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ALWSR for NAXO queries

N

nobeone

Total Member
Firstly, is this a suitable application?

The intention is to build four ALWSRs to separately power the sections of a NAXO with in the hope this gets me to somewhere near a SNAXO without the need for a Supercap and for a tiny amount of the cost.

I assume I aim for c.24V dc out of the AWLSR. As I understand it I need 2.5V headroom from the Hicap, so 26.5V out of the Hicap.

I have a TRP4ed Hicap so I can turn the wick up on the output voltage at will, or I guess I can just change the resistors on my standard Hicap to get the voltage up too. Not very interesting at this point beyond the concept that I can provide the headroom for the ALWSR, I will "worry" about which when I have on my bench four working ALWSRs!

I have the parts list google doc from another thread, and the ALWSR manual Andy provided updates to with the last group buy. These are a huge help, thanks for that!

First hiccup is the AD825 is not immediately available from Farnell but I can order from Digikey through work so not a real problem.

Second hiccip is the LM329DZ seems obsolete, though BZ are available through Mouser and Digikey. I note this is 6.9V zener yet the calculations for output voltage all assume 6.95V reference, what am I missing?

Now it seems Andy has previously suggested replacing the LM329 with something Walt Jung had identified, a couple of back to back 1N5234B zeners for a lower noise reference. Do I understand correctly Walk Jung is suggesting I stick a couple of 1N5234B back to back in a drinking straw filled with silicon to make a cheapo lower noise but lower DC stability than LM329 6.8V shunt reference? Obviously I would need to adjust the output voltage setting resistors R8/R9 if I went down this route, and perhaps also R5 to set the correct current through the zeners? Is this something anybody has tried or should I just stick with the LM329 rather than be the first mug to try something else?

I am assuming I don't "need" the tracking pre-regulator stage?

Any other tips before I crash into this would be appreciated ...
 
Mynamemynaim said:
2.5v. Headroom is a bit low
Aim for a few more volts if you have them to spare
Click to expand...
Understood, >=2.5V headroom required without pre-regulator, I am not exactly sure how far a Hicap will go but I undertand others have run them at 30V-ish output. So yes I can have more headroom. I suppose I might need all of that if I opted for the pre-regulator as then it is c.>=5V headroom. Hmm, another thing to think about :)
 
Hmm after re-reading the manual I will use the tracking pre-regulation, "The addition of a tracking pre-regulator brings further performance enhancements and adds all of the safety features and benefits of it’s internal protection circuitry to the super-regulator."

Who doesn't want better performance and more robust?

So add 1.3V extra for the tracking pre-regulator LM317 from the parts list and I need >= say 4V above 24V so >= 28V from the Hicap. Fair enough I think?
 
I believe the alwsr can take raw dc so in theory you don’t need the tpr4. Although if you do use the tpr4 you’ve effectively got a tracking prereg so don’t need that part of the alwsr. I think in effect you use either the tpr4 or the prereg part of the alwsr but not both
 
Well that makes sense to me, since Hicap is regulated output and TPR4 a series of regulators providing a regulated output I guess I don't "need" the ALWSR pre regulation ... but does it add anything having local pre regulation over the Hicap or TPR4 operating over a (relatively!) long piece of string from the load?
 
Teddy (Pardo) says that the more regulation the better ...ie there is gains to be had from feeding a regulated supply into another regulator close to the board being feed...and he HAS done a lot of work in this area...
 
Mynamemynaim said:
Teddy (Pardo) says that the more regulation the better ...ie there is gains to be had from feeding a regulated supply into another regulator close to the board being feed...and he HAS done a lot of work in this area...
Click to expand...
Kit Ryan has said similar, I think he said he found advantages in up to three levels, so a plain Hicap and ALWSR with pre-regulator would fit that. As I read it Andy is quite clear in the manual, he thinks pre-regulation is a good idea in all applications, so unless he pops up here and clarifies I'll work on the basis of pre-regulation.
 
Yes the manual does indicate that preregs are favoured ...i tried the output of my ALWsr on my 'scope and the output is very clean...but I do intend to up the voltage and feed that into onboard teddyregs on my preamp to get further improvement
 
Thanks to whoever put the parts list together I have been able to quickly stick a couple of orders for components. The bits that are not easily available at Farnell are available at RS for not too much so that is easiest for me:

AD825ARZ 183-2021
LM329BZ 779-890

and the oscons are a bit cheaper at RS too depending on how many you are making, and since I had to do a RS order anyway ...

16SEPC100M 179-3584

I also went cheap skate on the TO-220 insulating thermal pad and ordered the Multicomp 522636 which comes with an insulating bush as well as being 1/3 the price .

Otherwise all as per the parts list google doc, pedent alert: C4 has the wrong description I think, I think it should be the same as C2.
 
First ALWSR built, tested as per the user manual, stuck it on a 100mA load, provides the expected 23.7V using R8 1740 and R9 715 with the LM329BZ 6.9V reference.

But how to test the performance? I have access at work to some decent kit but as a softy I don't have a clue where to start :) would be nice to be able to post some measurements and have the benefit of the experienced pfm DIYers nod sagely and say it looks about right from a noise point of view, etc.
 
My experience has been that if they work, they work so just connect it up. By the way I did a thread a while ago about teddyregging a Naxo which showed how I mounted the regs on standoffs from the main board - might be worth a look
 
I have a NAXO 2-4 with Hicap, yes.

My plan is to make 4 ALWSRs, fit them inside the NAXO, two per channel, one on the LF, one on the HF, to give the sort of PSU upgrade a Supercap on a SNAXO provides only with local regualtion so in some ways better.

I can't just test this with one ALWSR though ... and there will be a fair bit more work before I can ... so I was looking to see if it was OK from a noise perspective as well as nominally providing correct output volts before I went further.
 
timH said:
My experience has been that if they work, they work so just connect it up. By the way I did a thread a while ago about teddyregging a Naxo which showed how I mounted the regs on standoffs from the main board - might be worth a look
Click to expand...

Exactly, and actually I have photos you gave me and dimensions of the internal mounting plate from your heroic efforts as the basis of my project. Only I am using ALWSR rather than TeddyRegs.
 
I remember swapping out the naim hicap regulator for a tpr4 in the psu for my cdp anologue stage which had local alwsr. It made a big difference.
 
I find the TPR4 much like a Hicap, a small uplift, not as as big a change as a ZapCap. If I were to have my time again I would stick RSL PSU1 modules in my Hicaps, might still, and flog the TPR4. l realise this is controversial on Pfm who generally love TPR4, so I will leave it there rather than derail my own thread. I will keep in mind you hear differences in upstream PSU through the ALWSR, thanks.
 
nobeone said:
First ALWSR built, tested as per the user manual, stuck it on a 100mA load, provides the expected 23.7V using R8 1740 and R9 715 with the LM329BZ 6.9V reference.

But how to test the performance? I have access at work to some decent kit but as a softy I don't have a clue where to start :) would be nice to be able to post some measurements and have the benefit of the experienced pfm DIYers nod sagely and say it looks about right from a noise point of view, etc.
Click to expand...

It is very difficult to measure super-regulators. I have (as you would expect) my own super-regulator designs and had to build a sub 1nV/RtHz balanced measuring amplifier as a pre-amp to my Bruel & Kjaer measuring amplifier, which itself has a 0.1mV FSD most sensitive range. The noise did not even register at all on the 0.1mV range without this pre amp. Output impedance is even more difficult to measure and is best simulated and then a "sanity check" just to see if there is "a rabbit away" and it is actually 100 or 1000 times worse than expected. They can have a lower output impedance than the resistance of an inch of thick wire!

I see no use for such super-regulators outside of powering discrete MC stages with poor PSRR. That is what I have used them for. I guess a Naim MC board falls into this category. With most Naim boards though ANY form of regulation is largely a waste of time as they have an RC filter at the power input anyway!! Remove this and then there could be some improvement...
 
Cheers Arkless. I have done a simple sanity check and the ALWSR output is measurably quieter than my bench PSU just with a 1mV/div scope envelope trace so I can't have completely crapped it up!

Yes super reg may well be overkill on an active cross over but it seems separate regulation for each channel and each stage is beneficial, hence the Naim SNAXO with Supercap. So overkill with a bunch of ALWSR can't hurt and is an order of magnitude cheaper and needs no more rack space and may be better with regulation closer to the load, well that is my theory.

Ok, so I will stand on the shoulders of giants and assume if they give the correct output voltage as I vary the input voltage and remain stable on load and are quieter then my bench supply they are good to go. I will build up the rest then work out how to sneak them in and connect them up taking inspiration from timH.
 
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