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Back to Basics: Audio electronics tutorials
  • goannagoanna

    Balanced and unbalanced mics and leads

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    Fig. 3: A balanced line system adds a "cold" line to the "hot" line of unbalanced systems.

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    Fig. 4: Conceptual equivalent of a differential amp.

    http://www.harmonycentral.com/t5/Lessons-Theory/Balanced-Vs-Unbalanced-I-O-How-It-Works/ba-p/34639794

  • 13 Replies sorted by
  • goannagoanna

    Impedance For Microphones, Instruments and Devices

    For practical use in the recording studio, impedance refers to resistance to an electrical current. The word impedance is often represented with the letter Z, and is measured in ohms (Ω).

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    Impedance Transformers

    from http://audio.tutsplus.com/tutorials/recording/everything-you-ever-wanted-to-know-about-impedance-but-were-afraid-to-ask/

  • goannagoanna

    Microphone Types

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    There are five key types of microphone you may use:

    • Moving coil
    • Ribbon
    • Condenser
    • Electret
    • Crystal

    All employ different mechanisms to convert sound energy to electrical energy. Hence all have different advantages and disadvantages. You will hence need to choose the right type of microphone for the right type of application.

    The microphone is not expected to deliver electrical power- it operates into HIGH ELECTRICAL IMPEDANCE such that there is (approximately) zero current - VOLTAGE is the output variable. Consequently, it is conventional to talk of the "Open Circuit" response.

    from http://www.acoustics.salford.ac.uk/acoustics_info/microphones/

    See also How to use an electret microphone

    Choosing a Microphone Type

  • DrDaveDrDave

    For all practical purposes, the information on balanced and unbalanced is fine, and most people will sort of skim over the science, which is really only touched upon. However it is missing one important detail, which is that a properly designed unbalanced circuit will outperform a balanced one. Most people leave that part out. The trade off is that you may (may) get some noise insurance, which is a really good thing sometimes. The other minor point is that the usual yardstick is the length of the cable run. This used to be important, but if you you are using MADI it isn't important at all, and the trend is towards shorter cable runs.

  • ppcroftppcroft

    @ DrDave

    However it is missing one important detail, which is that a properly designed unbalanced circuit will outperform a balanced one.

    I would like to know more about this, but from the sound reproduction angle.

    I have recently been swayed by the nefarious world of headphone audiophiles :-). Running balanced cables for high end headphones using balanced amp/dac seem to be in vogue. There is certainly an increase in available Amp power when running balanced. However while some swear by the sonic benefits of going balanced, skeptics claim such benefits will not pass a proper double blind test.

    I have seen articles explain benefits of balanced audio.....(of course they do benefit from such articles)

    http://www.headphone.com/learning-center/balanced-drive-article-series.php

    I would like to see some articles where it suggest unbalanced will be better, if implemented properly..

    I am about to take the plunge on a balanced DAC for myself for unbalanced use for the time being. Buying balanced cables costs a lot of money that may be the biggest rip off in the audio world. Any feedback will be welcome. Thanks.

  • goannagoanna

  • Vitaliy_KiselevVitaliy_Kiselev

    @goanna

    It really needs place in FAQs wiki :-)

    And yep, main advantage of balanced connection in short cable lengths is not really balanced stuff, but better connectors used.

    For on stage long cable runs you really need balanced connection as cables pick stuff with bunch of RF and other stuff.

  • goannagoanna

    Phantom Power For Microphones

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    1. The current leaves the DC power-supply positive terminal and goes through two equal resistors.

    2. The current travels along the mic cable to the mic.

    3. The current is recovered inside the mic and goes through the mic circuitry.

    4. The current returns to the DC power-supply negative terminal via the cable shield.

    from http://www.prosoundweb.com/article/audio_basics_a_primer_on_phantom_power/

    • The Phantom Power spec is 48 volts dc from a standard 3-pin XLR connector.
    • Phantom Powered microphones have a wide operating range, from 9vdc to 48 vdc.
    • Some console / mixer manufacturers take advantage of the above range by not supplying the full 48-volts. They do this because it is easier and cheaper.
    • Computer microphones that use a mini 1/8-inch (3.5mm) phone plug do require power, but not phantom power. No simple adapter will make these mics work in a pro system.
    • The power supplied by the computer / sound card to the 1/8-inch (3.5mm) jack not configured to power professional microphones (or powered direct boxes).

    from http://www.tangible-technology.com/power/Phantom_Power_connect.html

    @Vitaliy_Kiselev Perhaps even FAQ's need to be migrated to front page occasionally for people (like me) who forget the basics?

  • DrDaveDrDave

    @ppcroft The technical papers are published on the AES website, there are also technical papers in other languages. The de facto standard technical school is in Detmold, Germany, but you can certainly wade through the papers at AES. For your basic DAC, I recommend this one http://www.ebay.com/itm/HIFI-NEW-Version-DAC-Decoder-TE7022-CS4398-24Bit-96Khz-USB-RCA-headphone-output-/140751305382?pt=US_Home_Audio_Amplifiers_Preamps&hash=item20c56e7aa6

    It has a great design, and powers Sennheiser headphones, and costs $55. Wima capacitors, circuit designed by Weiliang. It has the TE7022 with the CS4398 chips. Pay the Ploytec guy a few bucks and get ASIO for your audio editing if you want it.

    You would be of course be completely wasting your money on balanced connectors for your DAC, but you could maybe upgrade the cable connector on the headphones, the latest Sennheiser cable uses thicker wire. Cost: ~$15. Take the HD 580 and swap out the old cable. Adding an extra line for the DAC just adds more circuitry and more cable. It is like putting extra filters on your lens, you don't always need to stack your filters. If you want your headphones 200 meters away, that's a different story. My house is less than 200 meters.

    You can take Gotham cable, or Belden AES cable, or Canare, and make your own cable. That's what the pros use, cost less than a dollar a foot. Play back the recording on the cables they were recorded on.

    Now in the field, you might want those XLR connectors just for a little extra security. If you wiggle an XLR, you will see that it wiggles. A well constructed phone plug will not wiggle. A locking XLR, that twists to lock, is what they use in well designed theatres, but you won't find twist locking XLRs on pro gear because they don't make money on it.

    If you want hum rejection, you want the Gotham Quad, it has extra shielding that AFAIK has no competition. Couple that with a preamp designed for noise rejection, which is basically the Benchmark Media preamp design, you can operate it next to a radio tower.

    If you just want to read one short book, this is the one I recommend and it is free http://www.benchmarkmedia.com/sites/default/files/documents/caig.pdf

    Notice he recommends Belden Data Cable for analog interconnects because of the measured capacitance. There are some superb cables available for cheap.

  • Vitaliy_KiselevVitaliy_Kiselev

    @DrDave

    Btw, we have small topic in Gear about chinese DACs/ headphone amps. One considered best by audio guys are based on ESS Sabre. I have amp and also headphone amp/dac and they are good.

  • ppcroftppcroft

    @DrDave

    Thanks. Let me read and comeback.

  • DrDaveDrDave

    Interesting about ESS Sabre, they are right down the highway in sunny Fremont. I will check them out. I think some of those chips are used in Oppo designs, the old Oppo's had good audio. I have tested the $55 Weliang design, and it sounds the same as my high end ones, but DAC's all sound pretty similar anyway. I noticed on the ESS website that they mentioned that their listeners could hear the difference in their technology, and I'm not saying they are mistaken, but I would have be willing to bet more than the price of a converter that in a blind test people could not tell pick out tiny differences in DACs. I didn't see anything about ASIO on their site. Would love to test a unit, maybe put some unlabeled samples online.

  • Vitaliy_KiselevVitaliy_Kiselev

    On ebay you can find not very costly versions on Sabre (more constly ones use 8 channel chip with 4 DACs used per one stereo channels, as I remember)

  • DrDaveDrDave

    Thanks Vitaliy--I will see if I can buy a board all put together and put it in the box I already have. The company that made my DAC makes an ESS version--it is pretty cheap, but still three times the price of the other one. http://www.ebay.com/itm/ESS-24BIT-192K-ES9023-DAC-decoder-Optical-Coaxial-input-TE7022-USB-Weiliang-/130927952097?ssPageName=STRK:MESE:IT

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