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Thread: Bgw amp plus eq for free!

  1. #601
    Senior Member DerekTheGreat's Avatar
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    Didn't know Petty had UREI's. Pretty cool to see them at random like that. I think John Mayer has 813C's, can't confirm that though.

  2. #602
    Senior Member RMC's Avatar
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    From time to time Riley refers to BSS on the forum. Here's an oldie pic from 1984, on the second half of the page attached, with their original name, years before Harman's purchase. Many audiophiles don't know about this. Didn't sound like audio gear...

    They appear to have entered the US and Canada markets back in 1984.

    The good old days.

    Richard
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    Last edited by RMC; 11-11-2023 at 12:53 PM. Reason: missing phrase
    POWERED BY: QSC, Ashly, Tascam, Rolls Mosfet, NAD, and Crest Audio

  3. #603
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    Lightbulb

    Iím my space thatís common knowledge.

    DDA who l think were acquired by Klark Teknik had a similar analogue crossover using Bessel filters.

    https://reverb.com/item/36927507-dda...crossover-unit

    Pink Floyd for the first to evaluate the OmiDrive.

    The story of Fairlight CMI is far more interesting
    https://en.m.wikipedia.org/wiki/Fairlight_CMI

    https://en.m.wikipedia.org/wiki/Fairlight_(company)

    https://en.m.wikipedia.org/wiki/Kim_Ryrie
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  4. #604
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    The BSS crossovers were game changers at the time. They were the first widely available crossovers to use the 4th order LR filters The crossovers widely available prior were the Ashlys using 2nd order filters or the Crown VFX with 3rd order. The 320s and 340s were a second generation product. The original crossovers from BSS were a card frame design introduce in 1979-80. http://www.gbaudio.co.uk/data/mcs200.htm

    Life got better for live audio people as the BSS units became the standard of the industry.


    Quote Originally Posted by RMC View Post
    From time to time Riley refers to BSS on the forum. Here's an oldie pic from 1984, on the second half of the page attached, with their original name, years before Harman's purchase. Many audiophiles don't know about this. Didn't sound like audio gear...

    The good old days.

    Richard

  5. #605
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    I think that claim belongs to where you lived in the world at the time.

    Rane were also popular as was the Jands (Aust) crossover used for the Clair Bris S4ís touring systems. JBL released the 5234/5235. The Urie active crossover with the digital readout was also widely used.

    But the industry standard of such equipment is not necessarily an indicator of good design. Moreover is was a matter of manufacturing to a cost using parts that were available at the time. This is the basis of this post.

    In the beginning-
    Unfortunately the numerous mass market pro analogue active crossovers using the antique TL072 Opamps werenít technically great. The TL072 has poor common mode distortion and sub par noise of Vn = 18 nV/√Hz (typ) at f = 1 kHz. A Vn of 2.9 is common in modern opamps. Referring to the data sheet below thatís 18db less voltage noise than the TL072. Subjectivity this source of distortion is heard as electronic glare. Noise in its many forms masks transparency.

    https://www.ti.com/lit/ds/symlink/op...=1699745104243

    The TL072 was the only Jfet input Opamp in that era with a low input offset. This kept pot noise out of the signal and manufacturing cost down. In an audio experience people accustom themselves with what they hear right up until they hear something better. To those that donít care we let them live in their ignorance because nobody knows cares and nobody knows what they are listening too.

    The arrival of the NE5542 Opamp
    It wasnít until sometime later that the NE5532 Opamp became available. But it was too expensive then for use in mainstream applications. The NE5532 found use in large quantities in parallel signal stages of analogue consoles requiring low impedances for optimal noise performance. This produced a lot of heat and the power supplies were massive.

    Myths about coupling capacitors
    The signal coupling capacitors used in these older consoles are continuously being replaced (ref Abby Road Studios). Douglas Self has identified various distortion mechanisms in audio capacitor applications. Selfís research proves audio designers mistakenly use too small a value of electrolyte coupling capacitors in signal path applications. The rising impedance of the capacitor in the passbsnd produces a significant increase in distortion. Mylar or polyester capacitors should be used with care in audio circuits.

    Bands set their own audio standards
    In real world applications during the above era some bands used their own sound systems flown in via air cargo with custom audio electronics designed by their own technical staff. One notable was John Curl who is a legend in the audio design community. John Curl once worked his magic on the Dead and on Jefferson Airplane. So it could be said bands had their own standard.

    The return of discrete audio circuits
    Nelson Pass recently designed & built a discrete J fet based analogue crossover to replace the Mini DSP Linkwitz crossover. See the Linkwitz website . It was unanimously agreed by Linkwitz and Pass that it was subjectively superior to the Minidsp and other analogue active crossovers.

    https://www.firstwatt.com/pdf/art_lx...0crossover.pdf

    https://www.linkwitzlab.com/products_LX521.htm

    https://www.firstwatt.com/pdf/art_lx...0crossover.pdf

    https://www.linkwitzlab.com/products_LX521.htm

    https://www.firstwatt.com/pdf/art_lx...0crossover.pdf

    https://www.linkwitzlab.com/products_LX521.htm


    Analogue signal paths are still used today
    Unfortunately through lack of awareness and populist opinions by many audiophiles and some professionals believe the monolithic Opamp is the accepted standard in audio components. Itís no wonder that studio engineers froth at the mouth when using Neve, SSL and ADI consoles. These high performance consoles use dozens of discrete class A analogue circuits who heritage dates back to the 1970-1980 vinyl era.



    (1) Ref Douglas Self former head of engineering at Soundcraft.

  6. #606
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  7. #607
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    Yes there are particularly as the join new member function is broken.

  8. #608
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    I should have worded the opening a bit differently.

    A good design might technically be good while an industry standard is generally what is widely adopted. But is an industry standard a high performance product and compared to what?

    At the time the limiting factor was the performance of the monolithic opamps used to make it a cost effective design to manufacture.

    In comparison to an ADI or SSL $150,000 mixing console it wasnít a high performance piece of pro audio equipment but it was fit for the purpose. That being a frequency dividing network in a PA stack.

    The former has discrete class A biased opamps with 100 x the driving current in class A or more compared to a monolithic opamp which is biased in class B. That at the time was the subject of a lot of scrutiny and scepticism in the recording and motion picture sound industry.

    The discrete approach was significant improvement in the performance of the numerous audio circuits used throughout a mixing console. Dean Jensen was a pioneer of discrete opamps. Tragically like James B Lansing Dean Jensen took his own life. Like Lansing Jensenís work had a profound influence in the motion picture and recording industry. Interestingly Dave Wilson another American with singularly impressive talent presented the Wilson Watt recording monitor to the motion picture industry. Within a short time the Wilson Watt became an industry reference. Today Wilson are a leading manufacturer of hifi loudspeakers.

    It was only much much later that monolithic op amp manufacturers started to design and manufacture opamps better suited for audio electronics. Inherent limitations remain that dependant on the manufacturing process. Heat dissipation and the inability to incorporate capacitors of sufficient values to incorporate two pole feedback circuits for a true high performance Opamp. This places real limits on the reduction of distortion by feedback at high frequencies in the audio band. Manufactures resort to other means to minimise distortion but itís like a cat chasing its tail as the problems pop up everywhere.

  9. #609
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    Quote Originally Posted by RMC View Post
    Eargle's quite simple explanation of the relation between efficiency, F3, cab volume, and distortion...

    Richard
    Now that post resonated with me. It reminded of a spy movie in which secret information was being trade by spies by using a Bible with the middle of it cut out with a boning knife. Youíre basically cutting out bits of information belonging to what was a whole document that is more than likely protected by Copyright.

    Why would you do that?

    See the post and with attachment by you below
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