SWR Aural Enhancer Bypass

Discussion in 'Amps and Cabs [BG]' started by duff2, Mar 29, 2010.

  1. greenbass5


    Sep 16, 2007
    Oklahoma City
    "Simplest is joining the output of the IC above the "threshold" label directly to pin 7 of the tube.
    Your volume will jump 8/10dB when you bypass that lossy network.. "

    Has anyone here done this?
  2. Lucas G

    Lucas G

    Jan 14, 2007
    masury, OH
    I am planning on doing this to my SM-900 this weekend. Are there any other known mods for this amp? I have mine wired so the fan is always on, and the guy who resurrected mine (I bought a broken one super cheap a while back) went through it and made sure everything was structurally sound, it has been a solid amp. I Haven't been able to fall completely in love with it yet, and I think flattening it out with this mod might be just the ticket.
  3. emjazz

    emjazz Supporting Member

    Feb 23, 2003
    Brooklyn, NY
    I can't thank you enough for this information. I've been feeling tortured by having to play through SWR amps at school for the last 2 1/2 semesters. I've really been struggling with getting a decent sound out of them. Today I took your advice and it worked. It was so much easier to be expressive and dynamic. I didn't have to obsess about my sound while I was playing because it just sounded good. I also was able to turn the volume down and be heard clearly. Before I had to turn up to the point where I was much too loud, but it was the only way I could get the amp to work for me. Anyway, you saved me a great deal of grief. I can't possibly imagine why SWR thinks pre eq'ing their amps this way is a good thing. It's been nothing but a headache.

    Oh, and I also got to hear another bass player play after me. I know her sound well and it was remarkably better...sounded so good.
  4. Lucas G

    Lucas G

    Jan 14, 2007
    masury, OH
    I just finished this on my 1994 SM900. Thanks to dmusic148 for doing all of the legwork and posting the pictures of where the caps are, it took me about 45 minutes. Of course, it's super late and I can't really see how it sounds, but it was a piece of cake! Can't wait to try it out.

    EDIT: Holy CRAP this is like a whole different amplifier, I am so glad I found this thread!
  5. I see that on the other forum you posted this in the directions were to swap the .22 and .1 capacitors...which version is correct? I'm getting ready to do this mod on my SWR SM-900 so I wanted to make sure I swap the right ones the first time, thanx!
  6. duff2

    duff2 Guest

    Dec 16, 2007
    Really?!? I don't remember doing that. Could you post a link to that 'other' forum so I can go there and make corrections?

    The capacitor swap illustrated in the schematic above is the way the mod should be done.

  7. fretno

    fretno Supporting Member

    May 10, 2009
    Los Angeles
    What a great read ! Much insight on a most unusual effect . I've spent a good long time shaking my head over how that knob affects the tone , I thought I was crazy hearing a cut after 2:00 . Thanks Fellas !
  8. basslinejam


    Mar 21, 2005
    New York City
    I sub'd this thread thinking I might grab a redface 350 cheap and try it with the mod. SWR amps have so many great qualities, except for me they always felt underpowered and lacking presence compared to my 800RB. It seems like this mod goes a long way toward correcting that problem. Talkbass rules!
  9. If you follow the link you posted in the beginning of this to the other thread it's a few posts down.
  10. SLIV


    Jul 16, 2009
    North Carolina, USA
    I want to do this mod so bad! I have a Studio 220 and would like to get it done with a push/pull knob that restores it to its "natural" setting.

    It seems pretty simple but I don't trust my own soldering skills. What do you suppose someone with experience would charge for a mod like this? To me its like getting a pedal out of it so I'd be willing to pay 50-80 bucks. What's reasonable?
  11. fretno

    fretno Supporting Member

    May 10, 2009
    Los Angeles
    I have my 220 racked up right now but I need to go back in because in this pic it looks like there is only a resistor behind the pot. So it seems this circuit is a little different .
  12. Zecchinus


    Apr 21, 2011
    Sorry to open this thread again,
    I just did this mod on my SM 400 and I absolutely love it!
    flat is such a better point to start with, when you've got such a versatile EQ section.
    I also changed the treble and the transparency response to better values and the amp is really fantastic now!:bassist:
    I'm still not a big fan of how the "bass" control works here, and my tests confirm that the bandwidth involved is too wide.
    anyone out there has tried anyting with it?
    I would also be curious about how the mod on the eden i quoted here has been done..
    thank you Roberto
  13. 12bass


    Jan 2, 2003
    Victoria, Canada
  14. Zecchinus


    Apr 21, 2011
  15. Zecchinus


    Apr 21, 2011
    I don't know if it's the same on te SM900
    but on my Sm 400 I also changed the Treble cap to 0,033 instead of 0,068 this is the value on the redhead circuit and moves the curve a bit higer, I also removed the black wire from the tranparecy control accordingly to the original "push pull" wiring, the control becomes boost only and it sounds better to my ear
    (still hoping in a nice mod for the boomy bass control)

  16. i use quite a bit of the AE on my IOD to tighten up the bottom of my Ampeg SVT 412HE. i'm interested in this mod, tho. do you still use the AE on your IOD? how does it work in conjunction with the drive control?
  17. DeadPoet


    Jun 4, 2003
    I have an SM-400s head in my big rig (+SWR Goliath III 4x10) and a headlite in the small one (+Ampeg 210av).

    the headlite has this 'aural enhancer' bypass switch which so I've experimented a bit with the two cabinets. On the small cab I prefer the enhancer bypassed so I can squeeze a little more stage volume out of it but on the big cab I really prefer the sound of the scooped mids. So I decided not to mod my SM-400 and keep it in the old 1 o'clock position. At 33 am I now officially a stubborn old fart? :D

  18. Zecchinus


    Apr 21, 2011
    I'm using my modded sm400 right now on stage playing "hair" on theater and I'm enjoying the best sound I ever had.
    I'm not good yet into reading schematics, but I was wondering if changing the AE pot with a higher value pot on a regular swr would kind bypass that circuit as well..
  19. Zecchinus


    Apr 21, 2011
    No, this is is exactly the same as the SM400.. you just need to put the bigger cap close to the pot in place of the blue cap..
  20. will33


    May 22, 2006
    What do you mean "close to the pot" 'cause that looks different. Just pull the red one out and put it where the blue one is?
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