Stingray aftermarket 2 band pre

[Andyman001]

Originally Posted by delta7fred

Don't put any resistance before it, i.e. volume or blend pots, it needs to be fed from direct from pup/s.

to maybe wire the pups with a series/parallel switch straight to the pre. (I usually run em both anyways

[Andyman001]

Also, what size wire did you guys use, 18? 20? does it matter if solid or stranded?

[SGD Lutherie]

Originally Posted by delta7fred

Don't put any resistance before it, i.e. volume or blend pots, it needs to be fed from direct from pup/s.

You can use volumes or a blend before the preamp if you have a two pickup bass. That works fine.

[Andyman001]

Cool, I probably won't put it in the 'vette, it is sounding better after I changed the strings, but I also have a passive MiM Jazz V that I will try it in.

[Stealth]

Originally Posted by NelsonVandal

I have simulated the circuit in LTSpice one can find on the Internet. It's definately boost and cut for both bass and treble. The odd thing about it is that it's not really flat when set to mid positions. There's a sligt midrange emphasis.

I know I'm a month late with the comment - do you have graphs showing its flat, boost and cut positions?

[delta7fred]

Originally Posted by SGD Lutherie

You can use volumes or a blend before the preamp if you have a two pickup bass. That works fine.

David

I haven't tried it with a 2 pup bass and balance pot but I know it looses treble response if it is not fed with a low(ish) impedance source.

I was using a 33k (or could have been 47k, it was a while ago) volume balancing resistor so that a series or parallel connected humbucker had equal volumes.

The resistor needed a treble bleed capacitor across it to bring the response back to what it was without the resistor. I forget the cap value now but it will vary with the resistor value.

[SGD Lutherie]

Originally Posted by delta7fred

David

I haven't tried it with a 2 pup bass and balance pot but I know it looses treble response if it is not fed with a low(ish) impedance source.

I was using a 33k (or could have been 47k, it was a while ago) volume balancing resistor so that a series or parallel connected humbucker had equal volumes.

The resistor needed a treble bleed capacitor across it to bring the response back to what it was without the resistor. I forget the cap value now but it will vary with the resistor value.

I think it was the 33k resistor doing that. Series resistance increases the impedance of the pickup.

The input impedance of the MM preamp is set by the 220k resistor into the inverting input. That's not super high, but is about the same as the input impedance of a Markbass amp.

I'm using one of these in my '87 Ibanez with two of my Neojazzbuckers and a 500k blend. It sounds great, and I have plenty of high end. I usually keep the treble control around flat.

[Passinwind]

I posted these sims done in LTspice on another forum but I figured they might be useful to some people here as well.

Originally Posted by Passinwind

Note on circuit mods: I used 180K in the feedback loop where 100K/220K is spec'ed, since that's what I have in the one in my bass (Travis Bean fretless). 1uF output cap, going to 10 doesn't really do much at all and I wanted to use nonpolar coupling caps where I could. 330K on the voltage divider resistors since I'm using LT1351 which is more current hungry.

So here are some curves that LTspice threw out. Scale for bass and treble controls is 0-10, I use 01 and 99 in file names to reflect min and max rotation because that's how LTspice specs them. Freq sweep is 20Hz-20KHz.

T=0, B=0



T=10, B=10



T=4, B=5



T=4, B=3



T=4, B=7



T=10, B=0



T=0, B=10

[Stealth]

This is very, very cool. Thanks for the graphs, they really do make quite a few things clear.

What kind of pickup model did you use for the graph? Did you feed it with a virtual pickup with a low impedance like a MusicMan with parallel coils (i.e. the standard wiring)? I'm just wondering because the treble control is effectively tied to the input and thus very much impedance-dependent.

Edit: Also, my own MM preamp will be done soon, made according to SGD's corrected circuit diagram and using an LM4250 like the original. It has a different layout, no strain relief wires, but has pin headers for input, output and pot connections. It'll be going into a Yamaha RBX375 after I record its current settings. Pics will follow, of course.

[SGD Lutherie]

Originally Posted by Stealth

Edit: Also, my own MM preamp will be done soon, made according to SGD's corrected circuit diagram and using an LM4250 like the original.

It's not really corrected. It's just that they changed the feedback resistor at some point. I had a Sabre preamp I was studying that used 220k. I use 180K, which I figured was a good compromise between the two. 220k is louder though, so that might be better for some pickups. I didn't like 100k in there.

Thanks for those plots Passinwind.

[Passinwind]

Originally Posted by Stealth

This is very, very cool. Thanks for the graphs, they really do make quite a few things clear.

What kind of pickup model did you use for the graph? Did you feed it with a virtual pickup with a low impedance like a MusicMan with parallel coils (i.e. the standard wiring)? I'm just wondering because the treble control is effectively tied to the input and thus very much impedance-dependent.

Hey Boris,

This was just a quick and dirty sim (only took an hour or so) and I didn't worry about pickup loading, I just fed it with a low impedance sig generator model. I will be happy to share the model and you guys can tinker with things like that all you want. I just tried throwing some series resistance and inductance in the generator model, it does behave as one might expect -- it makes a very big difference. I haven't tried running .wav files through it yet, but that's do-able. Also, I wouldn't put too much money on the pot taper models mirroring reality all that well. Still, this is probably a decent start to undertstanding the nature of the beast.

When I build up my next board I'll take a stab at doing some actual measurements.

[BassLife77]

Originally Posted by Passinwind

I posted these sims done in LTspice on another forum but I figured they might be useful to some people here as well.

thanks for the sims. I use the LT1351 in all my builds including the Sabres. now I see why I usually keep the controls at T=4 B=5 since I like mids. I didn't know the mids got scooped like that when the controls are maxed.

[Sinclair]

Do you thing it's ok to use 470p instead of 500p and 1n5 instead of 1n8? Those values are hard to find over here in germany.

[SGD Lutherie]

Originally Posted by Sinclair

Do you thing it's ok to use 470p instead of 500p and 1n5 instead of 1n8? Those values are hard to find over here in germany.

I use 470p and 1n8, but 1n5 should be close enough. It will change the frequency of the treble control slightly, making it lower. But you might not even notice.

[Sinclair]

Thx!

After some further research I've made up a shop which had all odd values in stock. For the volume pot I've ordered lin taper. 1M rev log was only available in 16mm, so I've ordered a 24mm 1M lin for test purposes.

Does anyone have the last PCB layout handy? Maybe even eagle-like or something? I'd like to add some solderpoints, the protecting 1k ohm resistor and the protecion diode from the later versions.

[UncleFluffy]

Originally Posted by Sinclair

Thx!

After some further research I've made up a shop which had all odd values in stock. For the volume pot I've ordered lin taper. 1M rev log was only available in 16mm, so I've ordered a 24mm 1M lin for test purposes.

Does anyone have the last PCB layout handy? Maybe even eagle-like or something? I'd like to add some solderpoints, the protecting 1k ohm resistor and the protecion diode from the later versions.

I have eagle files - PM me with an email address and I'll send them to you.

[LowGrowl]

Hi!
I just replaced the 3 band original pre of my 2010 Stingray with a john east 3 bands. I'm still waiting for the nordsrand MM4.2 to have the full pre-ernieball mimic but even with the stock ceramic pickup this pre IS a very noticeable improvement.

The variable mids are fantastic weapon! a common use would be to cut a little boxiness (half way) add clanking clarity (freq knob all the way up)... but the range is so wide that you can achieve very usefull uses to that little knobs.

One of the best sounding settings I have found so far is:

Bass set slightly past the center detent
Treble set almost all the way up (bright switch off)
AND
Middle freq set all the way down to 100hz (i would say that is not middle at all) and boosted mid way from the center dentent to the maximum position.

Sings beatifully while is kicking you in the chest...Try it!
Ray

[Sinclair]

Originally Posted by UncleFluffy

I have eagle files - PM me with an email address and I'll send them to you.

PMed - thanks!

[Tedward]

UncleFluffy, you have a PM

Tedward

[UncleFluffy]

Got the PM, thanks - there's 25 in my inbox right now, I'm working through them as time permits.

(NB, I'll be able to post in the other thread come payday, I need to renew the sponsored sales thingy for 2013)