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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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  • 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. Agree with your assessment. I would not purchase a McIntosh product today. McIntosh's best days are behind them.
  2. A few photos of a tube amp project completed recently. Two channels, about 20WRMS/ch into 8Ohms. Based somewhat on the Scott 299C output stage but using a solid-state, HV power supply design capable of substantially more power than is required for the push-pull 7591 pairs. Chassis CAD files were sent out for quote, the supplier (New England based) responded with pricing for larger quantities than I was considering. Placed an order for a small lot of chassis assemblies. All metal chassis assemblies are best for RFI/EMI/noise immunity. The chassis assembly is the high-cost item in the build. Uses oversized Hammond or Lundahl output transformers. Still waiting on a few finishing touches (knobs, graphics). Was considering silk screening the top plate but perhaps some other time.
  3. Water should be either deionized or distilled. A friend of mine uses distilled water and Simple Green surfactant solution. It's alcohol based. Chemical smell. The u/s cleaners that sweep the frequency clean better than those that sit at a single frequency. With the surfactant and swept frequency embedded particles can usually be extracted.
  4. It may be possible to remove the transducers from the plastic horn section and find ones that would fit. Can you provide photos of the rear of the assembly and, if possible, remove the transducers so we can have a peek?
  5. John Warren


    The WSJ had an article that talks to the concept of "health-span" rather than life-span. Health-span is the years one lives with good health and free of diseases that impact your quality of life and state of mind. The years past when the health-span ends are the years spent managing disease. Most medical interventions, especially for the 75+ crowd, increase life-span but not health-span.
  6. Common in industrial locations. If you have a portable water pump, wet-vac or using power tools in wet areas this is what you want. If you work on vintage, old and/or faulty electronics, lots of "gotchas" and surprises. Here's my take, connect chassis directly to panel Earth. Regarding Variac, the red, Chinese Amazon units are the POS. Can't run at rated kVA without getting hot AF. Wipers aren't accurate or don't function until the wick is turned halfway up then wham! The internal winding is likely a better fuse than the fuse. A Staco 12A variable transformer runs about $650 and will source 1.4kVA all day and barely get warm.
  7. Texas Instruments published a 2-stage, phono preamplifier design based on the LM833. Flat RIAA response with noise floor lower than -100dBV. Can be fabricated for about 60 USD at the board level.
  8. Are you running long cables at line level signals?
  9. The unity coupled transformer offers improved performance for CL-B vacuum tube operation only. CL-B amplifiers are somewhat higher efficiency than CL-AB.
  10. High BP can have nothing to do with weight. I recall a statistic that ~20% of the people on BP meds are at a good weight (i.e. BMI <24).
  11. It's dB (capital B for Bell as in Alexander Graham).
  12. John Warren


    A1C is the gold standard, most docs will prescribe an A1C if a couple of 12h fasting BG ratings are 105-115 (at least that was my experience). The correlation coefficient between BMI and A1C for the 50+y/o crowd is basically =1.0 so if you're heavy or obese you're most likely prediabetic or diabetic. To your point, you can live into your early 90s with all sorts of metabolic issues. I've got family members there now. And they're depressed, immobile (really crippled), fatigued, constantly panting and vision impaired. And that started 10-15 years ago. Not saying I won't experience same fate but if there's any opportunity to avoid it, I'll try. Genetics loads the pistol but it's lifestyle that pulls the trigger.
  13. John Warren


    In the meantime, researchers are still trying to figure out the causes of obesity in the USA.
  14. John Warren


    the health experts...
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