Which desktop amp with a sub output?

WiL11o6 · Feb 26, 2019

I have an old 12" Emotiva sub that I bought nearly a decade ago that's collecting dust. I want to connect it to my 2.0 setup I am currently running through a cheap Lepai desktop amp from Amazon. I issue I have is my sub doesn't have speaker wire outputs so I can't connect speakers > subwoofer > amplifer.

I haven't messed with audio stuff in a while so please advise!
Here's my subwoofer: https://www.audioholics.com/subwoofer-reviews/ultra-12
Here's a cheap desktop amp I'm looking at but not sure if it'll work without blowing stuff up: https://www.amazon.com/gp/product/B0070Z87YO/ref=ask_ql_qh_dp_hza

My question is R/W cable from subwoofer to R/W input of the amp, speaker wires into amp, and computer 3.5mm audio into aux?

Thanks!

Tiihokatti · Feb 26, 2019

You need an amp with subwoofer pre-out. So those 2.1 amps are a no go.
Especially the Lepai only has rca/3.5mm inputs. It can't output anything from those ports.

Amps that have the sub-out are not very cheap.
Micca Origain, Topping MX3, Sabaj A4, Smsl AD18, etc.

You could also use a splitter from your soundcard/dac to your subwoofer and amplifier. But that way you can't use the volume knob on the amplifier or else you need to recalibrate the volumes for the sub every time you touch it.

pioneerisloud · Feb 26, 2019

Could just buy a car audio line level converter, run it in parallel with your speakers off the Lepai amp, it'll convert the speaker wires into RCA's. Something like a PAC LC-2 would work great, and it'd give you a remote bass knob you could set near your Lepai, so you can adjust the sub's volume nearby without having to go over to it. Please note, you will need to figure out a 12v source to connect it to, any 12v adapter you've got lying around should do the trick, I'd probably want at least a 2a adapter though or more if you can. A spare old junk PSU would do the trick too.

I'd still suggest a bigger amp (having had 3 Lepai TA2020's myself). The Dayton DTA-120BT is amazing for its price and has bluetooth capabilities on top of RCA inputs.

https://www.amazon.com/PAC-LC-2-Output-Convertor-Control/dp/B0002J226Y
https://www.amazon.com/Dayton-Audio-DTA-120BT2-Class-Amplifier/dp/B07BKVP6B8

WiL11o6 · Feb 26, 2019

Thanks dude!

That answered my question. Guess I would need to spend roughly $125~ to get a decent small amp with a pre-out.

Edit: Thanks for some other suggestions pioneerisloud. I'm not handy enough to mess with electrical stuff though, but I'm sure your post would help others who stumble upon this thread.

pioneerisloud · Feb 27, 2019

If that's the case, you could also always check around for a decent used receiver on craigslist or ebay or something too. I just picked up a mid 2000's model Pioneer 5.1 unit for $45 myself on ebay (shipping made it nearly $90). That'd open up your possibilities alot, you could use a digital signal to it (it'd become your DAC), and you could eventually add on surround if you wanted. Most have a headphones amp too. Only downside is the size of course.

As a cheap alternative, you could run a 3.5mm Y splitter at your computer, and run one set of RCA's with a 3.5mm to RCA adapter to the sub (bridge down to mono via RCA Y adapter at the sub if your sub only has 1 input). Run the other set of RCA's also with a 3.5mm to RCA adapter (you probably already have this) to the Lepai amp. You'd have to use your computer for volume control once everything is set, but it would work.

You could also just look into a 2 channel amp that has a sub pre out like you mentioned. The SMLS Q5 Pro looks amazing according to the reviews on parts express, price seems absolutely fair too, and the specs look great. Also has a built in DAC that'd probably be a lot better than onboard sound too.
https://www.parts-express.com/smsl-...o-stereo-amplifier-usb-optical-coaxial-dac-with-subwoofer-output-2x40w--230-210

WiL11o6 · Feb 27, 2019

pioneerisloud said:
As a cheap alternative, you could run a 3.5mm Y splitter at your computer, and run one set of RCA's with a 3.5mm to RCA adapter to the sub (bridge down to mono via RCA Y adapter at the sub if your sub only has 1 input). Run the other set of RCA's also with a 3.5mm to RCA adapter (you probably already have this) to the Lepai amp. You'd have to use your computer for volume control once everything is set, but it would work.

I'm intrigued with this idea as it would cost me next to nothing. If I am understanding correctly, bear with me, is I need one of these:

https://www.amazon.com/UGREEN-Split...M0ZGK6/ref=sr_1_3?keywords=3.5mm+y+splitter&qid=1551242001&s=electronics&sr=1-3.
and
https://www.amazon.com/AmazonBasics...t=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9061271&hvtargid=pla-303037967706&psc=1

My current Lepai amp and my sub goes into the splitter > my computer? It sounds so simple. I'm not too worried about sound quality if it'll work for less than $20.

I was looking at the SQML Q5 as well if nothing else works. Looking at the pictures, the sub pre-out is also a 3.5mm on the Q5?

Lastly, I'm glad you're still active pioneerisloud. I remember seeing your name pop up helping people almost a decade ago since I've made my account here.

Tiihokatti · Feb 27, 2019

WiL11o6 said:
I'm intrigued with this idea as it would cost me next to nothing. If I am understanding correctly, bear with me, is I need one of these:

https://www.amazon.com/UGREEN-Split...M0ZGK6/ref=sr_1_3?keywords=3.5mm+y+splitter&qid=1551242001&s=electronics&sr=1-3.
and
https://www.amazon.com/AmazonBasics...t=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9061271&hvtargid=pla-303037967706&psc=1

My current Lepai amp and my sub goes into the splitter > my computer? It sounds so simple. I'm not too worried about sound quality if it'll work for less than $20.

I was looking at the SQML Q5 as well if nothing else works. Looking at the pictures, the sub pre-out is also a 3.5mm on the Q5?

Lastly, I'm glad you're still active pioneerisloud. I remember seeing your name pop up helping people almost a decade ago since I've made my account here.

Yes, those cables should work nicely. The biggest issue with that kind of setup is that you can't use the volume knobs on both the sub and speaker amp, and only use Windows volume slider.
Also the SMSL Q5 has a single RCA output for the sub (SW output).

There is also the pretty much forgotten solution: Bass Redirection
It's a feature of soundcards with 5.1/7.1 support. It has different name depending on the manufacturer (Asus: FlexBass, Realtek: Bass Management, Creative: Bass Redirection, etc.).
https://www.evga.com/support/faq/afmviewfaq.aspx?faqid=59674
"If your 2.1 or 4.1 Speaker configuration needs manual crossover frequency adjustment, set the
Speaker / Headphone Configuration to 5.1, and uncheck the boxes for speakers that are not connected to
the rear panel audio ports."

WiL11o6 · Feb 27, 2019

If I'm understanding correctly, the built in volume and crossover knobs on the subwoofer won't work? Meaning if I have the volume at 50% in Windows, it's also 50% to my subwoofer and there's no way for me to turn it down? That's an issue because 50% volume on my sub would be pretty damn loud lol.

Tiihokatti · Feb 27, 2019

WiL11o6 said:
If I'm understanding correctly, the built in volume and crossover knobs on the subwoofer won't work? Meaning if I have the volume at 50% in Windows, it's also 50% to my subwoofer and there's no way for me to turn it down? That's an issue because 50% volume on my sub would be pretty damn loud lol.

Both the speaker amp and subwoofer volume knobs "work". But the moment you change the volume on either one, you will need to change the volume on the other device accordingly to maintain equal volumes on both devices.
The Windows volume slider affects both the sub and speakers at the same time so in that case there is no need for extra fiddling around.

For example, if you want to tone down the bass during night, you will need to change it from the volume knob of the sub.
Also, if you forgot the windows volume to ear-shattering levels during the day and try to tone down the volume with the volume knob on the speaker amplifier... The speaker volume goes down but of course the subwoofer will continue to blast your ears off.

The crossover knob will also work, and it's extremely important to use it in this case as you are feeding the full-range audio signal to the sub. General idea for correct crossover is to set it to the lower frequency limit that is stated in the speaker specs (80Hz-20,000Hz, etc.).

With speaker amplifiers that also have the pre-out for subwoofers, the volume knob of the amplifier affects both the volumes of the speaker-outputs AND the subwoofer output.
And the sub-out usually has some level of crossover too (IIRC 200Hz is typical so the crossover of the sub will still have its uses).

lightsout · Feb 27, 2019

I asked this same question on reddit the other day, with a budge tof $100 and heres what I got:

SMSL Q5 Pro(Silver) - $115 https://smile.amazon.com/dp/B017W139EI/ref=twister_B0187WUBU6?_encoding=UTF8&psc=1

Topping MX3 - $130 https://smile.amazon.com/Topping-MX...=smi_www_rco2_go_smi_g5171374337?_encoding=UTF8&*Version*=1&*entries*=0&ie=UTF8

SMSL AD18 - $145 https://smile.amazon.com/SMSL-AD18-..._1_fkmr0_1?s=electronics&ie=UTF8&qid=1551133532&sr=1-1-fkmr0&keywords=smsl+adq8

These all get great reviews around here and elsewhere. I think the Topping is the current favorite. They all have a sub out as well as DACs, optical, and analog inputs. Just a bit over your budget, but close.

WiL11o6 · Feb 27, 2019

Tiihokatti said:
Both the speaker amp and subwoofer volume knobs "work". But the moment you change the volume on either one, you will need to change the volume on the other device accordingly to maintain equal volumes on both devices.
The Windows volume slider affects both the sub and speakers at the same time so in that case there is no need for extra fiddling around.

For example, if you want to tone down the bass during night, you will need to change it from the volume knob of the sub.
Also, if you forgot the windows volume to ear-shattering levels during the day and try to tone down the volume with the volume knob on the speaker amplifier... The speaker volume goes down but of course the subwoofer will continue to blast your ears off.

The crossover knob will also work, and it's extremely important to use it in this case as you are feeding the full-range audio signal to the sub. General idea for correct crossover is to set it to the lower frequency limit that is stated in the speaker specs (80Hz-20,000Hz, etc.).

With speaker amplifiers that also have the pre-out for subwoofers, the volume knob of the amplifier affects both the volumes of the speaker-outputs AND the subwoofer output.
And the sub-out usually has some level of crossover too (IIRC 200Hz is typical so the crossover of the sub will still have its uses).

Understood. I'm probably going to go this route as I won't use the sub that much and it's only $15 for the cables. It's just for the occasional times I'm home alone, (My girlfriend hates the slightest hint of low frequencies) and want that little extra bass in the bottom end with my Energy RC-10s. I'd probably just set up the volume once, leave it and turn off the sub when I'm done.

lightsout said:
I asked this same question on reddit the other day, with a budge tof $100 and heres what I got:

Thanks for the recommendations, I'd def go the SMSL Q5 for the looks, size, and functionality for when I do want to purchase another amp. I'll keep that in mind.

pioneerisloud · Feb 27, 2019

If you want to go the cheap route, you'll need another 3.5mm to RCA cable regardless. You probably already have one of these going to your Lepai, you will need 2, one to the Lepai one to the sub. If the subwoofer only has 1 RCA input, you'll also need a dual female to 1 male RCA Y splitter to convert the stereo RCA signals down to 1 channel for the sub. If it has 2 RCA inputs (white and red both), then forget that particular Y splitter.

On the computer end, you can either plug the sub's 3.5mm (cable I mentioned above) into the sub / center out on your sound card and use the sound card utility to 5.1, but "disconnect" the speakers that you lack. Or you can split the green out with a 3.5mm Y splitter (headphones Y splitter) and stick to 2.0 sound output on your soundcard. Either option here, you will HAVE to use your Windows volume control as volume. You'll set your Lepai at like 3/4 volume or so (and bass / treble where you like it, personally I like it off). You'll also set your sub to probably noon position or so, set your crossover on your sub around 80Hz or so (to your liking). And once those are all set, you forget it and use Windows for volume.

If you want a physical volume control to be usable like you have already with just the Lepai that'll adjust the entire system volume, you'll need a new amp with a proper LFE output (sub out) such as the Topping or SMLS mentioned above. Nothing "wrong" with using the splitters and cables like mentioned though; I've been doing it for years. I was actually just recently running 3 Lepai TA2020's and a Dayton DTA-120, all off my "home theater PC" to make a surround setup, until I buckled down and bought a proper receiver. It DOES work, it just has its own set of drawbacks, same as any other solution.

robert c james · Feb 28, 2019

doesn't your MB have a multi chanel sound card built in ?
Just wire your sub to the Sub output from your comp.
The sub listed has a built in amp
Windows can be set for surround sound and has it's own gain and crossover settings
no need to buy another amp unless the one in the sub is burnt
If your amp built into your sub is burnt the one you have picked will work for your needs With no extra input needed
It has a built in crossover with a sub output just drill a SMALL hole in the back of your sub to pass speaker wire thru Remove the plat amp so you can connect the speaker wire to the speaker inside the cab. then reinstall the plate amp to seal the cab. no need to plug anything into the built in amp if it's not working.

WiL11o6 · Feb 28, 2019

robert c james said:
doesn't your MB have a multi chanel sound card built in ?
Just wire your sub to the Sub output from your comp.
The sub listed has a built in amp
Windows can be set for surround sound and has it's own gain and crossover settings
no need to buy another amp unless the one in the sub is burnt
If your amp built into your sub is burnt the one you have picked will work for your needs With no extra input needed
It has a built in crossover with a sub output just drill a SMALL hole in the back of your sub to pass speaker wire thru Remove the plat amp so you can connect the speaker wire to the speaker inside the cab. then reinstall the plate amp to seal the cab. no need to plug anything into the built in amp if it's not working.

I never mentioned it, but this is for my laptop setup, so no multi channel sound card.

pioneerisloud · Mar 2, 2019

WiL11o6 said:
I never mentioned it, but this is for my laptop setup, so no multi channel sound card.

More reason for the SMLS with the built in DAC then if you ask me. Onboard audio headphones out on a laptop probably isn't the best source to use. Using a digital out of your laptop would probably clean up the sound tremendously, as well as having a little more power on tap than what the Lepai is capable of would help too.

WiL11o6 · Mar 5, 2019

Update:

Thanks for the help everyone. I went with the Y-splitters and for my application and this works just fine. The volume on my sub is at around 10% and I set in conjunction with the volume knob of my amp and I just use the windows volume slider to adjust. For my needs, the $15 worth of cables is just fine and my sub is no longer collecting dust.

pioneerisloud · Mar 9, 2019

WiL11o6 said:
Update:

Thanks for the help everyone. I went with the Y-splitters and for my application and this works just fine. The volume on my sub is at around 10% and I set in conjunction with the volume knob of my amp and I just use the windows volume slider to adjust. For my needs, the $15 worth of cables is just fine and my sub is no longer collecting dust.

Glad its working out well for you!

Which desktop amp with a sub output?

WiL11o6

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