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Cheap way to increase gain for a line level signal?

rockypunch

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I have a budget system with a receiver, two mains, and a subwoofer connected to the sub out on the receiver. The subwoofer's volume is too low, even with it's own gain maxed. The subwoofer can play plenty loud if I increase the overall system volume, but the relative volume is too low.

What's a cheap way to increase the gain of the signal going into the subwoofer? Low cost is more important than quality in this instance.
 

SIY

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Can you solder and follow a schematic? If so, for under $5, you could have a pair of opamps configured as non-inverting amps with whatever gain you think you need.

If you have to buy something, get a line preamp off eBay.
 
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rockypunch

rockypunch

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Thanks SIY. I can solder and follow a schematic, but I'm not sure which opamp to use or which schematic to follow :).

I'd be up for building my own if it's a lot cheaper, but would also like to save time by buying something. When I search, I seem to just find phono preamps or preamps that seem to be for car use with 12v in. I'm guessing that a phono preamp would not be a good choice, possibly due to impedance mismatch?
 

DonH56

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Define "cheap"?

Something like this? https://www.sweetwater.com/store/de...-plus-audiophile-phono-preamp-audio-interface There are many similar preamps on the Sweetwater site. They target pro audio, but all you need is an inexpensive signal boost and they should work. There are also a bunch on Amazon: https://smile.amazon.com/s?k=audio+interface&s=price-asc-rank&crid=3HKJVPTMDHGBG&qid=1558462392&sprefix=aud,aps,172&ref=sr_st_price-asc-rank Make sure the unit you get has line-level I/O.

HTH - Don
 

RayDunzl

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rockypunch

rockypunch

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I appreciate all the suggestions. It looks like I have some good options. Thanks!
 

nightfishing

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Seems odd that if everything is working correctly, even in a very budget system, that this problem would exist.

Is there a level control on the receiver that has somehow been turned way down? are there crossover settings on one or the other that can be set? is there anyway you can test the sub on a different system to be sure it is functioning correctly?

I'd hate to see you spend $50 on a fix, when you could probably ebay/goodwill/craigslist a different receiver that might work out of the box for a similar amount. Same with cheap powered subs if that is the culprit.

macguyvering can be very cost effective (and satisfying) but I worry that your use case points at a bigger issue.
 
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rockypunch

rockypunch

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nightfishing, thanks for the input. My description was a little simplified. The amp is external, and connected to multiple sub drivers. I think in my case the amp just doesn't deliver enough power for the input voltage when connected to multiple drivers like it is. I forget what the impedance is based on my wiring, but at the time I did it, it made sense.
 

andreasmaaan

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nightfishing, thanks for the input. My description was a little simplified. The amp is external, and connected to multiple sub drivers. I think in my case the amp just doesn't deliver enough power for the input voltage when connected to multiple drivers like it is. I forget what the impedance is based on my wiring, but at the time I did it, it made sense.

How many subs are there and how are they wired up? In fact, which amp and sub drivers are they exactly?
 

Blumlein 88

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So if I get this correctly, you have an amp, and it is connected to several subs, and you don't get enough output?

So yes how many subs, how are they connected? Series, parallel, combination of series-parallel? You might fix your issue with a different connection path between the multiple subs. If you had 4 subs in series, you'll likely get little output. If you had 4 in parallel the amp probably can't do much with it. If you had two in series and those two series paralleled you might get it to work just fine.
 
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