[geof]

A Happy New Year to everyone and a hearty congradulations to Hugh for expanding his product line!

I am getting ready to (slowly) assemble both AKSA-100Ns and a GK-1R, and have a few questions before doing so:

1. Soldering: Is there any particular solder that one would recommend. Jon Risch (AA) recommends Kester 63/37 solder. Unless anyone recommends otherwise, I will go with that. Also, I like to use a hot-air bath to preheat the PCB and components to 120-140 deg C. This way when the soldering iron is touched to the PCB metal pads and component leads, not as much heat is required from the iron tip to bring everything up to the solder melting point. This also reduces thermal stress and theoretically prevents microfractures in both the components and PCB. This is a good technique for surface-mount components. However does anyone here have a reason why this may not be wise with the components of these kits, particularly some of the components from the Nirvana upgrades?

2. Maximum capacitive load on the AKSA-100N: The instructions state that the amplifier should not be used on higher capacitance speaker cables. In my setup, the cables are DIY type with about 10-12 meters of Belden 95259 cable (I think that's the number- the stuff Jon Risch recommends), resulting in about 600pF to 1000pF load per channel. Is this too much for the AKSA?

3. Links between AKSA PCBs and speaker binding posts: What wire do you recommend? I still have over 100' of that Belden cable left over...

4. I've measured my AC mains several times and found the voltage to be hovering around 125Vac. I will be using 33-0-33 Vac transformers rather than 35-0-35.

I am looking forward to building these over the next month.

Geof

[Malcolm Fear]

I don't know much about solder and hot air bathing the circuit boards.

I would use the same cable internally as you use externally. If you like the 89259, then use it inside the box.
I prefer the Belden plenum CAT 5, braiding 8 strands together (4 for positive, 4 for negative). I use this from the pcb and the star earth, to the banana sockets. I also use it as speaker lead. 8 strands seems ideal for AKSA's I tried 4 strand. It sounded thin. I tried 16 strand. It didn't sound right. I tried 50 strand. It distorted. I think the extra strands bumps up the capacitance to an unacceptable level. I use a GK-1, an AKSA 55 and 16 ohm full range speakers (an easy load). A friend has an Audio Research SP-11 pre amp, an AKSA 55 and Ambience ribbon hybrids (a 6 ohm load at some point). We both prefer 8 strand of CAT 5, over any other CAT 5 configuration.

We have compared the CAT 5 to the cross paired 89259. We all preferred the CAT 5. We only tried the experiment with an AKSA 55.

[tropicalcb]

Gday geoff,     sounds like you're gonna be a busy boy for a while!!  but what a load of fun eh!?  set out below are a few opinions about tweaks relevent, and some not relevent, to your questiuons...feel free to check out further or dicard as you see fit.
  I reckon the LMP 2% silver solder is the go....and for my last few solder-ups Ive been combining 0.91mm(width) lengths of LMP (low melting point) with 0.9 lengths of 2% copper loaded solder - just your garden variety from the local dick smith store, and the lengths twisted together. What Ive found over the years is that the LMP with the silver content is very easy to work with because it flows beautifully. The first lot I used was from consolidated alloys, but Multicore has been the most obviously available since the early '90's....I did use wonder solder and some other exotics but couldnt honestly discern any difference so figured they werent worth the money in my world.
  For hook-up I'd agree with malcolm about using your existing solid core...but also I have used the cat 5 braided as per the Chimera instructions and it is very good. personally I can't tell the difference between the teflon insulated cat 5 or the local 75c/m ...as long as its solid core. The only exception to my solid core philosophy is the teflon insulated litz braided wire from the boys at Black Art Transformers in melbourne....that is very fine ofc wire and I use it from aksa 55 board to speaker outlets....and I run it around inside tube preamps and other high voltage devices - very, very, good...they have a site you can check out with some subjective descriptions of their items, and they will sell you a few metres at a time. They also have very excellent 0.5mm or 1.0mm solid silver wire drawn from australian 99.999% silver ingots...and it comes with clear teflon insulating spaghetti. I use this stuff from the xover on my aksonics to the tweeters...like all solid core in my experience, you need a lot of hours to run in. For mains leads heavy guage insulated copper wire from motor rewinders + earth +spaghetti insulation + foil and full braided shield is the go...trouble is no-one makes anything like this ex stock so it necessitates buying a few different things and making them up yourself - but definitely worth it. For mains conditioning, Thorstens megamania conditioners at the TNT site are simple and unbeatable and 7uf 250vac polyprop caps are available fairly cheaply. Same story as above, they take a lot of hours to sound good.
  Good luck & have fun building your toys...............cb

[geof]

I would use the same cable internally as you use externally.

Maybe I should just forget the binding post and run the cable directly to the PCB. Doh!

[Malcolm Fear]

I haven't done this yet.
I do have two sets of cable directly connected to my GK-1. One is for my CD in and the other is for my pre out. I use Eichmann bullets and 4 strands of braided CAT 5.

I have been thinking of soldering my speaker leads to the terminals on the Diatone full range, thus eliminating one set of bananas.

[andyr]

Good on ya, mate ... you will enjoy the AKSA 100Ns and the GK-1 when you've finally finished em!

I am sure Hugh will answer your queries but in the interim, here is my input on a couple of your points:

1.  The 120 deg C hot air bath.  As you say, this is a good technique for surface-mount board-stuffing, where presumably everything happens in a short space of time (on an automatic PCB-stuffing-assembly-line).

However, I would have thought for conventional PCB stuffing:
- it will get pretty uncomfortable trying to solder for a couple of hours if your hands are in a hot air blower at 120 deg C, or
- if you turn off the hot air then, yes, the first few components will be soldered to a hot PCB but the rest will be soldered to an ever cooler PCB, as it gradually cools down??  So you won't get much benefit?

2.  I believe AKSAs can take up to 2000pF of cable capacitance, so your JR cross-connected cables should be fine.

However, in your new system (with the two AKSA 100Ns) can you rearrange things so that you have the power amps directly behind your speakers - ie. long ICs and short speaker cables??

I used to have 11m speaker cables but I found a big improvement when I moved my AKSAs to just behind each speaker ... so I had 11m ICs instead.

Regards,

Andy

[abo]

Sorry, off topic, but I really want to know.

Can anyone tell me what the s means in AKSA 100NS?

Does this mean Hugh has developed a Nirvana plus or something?

[EchiDna]

Sorry, off topic, but I really want to know.

Can anyone tell me what the s means in AKSA 100NS?

Does this mean Hugh has developed a Nirvana plus or something?

Correct me if I'm wrong, but I think it is just refering  to the fact that there is two AKSA 100n amps - hence the use of the "S"

[AKSA]

Hi Geof,

You wrote:

1. Soldering: Is there any particular solder that one would recommend. Jon Risch (AA) recommends Kester 63/37 solder. Unless anyone recommends otherwise, I will go with that. Also, I like to use a hot-air bath to preheat the PCB and components to 120-140 deg C. This way when the soldering iron is touched to the PCB metal pads and component leads, not as much heat is required from the iron tip to bring everything up to the solder melting point. This also reduces thermal stress and theoretically prevents microfractures in both the components and PCB. This is a good technique for surface-mount components. However does anyone here have a reason why this may not be wise with the components of these kits, particularly some of the components from the Nirvana upgrades?

Several points.  SMD devices are designed specifically for complete immersion throughout the wave solder operation.  Leaded components are not, and their protective coverings are not always so robust.  I'd be leery of this for starters.  I suspect the Beyschlag metal films would cope OK but I feel a couple of the caps, specifically the Evox-Rifas and RelCaps, would not.

There's no empirical evidence that high thermal gradients during leaded component soldering affect either the integrity of the solder joint or the reliability of the component.  The non-planar shapes make for good thermal penetration anyway;  in the case of SMDs the further towards the center of the component you measure it, the lower the temperatures.  If you use LMP 2% silver solder (from Multicore), as suggested by Chris Blainey above, temperatures are lower anyway, typically 250C at the most (melting point is 172C).  And I have found that the Consolidated Alloys solder supplied with the kitset exhibits no sonic differences at all over the Multicore.
 
Some of the caps use polystyrene dielectric, which has low melting point and is highly susceptible to overtemperature.  To my knowledge there are no SMD ps caps available (though I only really know the Oz market, not the US or European, so I could be wrong here).  In any event, the low melting point could easily damage these caps, so I'd steer clear of it, at least with polystyrene.

2. Maximum capacitive load on the AKSA-100N: The instructions state that the amplifier should not be used on higher capacitance speaker cables. In my setup, the cables are DIY type with about 10-12 meters of Belden 95259 cable (I think that's the number- the stuff Jon Risch recommends), resulting in about 600pF to 1000pF load per channel. Is this too much for the AKSA?

This should be fine.  You can go to 2nF (2000pF total load) without problems.  Excessive load capacitance on any global feedback amplifier shifts phase;  and phase shift in turn can precipitate instability.  This is the main reasons why electrostatic speakers are a nightmare to drive, and why some amps and speakers don't marry well.

3. Links between AKSA PCBs and speaker binding posts: What wire do you recommend? I still have over 100' of that Belden cable left over...

I use CAT5E for signal wires;  auto multistrand 15A hookup wire for power and speaker wires.  People seldom agree on what wire to use;  Malcolm has suggested braiding CAT5 for speaker wire, and this is fine by me as long as there are no more than 8 strands in each braid.

4. I've measured my AC mains several times and found the voltage to be hovering around 125Vac. I will be using 33-0-33 Vac transformers rather than 35-0-35.

This is very common in Australia also;  overvoltage mains are the norm here since privatization of the electric utilities (Texas Utilities owns one of the largest in Victoria).  The theory goes thusly;  Private power company's play down maintenance on the distribution grid, preferring to indemnify catastrophe instead to save money, and as the grid runs down, higher voltages can compensate losses in outlying areas.  Further, overvoltage in a few areas is no bad thing;  the household power meters are not linear, and a 5% overvoltage increases billing by slightly more than 5%.

Yes, I'd recommend 33-0-33Vac for your secondaries!

Hope this is helpful, and thanks to all who answered Geof's inquiries.

Cheers,

Hugh

[geof]

Thanks for your feedback, everyone.

I had thought of placing the amps behind the speakers and using longer interconnects rather than cables. I would do this if I had a dedicated listening room, but right now everything is in the living room and the speaks are imposing enough as is!

Regarding solder- I didn't realize the kitset had contained solder in it. Honestly I haven't opened it up yet past the instructions because I wanted to clear a workspace and get all other necessary parts ordered first. The multicore provided is certainly sufficient, but I'll go out on a limb and try either 2% LMP  or WBT.

I think I'll pass on the air-bath...

As for cabling- when I first decided to upgrade from single-wired 14 gauge copper wire, I looked at both the CAT5 and JR cross-connected pair. I went for the latter because I didn't feel like braiding enough for 5 meters biwired!! (If the amps were right behind the speaks then would do CAT5)

Okey Dokey! Time to get busy!

Geof