Aksa 55N+ Monoblock

rookster · « **on:** 28 Mar 2005, 09:01 am »

Can the Aksa55 be convereted to monoblocks? I assume this only involves cutting the power supply board in half, if this is possible.

I would like to bi-amp, but may not have the cash to do so, so just investigating other options.

The reason for going monoblock (or bi-amp) is to place the amps next to the speakers as they won't fit in the rack. (I can use my integrated amp as a pre-amp for the short term until I save up for a GK-1, as I only have room for one component).

I am just trying to work out the cost of it all so I can commit to it this time, but probably over the space of 6 months, 55N+ followed later by a GK-1.

I also want a very stylish enclosure, but may need to make something to suit.

AKSA · « **Reply #1 on:** 28 Mar 2005, 09:37 am »

Hi Michael,

Absolutely no problem; cut the power supply pcb in half, then all else is in pairs, highly suited to monobloc. In fact, construction in a single box is effectively dual mono anyway.

Cheers,

Hugh

rookster · « **Reply #2 on:** 28 Mar 2005, 10:41 am »

Hugh,

Thanks for the reply. Is cutting the 55 PCB in half the same as cutting the 100 PCB board in half? Does it rquire any new holes to be drilled?

I just need a nice stylish enclosure to suit now. The 19" rack enclosures are a bit too big for a monobloc. I was thinking of a Hammond box, but they look a little plain. Any thoughts or recommendations?

AKSA · « **Reply #3 on:** 28 Mar 2005, 11:30 am »

Michael,

Yes, just the same, a thin hacksaw will do the job very neatly.

You need to drill two holes for the star earth, one for each 'half'. The holes are 1/8", or 3.2mm; it isn't too difficult but you need to be careful to locate it on the edge of the pcb so that the head of the bolt does not foul the caps.

Cheers,

Hugh

soitstarts · « **Reply #4 on:** 28 Mar 2005, 12:09 pm »

Rookster,
Don't know if you have seen this site. Reasonable choice and prices but not sure if they have sizes to suit you. (Even if they can't play cricket

)

http://www.designbuildlisten.com/index.htm

If you do build your own cases, can I suggest you do a rough working mock up. I found that I thought I had it all covered but once it was working a whole heap of new (better) ideas came flooding in. I'm now doing mark 2.

Of course you've probarbly done this before and you don't realy need any advice.

, if so, sorry.

andyr · « **Reply #5 on:** 28 Mar 2005, 09:02 pm »

Quote from: soitstarts

Rookster,
Don't know if you have seen this site. Reasonable choice and prices but not sure if they have sizes to suit you. (Even if they can't play cricket )

http://www.designbuildlisten.com/index.htm

....

What a great site, mate! I've bookmarked it.

Regards,

Andy

rookster · « **Reply #6 on:** 2 Apr 2005, 07:21 am »

soitstarts,

Thanks for the link. They certainly are great cases. Maybe a little larger than I would like.

I have read a lot of the threads about monoblocks, cases and shielding. Now I have a thought about buling a power supply case that contains the 2 55N+ trannies and PS PCB's as well as the GK-1 trannies. This box is shielded and has one input power cord, but with 3 power switches. This then feeds the 2 55N+ monoblocks (only contains the PCB and heatsink) and the GK-1 through 3 detachable umbilical cables. The power supply box will be placed at the bottom level of my cabinet with the GK-1 on the shelf above it and the 55N+ monoblocks on the ground on each side of the PS box. The GK-1 may have a stepped attenuator in it. As per Malcolm's theory, I will remove all unnessary connection where I can.

Am I being obsessive, or could this work OK?

If this is feasible I will design and build special cases for all. If I am spending the money then I want it to look good. I still see getting the cases made for sensible prices the greatest challenge.

andyr · « **Reply #7 on:** 2 Apr 2005, 09:05 am »

Quote from: rookster

... Now I have a thought about building a power supply case that contains the 2 x 55N+ trannies and PS PCBs as well as the GK-1 trannies. This box is shielded and has one input power cord, but with 3 power switches. This then feeds the 2 x 55N+ monoblocks (only contains the PCB and heatsink) and the GK-1 through 3 detachable umbilical cables. The power supply box will be placed at the bottom level of my cabinet with the GK-1 on the shelf above it and the 55N+ monoblocks on the ground on each side of the PS box. The GK-1 may have a stepped attenuator in it. As per Malcolm's theory, I will remove all unnessary connection where I can.
...

Hi, rookster,

Wot U want to do should work ... but I don't think anyone can give you a cast-iron guarantee!

However, you need to take particular care with the DC rails to the AKSA 55N+s in the "amp" case (as you will have longer wires than in a normal amp).

My own AKSAs are built this way ... 3 x power transformers and 3 x half-power-supply-PCBs in one case, with a second case holding 3 x AKSA modules.

This gives me a "3-channel" amp ... and I have two of them, one for each (active) speaker. 'Xept my GK-1 is separate!

For the AKSA 55s, your "star earth" is in the PS case. This means you have to run '+', '-' & 'earth' wires between the two cases for each AKSA module, plus the two 'speaker return' binding posts on the amp case have to be taken back to this "star earth". (The speaker 'hot' binding post on the amp case is simply connected to the 'output' tag on the AKSA PCB.)

Plus you need to take another earth wire from the amp chassis back to the earth bolt on the PS chassis, where the IEC socket earth pin is connected.

I used 30amp low-voltage vehicle wiring for this (from Bursons) ... if you want to get really 'sexy', I have heard 14awg, teflon-coated, silver-plated copper, Mil-spec wire is better (from www.worldwidewire.com).

One step better than what you are thinking of, so I've been told, is to just have the power supply rectifying diodes in your PS case and have the filter caps in the amp case, close to the AKSA modules - ie. you have to cut up the AKSA power supply PCB still further ... or simply use point-to-point wiring for the filter caps in the amp case. This is because the diodes radiate RFI - hence should be removed from the vicinity of the AKSA modules. However, having the caps close to the amplifier modules minimises any lag when the amps want to suck power.

With the GK-1 power trannies in the PS case, you will have to run quite a few wires across to the 'amp case' to take the various voltages (sorry, I forget how many!). But, again, this shouldn't be a problem if you use thick wire. However, remember these will introduce AC into the amp case ... which is something you are trying to avoid!

Re. removing unnecessary connections ... remember that you pay for the convenience of having a selector switch - you will get better sound by doing away with this!

Finally, you say you will have one input power cord for the PS case. I suggest you should get some extra thick mains cable for this (should be available from Lawrence & Hanson) or have 3 separate power cords.

Regards,

Andy

rookster · « **Reply #8 on:** 2 Apr 2005, 09:51 am »

Andyr,

Thanks for the reply. Sounds more complex than I thougt, but then that is why I asked. Thanks for the explanation. I will have another think about it.

I have seen your monoblocks and how you had seperated the power supplies, which was the basis of my inspiration. Perhaps splitting the GK-1 is too much work, but I will think further.

AKSA · « **Reply #9 on:** 2 Apr 2005, 10:58 am »

Andy, Michael,

I would suggest humbly that cutting up your pcbs to accord with purist notions of better sound and less interference is probably ill-advised. The reason is that it greatly magnifies the interconnection issues - themselves sources of RFI - and complicates the build enormously.

I designed things in an integrated way taking account of relative proximities, I can assure you!!

Noise levels can be brought to extremely low levels in the GK1 with care and attention to earthing.

Hope this is helpful,

Cheers,

Hugh

Rhythm Willie · « **Reply #10 on:** 2 Apr 2005, 11:10 am »

Some time ago I built some 100n monoblocks(they are now upgraded to +).

The original (just after completion) pics are below(numerous black gates ,silver micre's,bleeder resisters etc since).

The main aim in the layout was to completely isolate & shield mains and power supply etc from interfering with the low level signal input & to have a short distance between the power supply & the PCB to get a quick dynamic sound. The speakers are triwired with short cables.

Obviously I get no "crosstalk - even each power cable has it's own unswitched run to the fuse box which is on an outside wall just to the left of the left speaker. I am also fortunate(living in the country) to have a dedicated large transformer from a high voltage power line just for my home.

The original aims were accomplished with absolutely nil noise/hum & dynamics & bass to kill for.

Good luck - pics might give you some ideas.

http://au.f2.pg.photos.yahoo.com/ph/dennis_traeger/album

rookster · « **Reply #11 on:** 3 Apr 2005, 12:48 am »

Hugh,

Thanks for the reply, I think I will leave the GK-1 in the 1 chassis - certainly seems easier and more practical. I will also leave the tranny in each 55N+ monoblock chassis, but shield it as per other examples in the gallery.

Rhythm Willie,

I have seen your monoblocks before, very impresive. Where did you get your chassis parts made? I would like to use the heatisnk as a panel and then make the rest of it up with panels that bolt together. Just trying to work out where and how to do that.

Rhythm Willie · « **Reply #12 on:** 4 Apr 2005, 03:18 am »

Rookster,

I designed the cases on graph paper,but got a small aluminium/metalwork guy who lives/runs his business near where I live.
to cut them,recess the heat sinks & drill the panels & tap them for me.

I then got them anodised at the same place in Elizabeth,South Australia that also does Halcro Amps - cost about $100 for that and about $300 for the metalwork. If you want the cases perfectly smooth then the trick is to have them fine sandblasted first.