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John Warren

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John Warren last won the day on October 4 2014

John Warren had the most liked content!

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About John Warren

  • Rank
    "So much for the experts on this board"

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  • Gender
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  • Interests
    Engineering-Audio, magnetics, materials for electronic and magnetic applications, engineering models and simulation, SPICE, MATLAB, FORTRAN, acoustics, complex algebra, physics of sound, microphones, vintage audio, loudspeaker design, amplifier design, McIntosh amplifiers, discrete semiconductor devices.....and movies including silents, foreign and indies.
  • My System
    12" Utah Tri-axial drivers mounted in LRE bass "reflex" enclosures.

    Sony Superscope FM only

    Lafayette Solid State Stereophonic Integrated Amp

    16 GA Lamp Wire

    Koss Pro 4AA

    Technics SL-QD33

    CD Player:
    NAD 325i (modified)

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  1. Tubes bad in 80 days on new Mc275? Are they BS'ing me?

    Although true, anyone that purchases a tube amp should go into it with the understanding that tubes are consumables and an escrow account for replacements a necessity.
  2. CL-D Bi and Tri-amping (lots of photos and plots)

    FFT between 500-20,000Hz. Nearly 100dB of distortion free dynamic range(!).
  3. CL-D Bi and Tri-amping (lots of photos and plots)

    FFT of CH1 buffer out with 560 Ohm load, +/-100VDC supply, 1VRMS balanced input at 1kHz.
  4. CL-D Bi and Tri-amping (lots of photos and plots)

    The Plitron, the capacitor board and the buffer waiting for CL-D amps.
  5. CL-D Bi and Tri-amping (lots of photos and plots)

    The R/W/B leads source +/-100VDC to the buffer. The Fastons source to the amplifier. The buffer current draw is negligible (about 40mA).
  6. CL-D Bi and Tri-amping (lots of photos and plots)

    The XLR shield drains are connected to on-board RC hybrid filters with traces that back to a dedicated chassis ground circuit location for both XLR connectors. This keeps all shield garbage away for power supply reference and star grounds it back to the IEC plug. The green/black lead from "chassis" (in this case the Plitron mount) is attached to the RC filter on the buffer. The green lead with Faston female spade connectors to the IEC plug.
  7. CL-D Bi and Tri-amping (lots of photos and plots)

    Buffer board being supplied power from a +/-100VDC supply. The capacitor board consists of 40000uF of filtering. The voltage shown is voltage between the + and - power supply rails. Under these conditions the power transistors reach a temp of about 140C which is close to upper end of the recommended range of 150C. Maximum dissipation on the resistors is about 800mW.
  8. Class D

    I don't think it was revised, it's still Rev. A.
  9. Class D

    I did a get a couple of PMs. The TPA32xx family of UHD audio modules consists of five units: TPA3221EVM TPA3244EVM TPA3245EVM TPA3251EVM and TPA3255EVM So I checked the schematics and there's some inconsistencies on how to handle the shield drain conductor. The 21 and 51 seem to have a separate input grounds termed AUGNDR and AUGNDL (audio ground right/left) which has a different symbol than the amplifier ground. The 45 and 44 used a "routed" ground which might be referring to the star grounding scheme discussed in the application note.
  10. Class D

    Agreed, the changes were made a few weeks after initial release.
  11. Class D

    So I've been poking around the TI site related to this EVM and found this app note related to grounding problems associated with the TPA32XX family of amplifiers. The note proceeds to describe a "fix" to noise injected into the amplifiers associated with small potential differences between ground nodes at the input sharing the same ground plane as the chip (sound familiar?). It's not clear to me whether the note is describing a revision that's been incorporated into the board or something the user must do(?). Here's the problem, input ground shield shares same ground plane as amplifier and Vmid supply: Here's the "fix": Still really not a complete fix however but, based on the distortion results (which, BTW listening tests would not identify) it is significant:
  12. Class D

    That's why you really need to have measurements because if you're not sure then it's an issue. Also, if it is better how do you know it can't be even better? I'm not advocating getting test gear, the point I'm making is listening test leave us with this dilemma. I apologize, I'm thinking CL-AB. Any recommendation on a chip amp that can be driven from a +/- 40VDC supply (or +/- 80VDC).
  13. Class D

    Also, what boards have any of you used that are driven from +/- rails? I have two power supplies here, one +/-40V and one +/-80V that I can use to assemble a test amplifier.
  14. Class D

    Listening tests have practical limits but there's entitlement and it takes more than an audition with speakers. Look at it this way, your auditions tell you there's no difference between balanced and unbalanced. So either balanced signals are nonsense OR your noise floor is limiting in both configurations OR your setup is that the advantages of balanced signals aren't that significant. I suspect it's the last two. I'll bet you're not running 30' of cable between your hardware or powering it from different power branches off house power. One parameter that I consider important for headphone amps is the maximum spurious free dynamic range. It's simply the range (in dB) between the peak signal amplitude and the highest harmonic measured in FFT at, say 6kHz. This requires FFT and super-pure signal sources. Also changes in grounding are easy to see using FFT. That said, if you're pleased with the results then that's all that matters.
  15. Class D

    You've been warned!