Author Topic: DS-2 Powersupply mono (Read 476 times)

count · « **on:** June 10, 2013, 01:24:43 PM »

Just got my hands on a five pin cable. (FINALLY!)
But it was a little bummed to find out that my DS-2 doesn't switch to mono if I only plug in a jack to the bass output of the box.
Any suggestions how to rewire it to be mono-capable.?

count · « **Reply #1 on:** June 16, 2013, 02:29:10 PM »

Anyone..?

JimmyJ · « **Reply #2 on:** June 16, 2013, 03:47:45 PM »

Nicolai,

I've never heard of a DS-2, do you mean DS-5 ? (Not sure what DS stands for but I presume the 5 refers to the 5-pin connector, otherwise we would be on about DS-8 by now...)

Anyway, the 1/4 output marked bass and mono on the standard DS-5 was a normal jack. But the one marked treble incorporated a switch which would be thrown when a plug was inserted. I believe this was the 13e variation (though I can't remember for certain):
http://www.switchcraft.com/Drawings/13e_cd.pdf

So if you only plugged into the mono jack the two signals coming from pins 2 & 3 of the 5-pin connector would be summed to that jack by way of two 20k-ohm resistors. But when you plugged into the Treble jack the switch (somehow) broke that summing circuit and connected pin-2 to bass and pin-3 to treble for stereo outputs.

I can't remember the circuit exactly but if your PSU has no summing resistors I would suggest a mono switch would be the easiest mod to make. If you ONLY wanted mono you could even hardwire the resistors straight from pins 3&4 directly to the tip of the 1/4 jack.

Maybe you could open it up and post a pic for us? (Don't touch anything inside - those caps might be charged!) That would give us a better idea of what's going on.

Jimmy J

room037 · « **Reply #3 on:** June 16, 2013, 09:42:10 PM »

Hello,
Nicolai has very old series bass (SN is around 40) preowned Tilan Porter .
DS-2 comes with it that I think.

The pictures of inside is best way.

Eiji

growlypants · « **Reply #4 on:** June 17, 2013, 06:43:08 AM »

You mean Tiran Porter, of Doobie Bros fame?

room037 · « **Reply #5 on:** June 17, 2013, 07:11:01 AM »

Yes,
TIRAN PORTER !

Sorry for my mistake.

Eiji

count · « **Reply #6 on:** June 27, 2013, 10:59:53 AM »

I made a Y-summing cable today, with two 18Kohm resistors. One end has a mono plug, with the two signal cable soldered to the tip, and the ground to the sleeve.
The other two (separate ends) each hace a 18Kohm resistor soldered in series on the tip, and the (common) ground is soldered to the sleeve.

When I have both jacks connected I can only hear the treble/bridge pickup, but as I disconnect the jacks respectively I can hear the opposite pickup.

WTF..........??

(Message edited by count on June 27, 2013)

JimmyJ · « **Reply #7 on:** June 27, 2013, 04:27:40 PM »

Nikolai,

The description of your Y cable sounds exactly correct and it should work - provided your DS-2 is actually operating in stereo. Can you confirm that the bridge pickup signal comes out of the B output jack and the neck pickup comes out of A? And the resistor plugs of your Y-cable should be plugged into those two jacks (A & B) while the mono sum (no resistors) is plugged into an amp input? And the bass is only connected to the power supply by the 5-pin cable - nothing in the 1/4 jack, right?

Once again I'll ask if you could possibly post a picture of the inside of your power supply so we can see how the 1/4 jacks are wired? That would help us solve this puzzle.

Because of the long history of your bass you never know what may have been modified along the way. But figuring this out will be worth the effort!

Jimmy J

count · « **Reply #8 on:** June 28, 2013, 05:24:42 AM »

Here are some pic of the DS-2. Serial number 10 btw.

JimmyJ · « **Reply #9 on:** June 28, 2013, 10:34:18 AM »

Wow, thanks for the pics. That's a historic piece of gear! And indeed, no mono option whatsoever, love it!

But you know, thinking back ... a Fender Bassman (and an Alembic F2-B) had two input jacks per channel, right? There was already a resistor summing network built in, I believe. So the original concept would have been to plug the bass output into the amp's A-channel and the treble output into the B-channel giving you individual gain and tone controls for each pickup. But if you preferred you could simply plug the two short cables in to the two A-channel input jacks and they would have been summed internally.

Now back to Nikolai's puzzle. The next thing we need to know is, with your bass connected using the 5-pin cable does the neck pickup signal appear at the bass output jack and the bridge pickup at the treble jack?

A purest might say oh no you can't modify that piece, it's a collector's item. But I say function over ... history and I would add a mono switch and an LED. Kinda like below: (Please don't be put off by my horrible graphic!)

The less intrusive mod would be to replace the treble jack with the switching version mentioned above and wire it like the later DS-5. No front panel changes that way.

But first, let us know if the pickup outputs are coming out of the correct jacks.

Jimmy J

dfung60 · « **Reply #10 on:** June 28, 2013, 03:11:24 PM »

This is an interesting problem.

The wiring in the box looks unusual. It should work with blend cable, but generally won't work well. The treble output only has the hot wire connected from the 5-pin, and no ground, so if you plugged the Bass and Treble outputs into separate amps, there wouldn't be any output on the Treble channel. With your custom cable, since you tied both grounds together, it should work.

The problem you're experiencing sounds like the resistor value is too small (it's similar to the problem you'd see if you didn't use the resistors). They should be brown-gray-orange and some other band (the fourth band doesn't matter in this case). Just about anything with an orange band in the third position should be OK.

David Fung

xlrogue6 · « **Reply #11 on:** June 28, 2013, 03:14:25 PM »

The only problem with using both channels simultaneously on blackface and silverface Fender amps (most of them, anyway) is that the channels are out of phase with each other--not a huge problem, but there will be a sour spot (to coin a phrase) where you'll get phase cancellation when both channels are set for near identical output. If that's an issue, the both jacks of a single channel approach would be the mono option to use.

JimmyJ · « **Reply #12 on:** June 28, 2013, 03:58:21 PM »

I didn't know about the phase issue on Fender amps, that would not be ideal...

David, it appears there never was anything soldered to the treble jack's sleeve lug so it must be relying on the front panel to provide chassis ground to that output. That should work unless there is corrosion where the jacks are mounted, but it all looks clean and dry - like new actually! You're right, it could be the value of summing resistors causing his odd Y-cable results...

Jimmy J

keith_h · « **Reply #13 on:** June 28, 2013, 04:13:28 PM »

As Jimmy says the 1/4 runs signal ground through the chassis and not the lugs. It is the same on my DS-5.

Keith

count · « **Reply #14 on:** June 29, 2013, 03:49:45 PM »

Seems I'm gonna have to double check the resistors I put in then.. Pretty sure they were 18K, but they might be just 18. That would explain it then!

Regarding modifying it:
Completely out of the question.

At least drilling holes etc. I could but in a new switchcraft jack, but when I get my second GK 800rb up and running again I'll only be using it for stereo setup.
The y-cable will do the job until then though.