Hiraga "le monstre"

[neazoi]

I received the 80AH batteries today.
Well... they are really BIG
No way to make a box for them
The ecc83 in the lower corner is just for comparison.

[danieljw]

you have a nice power supply there neazoi !!!!!

i am jealous !

-Dan

[neazoi]

Dan, these are quite expensive, 270Euros including the charger!
That is what I said earlier to another member, it is a simple but not cheap amplifier, if you want the best performance out of it.

But... How much a PSU would cost with all these capacitors? (And it could never be cas lean as the batteries)

[Lumba Ogir]

neazoi,

But... How much a PSU would cost with all these capacitors?

The bad news is that you still need them (in fact, as already stated). A couple of Farads, however, will be sufficient. I recommend Mundorf MLytic.

[neazoi]

Lumba, to be honest I am not really confident why are they needed.
Does this has to do with rapid draws of current in sharp mysic cut offs?
Just a short explanation would be appreciated.

[AKSA]

Caps are needed for the batteries because the series impedance of the source rises rapidly after about 10KHz.

However, you don't need all that much, about 1000uF would be fine as long as it's good quality capacitance.

Hugh

[neazoi]

Ah right, so connecting a small 1000uF electrolytic in parallel of each battery will solve this right?

I think the schematic of audiomanics does this on the PCB. Just replace the 47uF with a 1000uF one?

Here is the link
http://audio-constructions.com/monst...alemonstre.png

Elna Cerafine will do better than Mundorf?

[Lumba Ogir]

neazoi,
the good news is that I over exaggerated a little bit, 1 Farad would be OK and the Chhsi brand is cheaper, but on the other hand, it has awful sonic properties and an extremely short life span. I`m somewhat hesitant about it...

[neazoi]

well 1F = 1.000.000uF it's still too expensive and difficult to find and I am really not too much convinced if so big capacitance is needed in battery only operadion.
I think for battery only operation it is better to have a high quality capacitor rather than a big capacitor.

Let me propose another scenario and I would like your comments on this.

I have used cerafine elna caps in tube preamplifier with great success.
Their price is very cheap on ebay http://cgi.ebay.com/10-X-ELNA-CERAFI...arms=72%3A1205|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A1|293%3A1| 294%3A50

I was thinking of connecting some of them in parallel. In that way the total resistance of the psu (battery and caps) is minimised too.
The total capacitance will be something about 5000uF, which would be enough for this...?

[AKSA]

Neazoi,

There are two issues with audio power supplies.

#1 Ability to supply large currents very quickly with little sag, and
#2 Series impedance for earth return of speaker currents.

The first issue is pretty clear; to reproduce sharp transients, a low source impedance is needed, particularly at higher frequency. Bass frequencies are not so bad because they are slow, and SLA has very little sag at high current.

However, about 50% of the energy in music is above 500Hz, where the deficiencies of a SLA battery are significant. Midrange and top end, which are faster but lesser current draws. Bypassing the battery with quality film caps is very helpful here.

Issue #2: All amps with bipolar power supplies alternately use the + and - rail caps to form the return paths for the two circulating currents from rail, though output device, to speaker, to ground, and back to rail. Therefore a high ESR in this link will affect the speaker operation. While the ESR of the battery is very low up to 10KHz, beyond this it rises rapidly and can affect damping factor. Balanced against this is less requirement for damping with rising frequency, but for neatness it's a great idea to have high quality caps bypassing the 1000uF battery cap. Say something like a 22uF silver/oil Mundorf. If you are spending a lot of money on the supply, might as well go the whole nine yards and use a few nice caps for bypassing. For electros, use something like Black Gates, or Nichicon Muse.

Hope this helps,

Hugh