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  1. 1

    Auraliti PK100 and DSD operation

    The Auraliti does not support DSD with its internal DAC. The hardware all predates DSD as a distributed format. Software decode on that platform was really beyond the processor so we don't support it. However we do support DSD/DoP with external DAC's.
  2. 1

    DSD Battle Royale!

    The linked download directory seems to be empty. Did we overstay our welcome? Were all the files encoded simultaneously or sequentially? Changes in the tape playback over repetition is pretty well known and at this level could be significant.
  3. 1

    Baffled about computer power

    What I really focused on was isolation. I did everything possible to minimize the coupling between the AC power connections and the power going on to the player. I need to recheck but I think the total coupling is around 100 pF. This plus a low noise power supply design to reduce the noises from...
  4. 1

    Baffled about computer power

    Aggressor vs. Victim is a good description. The noise can modulate the signal both in amplitude and time and can be synchronous (data related) or asynchronous (any un-audio related noise). The effects will be in the analog output, not particularly in the data stream itself. Digital data has what...
  5. 1

    Baffled about computer power

    Its not the noise that you hear, its the noise that modulates the signal you are listening to. There are a number of mechanisms that allow noise to essentially modulate the signal (audio) but have little or no presence when there is no audio to modulate. Jitter is one of these phenomena. Also...
  6. 1

    Spectral DMC 6 Preamp

    Those are the correct points. Good luck!
  7. 1

    Why DIY computer-based music servers are not ready for me

    First if jitter were the only issue it would be a simple problem to resolve. Nevertheless I have measured the master clock jitter of several sound cards and wound up focusing on the ESI Juli@. I got a 25 pS cycle to cycle jitter from a direct measurement of the clock, pretty much the noise floor...
  8. 1

    Spectral DMC 6 Preamp

    Its been years since I looked at one. The basics are as follows: The bias current is set via a resistor to the positive rail in series with the output FETs. If you are looking at the board with the controls toward you the component layout is very similar to the schematic. The resistors are 100...
  9. 1

    Spectral DMC 6 Preamp

    Thats almost a philosophical question. The Phono section rolls off following the RIAA curve starting at 2120 Hz and continues to about 50-80 KHz and then is flat to several MegaHertz, except the DMC6 may have the hybrid version which works similarly but not the same. The line section is flat to...
  10. 1

    Spectral DMC 6 Preamp

    I would just run it at full gain. The gain control is in the phono section which means the response will change when the gain changes. The unit has enough dynamic range to handle a high output cartridge at full gain. The volume control is positioned to handle managing the range and keeping the...
  11. 1

    Spectral DMC 6 Preamp

    (Dusting off very old memories) The only problem with connecting the crossover in the tape loop is that there will be no volume control for the bass output since the volume control for the system is after the tape loop.
  12. 1

    Absolute Sound Review Of Alpha USB on-line

    I think we are on the same page with jitter issues. They are quite complex once you get to actually making something. What is a Time Pod? I'm pretty familiar with available solutions for measuring phase noise and this is new to me.
  13. 1

    Absolute Sound Review Of Alpha USB on-line

    Since you started this thread, sure. The moderator can move it if desired. Its perhaps easiest to think of the box as an audio computer. It does what is necessary to take the content of a USB stick or USB connected drive and play it through the S/PDIF or USB output. You can find out more here...
  14. 1

    Absolute Sound Review Of Alpha USB on-line

    You can get whatever level of jitter you want if you spec it right. Most jitter specs for crystal oscillators are based on SONET specs, with a bandwidth of 12 KHz to 5 MHz. This can be misleading for audio. I did a quick calculation based on one of the best oscillators made for close in phase...
  15. 1

    Absolute Sound Review Of Alpha USB on-line

    Jitter Here is a bewildering number: To achieve 24 bit accuracy on a 100 KHz sine wave you need less than 100 FemtoSeconds Jitter. Any higher and you won't get the signal to noise that 24 bits offers. However there are no audio frequency 24 bit accurate ADC's also at lower frequencies you...
  16. 1

    Absolute Sound Review Of Alpha USB on-line

    Thunderbolt Thunderbolt will never replace USB for slow peripherals. Its an enhancement over Displayport with high throughput speeds and the ability to connect PCI express like interfaces to the host computer, but only a few. The power and overhead makes no sense for a mouse. The chip will be...
  17. 1

    Reflections and DACs

    A well made 75 ohm BNC can measure really well up to 3 GHz on a VNA. The Smith chart is a dot in the middle as long as its all well cared for. You would need the BNC adaptor Kit from HP. $1,000 for some 75 Ohm BNC to N adapters. The test cable for 75 Ohm N to N for Agilent VNA's is around the...
  18. 1

    Spectral vs. Threshold phono sections: Does one sound better than the other?

    No reason to split the grounds in this application. it might help the sound but an optimized output interface (inductor in parallel with the resistor and a suitable Zobel network) would make a bigger difference in the output and less hassle.
  19. 1

    Spectral vs. Threshold phono sections: Does one sound better than the other?

    The actual source impedance of the output circuit is close to zero. The 100 ohm resistor is for impedance matching to an unterminated twisted pair (audio interconnect) to reduce HF reflections and make it more tolerant of shorted outputs. I don't recommend directly driving the headphone because...
  20. 1

    Spectral vs. Threshold phono sections: Does one sound better than the other?

    Actually you can drive the headphones directly from the outputs. There is a 100 Ohm resistor in series with the outputs. For better sound I would replace that resistor with a 10 Ohm resistor. You should get a good one since it will have a more significant impact on the sound in this application...
  21. 1

    Quick Spectal and MIT Cable Questions

    Hardly very important. Many people (including those who should know) get confused by this stuff.
  22. 1

    Spectral vs. Threshold phono sections: Does one sound better than the other?

    I always found that it sounded better to have the gain at the high position. Enjoy.
  23. 1

    Spectral vs. Threshold phono sections: Does one sound better than the other?

    That's beyond my memory and the picture is a little too blurry for me. You might be able to tell by looking at the resistors next to the switch. My guess is that the switch closest to the left in the picture will change the phono gain from 32 db to 40 dB. it will sound better in the high gain...
  24. 1

    Quick Spectal and MIT Cable Questions

    Sorry, but the outputs are DC coupled and AC coupled. They are both the same phase. One has an output coupling cap. There is no intrinsic "better' to balanced and in many cases there is just an added inverting amp to create balanced outputs. Execution is the important part, including the...
  25. 1

    Spectral vs. Threshold phono sections: Does one sound better than the other?

    I actually had almost finished a matching phono section to the NuForce P-9. its still a ways off. nuForce is doing well with headphones and quite distracted. The line out would be very well suited for headphones. the 100 Ohm series resistor will limit the performance some. You could change it...
  26. 1

    Spectral DMC 6 Preamp

    I consult for all three companies and a few others. Monster Cable keeps me very busy, the others keep me sane.
  27. 1

    Spectral DMC 6 Preamp

    Peter: I'm pleased you are still enjoying the SW-5. it would be fun to update that technology but a lot of work and i have many other things tugging at my time. the auraliti player did start as an idle speculation on my part. I created the current version. If you have questions about the player...
  28. 1

    Spectral vs. Threshold phono sections: Does one sound better than the other?

    i know virtually nothing about the threshold stuff, but on the DMC-6 (10, 20) I can comment. The circuits are all very similar. The DMC-20 has higher rail voltages for more dynamic range and some other refinements. The phono section was designed to be an optional component and was removable. The...
  29. 1

    Spectral DMC 6 Preamp

    I thought I should clear up some of the history of the Spectral preamps here. I designed all of the Spectral preamps through the DMC-20. Keith O Johnson took over around that time. The first Spectral preamp was the MS-1, a true kitchen table product. We built 20 or so of those. The DMC-10 was...

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