[Felipe]

Hi guys,

I need your opinion on this matter, i know this has been discussed before, but i couldn't find the topic...

I am building brand new boxes for the AKSA, and because of size limitations (box too big) i will be mounting a separate power supply for it.
Now, what do you think is the best solution, in the noise/interference subject :

Plan A
Box1 - Toroidal transformers + soft starter pcb + power supply caps
Box2 - Aksa pcb

Plan B
Box1 - Toroidal transformers + soft starter pcb
Box2 - Aksa pcb + power supply caps

In Plan A i will carry a continuous current signal from Box1 to Box2, vs the alternate current signal in Plan B.

I can use shielded wire in both cases to prevent interference, but i suspect that Plan B would be more likely to imunity.

Nevertheless i prefer Plan A because of box limitations. The power supply caps would be very close to the aksa boards....

Hugh, can you give a hint here ?

Alternatively i could make 2 mono blocks. But i would have to figure out a way to split the soft starter....

Thank you for helping

Felipe

[andyr]

Hi Felipe,

I'm wondering why you are planning on using a softstart circuit?  If you are using the standard" 300VA transformer on an AKSA 100, I suggest it is not necessary ... my speakers are run 3-way active so the drivers are connected directly to the 3 AKSAs and I have absolutely no problem!

With no softstart circuit, you could build two monoblocks! )

If you want the softstart, I would do an arrangement half way between your A and B:
Box1 - Toroidal transformers (+ softstart pcb) + rectifying diodes
Box2 - Aksa pcb + power supply filter caps.

This puts the PS caps right next to the AKSA modules (where they should be) but keeps the "nasty" components (transformer and rectifying diodes - which generate RF) in the other case.

Regards,

Andy

[Geoff-AU]

You could put filter caps in both boxes, it would guarantee good local current availability and reduce the chance of DC ripple voltages going anywhere near your amp box.  Additionally you'd have more capacitance overall which would reduce the amount of ripple

Building 2 monoblocks would eliminate your need for the soft-start circuit.  I don't really think you need one anyway, but that's just me!

[AKSA]

Hi Felipe,

Thanks for posting, good question.

There is a very good technical reason NOT to use a soft start.  This will delay settling of the amp and create a largish DC offset, around 12V, for more than one second.  It's very briefly there at switch on, around 200mS, does not damage anything, but with a softstart it will be a significant issue, endangering your speakers.

I would go with Plan B, but delete the soft start pcb.  If there are problems with the house wiring, you should address them first.  Another option might be to use EI transformers, which do not have such a surge current (10X!!) as toroids.

Hope this is helpful and points the way!


Cheers,

Hugh

[andyr]

Hi Felipe,

Another option might be to use EI transformers, which do not have such a surge current (10X!!) as toroids. ...

Hi Hugh,

For us un-techernical types, can U hexplain how come an EI transformer does not have as big a switch-on surge current as a toroid?  One is still saturating a core on start-up, I would've thought?

Regards,

Andy

[AKSA]

Hi Andy,

A lot more copper, more primary inductance, and thus more resistance to surge at switch on.

Toroids have low copper content, and a fully enclosed, highly stressed magnetic circuit.  There's not the resistance in the windings at turn on, either, so much higher currents flow in surge.

Cheers,

Hugh

[andyr]

Hi Andy,

A lot more copper, more primary inductance, and thus more resistance to surge at switch on.

Toroids have low copper content, and a fully enclosed, highly stressed magnetic circuit.  There's not the resistance in the windings at turn on, either, so much higher currents flow in surge.

Cheers,

Hugh

Thanks, Hugh,

However to my tiny brain, your answer throws up more Qus!!  Can you possibly provide answers?

"Toroids have a low copper content" and "There's not the resistance in the windings" ... do you mean toroids have less wire in their primary circuit thus less resistance in their primary winding (for the same VA rating)?

Isn't this a good thing ...  given one is trying to make the lowest impedance mains power source for the amp power supply?

Also (talking about EIs this time) "A lot more copper, more primary inductance".
Shirley this extra inductance is a baaad thing?
Or is it this inductance which makes an EI power transformer a better inhibitor of mains-hash?

Regards,

Andy

[Felipe]

Hi,

Thanks so much for the answers !

About the reason for the soft star circuit :
- I keep blowing the phase down when i switch on the amp, with both toroids connected at the same time. Yes , probably the monoblocks would solve it. The problem persisted after changing the the electric board, main reason is the electric water motor i have wich uses all 3 phases. Just cannot be on when i switch the amp.
Going with PlanB without soft start circuit just isnt an option....

I can go Monoblocks without the soft starter  OR
I can switch to EI transformers (   give away the toroids $$ )  OR

Hugh, do  all soft start circuits do that to the DC offset? Its logical that they do....if i understood correctly the theory.

Monoblocks would be more costy...extra button....extra case desing....

What about a button between the Caps and the amps ??

[AKSA]

Hi Felipe,

Hugh, do all soft start circuits do that to the DC offset? Its logical that they do....if i understood correctly the theory.

Actually no, only if the current supply to the input long tailed pair is NOT a current source.

Monoblocks is probably the way to go if you say one trafo is fine on your house wiring.  Another option is soft start with a power relay to switch in the speaker once the amp is settled.

Andy, to answer your questions I'd have to do more research, which I'm hard pressed to achieve right now.  Give me a few days, and we'll meet over coffee, OK?

Cheers,

Hugh