[guest1632]

Hi Ray,

You keep me on my toes, but I love the careful thought behind your curiosity, thanks for the questions.....  forces me to order my thinking for my website copy, too, a very good thing!  You might appreciate that as the designer, and dominated by the design issues, I'm not so focussed on the issues of installing the completed module into a suitable enclosure, and the minutia of the connections.

Hi Hugh,

Thanks for the compliments. I had built from a preassembled kit from one of your mates there in Australia and I went through hell getting it finally to work the way it was to be set up. It wasn't his fault though. If I knew what I know now, I would have done things a lot differently.

So from what I read, then probably having each heatsink on the left and right side of the case respectively per channel, and then the transformer in the middle?  There's no separate PS board? Just trying to imagine how this would all fit together.

Will the heatsinks be already mounted on the board? Are the terminals clearly labeled on the board?

I presume you are at the input having the amp cap coupled? Ooh that's right, your keeping voltage on the caps minimizes any effects that caps can give.  On the output side, what sort of protection is built in there? So if there is a short or current spike at the outputs, I presume like the SkA amp you're using fuses?

on the 8 or 4 ohm or lower issue, is 35 V enough for the transformer? What about handling speakers with difficult loads, say Maggies, or if someone still happens to have a pair, Dolquists speakers. Well, probably not, but just trying to think of some speakers with difficult loads.

Ok, so on the mounting of the board or heatsinks to the case, I presume there's probably holes in the corresponding sides of the heatsink to mount them on there sides to the bottom plate of the case? The fins would stick out the sides of the case. The fins themselves are probably a couple of inches from tip to base, so just trying to get a handle on the case size. Maybe instead there are holes on the ends of the heatsink to mount the sinks that way.

What about fuse sizes at the input say 7A or so for a 500VA trafo?

Probably should have PM you about all this, but maybe someone who is buying and building your amp  kit for the first time might learn something from my questions here.

Thanks for answering my questions. As soon as I can get some cash together, will probably get this amp. I figure I could do a lot worse for the money spent, and it would be a standard for me and others for years.

Ray Bronk

[AKSA]

Hi Ray,

Nice questions - you clearly have been down this path, and know all the bumps in the road!   

So from what I read, then probably having each heatsink on the left and right side of the case respectively per channel, and then the transformer in the middle?  There's no separate PS board? Just trying to imagine how this would all fit together.

Yes, left channel mounted left side, right channel mounted right side, trafo in the center.  Ideal setup.  No, there's no separate PS board, you are correct, by mounting power supplies on board it great simplifies wiring and makes it difficult, VERY difficult, to create sparks!

Will the heatsinks be already mounted on the board? Are the terminals clearly labeled on the board?

Yes, the boards are mounted flat against the heatsink with four M3 screws which also secure the output devices.  It's a very compact arrangement, and with the amp boards vertical, it gives more space inside the enclosure for the trafo, which is about 4.8" in diameter for a 425VA.   Of course, for best cooling, the heatsinks should have their vertical fins exposed at the sides, which means the heatsinks, which are fine looking beasts, become a feature of the enclosure.  All terminations are very clearly marked!

I presume you are at the input having the amp cap coupled? Ooh that's right, your keeping voltage on the caps minimizes any effects that caps can give.  On the output side, what sort of protection is built in there? So if there is a short or current spike at the outputs, I presume like the SkA amp you're using fuses?

Yes, input is cap coupled, but carries about 2.5V of bias across this cap, greatly enhancing sonics.

Output has two protection systems, neither of them dynamic.  (I find dynamic limiting degrades must be quite complex to avoid degrading the sound quality, and prefer other means).  One is fusing;  2 x 7.5A fast flow fuses on the rails supplying the output devices;  and the other is a current limited emitter resistor on the output, which is designed to fail open just before the fuses.  In this way both the output stage and the speaker is protected.  This system works very well for direct shorts too.

on the 8 or 4 ohm or lower issue, is 35 V enough for the transformer? What about handling speakers with difficult loads, say Maggies, or if someone still happens to have a pair, Dolquists speakers. Well, probably not, but just trying to think of some speakers with difficult loads.

35Vac secondaries will deliver 48-52V DC to the rails, depending on your local mains.  This is enough for 100W into 8R, around 180W into 4R.  For 90dB/watt/metre speakers, a medium sized listening room, and moderate masochism, this is quite sufficient to bring pain to any listening session.  If you want even more, a 4R speaker is a good idea......  and the output stage is very robust.  But who knows?  In the future I might build something with more power than the PA on USS Ronald Reagan!!   

"Thanks for answering my questions. As soon as I can get some cash together, will probably get this amp. I figure I could do a lot worse for the money spent, and it would be a standard for me and others for years."

A pleasure, Ray. 

Hugh

[guest1632]

Hi Ray,

Nice questions - you clearly have been down this path, and know all the bumps in the road!   
Hi Hugh,

Just one last question I think? Ok, so to mount the heatsinks on the case, would you have holes on the vertical edges of the heatsinks to mount to the open sides of the case, or are there holes on the bottom and tops of the heatsink to mount to the bottom plate of the case?

Ray Bronk

[AKSA]

Ray,

My tentative answer to this would be that because you can choose to mount the heatsink either on the sides of the case, completely exposed, or internally, hidden, the choice would be up to you.

Therefore I've not supplied holes;  I have on the NAKSA 70, because in that case the heatsink is always internal, but for the 100, there is this choice.  I feel that drilling holes which may never be used is inappropriate, and since a simple drill and a cordless is all you need, best to not drill any holes.

But it's not a big deal, holes are very easy to drill in Al.

Cheers,

Hugh

[AKSA]

Folks,

I'm furiously assembling NAKSA 100s now.  Here's a piccie of four all complete, awaiting mounting on their heatsinks then testing:





These NAKSAs are premium, pricier versions with Nichicon Gold Muse caps;  regular NAKSAs have the Nichicon KZ.

This batch is ten;  all are accounted for, all overseas.  (Mind you, from Oz, just about everywhere is overseas!!   )

I cannot begin to describe how happy I am with the sonics of this amp, might even call it La Stupenda!   

Cheers,

Hugh

[guest1632]

Folks,

I'm furiously assembling NAKSA 100s now.  Here's a piccie of four all complete, awaiting mounting on their heatsinks then testing:





These NAKSAs are premium, pricier versions with Nichicon Gold Muse caps;  regular NAKSAs have the Nichicon KZ.

This batch is ten;  all are accounted for, all overseas.  (Mind you, from Oz, just about everywhere is overseas!!   )

I cannot begin to describe how happy I am with the sonics of this amp, might even call it La Stupenda!   

Cheers,

Hugh

Hi hugh,

How much for the premium version?

Ray Bronk

[AKSA]

Hi Ray,

Another $AUD90, making it $AUD1510 all up with the premium supply!

Cheers,


Hugh

[Jens]

Hi Hugh,

How are the modules coming along? - can hardly wait to get mine

Very much looking forward to giving them a listen 

Cheers,

Jens

[AKSA]

Hi Jens,

I'm mounting them up now;  have done four today, another couple tomorrow, Sunday, and Monday.  I believe yours will go out on Tuesday, in time for Santa Claus, Jens - I am sorry for delays, but believe me I'm pedalling as fast as I can!!

They look damned nice too.....   

Cheers,

Hugh

[Jens]

Hi Hugh,

No worries about speed - just wanted to know so I can start getting the trannies 

Would you say that 300VA, 35 volts would be fine for monoblocks?

Cheers,

Jens

[guest1632]

Hi Hugh,

No worries about speed - just wanted to know so I can start getting the trannies 

Would you say that 300VA, 35 volts would be fine for monoblocks?

Cheers,

Jens

Hi Jens,

Well, I'm not Hugh, but he kinda answered your question by answering mine. I had asked if a 425 VA versus 600 VA what would be the difference? I suggest you look up the page a bit, and you'll see the answer. To sum it up, I don't think if memory serves me right, that making these monoblocks would be of any advantage sonically. He said he had used 300VA but he would have preferred at least 425VA. So if you aren't gonna have them each behind your speakers, then make one unit with a 500VA 35 V and save yourself the cost of fabbing a case for two. If you want to put your money in to the sonics, then get the upgraded one for $1510 which has better caps and such. just a suggestion. That will be one sweet killer amp, no matter what version you get.

Ray Bronk

[AKSA]

Hi Jens (and Ray!!),

The two channels of the NAKSA 100 are normally served by one transformer, with rating from 425VA to 500VA (standard ratings, commonly available).

If you go for monobloc construction, a choice made quite deliberately so you can place the amps right up close to the speakers, then half these ratings would be fine, and more would be no bad thing.

So, you could go as low as 225VA PER CHANNEL, or as high as 300VA PER CHANNEL.  Again, these are commonly available ratings.  The choice would be entirely arbitrary.  Both would give very good results, and in fact would be a bit simpler to wire up because you would not have to splice two additional wires onto each secondary winding of a single transformer to accommodate two modules.

Yes, Jens, the 35Vac rating for each secondary is correct!

Ray, Jens has thoughtfully specified the more expensive caps...  a good choice, they are superb caps, I hope my supply holds out!!

Cheers,

Hugh 

[guest1632]

Hi Jens (and Ray!!),

The two channels of the NAKSA 100 are normally served by one transformer, with rating from 425VA to 500VA (standard ratings, commonly available).

If you go for monobloc construction, a choice made quite deliberately so you can place the amps right up close to the speakers, then half these ratings would be fine, and more would be no bad thing.

So, you could go as low as 225VA PER CHANNEL, or as high as 300VA PER CHANNEL.  Again, these are commonly available ratings.  The choice would be entirely arbitrary.  Both would give very good results, and in fact would be a bit simpler to wire up because you would not have to splice two additional wires onto each secondary winding of a single transformer to accommodate two modules.

Yes, Jens, the 35Vac rating for each secondary is correct!

Ray, Jens has thoughtfully specified the more expensive caps...  a good choice, they are superb caps, I hope my supply holds out!!

Cheers,

Hugh

Hi Hugh,

Well, I'm almost envious. I had suggested just one Trafo, so he wouldn't have to fab two cases. i figured if I read you correctly, no real advantage of having monoblocks unless you are putting them behind each speaker. The other way around this splicing stuff is to get a Trafo with two secondaries of the same voltage. This way you aren't doing to much sacrificing any current needs by pulling off of one secondary. Hey just some food for thought.

Ray

[guest1632]

Hi Jens (and Ray!!),

The two channels of the NAKSA 100 are normally served by one transformer, with rating from 425VA to 500VA (standard ratings, commonly available).

If you go for monobloc construction, a choice made quite deliberately so you can place the amps right up close to the speakers, then half these ratings would be fine, and more would be no bad thing.

So, you could go as low as 225VA PER CHANNEL, or as high as 300VA PER CHANNEL.  Again, these are commonly available ratings.  The choice would be entirely arbitrary.  Both would give very good results, and in fact would be a bit simpler to wire up because you would not have to splice two additional wires onto each secondary winding of a single transformer to accommodate two modules.

Yes, Jens, the 35Vac rating for each secondary is correct!

Ray, Jens has thoughtfully specified the more expensive caps...  a good choice, they are superb caps, I hope my supply holds out!!

Cheers,

Hugh

Hi Hugh,

Not to complicate stuff I hope, but this has to be center tapped? Also, can you use a higher voltage on the Trafo. I think I might have a 40V which would bring the supply voltage up to I think about 55 or 56 V. Would that be a problem?

Ray

[AKSA]

Ray,

CAUTION:  THERE IS NO CENTER TAP REQUIRED FOR THIS AMP.

BOTH SECONDARIES ARE USED INDEPENDENTLY AND ARE NOT INTERCONNECTED TO FORM A CENTER TAP.

I do not recommend 40Vac trafos, unfortunately.  This is taking the output stage a bridge too far, particularly risky for 4R loads.  Only two output pairs are used for this amp;  for 56V rails, corresponding to 40Vac trafos, you need THREE output pairs, not TWO.

Hope this helps,

Hugh

[guest1632]

Ray,

CAUTION:  THERE IS NO CENTER TAP REQUIRED FOR THIS AMP.

BOTH SECONDARIES ARE USED INDEPENDENTLY AND ARE NOT INTERCONNECTED TO FORM A CENTER TAP.

I do not recommend 40Vac trafos, unfortunately.  This is taking the output stage a bridge too far, particularly risky for 4R loads.  Only two output pairs are used for this amp;  for 56V rails, corresponding to 40Vac trafos, you need THREE output pairs, not TWO.

Hope this helps,

Hugh

Hi Hugh,

Ok, thanks for the info. I'm not wishing to bridge your amps. I was just wondering if that trafo needs to be center tapped. Ok, good deal.

So there you go Jens. Unless you are putting them each behind each speaker, or you just happen to have two trafos at 300VA, then just get one 500VA 35V, and one case, and be most blissfully happy, and know that you probably have something that sounds three times its value in sound.

meanwhile, I'll just sit here lol, and wonder where I can get approximately $1510 and a couple hundred more to buy and put this all together.

Back to you Hugh, Are you suggesting any types of wiring schemes for the input and speaker wires?

Ray Bronk

[Jens]

Ray,

Thanks for your input! I am indeed going to have the modules mounted on the back of my speakers

Here's a photo of one of my speakers:



As you can see, the speaker consists of three modules: bass, treble/mid, and bass. A NAKSA 100 will be mounted on the back of each bass module, and a NAKSA 70 (which is a 2-channel module) will be mounted on the back of the treble/mid module. Each NAKSA module will have its own toroid transformer.

The entire array will be 'governed' by DSP-controlled electronic x-over/equalizer units that will be housed in the treble/mid enclosure.

Bass drivers are 8 ohms, and since each NAKSA 100 module will be powering two drivers, this will be a 4 ohm load. In 4 ohms, the NAKSA 100s deliver close to 200 watts per module, so I'll have around 800 watts of bass power! And that is 'direct-drive', as amplifiers are connected directly to the drivers with no energy-consuming passive x-over inbetween

With this setup, speaker cables will be non-existent (apart from the very short lengths running from the amps into the enclosures) and speaker cable influence on sound will be eliminated. Also, with amplifiers mounted on the rear of speakers, it will be easy to hide the rest of the system (GK-1R, heavily modified Oppo BDP-83SE, and an old Denon tuner) and have a very 'clean' looking system

Cheers,

Jens

[guest1632]

Ray,

Thanks for your input! I am indeed going to have the modules mounted on the back of my speakers

Here's a photo of one of my speakers:



As you can see, the speaker consists of three modules: bass, treble/mid, and bass. A NAKSA 100 will be mounted on the back of each bass module, and a NAKSA 70 (which is a 2-channel module) will be mounted on the back of the treble/mid module. Each NAKSA module will have its own toroid transformer.

The entire array will be 'governed' by DSP-controlled electronic x-over/equalizer units that will be housed in the treble/mid enclosure.

Bass drivers are 8 ohms, and since each NAKSA 100 module will be powering two drivers, this will be a 4 ohm load. In 4 ohms, the NAKSA 100s deliver close to 200 watts per module, so I'll have around 800 watts of bass power! And that is 'direct-drive', as amplifiers are connected directly to the drivers with no energy-consuming passive x-over inbetween

With this setup, speaker cables will be non-existent (apart from the very short lengths running from the amps into the enclosures) and speaker cable influence on sound will be eliminated. Also, with amplifiers mounted on the rear of speakers, it will be easy to hide the rest of the system (GK-1R, heavily modified Oppo BDP-83SE, and an old Denon tuner) and have a very 'clean' looking system

Cheers,

Jens
 

Hi Jens,

Well, you have me at a slight disadvantage. I am a person who is totally blind, so sorry ol' man, can see your pics. But the setup sure is gonna sound good when it's all through being assembled. Looks like you won't need much case work. That would be worth listening to when it is all done. If I may be nosy, how much do you think it's gonna cost you total when it's all done?

Ray Bronk

[AKSA]

Jens, Ray,

I'm always amused when people slowly begin to see just how serious Jens is with his system.  He has NAKSA 70s already, so knows that the 100 is very similar, and to be selected in this company with some of the finest drivers and baffles on the planet is a great privilege....

Jens, one point;  you might consider a Zobel correction for all drivers to correct phase shift due to the inductance in each voice coil.  I have found this improves depth of image slightly.....  but I suggest this only because global feedback amps, even the NAKSA (which has 31dB of global nfb), always benefits with this slight amendment.

Thanks for sharing your system, truly impressive!!

Hugh

[guest1632]

Jens, Ray,

I'm always amused when people slowly begin to see just how serious Jens is with his system.  He has NAKSA 70s already, so knows that the 100 is very similar, and to be selected in this company with some of the finest drivers and baffles on the planet is a great privilege....

Jens, one point;  you might consider a Zobel correction for all drivers to correct phase shift due to the inductance in each voice coil.  I have found this improves depth of image slightly.....  but I suggest this only because global feedback amps, even the NAKSA (which has 31dB of global nfb), always benefits with this slight amendment.

Thanks for sharing your system, truly impressive!!

Hugh

Hi Hugh,

Well, lol, I didn't have any idea that was what he was doing.

Hugh, so what do you suggest for the leads for speakers and input? i'd probably use 18 gauge wire for the power side. The Trafos I've seen use 18 gauge, so anything bigger than that would seem ridiculous to use. Anyhow, just thought I'd ask your opinion.

Ray