[AKSA]

Mark, Dan, and others interested,

The Orion Power Supply is now available for $US300.  It has two +/-15V bipolar power supplies, for right and left ASP modules of Siegfried's Orion.  Lead time is around a week.  This was prototyped and trialled in both Oz and the US and comments from PT914 - Phillip - are on this forum.

Shortly (end January) I will also have a power supply using the same operating principle - feedforward current regulation - for the Squeezebox.  This is now prototyped, tested, productionised with all pcbs ready.  Its sonic benefits are the precisely the same as for the Orion PS - namely musical engagement and almost surreal presentation.  I'm just now finalising the enclosure - it will be universal mains plug and play, unlike the Orion PS, which requires a suitably finished diecast box and a couple of 20-50VA 15-0-15Vac transformers (the Tamura PF24 is outstanding, and economical).

Thanks sincerely for all the patience, I'm very sorry these things take so long - breeding elephants downunder is slow work   

Cheers,

Hugh

[mgalusha]

Hugh,

I haven't read the entire thread so I'm sure I've missed it but what is current capability of the new PS? I'm currently using a Marchand XM44 crossover and it draws about 250mA per rail. I recently built a new PS for it using the LT1085/1185 regulators. This was a nice improvement over the old 7815/7915's but your new feed forward design sounds very interesting.

Thanks,

Mike

[AKSA]

Hi Mike,

Thanks for the interest.....  250mA is pushing hard, I've tested my supply to 200mA continuous without problem but this would call for a redesign, chiefly of the heatsinking, which is not too difficult.

You could reduce dissipation by trimming AC supply to the bone, but you need four volts minimum between raw and regulated supply to avoid drop out.

This always happens, of course;  you design for one application, then the second or third inquiry is for yet another application, and a redesign is imminent!!   

Cheers,

Hugh

[mgalusha]

This always happens, of course;  you design for one application, then the second or third inquiry is for yet another application, and a redesign is imminent!!   

But of course, isn't that the nature of things. A four-way Marchand XM44 has 36 OP2134 op amps, each pulling a bit less than 10mA. The three-way I'm currently using had 28 of the dang things. Since I didn't need to use the balanced inputs and the option slots I was able to remove 14 of them, reducing current draw to about 130mA. This is of course within your 200mA limit but if I did need to add a notch filter of some other option I might run up against it. Since the unit I have is a loaner I'm still considering all options but I know how important the PS is to the final result and I appreciate you taking the time to respond.

Have a well and prosperous new year!

Mike

[AKSA]

Hi Mike,

130mA+ is just fine;  it will run easily to 150-180mA with existing heatsinking.

The power supply has enormous impact on the sound quality of any analog signal processor.  The reasons for this are not that clear, either!   

The supply does require that you remove all on board supply capacitance;  you should have not more than about 10uF combined on each rail, usually bypasses right at the ICs.

The principle benefit of this supply is musical engagement.  It makes involving music, rather than just clean sound.

Cheers,

Hugh

[Builder Brad]

Happy New Year to all on AC!!!

I have just had a couple of thoughts re. multi amping Orions with AKSAs

I allways felt that the bass output on my Orions was a little light with my multiple AKSAs 1 x 25w 1 x 55 and 2 x 100s, when compared to using a couple of pro amp modules on the bass drivers. I thought that all of the ASKAs gave identical voltage gains but have just noticed on the documentataion that there is a difference in then input sensitivity between the 100s and 55s the 100s are 748mv and the 55s are 550mv - and my pro amp modules are 500mv. Is this something that other AKSA/ Orion users are aware of? I know that I can increase the gain in the bass channel on the Orion ASP, but I dont even think that the 2.5db availible there will be enough to dial in an equivalent sensitivity to the AKSA 55s

[AKSA]

Hi Brad,

Thanks for your post, you raise an interesting point.

In fact, the AKSA amps are all gain matched within 1%, and ideal in multiamp systems.

The different sensitivites are for FULL power - but their voltage gains are all identical, fixed by the feedback resistor ratio.

This makes their output identical for the SAME input signal.  But for the higher power AKSA, 100W output does require more input since 100W is 80Vpp into 8R while 55W is 59.4Vpp into 8R.  Gain is the same for each, namely 38.27, or 31.65dB.

Hope this explains it!

Cheers,

Hugh

[PSP]

Hi Brad,
Just in case you haven't seen it, SL has a long discussion on bass response in the Thor section of his site ( http://www.linkwitzlab.com/thor_splmax.htm ).  You can use his "sealed box" spreadsheet to analyze the Orion by entering T/S parameters for the Orion woofers and by setting the "box volume" to a value much larger than the driver Vas.  For various amps and drivers, SPL at a particular frequency can be limited by the driver's Xmax or by the amp being either current limited or voltage limited.

If you read back through the early parts of this thread and the "Bass Impact of the 100N+" thread, you can see some of my thoughts on this problem.  How did it work?  Don't know yet.. my Orions are still under construction but they should be playing by mid-February.  Let's hope I did the arithmetic right!!

Peter

[Builder Brad]

Hopefully all of the current Orion owners and prospective builders are aware of the Orion++ revision:

http://www.linkwitzlab.com/orion++.htp

The dual tweeter upgrade is something that I want to do!

I am considering using my AKSA25N+ to drive those parallel Seas drivers and wondered if the low power AKSA will be OK with the low impedance presented. In time I would probably add another AKSA, or even upgrade to 2 stereo Lifeforces to drive those tweeters, but for now.....

Brad

[AKSA]

Hi Brad,

Thanks for raising this.

The AKSA25N+ can safely go to 3R impedance;  with two tweeters, this equates to 6R apiece nominal.  If they are four ohm, then the combined impedance will dip to 2R, and I do not recommend the AKSA25N+ with this load.  It would either necessitate moving to a double output stage like the AKSA 100, doubling up on the AKSA25N+ or using 8R tweeters.

I'm not fully au fait with Seigfried's design, but I suspect he is using 4R tweets, in which case the design may not be amenable to using 8R tweeters.  This is a conundrum perhaps you should ask SL about;  he may be able to rejig the design for the 8R tweets, who knows?

Cheers,

Hugh

[andyr]

Hi Brad,

Thanks for raising this.

The AKSA25N+ can safely go to 3R impedance;  with two tweeters, this equates to 6R apiece nominal.  If they are four ohm, then the combined impedance will dip to 2R, and I do not recommend the AKSA25N+ with this load.  It would either necessitate moving to a double output stage like the AKSA 100, doubling up on the AKSA25N+ or using 8R tweeters.

Cheers,

Hugh

Hi Hugh,

Youse have got me confooosed, here!   

I understood the AKSA 100 is "safe" down to 3 ohms and you advised PSP that if he lowered the rail voltage by using a lower-secondary-voltage power trannie, this would a) deliver more current and b) enable the AKSA 100 to drive a 2 ohm load ... which is what PSP needed for his dual-Peerless-woofers-in-parallel Orion (and the same applies to the LF models!)??   

I understood an AKSA 55 is "safe" down to 4 ohms and as a 25 is just a 55 with lower DC rail voltages, I would've thought the same would apply ... so the 25 should be "safe" with lower-than-3-ohm loads?     Maybe not 2 ohms but certainly 2.5?

Can youse elucidate?   

Regards,

Andy

[Builder Brad]

Thank-you Hugh,

There is quite a discussion re. this at the moment on the Orion Forum. The pair of parallel milleniums drop to 2.5r and SL sugests wiring them in series for amplifiers that do not like this load, with some additional component changes to the Orion ASP to deal with the reduced output.

http://orion.quicksytes.com/viewforum.php?f=1&sid=fc1dbfd118a5b460589f7baee67d4d72

I have a couple of options, but also some questions.


1. would it be a viable option to buy 1 x stereo 25w Lifeforce to drive the foward firing tweeters and use the N25+ for the rear firing tweeters?

2. could 1 x 25w Lifeforce handle the parallel seas drivers?

3. If I do want to try this Orion+ upgrade now, could I swap the 25wN+ with the 55w that is currently driving the mid range drivers, and at least reduce the current demands on that chanel.

Brad

[PSP]

Brad and Andy,
The 100 is more robust to low impedances than the 55.  I lowered the 100N+ rail voltage to 43v partially to enhance stability, but mostly to allow the amp to deliver 10 amps in the bass.  (If this is confusing, please see SL's pages on the factors that limit bass SPL... depending on the amp and the particular woofer, SPL can be limited by the woofer xmax, or the amp can be current limited or voltage limited between 120 - 20 Hz.  This page is referenced above, I'm sure.)

I like your suggestion of using LF55 on the front firing tweeters and a 55N+ on the rears, although once you hear the LF55, you  realize that there is so much more high frequency resolution in the LF that you might not achieve the goal of uniform polar response.  It's worth a try, I think.

I think I will wire my tweets in series, listen to that for a while, and then perhaps try an N+ on the rear firing tweeters.

Peter

[Brian T.]

I have to say that I am somewhat confused by this whole Orion business.  I have just moved and the removal guys managed to trash my AR925s.  I have been following this thread and am very interested in building a set of Orions.  I have also been following various threads on the Orion builders forum and have noted that a guy by the name of Vikash Chauhan has posted a comparison of various amps including AKSA and LM3886 chip amps at:     
http://orion.quicksytes.com/viewtopic.php?t=266&highlight=aksa (see the entry on Tue Dec 12, 2006 5:08 pm.  How can a ‘cheap’ chip amp compare with the AKSA?    I love my AKSA 100N+, so maybe using that for the woofers and using LM3886s for the mid-range and tweeters would be a good compromise given the impedance problems discussed above.

However, perhaps using an active crossover swamps all other quality criteria and the amplifier selection is fairly meaningless.  I am thinking that perhaps I would better leverage my AKSA investment by going for my alternative loudspeaker choice; the B&W 801D.  (I am aware of the price difference!)

I would be very interested in the thoughts of other Orion users/considerers.

Cheers!

Brian 

[Davey]

This is a conundrum perhaps you should ask SL about;  he may be able to rejig the design for the 8R tweets, who knows?

Cheers,

Hugh

I can guarantee that won't happen. 

The easy solution for those that have amplifiers that might not be comfortable with the load is as Peter mentioned......wire them in series.  The amplifier will have to swing a voltage about 4.5db higher, but that should be no problem.

The necessary resistor changes to the Orion ASP have already been calculated and are fairly easy to implement.

Cheers,

Davey.

[andyr]

However, perhaps using an active crossover swamps all other quality criteria and the amplifier selection is fairly meaningless.  I am thinking that perhaps I would better leverage my AKSA investment by going for my alternative loudspeaker choice; the B&W 801D.  (I am aware of the price difference!)

I would be very interested in the thoughts of other Orion users/considerers.

Cheers!

Brian 

Hi Brian,

I don't have Orions although I've heard some (driven by the same amps which I use for my 3-way-active Maggies) ... but I just wanted to say, absolutely, an active system does not "swamp all other quality criteria so amplifier selection is fairly meaningless"!!

If anything, I would say the reverse is true - ie. an active system is so much "sharper" that it will more easily reveal the difference between amplifiers.

Regards,

Andy

[ctviggen]

If that is so, then going active could be very expensive.  For instance, very few could afford to buy 4 channels of Jeff Rowland amps just to run one speaker.  I've been thinking of trying out the Orions for some time, but the only thing holding me back is lack of a center channel and the number of amps to properly implement a five channel system. 

[andyr]

If that is so, then going active could be very expensive.  For instance, very few could afford to buy 4 channels of Jeff Rowland amps just to run one speaker.  I've been thinking of trying out the Orions for some time, but the only thing holding me back is lack of a center channel and the number of amps to properly implement a five channel system. 

Mmmm ... but then I've absolutely no interest in buying 6 channels of Jeff Rowland amps to drive my Maggies!!   

6 channels of AKSA Lifeforce is what I covet!     Meanwhile, I'll "put up with" my AKSA N+s.   

Regards,

Andy

[Dan Kolton]

I had B & W 801s (with Van Alstine's crossover mods) driven by an AVA Ultra 550.  They were, and still are, wonderful speakers.  I far prefer my Orions.  Better image, definition, tighter bass, more  realistic tembre are all attributes I hear.  I've driven them with all AVA amps, Sony top and mid with AVA bottom, and with Siegfried's recommended ATI.  The Sony sounded inferior (edgy and less defined), but AVA was not distinguishable from ATI in my opinion.  Frank would probably point to the op-amps in the active crossover/equalizer as the limiting factor, but I'm not convinced.  The XO/EQ is the reason that there are no nasty high level XO components for the amp to drive, so it's an easy load.

[AKSA]

Hi Andy,

AKSA100N+ will go to 2.5R.  AKSA55N+ will go to 3.5R.  The 25N+ will go to 3R.  I don't recommend a 25N+ down below 3R;  it's risky.  Either dedicate one module, one tweeter, or use the 100N+.

Brad,

1. would it be a viable option to buy 1 x stereo 25w Lifeforce to drive the foward firing tweeters and use the N25+ for the rear firing tweeters?

2. could 1 x 25w Lifeforce handle the parallel seas drivers?

3. If I do want to try this Orion+ upgrade now, could I swap the 25wN+ with the 55w that is currently driving the mid range drivers, and at least reduce the current demands on that chanel.

I think #1 (and hence #2!) would work OK, though I've not done it myself.  The LF definitely has more drive than the AKSA, and for higher frequencies with much lower amplitude than is common with bass amp it would be quite suitable.  The LF would bring greater resolution to the front tweeters, which is no bad thing.

Not sure I understand #3;  but as a general rule, reducing the rail voltage of an amp increases its tolerance to low impedance loads by improving its SOAR margins (secondary breakdown with difficult loads), and enhances its stability margin by reducing phase shift across the amp at high frequencies.  For the lower impedance tweeter load, I'd stick with the lower power amp.

You commented earlier on the bass response of your AKSA100s with the Orion.  While you are able to adjust the levels conveniently with the Orion ASP, I would say that I've compared the subjective bass of the the AKSA100 with the LF100 and the latter is subjectively louder, despite measuring within about half a dB.  The subjective quality of the LF is different;  it sounds louder, too.

Brian T,

How can a ‘cheap’ chip amp compare with the AKSA?

I must admit I found this surprising too, but one thing is certain - people have differing opinions, and choose accordingly.  We do this with automobiles, wine, books, all the enjoyable things of life!  I don't say he's wrong, just that it's not my taste......

Dan,

I've heard the 801, agree, very nice speakers.  I've not heard them up against the Orions, but I'd probably agree with you if I did!!  In my opinion, the limiting factor with the Orions is less the many opamps used in the ASP than the power supply for same.  It makes a huge difference to the overall sound quality.  Just why, I cannot say, but it's the difference between a stunning loudspeaker and one which talks to its owner......


Cheers,

Hugh