Fitting Passive Switch and Circuit to Ibanez SRMD 200

[Obrienp]

 Looking for guidance, preferably from someone who has done this mod to their SRMD200 or similar active only bass. I searched and didn’t quite find this particular topic. What I want to do: replace the stock P Bass pickup with something better (I don’t care about the J pickup), fit a DPDT switch to switch the active electronics on/off and simultaneously route the P pickup to a passive circuit consisting of a stacked vol/tone control. Yes, I know I could just replace the preamp with a better 4 control unit with a push/pull active/passive switch but I don’t want to spend that amount of cash on a cheap bass.

 

Anyway my thoughts on doing this are as follows. Please let me know if this is not the way to do it. It will help understand this if you look at the attached SRMD200 wiring diagram I found on TalkBass (it seems to be accurate). Obviously I’m going to have to drill two new holes: one for the stacked pot and one for the switch. There seems to be enough space in the control cavity to accommodate this.

 

Now for the wiring. First to change the P pickup, I’m not going to try soldering onto the blend control circuit board: it looks too fragile and I might cook it if I keep the iron on it for too long. I intend to cut the original pickup wires, shrink wrap the new pickup ground wire to the original ground wire and take a separate ground wire from this joint straight to the chassis of the stacked vol/tone pot. The live wire from the pickup will go to one of the middle terminals of an on/on DPDT switch. The other terminals on that side will route the live output to either the preamp blend pot (using the original cable), or to the new stacked vol/tone pot. 
 

Currently the negative wire from the battery is routed directly to the spare terminal of the stereo output jack. This creates an on/off switch for the power to the preamp. When a jack plug is inserted into the socket it closes the circuit, when it is removed the circuit is broken. I intend to cut this wire and route it from the battery to the other middle terminal of the DPDT. I will then run the other half of the original wire will to the appropriate terminal on the DPDT, such that when the live output from the pickup is routed to the preamp, the power circuit will be complete and the preamp active. When it is switched the other way, the circuit will be left open and the pickup live output will be routed to the vol/tone pot.

 

The Vol/tone stacked pot will be wired in the conventional way with a .047 capacitor. The live and ground wires will be taken to the output jack socket where they will be in parallel with the live and ground from the preamp.

 

I think this will work but I just wonder whether there is any issue with the pickup ground wire being split so that it is connected to both the active preamp circuit and the passive circuit simultaneously. My feeling is that the live wire will only be routed to one of the circuits, so there shouldn’t be an issue. However, is it likely to cause any background noise?

 

I would have drawn a circuit diagram for this but I don’t have an editor that will do it, or the knowledge of the correct symbols. Your thoughts and experience would be welcome. Thanks in advance.

 

P.S. Is this likely to kill the resale value of the bass?

[itu]

Switching the battery on and off while the bass is connected to an amp is likely to pop loudly.

 

Consider finding a double pot for the bass and treble (or make a tilt eq from them) and you dont have to drill more holes.

 

I soldered a push switch to my former Modulus Graphite, but put it under the back cover. If a battery was empty, the instrument cable fit the small hole to push the override switch. Then I put the cable back to the amp, and continued. No pops, just funk.

[Obrienp]

@itu Thank you for reading through all the waffle in my post and for your suggestions. 
 

Yes, you are right. Switching from active to passive is going to create quite a loud pop. I will just have to remember to engage the mute on my tuner pedal, or amp when I do it. Especially when I DI into the PA. 
 

I like your hidden switch idea. If I was just adding the passive circuit in case the battery died during a gig, I would do this but my motivation is more about getting the classic passive P bass tone.

 

Unfortunately I don’t think it would be possible to replace the treble and bass pots with stacked pots, without messing up the preamp. The OEM pots Ibanez fit have circuit boards attached and mini connector sockets. The connectors are not an insurmountable problem but I think there might actually be some processing occurring in the circuit on the boards. The pots are also a weird impedance, which wouldn’t really be compatible with a passive circuit. I’m not sure I could find stacked pots with the right combination of impedance values for both the active and passive circuits.
 

If I was going to go down the route of not drilling holes, I think I would bite the bullet and buy a replacement preamp with an active/passive switch. However, together with a better P bass pickup, that option would cost as much as the bass itself did. In my experience, you never recover anything like what you have spent on modifications when you come to sell a bass.

[BassBunny]

I tried the Active/Passive mod in the attached diagram on my SRMD205. I ended up with a load of noise and quickly removed it.

It could be that I didn't actually mount the switch it was just loose in the cavity as I didn't want to drill any holes if it didn't work. Not sure if this was the problem or not.

I've gone the new pre-amp route as I reckon the Mezzo range are pretty astounding VFM and I have two of them. I actually prefer them to my other, considerably more expensive instruments.

 

[Obrienp]

2 hours ago, BassBunny said:

I tried the Active/Passive mod in the attached diagram on my SRMD205. I ended up with a load of noise and quickly removed it.

It could be that I didn't actually mount the switch it was just loose in the cavity as I didn't want to drill any holes if it didn't work. Not sure if this was the problem or not.

I've gone the new pre-amp route as I reckon the Mezzo range are pretty astounding VFM and I have two of them. I actually prefer them to my other, considerably more expensive instruments.

 

Thank you for sharing that. That is food for thought. I can think of a few possible causes for the noise:

 

1). I wonder if the problem was not switching the preamp off. If I have understood your diagram properly, your passive mode rerouted the output from the pickups directly to the output jack but left the preamp powered up. Perhaps that generated some kind of radio interference;

2). The bass doesn’t look very well shielded because the active electronics make it pretty quiet, so it’s not necessary in stock configuration but in passive mode there would be hum from the single coil jazz pickup. Although if they are both on in passive mode you would think this would be less of a problem. I guess it depends how they are phased;

3.) in passive mode was the bridge ground interrupted? According to the OEM circuit diagram, the bridge ground goes to the volume pot and then the circuit seems to go to the main board of the preamp, which means it might stop there in passive mode because that route is interrupted, or is it? I think I would need to test that one with a multimeter;

4). I am assuming that the input from the pickups was the hot wires only, in which case where did the ground wires go? Did they get a direct run to the output jack, or did they go to the preamp, in which case could that have caused noise?

 

I guess it could be a combination of some, or all of the above. I think the lesson for me might be to shield all the cavities with copper tape and run ground wires everywhere. I am only using the P pickup in passive mode, so hopefully there won’t be any out of phase issues with the Jazz pickup. 🤞

 

I’m thinking that, when I have done with adding the switch and extra knob, the controls will look like those on the more expensive SR series basses that have three band preamps and a three position toggle switch (coil tap, active, passive). Perhaps it won’t take too much of a value hit in that case.

 

I agree with you that they are great little basses. For me the only thing missing is a passive switch. In fact I did think of just removing the preamp and converting it to all passive: vol/tone, vol/tone but I quite like having the active option.

 

BTW, which replacement preamp did you use and would you recommend it? Just in case I decide my wiring plans are  too much like hard work!

 

Edited January 12 by Obrienp

[BassBunny]

I've got a Glockenklang 2 band in one bass. It's pretty much my go to pre-amp. I had them in all my three Bass Collections before I sold them and I've a 3 band in my Marlleaux. 

I picked up a second hand Norstrand 4 knob 3 band for the other one but have yet to fit it 

[Obrienp]

Just now, BassBunny said:

I've got a Glockenklang 2 band in one bass. It's pretty much my go to pre-amp. I had them in all my three Bass Collections before I sold them and I've a 3 band in my Marlleaux. 

I picked up a second hand Norstrand 4 knob 3 band for the other one but have yet to fit it 

Thanks, that good to know.

[Obrienp]

2 hours ago, BassBunny said:

I've got a Glockenklang 2 band in one bass. It's pretty much my go to pre-amp. I had them in all my three Bass Collections before I sold them and I've a 3 band in my Marlleaux. 

I picked up a second hand Norstrand 4 knob 3 band for the other one but have yet to fit it 

Sorry. Follow up question: when you put the Glockenlang in passive mode, does one of the pots act as a passive tone control, or is it straight through to the output?

[BassBunny]

14 hours ago, Obrienp said:

Sorry. Follow up question: when you put the Glockenlang in passive mode, does one of the pots act as a passive tone control, or is it straight through to the output?

Depends which version.

The 4 pot 2-band and 5 pot 3- band both do. The treble pot becomes the passive control.

The 3 pot 2-band doesn't as it's a stacked bass/treble.

What I like about the Glock is it doesn't colour the sound when set flat. In fact if you set it flat there is no difference between active and passive.

[Obrienp]

7 minutes ago, BassBunny said:

Depends which version.

The 4 pot 2-band and 5 pot 3- band both do. The treble pot becomes the passive control.

The 3 pot 2-band doesn't as it's a stacked bass/treble.

What I like about the Glock is it doesn't colour the sound when set flat. In fact if you set it flat there is no difference between active and passive.

Thank you. That’s very helpful. I would go for the 4 pot 2 band, if I decided to go down that route. I feel like I want to try my mod, just to see if it works but I am just going to wire it up to test it, before I drill any holes in the body, like you did. If that proves to be a failure, I might well go for a Glockenlang.

 

I suppose one benefit of going for a replacement preamp and pickups is that you can remove the existing electronics without cutting any wires, which would make it easier to put it back to stock to sell it. Alternatively I could just convert it to all passive and keep the stock electronics intact for resale: that would be the low cost option. Decisions, decisions!

[tauzero]

You might not find it easy to get a stacked log and lin pot, which is what you'd need for stacked vol/tone.

[Obrienp]

3 hours ago, tauzero said:

You might not find it easy to get a stacked log and lin pot, which is what you'd need for stacked vol/tone.

Yeah. You are right. The only thing I could find was from Allparts and it must have the smallest diameter pots in the world attached. They are barely bigger than the shaft and I have no idea whether it is log or lin. All the usual culprits are sold out and anything by CTS, or Alpha in 250k doesn’t seem to have a deep enough thread to mount through the body.

 

I am beginning to think it is going to be a lot easier to go the replacement preamp route (Glockenlang I think), or make it completely passive: vol, vol, tone, tone. Passive will be cheaper but not a huge amount: 4 x decent 250k long shaft pots, 2 x caps, more cloth covered wire, decent replacement mono jack socket that fits (difficult), or use a standard mono socket and a surface mounting plate, in which case I will have to ream out the hole for the jack socket. Although I might do the reaming anyway, as I am not a great fan of the acoustic style, cylinder jack sockets that Ibanez use.

[itu]

Bourns 500k MN for blend?

 

This is a special balance pot, where the tracks start from the middle.

[Obrienp]

9 minutes ago, itu said:

Bourns 500k MN for blend?

 

This is a special balance pot, where the tracks start from the middle.

Well it is marked concentric and it doesn’t look like the Bourne balance pot I also got from Allparts several years ago and haven’t used yet.

[tauzero]

Why cloth covered wire? Also, you don't need to replace the jack socket if you go passive, just leave ring unconnected or connect it to sleeve.

[PaulThePlug]

The Bourns i used on my SR600 needed the hole opening up... bigger threaded shaft

[BassBunny]

I had toyed with the idea of going passive but Vol/Blend/Tone and a rotary switch with some different capacitors in a bit like a ToneStyler.

Regarding cost, going passive would be a lot cheaper than a new pre-amp. A Glock 2-band is about £100 give or take.

[Obrienp]

3 hours ago, tauzero said:

Why cloth covered wire? Also, you don't need to replace the jack socket if you go passive, just leave ring unconnected or connect it to sleeve.

I find cloth covered wire easier to work with, especially when it is pre-tinned. You just push the cloth up to expose a bit of wire, instead of having to mess around with wire strippers, or a knife.

 

You are right about reusing the jack socket but those Ibby sockets do tend to fail after a bit and I prefer the more conventional Switchcraft type. They are more reliable and the Pure Tone ones give a very good contact.

[Obrienp]

2 hours ago, BassBunny said:

I had toyed with the idea of going passive but Vol/Blend/Tone and a rotary switch with some different capacitors in a bit like a ToneStyler.

Regarding cost, going passive would be a lot cheaper than a new pre-amp. A Glock 2-band is about £100 give or take.

I quite like the idea of a rotary switch like a Varitone but I have looked for one of those switches before and I haven’t been able to find one. Do you know a source?

 

WRT the Glockenlang. I guess it depends how much value you put on your time. The Glockenlang and the Bartolini preamps come prewired, which would save me several hours with a soldering iron (I am a bit clumsy in my old age, also lazy).

[PaulThePlug]

15 minutes ago, Obrienp said:

I quite like the idea of a rotary switch like a Varitone...

Got one of these in my Ibby SR Passive P with a Tonerider for the exact reason... to give it a bit more tone s-t-r-e-a-t-c-h...

Had one in my Squier P with a Kent Armstrong pickup, but it didn't seem to suit.

Still working out if it should go across the Vol input / Pickup ala '57 or... across the Vol output as Std...

 

https://www.ebay.co.uk/itm/403241742777?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=009VOmD9RYS&sssrc=4429486&ssuid=daj_hJ6fSo-&var=&widget_ver=artemis&media=COPY

Edited January 13 by PaulThePlug

[Obrienp]

On 13/01/2024 at 19:23, PaulThePlug said:

Got one of these in my Ibby SR Passive P with a Tonerider for the exact reason... to give it a bit more tone s-t-r-e-a-t-c-h...

Had one in my Squier P with a Kent Armstrong pickup, but it didn't seem to suit.

Still working out if it should go across the Vol input / Pickup ala '57 or... across the Vol output as Std...

 

https://www.ebay.co.uk/itm/403241742777?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=009VOmD9RYS&sssrc=4429486&ssuid=daj_hJ6fSo-&var=&widget_ver=artemis&media=COPY

That does look interesting! I hope it does what you want. 👍

[PaulThePlug]

1 is Bypass... and 4 R/C settings... bit more range than a conventional pot n cap...

[Obrienp]

I thought I should tie the thread up with what I actually did. Having considered the passive switch and the fully passive option, I decided to go for a two band Glockenlang preamp, as a drop in replacement (ha, ha). I didn’t want to drill anymore holes in the bass, so that ruled out the passive switch and stacked vol/tone pot. The Glockenlang has good write-ups and it gives me the passive circuit out of the box. I am holding the totally passive mod as a fall back, if I’m not satisfied with the active/passive solution.

 

As @BassBunny said above, the Glockenlang doesn’t colour the sound of the pickups but that also reveals their imperfections, so I decided I would upgrade in that department too. I set myself a total budget of £200 for the mods, so that limited my choices. I went for a Tonerider TRP-1 for the precision (£35 from their website) and stupidly didn’t go for the P/J set (£65), thinking I didn’t care about the J. I’ve had the Tonerider P before and thought it was as good as most more expensive aftermarket pickups I’ve tried. Later on in the process I decided I did want to replace the J but to keep within my budget I went for a Wilkinson WBJ. It came with wires in the same colour scheme (yellow and black) as the OEMs. I wonder if the OEMs come from the Wilkinson factory?  Still with a bit of cash left from my £200, I got a set of Wilkinson lightweight machine heads (£28). Strictly speaking this took me about £10 over budget when all the postage charges are accounted for.

 

Installation wasn’t quite as straightforward as I hoped. It turns out the OEM J pickup is not a standard J bridge size. I needed to enlarge the route at both ends, especially as I shielded all the cavities with copper tape. Despite using masking tape on the paintwork, the routing process caused a few chips around the edge of the pickup cavity. It seems the standard paint flakes off pretty easily. I’m now looking for a touch up stick in that shade of matte black.

 

It turns out that the wiring diagram that comes with the Glockenlang isn’t quite right. I had read about this elsewhere, so I used my multimeter quite a lot to sort out the ground connections from the battery positive and where the pickups connect to the balance pot. You have to solder onto circuit boards, which I am nervous about but managed without overheating them. I didn’t want to have to do it again, if I changed pickups, so soldered my own wires onto the boards and then joined them with connector blocks to the pickup leads, ground leads and battery lead. This will make any rewiring pretty easy but it did make the control cavity very cluttered, what with the boards on the preamp pots and the replacement Neutrik barrel jack I used, which protruded into the cavity much further than the OEM item. Having got it all connected, I discovered that the thread on the Glockenlang pots is barely deep enough to get through the body: with the locking washers on the pot shafts on the inside, I had to ditch the washers that go under the nut on the outside. Even then they only nipped up by about one thread. However, it does seem to be holding. The other little annoyance was that the leads on the battery clip provided by Glockenlang are pretty short. You have to extend them with extra wire to reach the sleeve terminal on the barrel jack and to have enough slack to change the battery.

 

After the hassle above, I was quite relieved that the Wilkinson lightweight tuners are a drop in replacement for the OEM machine heads. The jury is out on whether they are actually lighter than the OEM machine heads but they do have a better action. I guess they can make them look like Hipshots but can’t afford the same lightweight alloys at the price point.

 

I now have a pretty nifty bass. All the lightweight, ergonomics and playability of the original but with better electronics and machine heads. It still doesn’t sound like a good Precision to my ears but it’s close enough and I guess it could never get there, given the lightweight body and slim neck. I’m liking the Wilkinson Jazz pickup as well. Nice burpy sound with the tone rolled off and does add a bit extra bite blended with the P, along with that nasal tone when set 50:50.

[Obrienp]

P.S. Thank you for the suggestions folks. Quite a lot to try in the future!