Stingray 3 band eq mods.

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aphekgreg
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Stingray 3 band eq mods.

Post by aphekgreg » 08 Feb 2018, 17:47

I've been meaning to post this for a while and was reminded by the Stingray eq discussion in the classifieds.

I'm another player who generally finds the stock 3 band eq, a little too bright and scratchy. Years ago, when I owned a '93 maple neck Ray, I bought some boards to build the 2 band eq, as it sounded like what I was after, but ended up selling the bass instead. After playing the Sabre with the 2 band, I realised I definitely preferred that to the 3 band.

There is though, an extra punch and snappiness to the 3 band that I like too. When I bought another Stingray last year, I quickly installed one of the 2 band eqs and was very happy. It quickly became one of my most played basses. I always planned to have a go at modding the 3 band, to see if I could get the best of both sounds. Finally got round to it a few weeks ago. I'd been putting it off in part, as I was so happy with the 2 band eq.

Having modded the 3 band, I actually think I'm happier with it than the 2 band now.

This is what I did. I think there's probably room to make it slightly better again, but if somebody gave me this and I hadn't played a Stingray before, I think I'd be happy.



Looking at the schematic, there seemed to be a few obvious places to alter.

Image

The first being the 2.2n cap going to ground next to the IN on the left hand side of the schematic. The cool thing is, because I was wanting to increase the value of the cap, I could add to what was there, without doing any permanent alterations.

On the left you can see a 2.2nf cap added to the back of the board. For anybody playing at home, who's nervous about trying this, it's really very easy. If you can turn on a soldering iron and get it hot enough, you'll be fine! To do this, you just need to heat the solder terminal and put one leg of the cap into the golden solder. You then do the same for the other leg.
Image

I suspect this mod alone will be enough for a lot of people who find the 3 band Ray too bright. Adding the 2.2n cap to the existing 2.2n cap on the board, giving a total value of 4.4n, was too dark for me. An extra 1nf was good for me. I now have a 3.3n cap replacing the original. 2.7n might be enough for some. The good thing is you can experiment, without the risk of damaging the board or making any real alterations.

I then tried some other caps to lower the freq of the treb and mid controls. I was just using values I had on hand initially. Turns out I didn't have many small value caps.
Image

Bringing the treb eq frequency down with the extra 1nf cap made the eq more usable for me. I now have a 2.7nf cap replacing the original 2.2nf.

I added a 4.7nf cap to the existing 4.7nf cap on the mid control, bringing the centre freq down a fair way. I found this quite useful, particularly for slight cuts. I am considering adding a toggle switch, to change the cap value, to give it 2-3 options.

I currently have a 2.7nf cap replacing the stock 4.7nf cap, but will probably try something in between. If you want the mids at a higher frequency, you do need to remove the stock cap in this instance. If you like the stock 500hz centre freq, then you don't need to do anything. Personally, I never liked the stock mids, but I know lots of people love them, so either way is good.

As I say, adding a small value cap, like 1nf to the filter at the input will probably be enough to tame the high end for most people and very easy to try.
Greg

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Re: Stingray 3 band eq mods.

Post by Petebass » 08 Feb 2018, 18:41

Nice work, thanks for sharing! And thanks for making it look so un-scary.
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Re: Stingray 3 band eq mods.

Post by ozrider » 08 Feb 2018, 18:50

Petebass wrote:
08 Feb 2018, 18:41
Nice work, thanks for sharing! And thanks for making it look so un-scary.
I agree, thanks for showing how totally doable this is. I need to bookmark this thread in my favourites somewhere :thumbup:

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Re: Stingray 3 band eq mods.

Post by aphekgreg » 08 Feb 2018, 19:25

Petebass wrote:
08 Feb 2018, 18:41
Nice work, thanks for sharing! And thanks for making it look so un-scary.
I haven't seen a schematic for the eq in the SR5, although not sure I've looked either. It's different to the 3 band on the SR4. Well it was with the SR5 I used to own (ceramic magnets in the pickup). They may well have changed it when they made the SR5 into a 5 string Stingray, rather than a Sterling 5? The initial filter will be easy to find and the other caps I've changed all connect to the wiper (centre lug) of the eq pots, so should be the same and easy to find as well.

The '04 SR5 I owned, had a quad opamp in the eq/preamp, where the SR4 3 band uses a dual opamp. The 2 band eq uses a single opamp.
Greg

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Re: Stingray 3 band eq mods.

Post by aphekgreg » 08 Feb 2018, 19:30

Can someone explain what the different parts of the eq contribute to the way it works? I have a reasonable idea, but not 100% on top of it.

The questions I have, are:

1. The resistors either side of the mid and low pots. Are they adjusting the amount of boost and cut?

2. The resistors connecting to the wiper on the eq pots (through a cap on the treb and mids and directly to the wiper on the bass pot). What do they do?

Thanks.

Image
Greg

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Re: Stingray 3 band eq mods.

Post by noplanb » 08 Feb 2018, 21:28

Baxandall filter or variation thereof.
Some refs to trawl:
https://www.electro-tech-online.com/thr ... is.129124/
http://sound.whsites.net/articles/eq.htm
and....tada! - Tone Stack Calculator!
Image
http://www.duncanamps.com/tsc/index.html
"Components: Values can be altered simply by double-clicking on the component. With potentiometers, the taper can also be altered. The generator source impedance can be altered to give realistic simulation results for both cathode followers and common cathode drivers."
Enjoy
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Re: Stingray 3 band eq mods.

Post by aphekgreg » 08 Feb 2018, 21:33

noplanb wrote:
08 Feb 2018, 21:28
Baxandall filter or variation thereof.
Some refs to trawl:
https://www.electro-tech-online.com/thr ... is.129124/
http://sound.whsites.net/articles/eq.htm
and....tada! - Tone Stack Calculator!
Image
http://www.duncanamps.com/tsc/index.html
"Components: Values can be altered simply by double-clicking on the component. With potentiometers, the taper can also be altered. The generator source impedance can be altered to give realistic simulation results for both cathode followers and common cathode drivers."
Enjoy
I used to have that tone stack calculator, but no longer run a Windows machine, so can't use it. Used to use it all the time when working on valve guitar/bass amps.
Greg

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Re: Stingray 3 band eq mods.

Post by noplanb » 08 Feb 2018, 21:42

Oh dear, I can't help you then :rollno:
But all the best with theory otherwise! :)
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Re: Stingray 3 band eq mods.

Post by bassbass » 08 Feb 2018, 23:32

I'm another player who generally finds the stock 3 band eq, a little too bright and scratchy.
Did you try removing that cap altogether? I think this will give you a far more natural treble response. That cap is straight across the pickup. There's no pot or anything in there, so yes it's a LPF, but it is creating a huge resonant peak right before the roll off. By altering that cap slightly, you are simply shifting that resonance up or down in frequency.

Anyway, if the bass still sounds a little HiFi and unmusicmanish, I'd reinstate the cap, but start adding some resistance inline with the signal before that cap, essentially making it an RC LPF. I'd put in say a 100K linear pot temporarily between the pickup hot wire and the input. Initially, increasing the resistor will tame that peak, then as the resistance gets higher it will start to act more like a typical LPF and roll of at lower and lower frequencies.

Also be aware that the circuit you've found online may not be entirely accurate. I've come across several traces of the MM 3-band over the years and they are all slightly different. MM may well have tweaked the circuit over the years, but also people often make little errors when tracing circuits. (Myself included!)

Another thing you may try to move away from the typical MM sound is to lower the HPF frequency that is at the input. There is quite a decent bass roll-off below 100Hz (if memory serves) with that preamp. Increasing either or both of those 8n2 caps will lower that rolloff.

As for the treb mid bass filters, well I'm not sure Duncan's tone stack calculator will help as there's no 3-band baxandall in there. But it's not that hard to use a spice program, and that will easily show you what those resistors do.

Having three bands in a single filter like that is kinda pushing the love. Everything interacts, and adjusting one cap or resistor will start to effect the other. The mid control with this sort of circuit is fairly uninspiring. It has a very low Q, and maybe 6-7dB of boost and cut. But that circuit is over 20 years old. These days opamps are much cheaper, far higher performing and, with surface mount stuff, much much smaller. Most preamps will have a separate active circuit just for the mids.
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Re: Stingray 3 band eq mods.

Post by aphekgreg » 09 Feb 2018, 07:19

bassbass wrote:
08 Feb 2018, 23:32
I'm another player who generally finds the stock 3 band eq, a little too bright and scratchy.
Did you try removing that cap altogether? I think this will give you a far more natural treble response. That cap is straight across the pickup. There's no pot or anything in there, so yes it's a LPF, but it is creating a huge resonant peak right before the roll off. By altering that cap slightly, you are simply shifting that resonance up or down in frequency.

Anyway, if the bass still sounds a little HiFi and unmusicmanish, I'd reinstate the cap, but start adding some resistance inline with the signal before that cap, essentially making it an RC LPF. I'd put in say a 100K linear pot temporarily between the pickup hot wire and the input. Initially, increasing the resistor will tame that peak, then as the resistance gets higher it will start to act more like a typical LPF and roll of at lower and lower frequencies.

Also be aware that the circuit you've found online may not be entirely accurate. I've come across several traces of the MM 3-band over the years and they are all slightly different. MM may well have tweaked the circuit over the years, but also people often make little errors when tracing circuits. (Myself included!)

Another thing you may try to move away from the typical MM sound is to lower the HPF frequency that is at the input. There is quite a decent bass roll-off below 100Hz (if memory serves) with that preamp. Increasing either or both of those 8n2 caps will lower that rolloff.

As for the treb mid bass filters, well I'm not sure Duncan's tone stack calculator will help as there's no 3-band baxandall in there. But it's not that hard to use a spice program, and that will easily show you what those resistors do.

Having three bands in a single filter like that is kinda pushing the love. Everything interacts, and adjusting one cap or resistor will start to effect the other. The mid control with this sort of circuit is fairly uninspiring. It has a very low Q, and maybe 6-7dB of boost and cut. But that circuit is over 20 years old. These days opamps are much cheaper, far higher performing and, with surface mount stuff, much much smaller. Most preamps will have a separate active circuit just for the mids.
Thanks, that's helpful. A separate mid circuit would explain why they went to a quad opamp on the 5 string (and I'm assuming Sterling) preamp/eq.

I had wondered about playing with the 8.2n HPF. I'm fairly happy with the low end, but knew it was rolling off higher than most. The higher roll off is part of what gives the Ray it's punch. Once again something that can be experimented with, by piggy backing another cap to the board.

I knew the cap across the pickup, was a fairly crude LPF, but didn't know about the resonant peak. A lot of classic eqs, like the Neve 1073 circuits have a peak like that and it isn't something I always like. I wouldn't have thought that removing it completely would make the high end less scratchy, but if it's a large resonant peak, that makes sense.
Greg

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Re: Stingray 3 band eq mods.

Post by bassbass » 09 Feb 2018, 09:35

Yeah, it is kind of crude to just have unbuffered filters like that at the front end, but really, this was only ever designed to work with a specific pickup, so it's understandable. These days virtually all preamps, pedals and really every audio circuit will have a dedicated buffer right at the outset, and usually at the end of the line as well. This way the filters will act predictably no matter what pickup is on the input, and what the ouput is driving.

If you have a P bass say, with a regular passive tone control, you'll hear a little hump in the low mids just as the tone pot reaches zero. At this point, the tone pot is a short (so out of the circuit) and the cap is directly across the pickup (more or less). Well if you use a 22n cap instead of a 47n, this little peak is almost an octave higher and a little higher also in amplitude/resonance. Well keep going with this idea, with 10n, followed by 4n7, and finally 2n2, and you'll get where that resonant peak is heading. With a pickup like a P, it will be around the 1Khz mark, and still quite damped, because of the passive vol pot, and cable capacitance. But with a MM pickup, it's more like 2khz, and really quite peaky with no volume pot and feeding that preamp directly.

A MM pickup (coils in parallel) has a far higher treble response than that cap allows. If feeding a nice high z buffer, I'd think its resonance would be something like 2 octaves higher (around 8khz). In my stingray pickup P, I have a filter that allows me to sweep that resonance up and down and really tailor that peak.

Another issue is that speakers have really changed in the last 25 years. Neos especially, usually have a large resonant peak of they're own around that 1.5-2.5Khz mark as well. Bass guitar speakers didn't have this back when the MM 3-band was devised.

Also, fwiw, if you try to do an active/passive true bypass switch wiring with a pre like this, (say you built one as a pedal) you'll typically get a little pop from the switch, because that input cap is just floating there. You'd need a resistor to earth up front. Typically a 1M will drain the charge in that cap, but not effect the sound. Actually that's another way you can tame that resonant peak - by adding a resistor from the input to earth. Instead of 1M, perhaps in the 50K-100K range will damp that peak with a typical MM pickup. Again I'd use a temporary pot as a test, like a 250K linear pot, then put something in permanently. Or even a trimpot, so you can tweak. An educated guess says this is what the z mode switch on the Audere preamps is doing - simply a resistor across the input.
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Re: Stingray 3 band eq mods.

Post by ozrider » 09 Feb 2018, 10:09

bassbass wrote:
09 Feb 2018, 09:35
Another issue is that speakers have really changed in the last 25 years. Neos especially, usually have a large resonant peak of they're own around that 1.5-2.5Khz mark as well. Bass guitar speakers didn't have this back when the MM 3-band was devised.
That is interesting, so what does this resonant peak do? Do you just get a little extra boost in that region?

So the old sizzly ray was designed for muddy speakers?



The only sound I don't like out of my Berg neos is 800Mhz, but that seems to be coming from my passive BB. My ceramic SR5 through the bergs sound really nicely balanced unlike direct to headphones where I notice the crazy sizzle.

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Re: Stingray 3 band eq mods.

Post by Petebass » 09 Feb 2018, 11:38

bassbass wrote:
08 Feb 2018, 23:32
I'm another player who generally finds the stock 3 band eq, a little too bright and scratchy.
Another thing you may try to move away from the typical MM sound is to lower the HPF frequency that is at the input. There is quite a decent bass roll-off below 100Hz (if memory serves) with that preamp. Increasing either or both of those 8n2 caps will lower that rolloff.
According to my graphs, it's actually more like 60Hz, not 100Hz. Amd IMO, EVERY bass should have this! I had to install one onto the P pickup of my P-Ray because without it, changing from the MM pickup to the P meant going from articulate and punchy to, well, a pregnant elephant wallowing in a pool of mud.
* 2 Stingray 5's (one heavily modded), Ibanez SR805, Ashbory, + more...
* Carvin B1500, Epifani PS1000, Ashdown Superfly amps.
* Lots of DIY neo/lightweight cabs including one made from composites http://www.ozbassforum.com/viewtopic.php?f=5&t=2546

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Re: Stingray 3 band eq mods.

Post by ozrider » 09 Feb 2018, 11:49

Petebass wrote:
09 Feb 2018, 11:38
... changing from the MM pickup to the P meant going from articulate and punchy to, well, a pregnant elephant wallowing in a pool of mud.
that's a perfect description P pickup... :lol:

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Re: Stingray 3 band eq mods.

Post by Petebass » 09 Feb 2018, 12:15

ozrider wrote:
09 Feb 2018, 11:49
Petebass wrote:
09 Feb 2018, 11:38
... changing from the MM pickup to the P meant going from articulate and punchy to, well, a pregnant elephant wallowing in a pool of mud.
that's a perfect description P pickup... :lol:
Ha, Nah for me the P pickup has that rasp in the mids that make it snarl a little. And don't worry, mine still has plenty down low too :)
* 2 Stingray 5's (one heavily modded), Ibanez SR805, Ashbory, + more...
* Carvin B1500, Epifani PS1000, Ashdown Superfly amps.
* Lots of DIY neo/lightweight cabs including one made from composites http://www.ozbassforum.com/viewtopic.php?f=5&t=2546

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