[soitstarts]

Whoops, forgot. got another question. I have stripped a data cable from our home LAN. It has 3 twisted pairs in it that I was going to use for my signal wiring. Hows that sound? (I cant justify exotic wiring just yet).
also, I just got my 3 tranfos (Antrim, BTW Ron) whoo whee, 3 kgs each! These are big babies - 145mm diam. and to fit 3 in the enclosure I'm making is going to require them to be a bit closer than I expected.. is there a minimum gap I should have between them? I want my case to stay at a standard 435mm wide and 90 mm is already taken up by my heatsinks..
Sorry to waffle on, but... Would 1 16A impulse relay (if I can get one, out of stock at the mo.) for all 3 transformers be enough or will I need 1 for each channel?

[RonR]

Hi SIS,

It's marginal, but the 16A relay should be OK to handle the current of all 3 AKSAs. Hugh stated in another thread that the 100s can generate 80V peak to peak from a supply voltage of 50-0-50 (100V). Each module can therefore supply around 10A into 8 ohms, so 3 combined could draw up to 30A plus a bit depending on the amp's efficiency. Your relay is switching the power to the transformers at 240V, so actually you would draw a maximum of around 12.5A at mains voltage.

However, there are other considerations (e.g. speaker impedance varies with frquency, mains connections could be unable to supply the total current, etc). By having separate mains supplies to each transformer (including separate relays and split rectifier boards), there are sonic benefits in separation and transient response which perhaps someone better qualified than me could explain!

Cheers,

Ron.

[andyr]

Youse haven't specified what you intend building with 3 transformers in the one case but, with 3 trannies as big as that, it sounds like you are building 3 x AKSA 100 modules?

In which case, to avoid too much current (it's the switch-on current that's the problem!) going through 1 switch, I recommend you have a power cord, fuse and IEC connector for each transformer/power supply PCB.  That's what I did (xept I have a 25w, 55w and 100w in each case).

And, yes, the more distance between toroids the better ... to avoid their magnetic fields coupling.  For this reason, I have my power supplies in one case and the AKSA modules in another.

Finally, if your LAN cable is solid-core, teflon insulated then it will be fine for signal cabling.  If it's not then don't use it (bcoz you will compromise your fabulous AKSA amp!).  Hugh might be able to sell you some teflon Cat5 cable (Belden 1585a) alternatively I can, as I bought a 300m reel of it a while ago for speaker cabling, and have a lot left over!

Regards,

Andy

[soitstarts]

Im starting to wonder wether I should build 3 separate cases and have the standard heatsinks out the back..... Make it so that if I line 3 of them next to each other they will have a combined width of a standard 432mm.

OR... I have been toying with the idea of building the top and bottom of the case out of wood and arrange the torroids in a vertical arrangment but haven't seen this before and I guess there is probarbly a reason for it. Maybe I will have to mount the PCBs vertically if I can to make more room. I still have some ideas floating through my noggin so maybe there are even dumber ideas to come!! Could be an 'innovative' (crap) design comming up!!!!

Andy r, you are correct about the 3 X 100 W and how much would you want for 2 metres (ought to be enough, hey?) of the beldon cable. Go on, humor me...

[AKSA]

Hi SIS,

Signal wire from a LAN, rated at least 350MHz, is fine for signal wire on the AKSAs.  I supply a little CAT5E for precisely this purpose in the kit, so you need not make special provision.

Three 300VA toroids will create quite a thump when switched on, but you are dealing with 240V mains in Australia and the current at approximately 20A is not so great as in the States, where a power surge of around double this is to be expected for the first one or two mains cycles.  A 16A switch/relay should handle it well.

If you use a 3U case you can stack two toroids on top of each other.  A 3U is just over 5" tall (132mm);  each toroid is around 60mm tall, so three can be accommodated in the center of the enclosure.

However, with three 100W AKSAs you have a heatsink problem.  Two are just fine on the two heatsinks supplied;  but two 100W AKSAs on one heatsink is verbotten.  They will overheat.  But with judicious heatsink choice - namely one that is 100mm (4") tall - you could get away with it if the third channel was used as a center channel, for speech only.  I can supply a flanged, 100mm tall heatsink with a one week lead time if you need it.

Hope this is helpful!

Cheers,

Hugh

[soitstarts]

Thanks for the info Hugh.  I have a couple of flanged heatsinks that look the same as the ones on your recently shown case. (300mm long, 80mm wide and 80mm high) and was going to use those. Would 2 channels off 1 of those be OK.

Now that I've woken up properly.... If I use the above externally for the stereo pair and a supplied heatsink internally for the centre would that be OK? Now I understand the case with the 4 heatsinks..
I can see a budget overload.... May need a bigger fuse for the budget...


 
My wife when I report the budget blowout for this baby...