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  1. #1
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    Default Heathkit IM-48 audio analyzer

    Hello,
    I know this isn't exactly an audio device, but it can be used to understand all things pertaining to audio. This is a vacuum tube operated device that functions as three measurement tools. It is a VTVM (vacuum tube volt meter) which is still one of the best methods of making accurate voltage measurements without loading down the "device under test" (DUT). It is also Watt-meter, with built-in 4, 8, 16 and 600 Ohm loads and it is an intermodulation distortion meter (IM distortion). You can mix two frequencies, 60Hz and 6,000Hz in any ratio with it you can measure power output, noise, gain, overload and intermodulation characteristics. It uses 12AX7, 12AU7, 12AT7, 6C4 and 6X4 tubes (all British made Mullards!) and many precision value resistors.
    I repainted the back enclosure and replaced the front panel binding posts and did a general sprucing up, outside of the scratch on the meter bezel it looks pretty new.
    Cheers, Ken
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  2. #2

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    Default

    Do...want...
    "Unwad those panties and have a good time man. We're all here to help each other, no matter how it might appear." DSkip
    I may have an addiction... RTA-15TL, SDA 2, LSi25, LSi15, LSi9, LSi7, LSiCx2, LSiFX, LS/FX, RT/FX, DSW MP2000...and that's just the Polks...

  3. #3

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    Handy gizmo.
    How sensitively can that measure IMD, Ken?
    all the best,
    mrh

  4. #4
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    Hi Mark,
    Yea, not bad for $62.00 on eBay. Sensitivity is 10 millivolts for AC VTVM, .15 milliwatts for Wattmeter and .04 Volts minimum high frequency signal required and .17 Volts for LF and HF energy mixed 4:1 (SMPE standard) for IM distortion.
    Ken

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    That looks like something my dad once had. He had, and probably still does, several pieces if Heath Kit test equipment. He has been modernizing lately though.

    Seeing your post inspired me to Google for an instruction manual for a Micom (3M) 8100 flutter meter that I have had for a while taking up space in the basement. I played with it a while back but couldn't quite figure if I was setting it up correctly. Now I have the IM and I gonna' have to clear all that junk off my bench.
    Stan

    Main 2ch:
    Polk LSi15 (DB840 upgrade)
    Parasound: C/PT-600, HCA-800II; Denon: DVD-2910, DRM-800A; Monster HTS3600-MKII, Grado SR-225i

    HT:
    Denon AVR-888, Polk: RM7, PSW10, Marantz UD5005, Panasonic TC-P42S60

    Other stuff:
    Denon: DRA-835R, DRA-825R, DCD-660, DRM-700A, DRR-780; Polk: RTA11TL (RDO198-1, XO and Damping Upgrades), S8, Monitor 5A, TSi100; Pioneer CT-6R, PL-530; Onkyo CP-1046F; Ortofon OM5E, Marantz PM5004, CD5004

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    It looks just like my meter, that's up in the attic somewhere. I wounder if it still works?

  7. #7

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    Ken, see what you started... Time to start posting what we got!
    Stan

    Main 2ch:
    Polk LSi15 (DB840 upgrade)
    Parasound: C/PT-600, HCA-800II; Denon: DVD-2910, DRM-800A; Monster HTS3600-MKII, Grado SR-225i

    HT:
    Denon AVR-888, Polk: RM7, PSW10, Marantz UD5005, Panasonic TC-P42S60

    Other stuff:
    Denon: DRA-835R, DRA-825R, DCD-660, DRM-700A, DRR-780; Polk: RTA11TL (RDO198-1, XO and Damping Upgrades), S8, Monitor 5A, TSi100; Pioneer CT-6R, PL-530; Onkyo CP-1046F; Ortofon OM5E, Marantz PM5004, CD5004

  8. #8
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    Yea, old test gear! Sometimes you can see a few pieces of old stuff on shelves in movies, sweep dials and anything with a meter on the front face. I'm trying to find a Tektronix 570 tube curve tracer.

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