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  1. W

    Ultra high spec. opamp MC/MM phono, warp "elliptic" filter, line, headphone amps.

    Bill's making more progress. The "front panel" connectors are in place, and a number of things have been cleaned up.
  2. W

    Ultra high spec. opamp MC/MM phono, warp "elliptic" filter, line, headphone amps.

    I've sent the next tranche of changes to you. Alas, all of the fiddly wires to the ribbon connector/hard wired outputs are now needed.
  3. W

    Ultra high spec. opamp MC/MM phono, warp "elliptic" filter, line, headphone amps.

    Each input stage has a fixed 100K input impedance, at least above about 1Hz or so. Switching in the 91K gives a close approximation to 47k.
  4. W

    Ultra high spec. opamp MC/MM phono, warp "elliptic" filter, line, headphone amps.

    Bill's latest. Getting close... 290mmx250mm. All of the LED/control connections will be routed to connectors at the right for use with a secondary board with the remote functions or for "easy" wiring to a front panel.
  5. W

    Pyle PP999 phono stage

    Yes. I have the schematic and I've simulated it. However, I don't have time to go through the pedagogy now.
  6. W

    Ultra high spec. opamp MC/MM phono, warp "elliptic" filter, line, headphone amps.

    Thanks Bill. The board is generally looking OK, and I greatly appreciate the effort that you have put in. I've sent you a small list of specific issues which we should be able to resolve and move the project forward. Sean is making some progress in parallel, albeit very slowly due to his other...
  7. W

    Effects of MC Loading

    I'm a firm believer in the x10 DCR approach for LOMC cartridges. I've conducted considerable "research" into the loading "problem" and can see no evidence of the effect of loading on the cartridge frequency response, other than that which would be explained by the frequency response changes that...
  8. W

    The Official "Build" thread for the WYN Phono,Line,Warp,Headphone Pre amp

    Carbon pots are crap. Unreliable, noisy, certainly their linearity is poorer than metal film resistors, although I can't say just how bad they are. Their only benefit is cheapness. I've used DACT pots. They use metal film Rs and are quite linear and they have noise consistent with the resistor...
  9. W

    Phono Preamp Test for Mortals

    Yes. it's quite good- ignoring all of the other possible loading etc. impairments. A p-p error of about 130mdB, or a bit better than the Jung etc. network. By the way, this is the RIAA feedback design that I use. c. 0.009dB p-p error.
  10. W

    Phono Preamp Test for Mortals

    Just for completeness, and a touch of excessive pedantry, perhaps. With ideal components/source and R5 shorted the network shown, when simulated versus an ideal RIAA pre-emphasis curve, has about 180mdB p-p error versus the ideal, and with 1% caps and 0.1% Rs the peak-peak error is about 300mdB...
  11. W

    Phono Preamp Test for Mortals

    Perhaps for some engineers "close enough" is a tad closer...
  12. W

    Phono Preamp Test for Mortals

    Perhaps you can test the iRIAA circuit with REW and generate a correction file for it. REW will allow you to do this, and at the same time any doubts you have concerning the sampling rate etc. will be resolved. Sticking with a necessarily imperfect measurement technique without a known error...
  13. W

    Phono Preamp Test for Mortals

    The specified gain for phono stages is normalized to 1kHz as the reference velocity for phono cartridges is specified there, i.e. 250uv rms at 1kHz/5cm/sec is a typical MC cartridge output specification. Hence whatever the gain independent s-plane magnitude transfer function is it should be...
  14. W

    Phono Preamp Test for Mortals

    I guess that you didn't read my prior post. I supplied a txt file that you can use with REW as a cal file that would enable you to measure the response within mdB. Just do a linear sweep, set the levels up so that the output from the RIAA is neither clipping nor too noisy and use the cal file...
  15. W

    Phono Preamp Test for Mortals

    In the measurements I make the generator, receiver, and attenuator are part of the overall transfer function so a loop back test may be necessary to eliminate that error. Incidentally, that was not done for the posted response as the generator/measuring device transfer function is specified by...
  16. W

    Phono Preamp Test for Mortals

    I use REW plus an RME ADC/DAC and a resistive input divider to measure RIAA accuracy on my phono stage designs. I can measure repeatedly within a few mdB (yes, a few thousands of a dB) accuracy over the audio band and this accuracy has been verified with an APX555. If anyone is interested, I can...
  17. W

    Ultra high spec. opamp MC/MM phono, warp "elliptic" filter, line, headphone amps.

    I suspect things will change quite a bit, but it's a good start. The intent is to have the inputs/outputs and power supply connections at the rear, without cables, and there are lots of details that need to be considered. Also, provisions have to be made for connections to the possible digital...
  18. W

    Ultra high spec. opamp MC/MM phono, warp "elliptic" filter, line, headphone amps.

    Thanks Bill. I've been checking over the layout. It's a good start and much appreciated, but as expected there's much to do- it is a complex problem. I'll email you with comments/suggestions when I have a chance, however it's a busy day for me.
  19. W

    SOTA Pyxi has arrived

    I wouldn't hold my breath for the MM one if I were you. SoTa's focus lies elsewhere at the moment- principally their new field-oriented control direct drive turntable, and they have limited, even if very competent, resources for bringing new designs to market from the prototype stage.
  20. W

    Ultra high spec. opamp MC/MM phono, warp "elliptic" filter, line, headphone amps.

    I've supplied Bill with the new Kicad schematic. I will do the same for @HalfApt tomorrow. I've not heard from Sean for several days so I expect that his health issues are taking precedence, as they should.
  21. W

    Ultra high spec. opamp MC/MM phono, warp "elliptic" filter, line, headphone amps.

    The changes are in place, and I'm checking the schematics for consistency, so it might be a while. The new function only adds an extra cap per channel and also allows for the inclusion of a previously unavailable option that the prior WP phono stages had- the ability to add a volume control.
  22. W

    Ultra high spec. opamp MC/MM phono, warp "elliptic" filter, line, headphone amps.

    Thanks! For those interested, I've decided to add a 2nd order subsonic filter at 3.5Hz. This does two things- it improves the settling of the preamp, which otherwise requires incredibly long delays on the turn on circuit, and it greatly reduces the ultra-low frequency noise produced by the...
  23. W

    Ultra high spec. opamp MC/MM phono, warp "elliptic" filter, line, headphone amps.

    Bill, I sent you a PM. I cannot use AK to post the Kicad schematic.
  24. W

    Ultra high spec. opamp MC/MM phono, warp "elliptic" filter, line, headphone amps.

    Terrific! I'll post the latest Kicad schematic tomorrow, assuming AK will let me.
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