of (mains driven) power supply do you suggest for a high quality power amp, and what compromises are you willing to make, if there is a limited budget? Please think of it as a money-no-objekt project at first, then take away the least significant parts.

While something of this has been covered in other threads as "Regulated vs Traditional" and E-I core or Toroidal transformers,I now want a "holistic" approach, i.e. everything!;)

Transformers, regulated PSU or not, chokes and if you like them,where do you put them? Earting, rectifiers-single or twin bridges, capacitors;many small or a few larger? Slit-foil capacitors and T-network ones? Your considerations are most wellcome!
Do fuses make a difference to the sound quality of the amp?
Does a regulated supply have to be fast?

I hope I donīt ask to much......
:cool:

raidfibre 17th February 2005 12:12 AM

Large toroid, 2x required rating. Stiffer is better
A one or two mH inductor and cap filter on the AC input, hopefully would also keep the inrush current low enough. If the inrush current is too high I'd put an NTC resistor in there.

Very large rectifiers, >100A some people like to use "ultra fast" rectifiers, but they are designed for use at high frequencies, the line frequency is 60Hz...(50)

Unregulated is fine, as your amplifier should react to any 60Hz noise.

Several mF of smaller size capacitors for lower resistance.

The whole thing would be in a shielded grounded box.

Of course, this is all subjective that's why several people will probably reply with completely different ideas. I'm too practical to mention words like "silver" ..

Mr Evil 17th February 2005 12:24 AM

An SMPSU, for the size, weight and efficiency. With good shielding and filtering they can be very clean.

raidfibre 17th February 2005 12:42 AM

Quote:

Originally posted by Mr Evil
An SMPSU, for the size, weight and efficiency. With good shielding and filtering they can be very clean.

I was going to say that but then I figured that audiophiles really hate non-analog stuff. My educational work goes into designing SMPS.

SY 17th February 2005 12:45 AM

Before "designing" a power supply, it might be a good idea to specify the voltage, current, topology and class of each stage.... IOW, the actual engineering requirements. Once that's done, you've got a shot at coming up with useful answers.

Bob03 17th February 2005 03:08 AM

Designing your own power supply
 
You can start from here.

The golden mean 17th February 2005 01:15 PM

I intend to use a common supply for a four channel solid state
amp at approx 250w/channel in 8 ohm. Will use two 1000VA torodial transformers. They will very well be a rote for garbage (?) in , so some sort of filtering is necessary, problem will be to find a clean ground, as I live in a house with a lot of washing machines etc . in the basement. Grounding my equipment clearly makes it
sound of system less good.

Separate signal ground and "power" ground, may make sense, but they have to be connected in some way.
I will use a rather "slow" stabilized supply, then route the current to smaller banks of caps, near the amp modules. I donīt think a
stabilizer should be ultra-fast as this will lead to ripple and un- stability, because a servo-system can easely overreact if itīs to fast, i.e the stabilizer has to have rather "high" internal resistance, and more fill the caps in an even stream...
Sudden current demands should be managed by the caps,near the amp modules.
Regarding caps, I think quantity isnīt all ;a large bank of capacitors,may not stop unwanted signals from the mains to enter,especially if the supply is unregulated.
I believe in parallelling different sorts of electrolytic caps, as I think each brand has a signature, just a feeling of mine.

One very important thing is to be consious about the high currents that floats, thus all connections should have as little resistance as possible, soldered or screwed terminals are essencial.Some commersial amps seems to be designed with prime consern about seviceabillity, and I do wonder what will happen to them with time.
:whazzat:

Vibratation control is also important, to my mind, large transformers vibrate under use,so someting like mechanical decoupling will probably improve the sound. Vibration in cabels inside the amp, may effect the end result,I guess.

I will use this amp to drive the woofers (Volt RV 3143) and the
upper bass units (Accusound ceramic 8" units) . The later will operate from 80Hz to 280Hz. A friend is making a active filter for
the system. The speakers will weigh about 340 lbs each, not a
figure of quality in itself.
I will come back with some more thoughts.

AndrewT 17th February 2005 06:53 PM

Hi,
try separating the two transformers and rectifiers and smoothing into two boxes. Locate one box by each sub & bass with very short speaker cables. i.e. build two stereo amps with lots of smoothing and current capacity and save the subtle selection of components for the mid and treble amps again two stereo amps at the speakers. Long interconnects are much cheaper then long speaker cables especially if you go active.

SY 17th February 2005 07:36 PM

Toroids are nice with respect to size and radiated field, but the tight coupling between primary and secondary makes getting rid of power line disturbances more of a challenge. Some high end designers swear by EI power trannies despite their issues.

The golden mean 18th February 2005 05:38 PM

Toroid transformers may be a weak link, but here in Sweden I havenīt found an alternative. When it comes to tube amps, I have read a summery of a test, which concluded that people seemed to prefer output transformers with an amorphous(? not in my dictionary) core to other core materials,in otherwise "identical" amps. Amorphous should mean theat the material is not grained oriented, I think. Grain oriented sheets of core material are present in ordinary E/I cores or in toroid transformerīs core material. So, my ideal mains transformer would probably be a C-core transformer made of some expensive material, and with silver litz thread windings.:devilr:
As transformers are heavy stuff, importing them from e.g. the US
will cost a bit in shipping, in addition to the 37% we pay in customs duty and sales tax.....

Regarding the typology of amps, monoblocks or all in the same box, I agree that monoblocks are the better alternative, in many cases. However, if a PSU with some top-flight components like Mundorf M-Lytic HC capasitors (www.mundorf.com) , expensive
diodes, stabilazation and so on will be used , costs will in my case be a problem.
So, eighter I will build two stereo amps , and put each amp near the 12" and the 8" speaker boxes(there will be three separate boxes per channel), or I will perhapes build a central power suppy, and feed DC to four separate amp boxes, which will only contain banks of capacitors in their supplies for the output sections i.e.
I want to have regulated supplies for the output-stages, but
can think of unregulated, but well filtered AC/DC supplies for the driver stages.
A switch-mode supply is hard to realize, without disturbing some sensitive electronics elswhere in the set-up,thatīs my opinion.

And as we seldom deal with cost-no-object projects, and as I am a believer in that component quality counts,the question (here and now) is , where should I put the money, in a cost effective way?
The goal is clear, a very good sound quality,with the restriction of not too much current consumption, as I intend to drive the mids/treble (2*C79 and an Eton ER4 drivers per channel) with
my sturdy LC-audio Patriot class A 100W/channel amp.This amp alone runs hot enough!

In may temporary system, I run everything in mono, but with two
"subs"driven by my old monoblocks and short speaker cables , and I use a J Rowland Synergy II preamp , a VMPS(modified PSU of course ;) and better ICīs) , a Sony SACD-777ES with a home made DAC.
Room treatment have had the best pay- off with regard to time spent and money payed, especially trapping some low bass, has made rythms more intelligible and in fact "faster" ,wow!I often listen to Reggae, Afro music , jazz , Mary J. Blige. And IMHO,some systems , -even expensive ones, dosenīt let the "soul " of this type of music out!
I even think that amps with NFB networks profit from room treatment, because there will be less back-EMF to be handled by the amps! Just a speculation, though.


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