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Graphic equalizer

Discussion in 'Audio' started by capt ken, Nov 18, 2020.

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  1. capt ken

    capt ken

    4
    0
    Nov 18, 2020
    On my old receiver I had a tape monitor circuit that the EQ used. My current receiver does not. Is it possible to wire the EQ into the receiver? Expert on "just answer" said it needs to be done between the pre amp and power amp. He also mention the volume circuit. This is the best schematic that I can find.

    https://riverparkinc.com/wp-content/uploads/import/2014/11/strdh130-service-manual.pdf

    Can anybody help? On an old tube system I could handle it, this integrated stuff is mind blowing. I can trace wires, solder etc. Thanks
     
  2. Audioguru

    Audioguru

    3,305
    703
    Sep 24, 2016
    Why do you need EQ? Is it because you have cheap garbage speakers?
    I designed and built and modified purchased speaker systems to sound good.
    The only EQ I use is a bass boost circuit for my smaller speakers.
     
  3. capt ken

    capt ken

    4
    0
    Nov 18, 2020
    Initially it was a Pioneer receiver with Bose 301s. Couldn't get the sound I wanted so I added the EQ. Pioneer died replaced with the Sony. Moving, sold the Bose, not sure what will replace. I like good sound, speakers are not low end. The EQ works fine, but is almost 40 years old. Rather try to incorporate than trash.
     
  4. bertus

    bertus Moderator

    1,864
    707
    Nov 8, 2019
    Hello,

    Looking at the schematics IC400 is the selector and IC700 is the power amplifier.
    The volume control is done inside IC400.
    You could likely put the EQ in between:
    sony_strdh130-EQ_insert.png

    I have marked the output of the selector, the channels and the input of the power amplifier.
    Put some capacitors on the outputs of the selector, go to the EQ and connect the output of the EQ to the power amplifier input.
    Also connect the grounds.
    I would use shielded cables to go to and from the EQ.

    Bertus
     
  5. shrtrnd

    shrtrnd

    3,821
    519
    Jan 15, 2010
    Sheez, sounds like your equipment is/was as old as mine.
    It was a mistake to trash that Pioneer instead of fixing it. The Sony stuff is made in China now, … not worth the money.
    Anyway, my Pioneer has RCA jacks on the back to integrate my graphic equalizer and a reverberation amplifier I like.
    Apparently, your new Sony doesn't have that capability?
    If you're as old as me, and actually remember what music sounded like before the college boys digitized it for everybody
    (losing all the harmonics we used to hear), good luck trying to get any new sound system to recreate what we used to hear.
    Play with what you've got to get something going. But if you've got the money check into MacIntosh Labs, they're
    the closest to getting the sound you want in today's market.
    I'll keep my Pioneer going until I die, and won't regret it.
     
  6. capt ken

    capt ken

    4
    0
    Nov 18, 2020
    Thank you Bertus. Just to be sure I understand. I cut the JW492 & 3 bridges. Add a capacitor to each selector output which is then connected to the EQ input. How big a capacitor? Wire output of EQ to Power amp input. Does it matter where I connect the grounds. I was planning on adding 4 RCA jacks to the back panel for EQ in and out. Is that a good idea or just wire directly to the EQ.
     
  7. bertus

    bertus Moderator

    1,864
    707
    Nov 8, 2019
    Hello,

    I would take the same values as C701 and C751, wich are 10 μF / 50 Volts.

    Bertus
     
  8. capt ken

    capt ken

    4
    0
    Nov 18, 2020
    Thank you. Still unsure about where to run the ground wires. I don't see anything on the board that indicates ground.
     
  9. bertus

    bertus Moderator

    1,864
    707
    Nov 8, 2019
    Hello,

    In the PCB drawing JW494 is ground.
    It is also connected to pin7 of IC700.

    Bertus
     
  10. Harald Kapp

    Harald Kapp Moderator Moderator

    11,513
    2,651
    Nov 17, 2011
    Don't forget to use shielded cabling to minimize the risk of introducing additional noise to the audio path.
     
  11. Martaine2005

    Martaine2005

    3,489
    944
    May 12, 2015
    I don’t see any reason why you can’t install 4 RCAs on the back panel. But also make two Short RCA/phono leads for bridging in case the EQ should fail in the future.

    Martin
     
    shrtrnd and Harald Kapp like this.
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