OLP customisation - homebuild active conversion (FINISHED)

[garethfriend]

EDIT: Build pics down page.

So a few weeks ago I was looking for a 5 string, was all but ready to buy a squier VM jazz V from the local music shop but stopped into PMT Birmingham on my way home and came across an OLP MM3 in the ranks of their used guitars. On picking it up I realised that the neck was the most amazing 5 string neck I have ever played (for me it felt more comfortable than even the real SR5's I've tried) and so on that basis I thought I'd take a punt - find any bass with a neck that really works and price and prestige be damned, had to have it.

So there were a few bad points, frets had seen better days but with any new bass I tend to get the frets levelled regardless as in my experience unless you are spending quite a few thousand £ there is always room for improvement when you get the action low. Other bad point was the lack of a preamp and the useless VVT controls. Pickup sounds OK, nothing amazing but was aware that I wasn't really giving it a fair chance in passive mode.

At this point I apologise for the lack of pictures, I pretty much sent it straight off for the fretwork and forgot to take any before hand.

Being as how I had three holes for pots in the scratchplate I thought I'd go for a 2eq setup on the preamp, I tend to set everything on the amp and just roll on or off treble as needed live so 2eq should be fine. I came across a veroboard layout for a classic stingray preamp on the net and found that I could get all the parts to make it for less than a tenner including the pots which I had to order from Germany.

So breaking out the soldering iron I came up with this:

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Not finished yet but can't finalise the wiring until I get the bass back and figure out where everything is going to go. Eyeballing it I reckon there's enough space under the scratchplate for everything but will make changing the battery awkward, not a big deal but may end up routing a battery box at a later date if it becomes an issue.

When I get it back from the fretjob I plan to upload before and after sound samples to see how it compares.

Future projects may involve either a new pickup or re-winding the existing or similar cheap one (should be cheapest option although I've not done winding before so is purely a learning experience). Also plan to put in a series/parallel switch if space allows. Not because it is the cheapest way but because it is the most engineeringly interesting way of doing it I am toying with the idea of designing and making my own bridge for it too - I have access to CAD software, a workshop and tame machinists through work so might be an interesting project.

Not that I think anyone will miss the point but in case anyone is wondering this isn't about getting a stingray on the cheap it is about getting vaguely the sound for considerably less and more importantly learning a lot along the way.

Edited June 3, 2012 by garethfriend

[Rumple]

I have a bog standard OLP 5 string that I love playing, great bass for what I paid for it secondhand, I quite like it's passive tone and the fact that the VVT means you can mix the coils, I did consider changing the pick-up.

Interesting project, I look forward to hearing your pre amp sound clips.

What sort of bridge will you be making?

[garethfriend]

well for the bridge I am thinking I will make something the same sort of style i.e. a folded plate but make it from thicker material and and get some shallow guide slots machined into it to restrain the saddles laterally. For the saddles I am thinking of just beefing them up and making everything just a bit better tolerance than the stock one. That is my first thoughts but I may come up with something a bit more radical once I sit down and do the design work, I want to keep the machining operations to a minimum so it's not going to be something that requires a great deal of CNC or anything like that, just a simple improvement on a basic but effective design.

[Rumple]

Sound interesting, I just looked at a MM SR 5 bridge and they don't have guides but then it is a much sturdier bridge.

[garethfriend]

yeah my SBMM doesn't either it's just massively more substantial, might just get away without

[muttley]

You might want to switch that 741 for a decent low noise audio grade op-amp.

[garethfriend]

Yeah, only used that as it was althe local shop had in, there were about three different op amps listed in the schematic so I socketed it so I could try different ones. Recommendations welcome.

[muttley]

Furry 'nuff . When I built a MM phono pre-amp some years back I used a Nat Semi LM833. I think this is a dual device but in an 8-pin package. Noise performance is excellent (but I run it +/- 9V using 2 batteries). The NE5532 is also a commonly used device for audio circuits. A quick search reveals that the Linear Technology LT1115 looks like the dBs but costs pounds rather than pence. If you are going to use one of these I would also replace all your capacitors for the highest spec you can get/fit.

Disclaimer: I am not an EE (but I did work in the audio industry for 20 years).

[muttley]

Some links:
LM833:
http://uk.farnell.com/texas-instruments/lm833p/ic-op-amp-16mhz-7v-%C2%B5s-dip-8/dp/1863700
NE5534 (NE5532 is dual version)
http://uk.farnell.com/texas-instruments/ne5534ap/ic-op-amp-low-noise-5534-dip8/dp/1106093
LT1115:
http://uk.farnell.com/linear-technology/lt1115cn8-pbf/ic-audio-op-amp-40mhz-dip-8/dp/1556436

[Beer of the Bass]

Bitsbox ([url="http://www.bitsbox.co.uk"]http://www.bitsbox.co.uk[/url]) stock the LM4250, which was used in the original MM design. I don't know how they compare for noise etc. to the other opamps, but they're at least a known quantity in this circuit. I was thinking of building a similar preamp for my bass a while ago, but decided to go passive in the end.

Edited May 14, 2012 by Beer of the Bass

[muttley]

[quote name='Beer of the Bass' timestamp='1337016941' post='1654101']
the LM4250, which was used in the original MM design.
[/quote]

Wow, that thing will work down to +/-1V supply voltage, which is probably why they chose it.

[janmaat]

BC's own Higgie made a MM-2-band for me, which does a perfect job in my OLP MM3.
That said, I believe he's playing the bass on a cruise ship right now...

[garethfriend]

[quote name='janmaat' timestamp='1337026377' post='1654347']
BC's own Higgie made a MM-2-band for me, which does a perfect job in my OLP MM3.
That said, I believe he's playing the bass on a cruise ship right now...
[/quote]

That's encouraging, worth it then? Big difference or subtle? Did you keep the stock pickup?

I think if it gives me back control over the bass and treble without having to turn around and fiddle with the amp on stage it will be worth it for me.

[janmaat]

Yes, huge change, and if it is just this: now I can control the sound. The B is huge. The whole thing now makes sense as an instrument, couldn't possibly work with the VVT.

Stock pickup. Different jack plug socket which was a bit difficult to squeeze in there.

Still wanting to route the battery compartment but have not found decent set of chisels by now. The preamp is actually wrapped in some plastic foil and the battery is squeezed in under the scratchplate too, which was a bugger to fiddle together and it will be a p.i.t.a. to exchange the battery, should that day arrive.

One more thing I did was to add another washer on the headstock since the G string tended to pop off the nut, which of course fixed that problem. Now it's "weapon of choice" when I want to be really noisy.

[garethfriend]

LM4250 arrived Friday, got that bad-boy in there and soldered the ground wires to the pots today. Should get the bass back this week I think so looking forward to cracking on with this.

[garethfriend]

Update with pictures:

First I took some advice and replaced loads of the caps with various better ones, a bit of research threw up some parts that people had had good results with.

Got the bass back from fretwork and set about getting the preamp installed. Space is tight so I had to out some length from my control wires to get it all in:

[attachment=109383:2012-06-02 21.50.13.jpg]

[attachment=109384:2012-06-02 22.21.39.jpg]

Battery fits in under the pots nicely but took some real thinking to get it all in there. Worked first time except I wired the bass knob round the wrong way but was only a quick thing to fix.

Took it to practice today to try it out. Completely different bass, B string is bowel quivering!!!!! Got some before clips recorded will get the after ones done tomorrow probably if anyones interested.