Topic: Bass Roll off capacitor values?

[lordbelial]

I there.

I'm wondering what are the values of the capacitors that most of the manufacturers (CoreSound, SoundProfessionals, microphone madness... etc...) use in their battery boxes. I'd like to build a battery box with switchable bass roll off, and, taking a look to my SP-SPSB-1 battery box, the only value I can see is the following...

Capacitor labelled L30 105 (the big one) is 1 microfarad.
But I can't see the other labels...

I don't want to destroy my battery box to see or measure the value from the capacitors, so I hope someone knows...

Chris from SP told me a few weeks ago that their battery boxes were designed for an input impedance of 10Kohm, so I guess the capacitors are selected based on this resistor value. Since capacitors in parallel work like resistors in series, every time you "switch on" the DIP selector you're adding the values from the capacitors.

I'm trying to manage the values based into this 1 microfarad big one, but, damn, it's quite bored... XD

Thansk to everyone.

EDIT: Capacitor can't be of 1microfarad. I was performing some maths and the results for the 4th capacitor are neggative???
EDIT2: Capacitor IS 1uF. I was doing wrong... 

[Humbug]

http://taperssection.com/index.php?topic=42138.0

at least gives the bro..there's some math on page two you might be able to adapt.

[lordbelial]

http://taperssection.com/index.php?topic=42138.0

at least gives the bro..there's some math on page two you might be able to adapt.

Well, supossing that the condenser in switch 1 is the one that labels 105 (1 microfarad), I can figure out the other values by calculating them by hand.

[lordbelial]

DAMN!!!

I finally found out the capacitor values, are as follow,

C1 - 105   1   uF
C2 - 154   0,15   uF
C3 - 823   0,082   uF
C4 - 183   0,018   uF

BUT there's something I have figured out with the selectable bass rolloff.

When you select 16Hz (2,3,4 switch to open) you're making the capacitors (all the four) behaviour this way

Capacitors 2,3 and 4 are in SERIE so you need to calculate the Total serie capacitor,

1/CT = 1/C2 + 1/C3 + 1/C4 = 0,0008856 uF

And then, this total capacitor is in PARALLEL with the capacitor that remains to CLOSE, I mean, C1, which value is 1 uF.

That way you've

Ctotal = CT (series) + C1
Ctotal = 0,0008856 uF + 1 uF equals nearly 1uf.
So there's the 16 Hz bass rolloff for an imput impedance of 10KOhm.

I'm trying to figure out the schematic to build a switchable bass roll off. As I said, I don't want to break my BBox. So I keep on thinking... or, Maybe one of you has a broken battery with switchable bass roll off and can take a photograph of the PCB? That way I could figure out HOW DAMN ARE THOSE CAPACITORS MOUNTED!!! XDDDDDD

I hope this help you guys.

[cgrooves]

Keep in mind, that none of the battery operated recorders commonly used in the field have a line input impedance of 10KOhm (that I'm aware of).  There seems to be a market for battery boxes designed specifically for use with the JB3, m1, etc.  (Those two recorders have different line input impedence values, BTW, just using them as a reference). 

Basically, I'm just trying to say that if you take the time to make your own battery box, you should base the design on your specific recorder's line in impedence value instead of the 'generic impedence of 10KOhm'.  If not, the roll-off values will not be accurate for your specific recorder.  There are threads here that correlate the actual roll-off values for different recorders (correlated from boxes designed to the 'generic impedence of 10KOhm').  If you look at the correlations, the common battery box roll-off values are of little use, IMO.  You either roll off way too much or not enough with the JB3 or m1 for instance.  I don't know why nobody has filled the market need for battery boxes that are designed for specific recorders.  Start production now and become rich 

[lordbelial]

Keep in mind, that none of the battery operated recorders commonly used in the field have a line input impedance of 10KOhm (that I'm aware of).  There seems to be a market for battery boxes designed specifically for use with the JB3, m1, etc.  (Those two recorders have different line input impedence values, BTW, just using them as a reference). 

Basically, I'm just trying to say that if you take the time to make your own battery box, you should base the design on your specific recorder's line in impedence value instead of the 'generic impedence of 10KOhm'.  If not, the roll-off values will not be accurate for your specific recorder.  There are threads here that correlate the actual roll-off values for different recorders (correlated from boxes designed to the 'generic impedence of 10KOhm').  If you look at the correlations, the common battery box roll-off values are of little use, IMO.  You either roll off way too much or not enough with the JB3 or m1 for instance.  I don't know why nobody has filled the market need for battery boxes that are designed for specific recorders.  Start production now and become rich 

Man! That's what I'm trying to do!

I'm trying to build custom battery boxes for my three recorders. Sony MD, Sharp MD and NJB3!

I have a lightly idea of how this works (the capacitors and the switchable selector), but I need to be SURE of how it works. I know that battery boxes are build for an impedance of 10Khm! Wow, Line inputs are 47K (sony dat's and MD), 20K in sharp models and 37K in NJB3 models. Some Compact Flash recorders have a line input impedance of 100K and that makes 8,8 Hz of bass roll off when switching to the 888HZ setup...

Also the sliders of my battery boxs act as attenuators of signal (maybe from -20db to 0db), I don't know surely, just was wondering.

As soon as I figure out how this works 100%, I'll start the search for the capacitor values for higher impedances.

I'll keep you all noticed on this.

[deadhoarse]

As soon as I figure out how this works 100%, I'll start the search for the capacitor values for higher impedances.

I'll keep you all noticed on this.

This has already been covered on this forum.  TS poster DKlein posted an Excel file which allows you to determine what capacitors are needed for different impedance values.  You should be using 10kOhm resistors in any generic battery box you make.  What will change is the capacitor value, which is based off of the input of the recorder.

[lordbelial]

As soon as I figure out how this works 100%, I'll start the search for the capacitor values for higher impedances.

I'll keep you all noticed on this.

This has already been covered on this forum.  TS poster DKlein posted an Excel file which allows you to determine what capacitors are needed for different impedance values.  You should be using 10kOhm resistors in any generic battery box you make.  What will change is the capacitor value, which is based off of the input of the recorder.

Yes, I already knew of that.

The problem is the mounting of the capacitors and the DIp switch.

[deadhoarse]

Yes, I already knew of that.

The problem is the mounting of the capacitors and the DIp switch.

I actually made a switchable box last year.

JKLabs suggested this diagram to me for building a custom switchable box.


This offers 6 different levels of rolloff in one battery box.  I used this design to make a super-battery box that allows 2 levels of rolloff for my DAT line in, 1 level DAT mic in, 2 levels Minidisc line in, and 1 level Minidisc mic in.  (The 2 levels were no-rolloff, and 85Hz rolloff. I used no rolloff on the mic-in's, since I only use mic input when recording really quiet material, no bass).
I used two 10kOhm resistors in the design, and twelve capacitors.  I used DKlein's calculator to determine what capacitors I needed. Everything was mounted in a Curious George Altoids tin.
Here is a pic of my project:

[lordbelial]

Yes, I already knew of that.

The problem is the mounting of the capacitors and the DIp switch.

I actually made a switchable box last year.

JKLabs suggested this diagram to me for building a custom switchable box.

Mmm. I have heard several times of JKLabs but found nothign about him/them...

Could you tell me if they have webpage or if he's a member?

[deadhoarse]

Mmm. I have heard several times of JKLabs but found nothign about him/them...

Could you tell me if they have webpage or if he's a member?

Unfortunately, it seems like he dropped off the face of the Earth.  Many people here have been attempting to contact him over the last year.

What is that chicken staring at the eggs from?

[lordbelial]

Mmm. I have heard several times of JKLabs but found nothign about him/them...

Could you tell me if they have webpage or if he's a member?

Unfortunately, it seems like he dropped off the face of the Earth.  Many people here have been attempting to contact him over the last year.

What is that chicken staring at the eggs from?

Mmmm, what a mess... I didn't know about JKLabs and there are some hardware made by him/them around the internet... but no description at all.

Concerning the chicken... are you talking about my avatar? LOL. Nice picture, you can even see the sadness in the eyes of the chicken, who's going to eat his own child... or something like this.

[prof_peabody]

Interesting read, +Ts

[lordbelial]

Interesting read, +Ts

Thanks! I'll write more soon or later. I'm still studying different configurations on the four capacitors and the DIP Switch.