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SWR Aural Enhancer Bypass

#82
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.
 
#83
alexclaber said:
With my old SWR GP the closest to flat response was with the aural enhancer off and everything flat apart from the lower mid semi-parametric EQ which had an 8dB boost at 250Hz. I also found the the aural enhancer did was just a simple boost for the first third of its rotation, after which it added yet more cut at 250Hz. If the SM400 is similar I'd try that first.
Click to expand...

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.
 
#84
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!
 
#85
duff2 said:
Here's how it's done folks (well everything except the push/pull addition that is).

swrmod.jpg


In text format:
1. remove the 0.1 uF capacitor
2. Use it to replace the 0.001 uF capacitor

This most awesome modification will apparently flatten the preamp voicing and leave the added gain available by turning up the aural enhancer knob intact.

Thanks to kringle77 and Walter Harley (of Cafe Walter headphone amp fame) for all their help in this matter.

I am planning on taking my amp to a tech later this week. I'll let you know how the mod turns out. :bassist:

Cheers,
Duff2
Click to expand...

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!
 
#86
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.

Cheers,
Duff2
 
#88
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!
 
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#90
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?
 
#92
12bass said:
Missed this thread until now.... always cool to read about hardware mods.

When set flat, the Eden WT preamp is flatter than the (stock) SWR curves shown here. However, there's a considerable roll-off of high frequencies above 12 kHz, which might explain why you're wishing for more upper harmonics. I've modded mine so that it goes all the way up to 20 kHz, and it sounds considerably more open now.
Click to expand...

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
 
#93
#95
Lucas G said:
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.
Click to expand...

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)
 
#96
alltube said:
Subscribed...

You guys have no idea how well timed this post is... I was about to sell my IOD next week on the bay because i did not like the direct sound... although i liked the OD tube side....


So... I ran into this post which made me open up the IOD and see if its similar to the same circuit... low and behold it is and I did the mod.... less than 1hr...

Now the pre is a keeper....

Thanks guys..


now about those orange drops... where exactly and which could be changed?
Click to expand...


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?
 
#97
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



Herwig
 
#98
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..
anyone?
 

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