Circuit Help. - Home Theater Forum and Systems - HomeTheaterShack.com

Old 04-29-08, 08:40 PM Thread Starter
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Mike

Join Date: Jan 2007
Location: Chattanooga, TN
Posts: 292
Circuit Help.

I'm seemingly having a hard time figuring out how I would wire this variable BSC (eq) up, in line with my amp and what-not.

I've got a 10k pot, 10k resistor, and my 0.022 Kimber cap, but realized I'm not entirely sure how to make it work.

Is the diagram, and while I think I can wire that up, I'm finding it hard to think (tonight) of how I'm going to run it through (in) RCA audio cables.

Would the red go in to leg 3, out leg 2, with the black going past (through?) the cap, which would be connected to the resistor, which would be connected to leg 1, correct? Or do I have everything mixed up?
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Old 04-30-08, 07:48 AM
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Anthony

Join Date: Oct 2006
Location: Virginia
Posts: 2,213
Re: Circuit Help.

I'm not sure what you asking:

Edit: I looked at it all again and the main confusion is that you refer to legs by number and your diagram has no such markings.

For signal level, the shield or outer contact is ground and the pin is signal.

You would need a matched pair for both speakers (assuming a LR and that they needed the same BSC based on room position).

Edit:
It looks like signal would come in top left leg and the shield/ground would be the bottom.

I hope that clears things up a bit (as I understood the question at least).

Good luck.
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Old 04-30-08, 04:13 PM Thread Starter
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Mike

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Re: Circuit Help.

I was using this link - here as a reference for pots as this is the first/second time using them.

This variable BSC is for use in between a preamp and power amp, so I thought I could use it through ( in? ) RCA cables, going from a preamp to power amp. That's what I gathered from this page. If I'm mistaken, then I'll just stop here because it's a 'waste' of money.

And just for clarification, I'm using a 22nF cap, not a 27nF cap as called for by the equation on the aforementioned BSC page.

The legs were in reference to the outer, middle and outer pins. I hope I've explained this a bit better.
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Old 05-01-08, 04:07 PM Thread Starter
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Mike

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Location: Chattanooga, TN
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Re: Circuit Help.

Quote:
mgboy wrote: View Post
I was using this link - here as a reference for pots as this is the first/second time using them.

This variable BSC is for use in between a preamp and power amp, so I thought I could use it through ( in? ) RCA cables, going from a preamp to power amp. That's what I gathered from this page. If I'm mistaken, then I'll just stop here because it's a 'waste' of money.

And just for clarification, I'm using a 22nF cap, not a 27nF cap as called for by the equation on the aforementioned BSC page.

The legs were in reference to the outer, middle and outer pins. I hope I've explained this a bit better.
It seems that I didn't explain it much better, or I'm not doing something right..
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Old 05-01-08, 04:16 PM
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Anthony

Join Date: Oct 2006
Location: Virginia
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Re: Circuit Help.

Your assumption that this is a signal circuit are correct. It's a passive signal circuit, so it eats headroom in your overall amplification chain -- however, it is still more efficient to do it this way than at the speaker.

Okay, onto the circuit: Ground for both would be the shield conductor or black wire on a twisted pair RCA cable. Red in from the preamp to the pot body, red to the power amp from the wiper arm in the pot.

The outer middle and outer pins on the pot are usually the in, wiper, and out of the potentiometer. IIRC, 1 is the in, 2 is the wiper, and 3 is the out. 1 to wiper + 3 to wiper usually sum to the same resistance. However some pots are different, so someone with more experience on these should chime in.

the position of the wiper sets the resistance from 1 to 2 and the remainder of the pot creates a resistance from 2 to 3. So for a linear pot, it wouldn't matter if you have 1 and 3 reversed. However, some volume pots are logarithmic and I have no idea which end is which then.

I probably added more questions than answers, but I hope this helps some.
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Old 05-01-08, 04:22 PM
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Anthony

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Re: Circuit Help.

Ah, found something on the Westhost site:
http://sound.westhost.com/pots.htm

1 is ground, 2 is wiper, and 3 is source. Good diagram lower on the page with a view to ID 1,2, and 3.

Hope this helps.
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Old 05-01-08, 05:26 PM Thread Starter
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Mike

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Location: Chattanooga, TN
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Re: Circuit Help.

Quote:
Anthony wrote: View Post
Ah, found something on the Westhost site:
http://sound.westhost.com/pots.htm

1 is ground, 2 is wiper, and 3 is source. Good diagram lower on the page with a view to ID 1,2, and 3.

Hope this helps.
Heh, I posted a link to that page in my second post, but I was only really looking at the pictures. =P

I'm just not sure how to set up the diagram I posted. Red to the in, then red out to the amp, and the resistor and capacitor from the "lower" arm going to the black wire? ( ground )

I just want to make sure I'm seeing this right.
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Old 05-01-08, 06:29 PM
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Anthony

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Re: Circuit Help.

3 is red in.
2 is red out.
1 is R1 then C1 then a node for both blacks / shield for both in and out.

I saw the page you referenced in your second post when I originally read it but forgot. So I got to have a eureka! moment today DoH!

Let us know how it turns out.
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Old 05-01-08, 06:31 PM
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Anthony

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Re: Circuit Help.

Also, if you are using twisted pair RCA's, you may want to verify that red is indeed the pin (use a multimeter with a continuity tester to verify -- most have this feature, they beep when your are touching both leads to the same wire).

I'm 90+% sure red is pin and black is ground, but I've been wrong before
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Old 05-01-08, 09:13 PM Thread Starter
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Mike

Join Date: Jan 2007
Location: Chattanooga, TN
Posts: 292
Re: Circuit Help.

Quote:
Anthony wrote: View Post
3 is red in.
2 is red out.
1 is R1 then C1 then a node for both blacks / shield for both in and out.

I saw the page you referenced in your second post when I originally read it but forgot. So I got to have a eureka! moment today DoH!

Let us know how it turns out.
Haha, alright thanks for the final explanation.

I will let you know how the final project turns out. I've had this speaker build on hold for months but just bought all of the stuff and am now waiting for free time to get the wood cut and routed, then will put the crossovers together, and finish up the speakers for good. I was using this "active" bsc (if you will) to have something adjustable as I move things around in my room a lot and the speakers are never the same distance from the wall. =P And I can use this for multiple sets of speakers, I just have to keep the baffle size the same - roughly 9.5 inches wide.
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