AFAIK PCI is not fast enough for USB3. At least not for the common two port USB3 cards.

regards, Coen

Think about the distance a speaker travels in 1 second for 50Hz and for 5.000Hz. That's 100X more movement for the 5.000Hz one. You gotta have higher speed to do that !

The caveat is that I assume equal amplitude for this reasoning. That is not the same as equal loudness. The higher tones need less excursion for the same loudness given a certain speaker surface.  In the end equal loudness equates to equal velocity (if I am not mistaken).

regards, Coen

Right...but mid has higher velocity...

If I look at my Iphone FFT app, most energy is usually in the 80-800 region (voice and instrument fundamentals). Make shure you have some surface there to reduce the excursion. A subwoofer is wrt this issue a good idea.

Though this doppler thing likely clutters our sound reproduction, many musical instruments could derive character from it (ie singing of snares).

regards, Coen

p.s. Phono cartridge flashback!

Thanks Peter for the elaboration.

It appears that our ear/auditory system is extremely sensitive to pitch . I found this on the net:

"The normal human ear can detect the difference between 440 Hz and 441 Hz"

So the case for audibility is there.
The two tone analogy may work for explaining the effect when there is a substantial difference in frequency but what happens for multi tones or tones that are close together. What part of the spectrum can be considered "carrier" and what "modulated". When you try to envision music through this effect it becomes a complete mess. Well maybe it is the mess we listen to in our daily lives .

Regards, Coen

I find this doppler distortion rather acedemic. You have to have excursion ánd wide bandwidth to theoretically detect this effect. And how do you measure the effect of the pitch variations, how do they show in the Distortion measurement when they are a tiny modulation of the fundamentals? You may integrating the FFT over a time period of a two tone testsignal and see how wide/high the tone comes out of the speaker...

Besides that the "higher" tone's velocity also influences the pitch "lower" one if you wnt to be complete in the explanation .

Is this 4 real? Did you ever hear it and how does it sound?

Regards,  voen

That noise figure may turn out to be important or not, but I see other problem areas that need much more attention and are more likely to correlate with "better" sound.
Nevertheless the LT1083 also looks impressive, they have a price for a reason. There is also a 15xx series that raises my interest.

Warning/Teaser: If you converge on your regulation setup the next challenge will be a healthy supply and groundingplan. This will make or break all the hard regulation work. Next to theory and opinions it will reqiure practical experiments to find out whats best.

Regards, Coen

Arjan,

Which picopsu do you intend to use? I wonder if any of them is fit for being a xxhe supply.

As Anthony posted before a pc supply has to conform to the ATX standard for a board to start and function properly. This is about having voltages within the specs before supplying them to the mobo. You get yourself into trouble if you use two (or more) supplies. Who is doing the powermanagement?

So what may work is one supply for the mobo 24 and 4/6 pin connectors and one more for the periferals (fans hdds etc.). You have to orchestrate the power up and make shure the sata hdds etc have power to be recognised by the BIOS.

Regards, coen

Ok, you're right  no heat capaticance that keeps charging for 8 hours in such a small casing. But is remains an odd statement to me and will probably have to do with the lifespan/guarantee at serious lab loading (hence heat).

Regards,  Coen

I found the nice LDO regulators in my archive. The typenumber(s) is:

Micrel MC29750 to 29753.

 "Only" 7.5 amps but very nice specs. A few of these should do a music PC. Only0.5V dropout so you can keep input voltage close to the desired voltage (under minimum volt line condition).
There is also a nice LDO design section in the datasheets that covers most implementation aspects of safe operation.

I once thought of these to reduce the ripple of a normal switching supply. That is: readjust the ATX voltages to a minimum 0.6v overvoltage (under load) and kill the ripple with these LDO babies.

Intriguingly the Velleman labsupply has an "operation" of 8 hours....
Undoubtably this is about the heat building up.

Regards, coen

The lt series is only good for a few amperes of regulated current. That will do a HDD or a fan best. There are other more capable monolithic solutions. The datasheets also tell you how to boost the current with extra power BJTs. They are very low drop and available in the needed voltages.

I feel heat is still an issue. I know that you can get away with other constraints ie a lower ambient temperature, but as Peter said, component life expectancy progressively reduces with increasing remperature.
You also have to realise that most regulating solutions do NOT regulate transients or hf components. Actually the regulator may have an inductive output feeding oscillations.

The shuntreg is a worst case class A circuit, that is that is has to provide the peak current all the time, so if you need say at peak 2.5 Amps, the currentsource and sink have to both dissipate at least this 2.5 Amps. For a 12v currents sink alone this is 30Watts. Adding the source, you easily end up with a 40-50 Watt dissipation. You should save those for small signal audiocircuitry or ultra energy efficient PCs.

As they say on the silentpcreview site: a little air goes a long way. This is very true for the heatsinking of my cpu. When called for duty very little airflow can keep my megahalems cool compared to a hot touch  when absent. If you decide to go the powerdissipation route, you might consider previous generation cpu coolers as heatsink (to save some money). The are designed to get 100+ watts out of the CPU and keep it cool with a little air. As can be seen on the heatsink datasheets forced air can get small heatsinks to archieve 0.8deg/watt or lower.

As you will know most switching PSUs are not very efficient in the low wattage. If you measure the powerdraw on the AC side, the real powerdraw by the motherboard and components will be less so that helps a little.

I fully agree with minimising the powerrequirements for the PC first. This will make life much easier. I hope Peter will share some ideas on the "unconnected" PC he talked about before. Undervolting and undrclocking are a good start.

Regards, coen

I think the linear psu will run quite hot especially when challenged, not an ideal match with a hot running processor in one casing. Regulators have to drop voltage to operate so amperes=heat. You will need an awfull lot of cooling surface to keep within thermal operating range of the regulators. To get the necessary thermal resistance with a small cooling surface you may have to resort to active cooling.

Furthermore the 7+ amps let the voltage droop and increase the ripple on the input of the regulator. To fight that you need a lot of smoothing capacitance or a higher input voltage (which means even more heat). This may not be at the important music playing moment, but you really have to overspecify the transformers and capacitance nog to run into out of spec voltages on start/shutdown transients.
(To get the idea: in the priomordial phase all computers used to have -large- linear supplies. You can still find the very large capacitance, low voltage "computergrade" capacitors that were specified in surplus stores)

I think the teradac option and build looks sound to me: plenty real estate, sufficient capacitance, necessary ss for regulation, big recitifiers and a large cooling surface.
I ve been thinking of a setup that provides additional stabilised voltages to the pc wherefrom the voltages of the sata drives/PCIe card will be stabilized in the pc or any "low power" powerline.

I thought of this as a too big a project to pull off in my spare time. I also wondered and still do if a linear supply in combination with multi picopsus is the way to go. As i stated before, it may just be the switching input with PFC on the AC alone that is the culprit of the "lesser" sound of switching psus. You may reap 80% or more of the sonic benefits when changing that input to a linear one providing ie 24 or more Volts and have the wide range picos do the supply duty to the pc components. The 24v+ is just to minimise the current for a given power requirement (with only 4A you allmost have 100Watts available...) and ease the design of the linear part of the supply. Remember that there is allways some serious switching action on the motherboard to provide the cpu with 50-100Amps@1.5V from a 12 V powerline...

Regards, coen

Thanks Alain,

I'm afraid I drew conclusions on the wrong information. Xx allways reformats the Playback drive to exFAT. This might even be specified in the xx "manual". I deceived myself by looking at the IMDisk console without pushing the refresh button first.
Nevertheless I am shure there is a reproducable difference in sound between the reformats. So it must be some secondary effect that causes the difference (in all cases xx will play with an ExFAT formatted drive).

Regards, Coen

After my experiments with the ramdisk clustersize and filesystem, I never got back to the sq archived during the experiments.
I have looked in many places to only recently discover XXHE reformats the Playbackdrive to ExFAT the first time after a restart.

Now is there any setting with IMdisk to avoid this or should I request for a feature to keep the filesysten as is when starting play at XX?

Thanks,

Regards, Coen

Hi Peter,

Thanks for sharing your ponderings on the sub frequencies!


Well, it's based upon me being practical on classic horn theory. For -resistive- loading down to the Fc you need at least a 1/4 of the wavelength as horn length. So that will be about 2,5 meters for 35 Hz. Even with a 1/8 space loading the mouth area will still be about the size of an AN-E. Iow these will allready be HUGE. If you don't follow the rules you are either stuck with severe peaking/notching or reduced loading (ie derate the driver and EQ whats missing). Didn't Bert have such a monster basshorn in his showroom?

Now the Orelinos are somewhat of a horn, but they are also something else. On classic theory they won't qualify neither on horn length nor on exitsurface as a horn for an 18Hz tone...
They do have a lot of surface though to move air, about the equivalent of an 18" (or two 15") for the piston. For shure they act as a waveguide given the silece behind them.
It remains a very intriguing desing that seems to work very well.


This is really odd  ! Because of the drive symmetry between forward and backward movement I would expect a perfectly executed driver to have way more 3rd H distortion than second. Usually they are in the same ballpark. If I am correct this is also the case for the infinite baffle measurements on the driver's datasheet.
Some cancellation, ok, but NO third???

regards, Coen

Just to support the long post about audibility of the extreme LF (sub) I post the famous Fletcher Munson "equal loudness" curves. The slope to the start of the curves (starting at 20 Hz) is very steep down , that means you can have only very little distortion before it appears above the audibility threshold. So a 89dB sound pressure 20 Hz tone will produce a second harmonic of 40 Hz that will be audible at a level of about 50 dB pressure. That is about 1% (-39dB) max for the second, but the third and fouth are even more important (38 or 30db threshold or less than 0.1%). The audibility of these is speculative though since they could well be masked by noise or music.

The classic way to reduce distortion is to reduce the motion of the bassdrivers (or linearise them by motion feedback). Usually this means more woofer surface and/or horn loading which has a practical limit of 35 hz is a domestic environment.

Anyway it is great to learn about the Bass of the Orelinos which does something special to the listening experience even with the distortions in place.
Please keep posting your progress!

Regards, Coen