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Want to convert an SWR SM400 to have a headphone jack - any ideas?

Jim C

Jim C

I believe in the trilogy; Fender, Stingray, + G&L
Supporting Member
Nov 29, 2008
15,870
14,111
Bethesda, MD
#1
I know that SWR offered a headphone out on an SWR SM400; not sure if it was an after sale mod or wether it was offered on later production models (maybe 400S series?)
Would like to add this to my standard SM400; any ideas or schematics floating about?
Still waiting for SWR to return an email from 2 months ago about another question so don't think that's the way to go.
 
#2
Hi.

I don't have a schematic for such a mod, but I'd tap between the pre and the power amp PCB.

Possibly the FX loop send or the pre-amp out could be used for a place to take the signal for a small headphone amp as well? I've heard about mods like that, but I have never done so myself.

Regards
Sam
 
#3
Well maybe not really the answer- and you may have thought of this- but what about running the DI on back of your SM400 to a small mixer? Plug in yer cans, badda-bing? If you just need it at home, that might be a straight-ahead solution...

Right, not the answer!

And I have never received a reply from SWR about anything. What a joke... sorry about it.
 
#4
The thing is, I saw this mod somewhere on this board but can't find it now.
Want to say that Randy Jackson had it done to his amp first.
Imagine how simple it would be to be able to plug headphones into the front of a clean amp and potentialy get clean, clear, head phone volume with EQ, compression, and aural enhancement without having any more gear.
 
#5
Jim C said:
The thing is, I saw this mod somewhere on this board but can't find it now.
Want to say that Randy Jackson had it done to his amp first.
Imagine how simple it would be to be able to plug headphones into the front of a clean amp and potentialy get clean, clear, head phone volume with EQ, compression, and aural enhancement without having any more gear.
Click to expand...

That's cool, yes. Have you checked out the Bryan Beller site? He'll answer you back (SWR won't), and he might well be the guy to know about that.
 
#8
Bryan Beller is a fantastic guy; got this response back in a couple hours:

Jim-

Hey, thanks for writing...I know of which you speak, but this is kind of ancient history at this point. These mods haven't been performed at the factory for over 10 years, and all of the personnel who did them are pretty much gone. I can almost guarantee you that even the head guy at Fender/SWR service doesn't know about it, so don't worry about trying to get answers there. It was never captured on any schematic that I know of, and I saw them all, and I was the one who transferred the tribal knowledge over to them about stuff like this. Not like it's that complicated, probably - but I'm not a bench tech and I just have no idea. It's esoteric stuff even by "SWR expert" standards is what I'm saying.
 
#9
Hi.

This has been buggin' me quite a bit and so I took the ST220 out of the mothballs.

This all is with the assumption that the ST220 and SM400 share the same design. I sold my SM400 about 15 years ago so I'll be damned if I remember how it looked inside ;).

The FX out will drive the headphones but without tone controls.

The pre out works well and that will be the feed You want.


Three options:

#1 Use the pre-out and live with the "one ear only" signal.

#2 Drill a hole and install a stereo jack with T&S jumpered and take a signal from the Pre-out jack lug.

#3 Convert either of the parallel speaker jacks into a headphone out as in #2.

Regards
Sam
 
#10
OR just make a Headphone adapter box. You'll need a plastic box,from Radio Shack maybe. A stereo phone socket to suit your phones, a mono phone socket and two 1KΩ 5W resistors. Mount the two sockets into the box. Connect the sleeve tabs together. Connect one resistor to each of the stereo sockets tip and ring tabs. Connect both of the other ends to the tip of the mono socket.

Connecting a speaker cable to the mono socket and your amps output and the headphones into the stereo socket will enable you to listen to your amp at a much reduced volume.

Paul
 
#11
Thanks Paul
About 100 years ago I built something similar for use with an old Dynaco 70 from an article from either Stereophile or VanAlstein
Remembered that it was simple and seemed to remember that it just had resistors but thought that was much too simple and that my memory was going south

This sounds like a great project for the weekend!
 

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