[soitstarts]

Hello there,
Now that I have finally ordered my kit    I now feel its time for the basic (dumb) questions.
I'm currently designing my case and will have the heatsinks on the outside. Will I still need venting on the lid? If I do, what is the source of heat? Is it the amp and heatsink ledge or maybe the tranfos?
Any advice will be much appreciated..

Regards,
Martin

[Lost81]

Hi Martin (Is your first name "Austin"? I certainly hope they do start--with the kind of prices they command these days ),

If the kit you ordered is the 100W version, there are 2 heatsinks for the drivers on the PCB itself. I do not know how much heat is emitted through them though...


-Lost81

[AKSA]

Martin,

I little heat does come off the drivers, just as Benny states.  So you need a vent hole(s) about an inch and a half in from the vertical face of the heatsink base.

Benny,

Resistors as loads to run in the AKSAs are just fine.  Be sure they are suitably rated for power, however;  I'd use at least 25W for the 55W AKSA, and around 50W for the 100W module.  Of course, if you are running them very low, these ratings are probably overkill.  Best test is to use your finger - if you can hold it for ten seconds on the body of the resistor, all is well.  Otherwise, go up for dissipation!

Cheers,

Hugh

[EchiDna]

Hi Martin (Is your first name "Austin"? ....

-Lost81

  that would ASTON not Austin

sat in a vanquish a few weeks back for fun, then politely ran away when the car yard told me the price for it (second hand, 35,000km, 2 years old and still over S$750k!!! yikes...)

anyway, back on topic, I'm living in the tropics and I've got no ventillation holes in my case at all, typically it is 32-35 degrees celcius and 90+% humidity here EVERY day and I've not had a problem in neraly 2 years of almost constant use.

[Seano]

Hey now this sounds like my kind of thread!

Martin, the transformers will throw out a bit of heat (not much) but the heatsink ledges are your greatest source of internal heat. Most rack cases come with vented lids as standard but they can be a bit of a pain to adapt your heatsinks to.  
Given your likely access to machinery, raw material and metal engineering in Newman see if you can find a sheet or two of 1 or 2mm perforated steel plate (the one with lots of holes punched/drill in it).  If you use those as your top and bottom then you'll have more than enough through ventilation. You won't have to drill any holes to mount the feet too!

If you can get a 1 or 2mm deep ledge milled into the top of each heatsink then your top will fit nice and flush too.  You'll need to get the bottom folded up on either side about 50mm to get the necessary height for the power supply

[soitstarts]

Thanks for the advice guys. Things are starting to come together now.

Hey now this sounds like my kind of thread!

Given your likely access to machinery, raw material and metal engineering in Newman see if you can find a sheet or two of 1 or 2mm perforated steel plate (the one with lots of holes punched/drill in it).  If you use thos ...

The way things are booming at the moment you can't get a look in unless you're a huge mining company, we have one hell of a skills shortage at the moment so I've had to improvise a bit. Oh yeah, that and the fact I basicly doubled my estimate given to wife at the birth of this idea

Stay tuned for more dumb questions comming soon...

Martin.

[soitstarts]

Hi again,
Okay, heres another one. Would a thin (1.5 mm) plate between the tranfos and PCBs have any benefits? I noticed people separating componets with different cases but I am not sure if an aluminium plate has any benefit. I would also use this plate for my earthing as the back of the case is going to be pretty crowded as it is..

Martin.

[andyr]

Hi again,
Okay, here's another one. Would a thin (1.5 mm) plate between the tranfos and PCBs have any benefits? ... Martin.

Hi, Martin,

I presume you intend to isolate the 2 traffos from the PCBs?  I guess this depends on the case layout you are adopting ... yes, shielding the traffos behind a 1/16" (1.6mm) metal plate would certainly do good - rather than harm - but it may be difficult to effect.

I make a point of doing this with source components (phono stage, GK-1 and active crossovers) but I didn't bother with my AKSA 55 and this has not resulted in any hum that I can hear.

You need to ask somebody who knows whether steel, aluminum or copper plate would be best (I've just used mild steel but maybe a non-magnetic metal is better?).

Regards,

Andy

[AKSA]

Martin,

You can certainly put a thin sheet of mild steel (tinned steel is fine) between toroids and modules, but with sensible wiring routing it will make no difference to hum, even when the bits are crowded together.  Aluminium is not an effective shield against magnetic fields, which is the only possible hum mode we are concerned with here.

Cheers,

Hugh

[SamL]

Hi again,
Okay, heres another one. Would a thin (1.5 mm) plate between the tranfos and PCBs have any benefits? I noticed people separating componets with different cases but I am not sure if an aluminium plate has any benefit. I would also use this plate for my earthing as the back of the case is going to be pretty crowded as it is..

Martin.

The Antrim transformer from Harbuch fit nicely inside most can food container like Milo/baby milk powder etc. That's what I used for mine.
However, there's not a lot of space to work with and it is difficult to make it look tidy. Going mono with extra power cap is not helping but that's my fault. With other bit and pieces that I've done to the amp it is impossible for me to tell if the isolation help with sound quality.

Have a look at the photo ->
http://www.audiocircle.com/index.php?action=gallery;area=browse;album=108

Will post more photo once I have the time to take them.
Oh yes! My custome SS case is 18in wide.

Have fun,
Sam

[AKSA]

Sam,

Very nicely made amp, good attention to detail.

Really like the canned food covers for the trafos!

Have you listened with and without the extra caps?

How does it compare to the Plinius SA-100?

Cheers,

Hugh

[SamL]

Sam,

Very nicely made amp, good attention to detail.

Really like the canned food covers for the trafos!

Have you listened with and without the extra caps?

How does it compare to the Plinius SA-100?

Cheers,

Hugh

Thanks Hugh. Your complement mean a lot  
I have not tried the amp without the extra caps, will try that some day. Right now I'm busy getting the study room ready for oversea visitors.
As for the SA100, what I can say is I'm happy to sell the SA100 so that I can build more aksa. Replacing lots of stock aksa resistors with Riken and using long run of Cat5 cable does make AKSA high & mid sounds like SA100 (SA100 partner with Kimber 8TC). The change and combination is actualy 2 big step backward for AKSA. I plan to return to stock resistor and get the Tara cable. Will give a better comparision once the AKSA is back to "normal".
BTW, I have replace all the stock AKSA100n amp caps with BG std and N/NX. So it is about 1/2 way to AKSAn+. It is a move I now regraded as upgrade to N+ now means I'll end up with extra BG caps

Sam

[soitstarts]

Hi all,
I'm a coupla hours into my foray into DIY amps and have just hit a snag (is that a record?)  Step 8 of the 100W tells me to weld.. errr... solder a 0R link into R4, R5 and Link 0R.
Easy, must just be an offcut of a tail and use it to bridge the circuit until I look at the reference picture. Those positions have resistors in them.. Okay look at resistance chart and see what I need - Black, black, black black.... Hmmm, didn't think so. Can some one point me in the right direction, please. (newbies need colour pictures, I think)    

Thanks,
Martin

[AKSA]

HI Martin,

You are building the Nirvana, so put in wire offcuts to bridge R4 and R5.  Just use offcut wire from other resistors which you have mounted and trimmed.

Cheers,

Hugh

[soitstarts]

Thanks Hugh, just wanted to be sure.. It was late....

[soitstarts]

Hi again,
This time its about shielding...  I have mocked up a 3 channel configuration and can't avoid putting the centre channel amp. module above 1 tranfo and next to another...  
I have ideas on how to shield the tranfos so if someone could answer a few questions I would be much obliged..
Is shielding necessary above the tranfo? I see a lot of pics with only the outside shielded.
Would solid or perforated steel be better? does it matter?
Can I get away with just shielding adjacent to the module?
Is it a good idea to twist all pairs of wires or just the power wires? OR
Am I just going to have to experement...
I have included a picture to illustrate what I mean with the layout. Those purists out there may want to look away..
 

Thanks,
Martin

[AKSA]

Martin,

Try to secure some 1/16" (1.6mm) thick steel plate between the trafo and the center amp pcb.  This is necessary to avoid magnetic lines of force passing through the pcb and disturbing proceedings......

You could support it from the trafo mounting bolt, I'd say.

Cheers,

Hugh

[soitstarts]

Hi there, I hope you and yours have had a safe and enjoyable christmas.
I have been identifying my transformer wires and decided to check between the earth wires of one tranfo and the rail wires of the adjacent tranfo and am getting over 100 VAC between the 2 tranfos   . I just want to see if this is a normal occurance or if I've stuffed something up.. I checked because I'm stacking 1 tranfo on top of 2 others and wanted to make sure they weren't doing anything wierd. I removed the top tranfo but nothing changed. I am a bit worried as all the earths will be common so it may mess up my voltages . Any ideas will be happily digested. (why stop now, nothings been safe today..)

Thanks
Martin.

[PSP]

Hi Martin,
There are at least two good reasons for twisting wires...

 - noise:  The amount of noise emitted from a noise source (like AC mains or 6VAC heater wires in the TLP and GK-1) increases as the loop area between the wires increases.  An AC pair parallel and spaced an inch apart would have a very large loop area, a loosely twisted pair would have a much smaller loop area, and a tightly twisted pair would have a very small loop area.  Also, the ability of a second pair of wires (for example, the signal input to the AKSA) to pick up noise is dependent on its loop area.  So, tightly twist wires that can be sources of noise (to limit how much noise they can broadast) and tightly twist signal wires (to limit how much noise they can recieve).  Reduce--as much as you can--any loop area between hot and neutral leads.

 - inductance:  When a high current flows through a wire a magnetic field is established which tends to resist the flowing current.  If we twist a + and - pair however, the inductances of the two wires are opposite and partially cancel each other.  This reduces the inductive impedance in the wire pair (and contributes to sharper, more well-defined transients, i.e., a faster amp).  Inductance is an important factor whenever high currents are involved (i.e., mains wiring, to and from the transformers, the power supply to the amp, and speaker cables).  When twisting is impractical (for example, the high level output from AKSA amp board to amp binding posts) keep leads as short as reasonably possible.

Peter

[soitstarts]

Hi again....
Okay, Mark 2 of my case is near construction stage. 2 more questions for anyone who cares to answer..

1- How would I go if I put in some fly leads from the copper side to the component side to make testing easier if I were to upgrade in the future   . These would be from TP 1 and 2 and would be well insulated. Would this affect the sound at all?
 
2- Could I run 1 earth for my negative speaker wires. I have a 3 channel amp and was wondering if I could run a single earth wire between the 3 teminals as they are going to be located next to each other, anyway. This will also eliminate 2 wires fro my star earth.

Thanks for your time.
Martin.