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Old 20th April 2005, 06:28 AM   #1
jarros is offline jarros  Canada
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Default Adding a sub output to a SI

Hey guys! I've been lurking around for quite some time now, and I'm just putting together some plans for a 2.1 computer system consisting of Hi-Vi B3N's, a Sonic Impact T-Amp, and a 8" Dayton DVC with a 70W plate amp.

I'd like to be able to control the volume for both the sub and the main speakers with one volume control in a modded case for the SI. I plan on using RCA inputs going into a 100K pot like AMT's mod. From there, I think I'll split the signal: one path going to the board the other going to a set of line outputs which I will use for the subwoofer.

Is there any risk with using parallel outputs like this? I know that the output signal is FULL RANGE. I plan to use the subwoofer's crossover to filter out the highs, and I'll have a crossover on the mains to roll off the lows at around 150Hz. Should this work?

Side note: I know I could use speaker level inputs on the plate amp and then use the speaker level outputs to send the signal to the mains. However, John from Zaph Audio recommended against it. I'd like to try sending a full range signal to both the sub and the mains.

Thanks in advance!

Jared
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Old 20th April 2005, 07:35 AM   #2
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Location: Seattle
Default Re: Adding a sub output to a SI

Quote:
Originally posted by jarros
Hey guys! I've been lurking around for quite some time now, and I'm just putting together some plans for a 2.1 computer system consisting of Hi-Vi B3N's, a Sonic Impact T-Amp, and a 8" Dayton DVC with a 70W plate amp.

I'd like to be able to control the volume for both the sub and the main speakers with one volume control in a modded case for the SI. I plan on using RCA inputs going into a 100K pot like AMT's mod. From there, I think I'll split the signal: one path going to the board the other going to a set of line outputs which I will use for the subwoofer.

Is there any risk with using parallel outputs like this? I know that the output signal is FULL RANGE. I plan to use the subwoofer's crossover to filter out the highs, and I'll have a crossover on the mains to roll off the lows at around 150Hz. Should this work?

Side note: I know I could use speaker level inputs on the plate amp and then use the speaker level outputs to send the signal to the mains. However, John from Zaph Audio recommended against it. I'd like to try sending a full range signal to both the sub and the mains.

Thanks in advance!

Jared

I personally would skip the volume control in the T-amp, and use a preamp to drive both. You could make your own, or use any number of kits/schematics. There's a pretty active thread about the OPA627 + BUF634 preamp in the chipamps section.
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Old 20th April 2005, 05:00 PM   #3
jarros is offline jarros  Canada
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Default Re: Re: Adding a sub output to a SI

Quote:
Originally posted by motherone

I personally would skip the volume control in the T-amp, and use a preamp to drive both. You could make your own, or use any number of kits/schematics. There's a pretty active thread about the OPA627 + BUF634 preamp in the chipamps section.

Thanks for the suggestion. While I may build a preamp in the future, this is my first real DIY project (for woodwork and some electrical), and I'd like to keep it as simple and wallet friendly as possible. The whole project is running up in the $200+ range, so building a preamp isn't in my budget right now.

Should my original plan work?

Jared
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Old 21st April 2005, 08:05 AM   #4
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You can do it, and it will probably work fine. However, between the T-amp and the subwoofer amp, it may do funny stuff with your source. Also, make sure you compensate for the gain difference and/or speaker efficiency difference between your sub and sats.

To be honest, the absolute easiest/best way to do both, sans preamp, would be to buy a 3/4 gang pot (maybe a nice alps blue one?) and use one pair for the sub and the other pair for your sats. Just take your sub output on your soundcard to the soundcard, and the other to your SI. Then you can adjust both the sub and the SI, but you don't need to worry about your soundcard.
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Old 21st April 2005, 08:22 PM   #5
jarros is offline jarros  Canada
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Join Date: Feb 2005
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Quote:
Originally posted by motherone
You can do it, and it will probably work fine. However, between the T-amp and the subwoofer amp, it may do funny stuff with your source. Also, make sure you compensate for the gain difference and/or speaker efficiency difference between your sub and sats.

To be honest, the absolute easiest/best way to do both, sans preamp, would be to buy a 3/4 gang pot (maybe a nice alps blue one?) and use one pair for the sub and the other pair for your sats. Just take your sub output on your soundcard to the soundcard, and the other to your SI. Then you can adjust both the sub and the SI, but you don't need to worry about your soundcard.

Thanks for the input. Excuse my ignorance, but is a 4-gang pot a potentiometer with 4 different "channels"? In that case, my stereo audio taper pot would be a 2-gang pot, right? What's the advantage of splitting the signal before the pot compared to splitting the stereo output after the pot? I may want to try the amp with a seperate source as well, so I'm not sure if I want to wire it so I need to have a stereo input AND a sub input. I can see how your idea would work great if I was just using it for a computer system, though, so I appreciate your advice.

Jared
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