pi-filter Power supply for Alephs

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I would like to have your support guys, some hints about CLC pi power supply.
I'm actually building the pre Aleph P1.7 and i'm trying to evaluate the possibility of having a more refined power supply stage.
I was thinking on building a PI CLC stage.

Would it be better of a regulated power supply?

is this type of power supply always better in absolute or a regulated power supply is better for pre stage and a clc pi filter is better for a power amplifier?

Could you guys give me some hints on how to build an efficient pi-clc power supply?

Thanks in advance.

Best,
Stefano.
 
I am just finishing rebuilding the PS for my Aleph mini.

I first tried a regulated supply, then I went back to the CLC. But this is for a power amp. Looking at the experiences from the above and the PS I had for my BOsOZ, I believe the regulated supply, slightly modified, shown in the BOSOZ article is best.

The differences I had were:

1) I used a single transformer, 350 VA, 55v secondaries.
2) I used a regular amp PS board (with rectifiers) and 6800 X 3 microfarad 80V caps (panasonic) for each rail. (this is a Marchand electronics PS15 board).
3) Output from board above is fed into the regulated PS board shown in the BOSOZ article.
4) I put much larger output caps on the BOSOZ board.

This PS showed absolutely no ripple or noise spikes that I could see on my scope. I think I was using about 100 ma current all told from the PS.

Of course, this is kind of the big stupid way to do it, I am sure there are more succint methods for getting no ripple. And it may not even be necessary for the aleph p 1.7, but this was really easy to implement and worked exceedingly well.

I think you will still have ripple with a CLC.

JJ
 
CLC filtering is used for;

-glasswork amplifiers, where the high voltages makes a regulator expensive and bulky.
-(Class A) power amps, for very effectively reducing ripple voltage at the high bias levels.
-digital stuff, for high frequency filtering.

Where does that leave a P1.7 ?
Already thought of what the values for the coil and the lytics will be like if you desire it to be "efficient" ?

regulated
 
thanks a lot.

just thought: why would you let follow the regulated part with RC filter of few ohm? (i mean in the schematic you are using an R=3.3)

Just another though passes through my head right now:

I would like to build a separate box with the power supply that ...stayed on what you guys and Nelson have just said to me here.... will be regulated.......and...the thought is:

since after the regulated part (let's say after Q23 quoted from the Power supply sheet) i would place a large amount of uF ...or better...F :cool: ..........

is it true that it is always a good rule of thumb to place the filtering as close as possible at the board?
Although, should i place another filtering directly on the box containing the pre board or it doesn't matter?

I don't know if i was clear by eplaining my thoughts and if not, i'm sorry ...but this is not my language and sometimes it's difficolt to explain what passes as a lightening on my mind... :bawling: :cool:


One more question: where can i find very good and fine power tranformer? i did read on the forum something about piltron transformers, but i don't know what they are made researches but without results.

Can anybody give me some good advice on where to find a very high qulity 60V transformer (i will need 2 of them)

As the my very last thought...if anybody may give good hints on how to improve at the maximum state the power supply stage...i don't know replacing the zener in series...or something....

every good suggestion is welcome...
 
sorry i haven't understood what you meant with A4 plain.

But i did understand that up to your experience the chocke (pi-LCL) filter sounds better than a regulated supply? is that correct?

could you share in more detail your experience with CLC power supply...i mean... what have you tried to compare the different supplies on? pre amp-power amp-pre phono....and so on?
 
Stefanoo said:

just thought: why would you let follow the regulated part with RC filter of few ohm? (i mean in the schematic you are using an R=3.3)

I would like to build a separate box with the power supply
is it true that it is always a good rule of thumb to place the filtering as close as possible at the board?
Although, should i place another filtering directly on the box containing the pre board or it doesn't matter?

One more question: where can i find very good and fine power tranformer? i did read on the forum something about piltron transformers, but i don't know what they are made researches but without results.

Can anybody give me some good advice on where to find a very high qulity 60V transformer (i will need 2 of them)

As the my very last thought...if anybody may give good hints on how to improve at the maximum state the power supply stage...i don't know replacing the zener in series...or something....



--The 3.3 Ohm resistor reduces inrush current (not really a big problem in this case) and provides a bit of extra isolation.
--An external power supply is a fine idea. My feeling is that you should have some capacitance in the power supply and next to the circuit. If it comes down to a choice of one or the other, put the capacitance next to the circuit.
--If you put the term Plitron into Google, you will find that they have a website at www.plitron.com. There are plenty of good transformers out there. That said, I have used Plitron many times and like them.
--I don't understand your last question. Give it another try.

Grey

P.S.: I suspect you will find that A4 is being used to mean Aleph 4.
 
Stefanoo said:
sorry i haven't understood what you meant with A4 plain.

But i did understand that up to your experience the chocke (pi-LCL) filter sounds better than a regulated supply? is that correct?

could you share in more detail your experience with CLC power supply...i mean... what have you tried to compare the different supplies on? pre amp-power amp-pre phono....and so on?

A4 means Aleph 4

Haven’t tested a regulated supply to compare with, what I said is that a CLC or LC has very good regulation -and very clean supply at it- and think it would be similar to using a regulated supply, if not better soundwise.

Building a regulated supply for this type of amp - taking in consideration the amount of current draw and power required – would be a nice challenge and to my opinion not worthwhile having the alternative of a choked Pi filter.
All the power Pi filters mentioned were tested on the Aleph 4. But I have also tested CLC and LC on preamps with nice results too.
:) :)
 
:) sorry my question was really confusing, i'll try again:

may anybody give some idea on how to improve the original power supply for the PREAMPLIFIER Aleph P 1.7?

I would like to have the best supply as possible.

About the filtering: yes, i was thinking on having capacitor filter on the separate box and another block close by the main board.
 
I thought that the big guy just gave you your answer.

If you add an RC filter after the regulator, the resistor isolates the lytic from the regulator output.
The BIG cap combined with the RC filter on the Aleph P board makes a CRC, or RCRC if you include the resistor at the output of the regulator. With the regulator stage added you'd have a 3-step filtered powersupply.(if the voltage regulator counts as 1)
The single ended Aleph P already has the huge advantage of drawing a constant current.
99.99% or 99.991% efficient rail filtering is interesting only for number addicts, imo.

On push pull amplifiers there's the option of using a resonant choke supply, something i've done to compare it with bulky hardware fully regulated output amp designs such as the L'Ampli Fou Fou by Gerard Perrot that i copied/cloned. (or whatever the proper word is) At some point the level of the powersupply will surpass the amp design, like for instance what the French L'Audiophile guys clearly did in the early 80s.
 
Now i'm totally guessing, so i'll say my idea and if it's wrong...please correct me... :angel: :

if i would add before the regulated part, after the bridge, a 1 or 2 stage of pi-filter and then, after this,the regulated circuit with the mosfet q23,capacitors, the zeners (that i would consider,at this point, to take them away since i would regulate the supply voltage in first step with the chokes)
Wouldn't this topology get the benefit of high frequency filtering responce from the choke filtering and the good ripple response from the regulate part?

Is this idea crazy?

If not...could somebody here help me to develop better this idea?
 
Formerly "jh6you". R.I.P.
Joined 2006
I hope that you be more specific.
As the PSU is part of a target amp,
the types of PSUs must be depending.

Hardly do I think there is one answer
that is applicable for all different amps.

I think that finding what is good enuf
for the purpose could be the best thing
we might get through this forum.

For P1.7,
the original PSU is more than good enuf,
IMHO.
I think Papa has long experience in
this area.


:darkside:
 
Stefanoo said:
Is this idea crazy?

Nope.

But as an alternative you might go one step further and do what i do with all my audio gear.
Place a symmetrical filter behind the (grounded) wall socket and a balanced separation transformer after that before feeding the 240 Vac mains to the amplifier (transformer).
I use 10 or 20 amp filters with an oversized separation transformer (unfused, each separation toroid is around 5KVA nominal, all foil caps in the filters on the picture are MKPs)
2 of those setups for the monaural power amps, 1 for the pre-amp, 1 for the other stuff.
All four filter/transformer sets together weigh in at around 100kg.(perfect stuff for audio fools on steroids)
Peter Daniel posted on balanced separation transformers, how to convert a regular one to balanced operation, plus the production number of (an expensive) one made by Plitron.
 

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I understand that Mr Pass is the best experienced project developer on all over the Audio Panorama.

But, let me give you an example:

The Aleph Ono...the Pre Phono:

The newer version of the Xono, accordingly on what written on the forum, the majority of the improvements are made on the power supply.
What does it mean?
It means that, at the time of the first version, Nelson decided that that PSU was enough for its purpose.
he probabily traded parameters as performances-expences-stock available.
Let's say that somebody at that point would have wanted to improve the power supply.

:rolleyes:

Nelson when develops a commercial project, has to trade a lot of factors like the cost of the project ,the left over stock material available to keep in consideration (if i'm wrong...my best apologies to Nelson) and the sound qulity (this is certainly the first but not the only)
Pease Nelson, correct my view if it's wrong.

Since i'm building one unique piece for myself and i don't have to gain any money...i don't care if i end up spending few $$ more as long as i'm taking the maximum out from the project.

For instance my layout is made for the Auricap Capacitors, Naked S102 Vishay and Riken Resistors.


I would like to improve the PS Unit even if it would end up being better than the project for itselfs.
The PSU is the very base of each project: just reflect on the special filtered chord or the external filter unit that most of the audio users employ with great results.

So every suggestions on power supply filter improvements are very welcome.
 
Member
Joined 2004
Paid Member
Stefanoo:

I agree with you on this, but don't know how to calculate the values for a pi filter. I have a set of Veteran's Aleph P 1.7 PCBs and am planning on building a 2 box preamp. I'll use Veteran's PS boards in one box and would like to add additional filtering in the preamp enclosure.

Can someone explain how you determine the values of the capacitors and inductance (is that a resistor or a choke)?

Thank you,
Scott
 
Stefanoo

If it helps here is what I do - I guess others may have different ideas and may not agree - but here goes expecting to be shot down.

If you refer to the Nelson Pass drawing on page 2 of the "Balanced line zen stage", I basically use that design with c103 to c106 increased to 1000uf and c101 and c102 increased to 3000uf. The zener values and r101 and r102 values are calculated for the voltage and current you require from the regulated supply. The Nelson Pass article "the zen variations part 3 - Active supply regulation" shows how to calculate these values. I then add a rc filter after the regulated stage with 3ohm and 3000uf. All of this is remote from the pre amp in a case with the transformer.

In the pre amp I add between 250uf and 3000uf on each rail next to the pre amp module. The uf that I add here depends on the particular pre amp, For the Aleph P1.7 I added 1000uf. I do find that the final capacitor in the pre amp case is important and normally fine tune that by listening to transients and base responce of the pre amp.

Don
 
jacco vermeulen said:


Nope.

But as an alternative you might go one step further and do what i do with all my audio gear.
Place a symmetrical filter behind the (grounded) wall socket and a balanced separation transformer after that before feeding the 240 Vac mains to the amplifier (transformer).
I use 10 or 20 amp filters with an oversized separation transformer (unfused, each separation toroid is around 5KVA nominal, all foil caps in the filters on the picture are MKPs)
2 of those setups for the monaural power amps, 1 for the pre-amp, 1 for the other stuff.
All four filter/transformer sets together weigh in at around 100kg.(perfect stuff for audio fools on steroids)
Peter Daniel posted on balanced separation transformers, how to convert a regular one to balanced operation, plus the production number of (an expensive) one made by Plitron.


Referring at this: sorry i haven't understood very well the topology.
I don't know if you could explain to us with different words...may be using a schematic to support the concept.

About Piltron: what trasformer would you use for the Aleph P1.7?

And one last thing....may someone give an insight on how to calculate a pi filter?
 
this is the one P-D used.
Some basics on choke supplies: here
and here
Find a HAM/ARRL handbook for more on choke filtering.
To model a pi filter you can try SwitcherCad or download PSUDesigner2 from Duncan Amps.

A fast approximation:
-choose an inductor size.
-current through the coil= 1.2*bias current.
-divide this by the maximum ripple voltage level you desire.
-divide by frequency (100Hz or 120Hz)
-divide by 2.
-subtract the inductor value(H) from this.
-divide by 2 again.
Gives you the lowest capacitor value.

Online from our dog lover Jim Hagerman in Hawaii: here
 
Stefanoo said:


I would like to have the best supply as possible.


I used to wonder who the most beautiful woman in the world was. The question tormented me. For years I was convinced that there was, in fact, one single woman who was the finest in every conceivable way.
I got over it.
While it is laudable to want to build the ultimate power supply, I fear that the real problem is that you're seeking an absolute answer to a relative question.
Asking such an open-ended question will result in twenty different--and contradictory--replies. In spite of your earnest desire to learn, you will only achieve confusion and frustration, in part because you're asking the wrong questions.
So what are the right questions?
In a year or two you will know what the right questions are...for you.
In the meantime, may I suggest that you simply build the circuit as it's shown in the schematic, perhaps with a little additional capacitance. Use good parts and you will be happy. One of the nice things about an external power supply is that it's easy to change it later, after you've had time to think things over. In the meantime you will have had the benefit of music to help you ponder the eternal mysteries...
Such as: Is Jessica Alba really more beautiful than Scarlett Johansson? How about Halle Berry? Or that girl who worked at Hooters?
Like I said...mysteries...

Grey
 
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