Author Topic: 1/4" Mono Jack in the bass (Read 417 times)

jwkelley · « **on:** February 25, 2012, 09:39:58 AM »

I know this may be sacrilege to suggest, but for me it would be very useful to have the ability to use a regular mono guitar cord, and power the preamp with the onboard batteries. I tend to like to just plug and play, and it would be nice not to always have to set up the power supply. Perhaps I'm in the minority here, but I don't use a stereo rig. In 40+ years of playing bass (much of that time with an Alembic), and I say this with all due respect, I've never needed or wanted to be able to amplify each pickup individually or separately outside the bass.

I've had a look at the 1/4 jack in my Series II and it's quite a 'Rube Goldberg', so here's my question: has anyone worked out a straightforward mod for rewiring that jack with a couple 10K or 20K resistors so that it can be used with a mono cable?

Thanks very much. This forum is a tremendous resource.

pacificshine · « **Reply #1 on:** February 25, 2012, 10:36:11 AM »

I probably wouldn?t modify the output jack on instrument. Instead, I would install the summing resistors inside the guitar cord. It will achieve the same result and preserve the original guitar or bass. It is also much easier to perform. I made a stereo to mono cord for my Series II bass a couple of years ago in an attempt to accomplish what you?re looking for and it works fine when I don?t use the rack mounted power supply.

The following text from the FAQ section shows how to do this.

Note: Series I/II instruments were supplied with prewired stereo jacks until about 1988. This is only useful if your Series I/II 1/4 is prewired in stereo.

Instrument end: Tip Ring and Sleeve plug
Preamp end: Tip Sleeve plug

Preamp end: The tip of the preamp end goes to the signal wire of the shielded cable.

Instrument end: uses 2 resistors of approximately 20KOhms (10K or 22K are OK). Connect a 20K resistor to the tip terminal. Connect another 20K resitstor to the ring terminal. Take the free ends of the resistors, connect them together then connect them to the signal wire of the shielded cable.

You can now hear both pickups without using the power supply.

Bradley Young · « **Reply #2 on:** February 25, 2012, 06:19:43 PM »

The later Series 2 instruments (maybe after 2005 or so) typically have a stereo/mono switch onboard.

dfung60 · « **Reply #3 on:** February 25, 2012, 11:58:29 PM »

The 1/4 jack on a Series bass is by far the most complicated output jack on any musical instrument! The reason it's so complicated is that, in addition to two pickup outputs and a ground, there's a separate switch that turns on the onboard batteries when you insert a plug.

You can see the 1/4 jack wiring in this sheet from Alembic:

http://www.alembic.com/support/PF6_quarter-inch-wiring.pdf

In theory, this is an easy mod. You take the wires off of pin 4 and pin 8 of your current jack. You add 20K resistors inline on those two wires, then connect them both up to pin 4.

In practice, this is a little tricky because adding inline resistors isn't trivial. You need to make a solid solder connection between the wire and the resistor lead, and you'll need to insulate this perfectly. Alembic did this with clear teflon insulating tube, or you could use regular heat shrink tubing. But the connection has to be really perfect because your output is depending on this. Getting the two wires on that small target may be a test of your soldering skill as well (the insulators needs to run right up to the jack lug and the conductor has to be properly trimmed). If you're really ambitious, you can cut a little piece of pc board and build the resistors there so you can more easily make a solid connection.

Once you've made the mono conversion, if you decide to break with tradition and go stereo, you can still do that on the 5-pin connector, which is unchanged in this mod.

One other consideration, which you may have seen in the forum before. When Alembic designed the EQ circuit, they optimized for sound with no consideration of battery life, since the external power was an integral part of the design. When I run with internal batteries (I did this mod so I could easily use wireless), I don't think I see even 40 hours of battery life before the output goes farty. The energy sipping circuit in an EMG system is more like 1000 hours life, or change it once a year if you're a weekend warrior. So going the battery route does take a toll on your sound.

Good luck,

David Fung

jwkelley · « **Reply #4 on:** February 26, 2012, 08:20:33 AM »

Hello David -

Thanks very much for your thoughtful, and very helpful reply. Yes, I had a hunch that the primary advantage of the external power supply might be finite battery life. How would you imagine one might arrange a configuration in which rechargeable batteries could be charged using the power supply? With regards and thanks,
Jim

dfung60 · « **Reply #5 on:** February 26, 2012, 07:13:04 PM »

Jim -

The Series electronics are really totally optimized for bandwidth and sound with no regard to battery life. The other basses from Alembic are no slouches in the sound quality department, but have much more typical battery life.

It's hard to find good quality batteries that can take the heavy current drain. Alkalines are good in this respect but the common rechargeables - NiMH and NiCad aren't a good match. The lithium polymer batteries that are common in cameras, laptops, and Tesla Roadsters are a better match, but at much greater cost. Lithium batteries are not only expensive, but require a smart charger to charge properly which often involves running the chemical reaction just a step short of lighting the batteries on fire. Laptop batteries have built-in temperature sensors and a microprocessor to control charging which is why they cost $100+.

With any rechargeable, there's another problem - you need to have a charger and you need to have time to charge the batteries as well. Hard to charge your bass up while driving to the gig.

I think it would be easiest to charge a battery pack externally, maybe have some spares around too.

David Fung

terryc · « **Reply #6 on:** February 28, 2012, 05:58:09 AM »

This is interesting and this is my two cents worth.
I don't own a SI or II but a MK Signature which I had SIMS LED's retro fitted.
Now the same 9V battery that powers the pre amp and filters also powers the LED's. Obviously the more modern LED's use less current with the same light output than those of 10-20 years ago. I use a wireless sytem because I was sick of tripping over wires( I like to move around on stage)
I ain't bothered about stereo either like you Jim so I bought 4 expensive NiMH rechargeables and looking at USA prices they are a lot cheaper than the UK. Two are for the bass( one installed, one spare) and the other two for my transmitter)
They don't last as long as alkalines, especially with the LED's but I don't mind changing them out after a couple of gigs.
So the rule is, have four of the highest quality rechargables(280mA) with a good charger.
Good luck Jim

jwkelley · « **Reply #7 on:** March 19, 2012, 09:21:14 AM »

The op amps in the Series II preamp are socketed. Is there a more modern replacement that might have suitable characteristics and lower current draw?

Thank you.

terryc · « **Reply #8 on:** March 19, 2012, 12:38:47 PM »

jwkelley..the op amps in the SI/II electronics are matched to Ron W's specific pre amp design so there may be no alternative although I did read somewhere on here a long time ago about a low current chip for Signature electronics..I guess someone will chime in and put me right on both items in this post

olieoliver · « **Reply #9 on:** April 18, 2012, 07:48:48 PM »

Hi Jim, BEAUTIFUL bass bro and I LOVE those Knobs! OF course I may be a tad bit partial. Not sure if you ever got the cable situation straightened out or not but I had a 1/4 cable made by Bayou Cables for me a few years back and it worked good but I never thought the bass had the punch it did using the DS-5.

OO
PS. Me being a huge Cowboy fan (especially in the 90's) find it ironic one of my favorite bass to ever play ending up in the hands of Jim Kelley.

jwkelley · « **Reply #10 on:** July 06, 2012, 03:53:24 PM »

OO - Yes. It certainly does have beauty going for it. I managed to move a couple of wires and install the resistors right there at the stereo jack, as per the instructions above. So I can just use a regular cable now.

I can also report that, in the interest of prolonging battery life, the LT1012 op-amps work well in the preamp. No discernible change in sound. Battery life should increase to a more practical length of time.

I'm now chasing after the cause of nasty dead spot (region) at the 7th, 8th and 9th frets on the D string. It almost seems like a truss rod is vibrating.

I don't know if any of you have seen this before, but whenever I play an E or even an A in one of the upper octaves, the E string vibrates sympathetically. Gives a kind of cool bagpipe effect which I don't mind it as long as the song is E, but I suspect this may be related to the dead spot problem. (Let me hasten to add that I would prefer not to use a hair scrunchie on my bass thank you. :-)

Bradley Young · « **Reply #11 on:** July 06, 2012, 04:56:10 PM »

Jim,

That's totally normal, and can be fixed by muting the string. the aforementioned scrunchie is one method, but there are others:

1) the wrap the left thumb over the top method, which is supposedly bad pedagogy, but lots of people do it.

2) the floating thumb right hand technique (where the thumb of the right hand mutes the strings above the ones you're playing).

Bradley

jwkelley · « **Reply #12 on:** July 24, 2012, 12:40:59 PM »

Thanks, Bradley.

jazzyvee · « **Reply #13 on:** July 25, 2012, 12:40:28 AM »

I use both techniques you mention Bradley, however since adding Marcus Millers version of What is hip? to my band's set list, which uses the double thumbing technique, I've been trying to find a way of fingering and damping the any resonating strings lower in pitch than the one I'm playing at the time. If they aren't damped properly, a resonant sound/chord starts to grow from the sympathetically vibrating strings.

Not sure if this is good or bad but I've started fingering the notes so that the very tip of my fretting finger just touches the lower edge of the lower pitched string next to it.

In other words anything I play on the A-string for example, my fretting finger would gently touch the lower edge of the E-string, just enough to stop it ringing or picking up any inaccurate thumbing action from my right hand.

So far I'm managing to keep much of the unwanted vibrations down without losing any accuracy or momentum. If anyone has any experience on that to share I'd be grateful.

Like you jwkelly, I don't really want to start using hair scrunchies, although it works well for Victor and his brothers and seems to be part of their stage act.

Jazzyvee