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In Reply to: Not necessarily posted by Christine Tham on April 6, 2007 at 15:31:34:
There is a connection between latency jitter (variations in latency) and transmitted jitter. I found that reducing latency helped in overall sound quality. Why this is so I don't understand.On USB, yes if mobo has dedicated USB bandwidth then you would avoid conflict described earlier.
On IDE, I found its best to avoid this interface as it lends itself to electrical noise pickup. Also, using Windows IDE drivers is not an optimal choice. However, I'm keen to use CF technology implemented as a disk drive. No moving parts and even less power! Price is high and storage capacities low but as most pc harware goes, this will improve very quickly.
Follow Ups:
*** There is a connection between latency jitter (variations in latency) and transmitted jitter. ***That could well be true. But I'm not sure what you mean by latency - do you mean bus latency, or audio delay latency?
As I've pointed out before, *increasing* audio delay latency (through buffering) actually *reduces* jitter.
*** I found that reducing latency helped in overall sound quality. ***
If you mean bus latency, then possibly. Although ThomasPf and I disagree on this - I feel it could make a difference, Thomas seems to think (and I'm paraphrasing him) as long as the buffer on the soundcard never becomes starved, PCI bus interrupt processing should have a negligible effect.
If you are interested in reducing bus latency, you may want to consider using Vista with a WaveRT audio driver - Microsoft promises that WaveRT has much lower latency than either WavePCI or WaveCyclic (which are the traditional models for audio drivers used in XP).
*** On IDE, I found its best to avoid this interface as it lends itself to electrical noise pickup ***
That's probably due to EMI generated by the IDE cable. You can take various steps to reduce this. For example, you can try shielding the IDE cable.
Since you are interested in latency, are you aware that some SATA drivers generate more interrupt processing latency than IDE? There have been cases of SATA drivers causing audio/video stutter. So in that respect, I'm surprised that you consider IDE to be non-optimal.
*** I'm keen to use CF technology implemented as a disk drive. ***
I'll be keen to find out whether you notice any differences switching to CF. I've noticed an improvement getting rid of my laptop hard drive and using a CF card. I've also noticed an improvement applying shielding to the audio card.
Pricing is pretty good - I bought a 4GB CF card for around $100 and you don't really need more than 4GB (provided of course the music is stored elsewhere on the network).
On latency/jitter stuff I suspect its a combination of both. I'll need to do more research. For now I want to test the Zalman TNN-300 case - it does a few things right and PSU may even better Enermax. I use a basic mini tower case with heavy non-metallic object on top (the added inertia helps). For EMI shielding, I use Quantum Physics noise disruptor on soundcard (other methods risk short circuiting).IDE/SATA. Yes you can buy shielded IDE cables and it would help. I still prefer SATA as you can disable IDE. I found playback latency to be important - SATA latency has no impact (as long as Foobar is never starved of data and drive has at least 8MB cache). Makes sense on video stutter as video application demands factors more data from disk. SATA RAID 0 would solve this.
BTW - On toslink, yes DAC should do reclocking - I use AA Prestige SE. I like your point on under-clocking. It got me thinking on how to do this permanently with Core 2 Duo processor. This processor is great as it optimises for low power (and therefore lower voltage, lower RF radiation, harmonics) - current suggested setup in paper does this. But during playback, clock frequency hops to higher levels to its max of 1.86GHz. Fortunately these (voltage) transitions occur infrequently. But getting it to stay at its lowest level permanently is best - I'll post a solution.
*** I still prefer SATA as you can disable IDE. ***Since SATA has higher bus latency than IDE why not disable SATA?
*** SATA latency has no impact ***
In that case, why worry about PCI bus usage at all?
I'm not sure why you would be worried about USB and Ethernet PCI usage (when these devices typically don't impact the PCI bus) but then say a device that has latency high enough to potentially cause audio/video stutter has "no impact"?
*** SATA RAID 0 would solve this. ***
I'm not quite sure how using RAID 0 can reduce the bus latency of a SATA chipset? Wouldn't it actually *increase* latency (because the chipset now needs to do more work for each I/O request)?
*** On toslink, yes DAC should do reclocking - I use AA Prestige SE ***
If the DAC is reclocking and resamping the SPDIF input, then why optimize the PC at all (since any jitter in the input signal to the AA will be discarded by it's resampling)?
Also, why upsample in Foobar using SRC? You'll end up triple filtering the audio (SRC upsampling, and another layer of resampling by the AA Prestige, followed by final filtering in the DAC itself). Each filter will add an additional set of artefacts to the signal.
Of all latencies in computer, I find reducing playback latency to have a large impact on sound. Sound delivery happens in realtime, hence preference for soundcard having lions share of PCI bus.On SATA/IDE, SATA latency may be worse than IDE (but biggest latency is at hard drive irrespective of interface @ ~5-6ms). Of course, you raise a valid point why this latency is less important?
My thinking: disk read latency happens only once at start of play where Foobar through Windows (through interface, data bus, disk controller, cache and finally disk) establishes a data read stream. Since this sequential read stream rate (@ 42.9MB/s for Seagate 5400.3 160GB) is factors more than what Foobar needs there is minimal effect (as disk data is available to Foobar ahead of time –Windows/disk controller prefetch & block reads occur). For example, on my setup, an hour long CD (600MB) takes ~10 seconds to load into RAM, yet playback takes an hour.
Let me preempt your question here, 600/42.9 = 14 seconds, how do you get to ~10 seconds? RAID 0. File data is stripped sequentially across drives thus on read, you get both drives performing sequential read in parallel. In theory you should get double throughput but some serialization occurs and throughput improves by ~30-50%. RAID 0 does away with Windows IDE drivers (and all its overheads including SATA in IDE mode) which I found beneficial.Most optimal is when NO disk reading occurs during playback. By this I mean entire CD .wav file is read into RAM (using Foobar’s full file buffing). There is a bug when playing .cue files where foobar ignores file buffering – playing .wav files, buffering occurs (and 5-15 seconds elapses for playback to start). Hopefully this bug gets fixed in next release. This way, disks go into idle state consuming 40% less power (meaning less EMI, etc.).
*** If the DAC is reclocking and resamping the SPDIF input, then why optimize the PC at all (since any jitter in the input signal to the AA will be discarded by it's resampling)? ***There is good sonic improvement. Like all DACs I suppose the one I’m using is not perfect. Others have found this too with DACs that do internal jitter management.
*** Also, why upsample in Foobar using SRC? ***
To bypass DAC’s inferior 16/44.1 -> 24/96 upsampling. DAC further upsamples to 24/192 but most ‘damage’ occurs on former. DAC sees 24/96 feed as native input (with music information to 22.05kHz only).
Two immediate points:1. Raid - unless you have a premium raid card, raid support is software based.
Recommended Windows settings as set out achieves this by:1. Having no paging file (no VM)
2. Stopping all unnecessary services (task scheduler, disk indexing, etc.)
3. Remove unnecessary programs (many sw installations do sneek in startup actions)
4. Remove Windows components (disk indexing, messenger, etc.)
5. Only have foobar in startup
6. Perform boot only prefetch (and deleting all contents of c:\windows\prefetch)
7. Install no virus protection swTest this and let me know what you get. After bootup, with Foobar started but not playing, there should be no disk activity whatsoever no matter how long system idles. Only disk activity would be the disks themselves (Windows has no control over this), e.g. parking drive heads and thermal recalibration.
Recommended Biostar mobo implements SATA RAID at hardware level. Check out the VIA chipset it uses (link below). No need to get additional RAID hardware if using this mobo.Once BIOS is set to SATA RAID, Windows installation CD will not recognize disk. VIA chipset driver for Windows needs to be supplied on floppy.
Hi cics,For underclocking or undervolting a Core 2 Duo chip, try a program called RMClock by Rightmark (see link below). For underclocking an AMD 64, try CrystalCPUID. The standard version of RMClock is free.
RMCLock is easy to use and excellent. You can specify four different modes of operation and customize the CPU frequency and throttling of each. One mode, called Performance On Demand, will automatically jump between the modes as needed. You can also lock to a specific power saving mode if you prefer.
I have found that the RMClock utility makes a cooler running system. In combination with the Speedfan utility, fan speeds can automatically be knocked down according to system temps, allowing for a quieter system as well.
oops, just saw that you already found it!
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