JBL LSR305 - God, These Are Amazing!

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  1. watchnerd
     
    What modifications did you make?
     
  2. germanium
     
    Change input apacitors to 4.0uf metalized film. They were 22uf electrolytic.
    Changed coupling capacitor between input opamp & ADC to 4.7uf electrolytic to 4.7uf metalized film.
    Changed input opamps negative feedback bleed capacitor that controls the gain of the amp from 100uf electolytic to 12 uf metalized film.
     
    The smaller size of the input opamps input coupling & negetive feedback bleed caps than stock are of no consequence as the smaller caps are still more than big enough to support the full frequency response that these speakers are capable of due to the high impedance of these circuits. The coupling capacitor going to the ADC is more important to keep the original size due to the impedance characteristice of the ADC input in order to maintain correct frequency response. Metalized films provide a much better coupling than electrolytics do. They however are much larger physically so they have be placed outside the little sealed box where the input circuitry is, I had to drill a few small holes in this box & run wires to the outside of this box in order to place capacitor outside of box & i sealed the resultant holes with hot glue as well as used hot glue to  attach the capacitrs to the outside of the box.
     
  3. watchnerd
     
    Pics?
     
  4. germanium

    This week end.
     
  5. germanium
    Took some pictures but decided to take things a little further as I felt that the treble was a little too soft even though it was very detailed so I changed the other input coupling capacitor that wasn't being used as it was on the negative input which is not used when you are using an unbalanced but is instead shorted to ground by the RCA to Tip/sleeve phono plug. While it is not being used as an input in this configuration it is providing a route to ground for the negative feedback to ground & as such controls the gain of the other half of the inpur opamp. Both halves of this opamp are used. When I changed this cap to metalised film the sound got brighter, bass is still very good but not quite as strong as before so I feel I do need to increase the capacitance for each of the input caps so I will be posting pics when everything is actually complete & sounds to my satisfaction. It is very close to that point now. Everything is clearer than stock & still has some nice warmth when called on but would like just a little more without sacrificing the excellent detail or making the treble to soft as it was in a previous mod stage.
     
  6. watchnerd
     
    If you're looking for tonal adjustments, wouldn't it just be easier to use EQ?
     
    You know this thing has a DSP chip in it, right?
     
  7. germanium
    Not really looking for tone adjustments, looking for better resolution. latest mods returns the tone to be identical to stock but with better resolution. I have 2 sets so I can compare them, one set modified one not ​modified. They were really impressive stock but even more so now.
     
    Yes I know it has a DSP chip on it but I have no access to it's programing.  Reprograming the DP won't do what I want anyway.
     
  8. trend
    For best results it may be even nicer to bypass the DA and AD convertion, input caps etc and get a I2S signal directly into the STA350BW no ?
    I saw a few SPDIF to I2S converters, they are cheap, i wonder if this would be very difficult to achieve...
     
  9. MMeirolas
    Hello guys

    This noob is trying to put his first audiophile setup together.

    Would these speakers be a good start into the audiophile world pairing it with something like the Onkyo A9010 amp and a vinyl table like the Rega RP1?

    Thanx and sorry for hijacking the thread :thumbsup:
     
  10. watchnerd
     
    You don't need an amp -- the speakers are active, meaning they have amps built-in.
     
    You need a phono stage and a preamp.
     
  11. SilverEars
    Since these are near-field, what is the optimum triangle(speaker distance widths and distance to the listener) dimension?
     
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