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John Warren

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  • Content count

    1969
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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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139 Excellent

About John Warren

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

Profile Information

  • Gender
    Not Telling
  • 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
    Speakers:
    12" Utah Tri-axial drivers mounted in LRE bass "reflex" enclosures.

    Tuner:
    Sony Superscope FM only

    Amplifier:
    Lafayette Solid State Stereophonic Integrated Amp

    Cables:
    16 GA Lamp Wire

    Headphones:
    Koss Pro 4AA

    Turntable:
    Technics SL-QD33

    CD Player:
    NAD 325i (modified)

Contact Methods

  • Website URL
    http://www.northreadingeng.com

Recent Profile Visitors

5924 profile views
  1. John Warren

    Proper care for Raw Birch Klipschorns

    Looks like the bottoms have seen water.
  2. John Warren

    djk?

    I thought the world of djk. His contributions to on-line forums made them worth visiting. RIP djk.
  3. John Warren

    HD closes KC manufacturing plant

    Truth is, I think to drive a motorcycle in a major metropolitan area (like Boston) you have to have a big appetite for risk given that there's always a significant fraction of drivers that are either distracted with their cell phone, stoned because pot is legal, too old to be driving or inexperienced junior operators. Then there's the potholes and overall poor condition of the roadway in the greater Boston area. Then there's the high healthcare insurance deductibles companies offer today that can require the insured to cover up to $20K before the insurance "kicks" in making even a minor motorcycle accident (if there is such a thing) a bank breaker for many. Common motorcycle injuries seen in Boston City Hospital or MGH ERs are compound fractures of the ulna + radius and or femur plus extensive body trauma. Rehab can go on for years ending in limited or no use of the distressed limbs. The insurance bill is around $140-160K plus lost time from work. I just don't see the Millennials buying into this scenario. The ones that have money that is.
  4. $100 is a bargain, these things go $1000 new. https://www.markertek.com/product/ev-cdp850t/electro-voice-cdp-850t-indoor-outdoor-60-watt-horn-and-1828t-driver?utm_medium=shoppingengine&utm_source=googlebase&cvsfa=3786&cvsfe=2&cvsfhu=45562d43445038353054&ne_ppc_id=946758658&gclid=EAIaIQobChMIvqifjs_02gIV1oWzCh3yagD9EAQYBSABEgLpZvD_BwE
  5. John Warren

    EV Georgian

    ? Here's a factory original-
  6. John Warren

    Developing a network for the Forte

    Used a model of the T2A to simulate the autotransformer. Model outputs are voltage levels across drivers expressed in dBs. The T2A attenuates midrange about 9dB on tap#2.
  7. John Warren

    The Fifteen

    Perhaps they sounded too good?
  8. John Warren

    Crown D-45 schematic

    Above, decidedly, demonstrates that audio amplifiers are voltage sources and that all design considerations are to preserve accurate voltage transfer.
  9. John Warren

    Crown D-45 schematic

    Feedback is sourced to the INV pin which has same phase relationship as non-INV signal from the gain pot. The op-amp takes the difference (fractions of mV range) and amplifies the result (the error signal) and that's what drives the amplifier The open loop gain of the op-amp is large and applied to the differences (both AC and DC). SPICE simulation shows the difference signal (blue) and the output (red) of the second op-amp (in this case the MC33079) at 20kHz sine wave, 0.5VRMS balanced signal sourced from 660 Ohm source impedance, gain and CMR pots at nominal. The "glitches", when sent thru the amplifier, correct the signal to reduce distortion. The plot is taken a few milliseconds into the signal allowing caps to charge.
  10. John Warren

    Crown D-45 schematic

    Yes, Q107, my copy of the schematic isn't clear. I did explain the second op-amp. It provides the error signal and that's its only job.
  11. John Warren

    Crown D-45 schematic

    At max input (~0.7VRMS) the op-amp serves as a differential input amplifier capable of ~2Vp-p ground referenced error signal. Q102 is an emitter degenerated voltage-in, voltage-out amplifier with Q101 providing current limiting at clipping. At max input, the signal at the base of Q102 is about 50mVp-p referenced to the -30V rail and, by way of the effective load on its collector, produces ~40Vp-p ground referenced signal at the bases of Q110 and Q187.
  12. John Warren

    Crown D-45 schematic

    So where are you on this? Are you listening to your modified amps?
  13. John Warren

    Crown D-45 schematic

    I have a somewhat earlier D75 that I'll teardown here: http://www.northreadingeng.com/Audio/group/ Might give you some clues?
  14. John Warren

    Crown D-45 schematic

    On the ones I've seen, Pin 1 on both XLR input sockets are on dedicated trace to chassis ground which ties to Earth plug on 3-prong. P16 is circuit ground last time I looked. Curious to see what your seeing, can you post photo?
  15. John Warren

    Crown D-45 schematic

    I'm interested in changes, not absolute magnitudes. My anemic 3V/us is not a slew-rate, it's a compensated slew-rate, measured at 15kHz. I spooled-up the potentiometer to output a healthy voltage, in this case ~23Vp-p and then simply measure the time required to settle after responding to a 15kHz pulse. By comparing the time required to reach steady-state, an "apples to apples" comparison between op-amps, changes in compensation, output transistors and so on can be readily determined by storing the image before the change and then comparing after. An alternate approach would be to set the goal posts at 10 and 90% the vertical response and measure the time between. Plot below is example using the TLE2079 op-amp with compensated slew-rate of a bit over 3V/us loaded with 8 Ohm power resistor. Thought this thread had died, fancy that.
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