OBP3 Mid range switch capacitors

[QuickNasty]

Im trying to raise the Mid_low setting on my aguilar obp-3 to 550hz.

The schematics call for a 0.0016uF and a 0.072uF. I couldn't find the exact capacitors, so im trying to combine 2 to make the desired range.

I found 0.0016uF labeled as 1600pF
I found 0.062uF and am wanting to combine with 0.01uF to achieve 0.072uF.

Question is, will this work?

Here is a picture of my intended order form from mouser, does it look correct?

 

[BruceWane]

Yeah, it'll work. Just be sure to connect the capacitors you're combining in parallel, not in series.

 

[line6man]

You have selected rather high voltage capacitors. They are likely to be excessively large. Choose lower voltage capacitors to save space.

 

[QuickNasty]

You have selected rather high voltage capacitors. They are likely to be excessively large.

Thanks, that was my main concern. Would ceramic disk be best for this? All of the films that were in stock are large. What is the minimum voltage to use for this?

 

[line6man]

Thanks, that was my main concern. Would ceramic disk be best for this? All of the films that were in stock are large. What is the minimum voltage to use for this?

Ceramic disk capacitors are notorious for having loose tolerances. This is an application where actual capacitance is very important, because you are trying to configure the circuit for a particular frequency range. With that being said, you want to pick something with a nice tight tolerance, so that the actual capacitance will not be far off from the rated capacitance.

Just about any film or ceramic capacitor will have a high enough voltage for this application, so you don't need to worry about it. To be technical, however, I would make sure the voltage rating exceeds the voltage of the power supply for the circuit, even though it won't see all of that voltage. Anything above 9V or 18V.

 

[QuickNasty]

Great!
What is the best capacitor material to use when looking for small size and tight tolerance?

 

[QuickNasty]

Best thing i have found are Multilayer Ceramic Capacitors with a 1% tolerance at 50v. Thank you for the help!

 

[QuickNasty]

Additional update for anyone looking to do the same thing with their preamp.
I ended up going with these values to get 0.0016uF and a 0.072uF at a 5% tolerance.
1600pF = 0.0016uF
0.033uF + 0.039uF = 0.072uF

 

[ex-tension]

That 1600pF cap is SMD 0402 size. Which is like this:

If you think you can solder it, better buy some spares

 

[QuickNasty]

Oh, haha need to change that. thanks lmao

 

[Marcus Willett]

Additional update for anyone looking to do the same thing with their preamp...

Some good info here. I had a heliuva time trying to find correct value caps when I was wanting to do something similar with an OBP3 equipped bass....I wanted the low mid at 250Hz. Fortunately my repair guy is a bit of a pack rat and he had some random caps lying around that were within a few % of the needed values.

I was originally hoping for 200Hz to have more control of low mid mud, but since we were able to find almost the exact needed caps for 250, I went with that. Turned out good.

 

[QuickNasty]

I agree, maybe this can help people find a shortcut to doing this mod. I wish the preamp would allow changing both mid-points. My ideal would be 200 and 550.

I wanted to get capacitors with leads on them to solder to. At the same time I needed small size and decent tolerance of the values, so i needed to make a few compromises based on what they had in stock. I'm going to run the capacitors to wires and cover the connections with heat-shrink tubing. That way I can tuck them away in the control cavity.

Here was my final purchase from mouser.
1500pF + 100pF = 1600pF = 0.0016uF
0.033uF + 0.039uF = 0.072uF

 

[Marcus Willett]

....I wish the preamp would allow changing both mid-points. My ideal would be 200 and 550.

Agreed, that would be cool. My ideals would probably be around 150 and 600, that way I have roughly 2 octaves from the low to low-mid then another 2 up to high mid.

It would be nice if they either sold, or could recommend/link certain caps. Switchable lows would be awesome too, kinda like the Pope pre, but at least we have this option.

 

[gpx1200]

john east makes a sweepable mid that can supposedly be added inline with any preamp.
the pope has almost to many options but out of the aggie,john east and mike pope the pope is my favorite.
thanks for posting this info, I might try fine tuning one of my aggies now that you brought it up

 

[kybu]

Best thing i have found are Multilayer Ceramic Capacitors with a 1% tolerance at 50v. Thank you for the help!

Make sure that your ceramic capacitors are Class 1 C0G. Those have stable capacitance characteristics and they should not have a piezo effect.

 

[LoveThatBass]

I use a push/pull switch on a pot to achieve this

 

[gpx1200]

I use a push/pull switch on a pot to achieve this

yes everyone uses the switch, this post is about altering the frequency that the switch selects