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post #1 of 98 Old 01-27-2019, 12:36 PM - Thread Starter
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Stereo mini amp with subwoofer out?

I'm looking for a small (narrow) mini amp (Class D is OK) to power a set of bookshelf speakers on my computer desk. I also want it to have a subwoofer pre out. Can you suggest anything out there under $100 that fits the requirements?

Or should I forget the subwoofer pre out and just use speaker level connections to feed the subwoofer?

I am currently using a little Onkyo mini-receiver from a small executive system, but I feel like it's rather weak and not doing my bookshelf speakers justice.

So far, I found this:
https://www.parts-express.com/smsl-q...2x40w--230-210

But I was hoping to spend less, plus this one is only 2x20W at 8 Ohm, but maybe it's enough?


Thanks!

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post #2 of 98 Old 01-27-2019, 02:15 PM
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Stereo mini amp with subwoofer out?

Check out the SMSL AD18 or this
Micca OriGain Compact Stereo Integrated Amplifier and DAC, 50W x 2, 96kHz/24-Bit, USB and Optical S/PDIF (Black) https://www.amazon.com/dp/B01LXV4O6B..._55ItCbWGY1S77

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post #3 of 98 Old 01-28-2019, 01:18 PM - Thread Starter
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Thanks.

I'm also looking at Fosi TB10A, even though it doesn't have sub pre out. I've decided I'm OK just using the speaker level signal to feed the sub.

Some reviews on SMSL AD18 noted its sub out is not very good, but unfortuntely they did not go into specifics.

The Micca one does look interesting.

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post #4 of 98 Old 01-28-2019, 01:29 PM
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Keep in mind just because a system has a subwoofer out doesn't mean it necessarily has bass management, in fact I believe most don't.
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post #5 of 98 Old 01-28-2019, 01:39 PM
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Stereo mini amp with subwoofer out?

Indeed, they don’t. The next best thing after bass mgmt would be to have some auto crossover cut off at like a default 80 hz.
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post #6 of 98 Old 01-28-2019, 01:46 PM
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Quote:
Originally Posted by Pete7874 View Post
I'm looking for a small (narrow) mini amp (Class D is OK) to power a set of bookshelf speakers on my computer desk. I also want it to have a subwoofer pre out. Can you suggest anything out there under $100 that fits the requirements?

Or should I forget the subwoofer pre out and just use speaker level connections to feed the subwoofer?

I am currently using a little Onkyo mini-receiver from a small executive system, but I feel like it's rather weak and not doing my bookshelf speakers justice.

So far, I found this:
https://www.parts-express.com/smsl-q...2x40w--230-210

But I was hoping to spend less, plus this one is only 2x20W at 8 Ohm, but maybe it's enough?


Thanks!
Depending on the speakers your using 20w might be plenty since its near-field. Look at the sensitivity rating of the speakers, if your looking at a pair of bookshelf speakers that are say 90db/1w/m sensitivity they will produce about 90 db from 1 meter. 90db is about as loud as a lawn mower.
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post #7 of 98 Old 01-28-2019, 03:27 PM - Thread Starter
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Quote:
Originally Posted by m. zillch View Post
Keep in mind just because a system has a subwoofer out doesn't mean it necessarily has bass management, in fact I believe most don't.
Oh, I know. I am not looking for bass management. Thanks.
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post #8 of 98 Old 01-28-2019, 04:45 PM - Thread Starter
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Originally Posted by liffie420 View Post
Depending on the speakers your using 20w might be plenty since its near-field. Look at the sensitivity rating of the speakers, if your looking at a pair of bookshelf speakers that are say 90db/1w/m sensitivity they will produce about 90 db from 1 meter. 90db is about as loud as a lawn mower.
The speakers are PSB Alpha B (89 dB sensitivity).

My current receiver delivers 2x20W @ 8 Ohm. When I sit in front of my computer, this is plenty enough, but sometimes I like to crank it up a bit more when I'm not sitting at my desk.

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post #9 of 98 Old 01-28-2019, 07:39 PM
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Quote:
Originally Posted by Pete7874 View Post
Quote:
Originally Posted by liffie420 View Post
Depending on the speakers your using 20w might be plenty since its near-field. Look at the sensitivity rating of the speakers, if your looking at a pair of bookshelf speakers that are say 90db/1w/m sensitivity they will produce about 90 db from 1 meter. 90db is about as loud as a lawn mower.
The speakers are PSB Alpha B (89 dB sensitivity).

My current receiver delivers 2x20W @ 8 Ohm. When I sit in front of my computer, this is plenty enough, but sometimes I like to crank it up a bit more when I'm not sitting at my desk. [IMG class=inlineimg]/forum/images/smilies/smile.gif[/IMG]
You can always go for more lol this IS avs after all. I actually really dig my klipsch pro media 2.1 set up at my computer. Although I WOULD like to find a small 5.1 amp.
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post #10 of 98 Old 01-29-2019, 12:06 PM
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IF your Sub-Woofer has L/R Speaker Level In/Out Connections [in addition to L/R RCA], then you can use ANY 2-Channel Amp or Mini-Amp, such as fol. that use push-pull 2xTPA3116D2 Texas Inst Chips on each of 2 channels (4 total), providing 2x100W into 4-ohms (20 Hz - 20 kHz, 0.04% THD) or 2x60W into 8-ohms: [S-W controls LFE Crossover Frequency & Bass Re-Direction]
http://www.ti.com/product/TPA3116D2
http://www.ti.com/lit/ds/symlink/tpa3116d2.pdf
https://www.amazon.com/【Update】-Audi.../dp/B076P2VS9H
https://www.amazon.com/BT20A-Bluetoo.../dp/B07BQC7GNL

If NOT, then you can use a LINE OUTPUT CONVERTER paralleled across L/R Speaker Outputs of ANY Amp or Mini-Amp, to drive L/R RCA Inputs on your Sub-Woofer, such as following examples: [S-W controls LFE Crossover Frequency but NO Bass Re-Direction from L/R Speakers]
https://www.amazon.com/s/ref=nb_sb_s...=21QPN4WAGB0WW

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post #11 of 98 Old 01-30-2019, 07:04 AM
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Quote:
Originally Posted by Pete7874 View Post
I'm looking for a small (narrow) mini amp (Class D is OK) to power a set of bookshelf speakers on my computer desk. I also want it to have a subwoofer pre out. Can you suggest anything out there under $100 that fits the requirements?

Or should I forget the subwoofer pre out and just use speaker level connections to feed the subwoofer?

I am currently using a little Onkyo mini-receiver from a small executive system, but I feel like it's rather weak and not doing my bookshelf speakers justice.

So far, I found this:
https://www.parts-express.com/smsl-q...2x40w--230-210

But I was hoping to spend less, plus this one is only 2x20W at 8 Ohm, but maybe it's enough?


Thanks!
In my opinion, with small main speakers, it's much better to drive the sub with the amp's speaker-level outputs because the sub's speaker-level output will typically have the low bass filtered out, which offloads the main speakers from trying to produce bass signals than can't produce anyway.

I've been into stealth systems lately. The cheap Lepai LP-2020TI amp is deathly ugly in my opinion, but it's sound quality is very good among t-amps. I hide the amp, bluetooth receiver, and a low profile subwoofer behind the refrigerator in our kitchen, with only two small speakers under cabinets, so it is a stealth system that rocks and the source content is controlled completely by a ipad/iphone (spotify, pandora, TV streaming, etc). The Lepei comes with a 2-amp power supply, so you need to get a larger power supply to produce full power.

I would try your Onkyo again using speaker-level outputs to drive the sub (and the sub's speaker-level outputs to drive the mains) to see how that sounds before changing out the amp. Which Onkyo model is it?
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post #12 of 98 Old 01-30-2019, 07:14 AM - Thread Starter
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Originally Posted by pjp View Post
In my opinion, with small main speakers, it's much better to drive the sub with the amp's speaker-level outputs because the sub's speaker-level output will typically have the low bass filtered out,
Yeah, unfortunately, reading the owner's manual of my Velodyne VX-11 sub, I don't believe that is the case. It still sends full frequency spectrum to the speakers.
Quote:
Which Onkyo model is it?
CR-445.

https://www.onkyousa.com/Products/mo...class=Audiosys

Although the specs on the above page are wrong. If you read the owner's manual, it states:

Power Output:
- 2ch x 40 W (4 Ohm, 1 kHz, 10% THD, 2ch driven, FTC)
- 2ch x 20 W (8 Ohm, 20 Hz–20 kHz, 10% THD, 2ch driven, FTC)

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post #13 of 98 Old 01-30-2019, 07:55 AM
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Originally Posted by Pete7874 View Post
Yeah, unfortunately, reading the owner's manual of my Velodyne VX-11 sub, I don't believe that is the case. It still sends full frequency spectrum to the speakers.
Bummer. Small world, I have a Velodyne VX-10 on my computer system that is about 1 foot from where I'm typing (it's identical to the VX-11 except is has class A/B amp instead of class d).

I think the CR-445 does have an RCA sub output, so you should be able to connect it directly. Or are you already doing that and you just aren't happy with the sound in that configuration?

I don't think there is any sonic advantage to line level connection over speaker-level connection, so a line level output wouldn't be very important to me in a budget amp. I like the idea of line level better, but I don't think it performs any better (<- happy to be corrected if somebody has info to the contrary).

Last edited by pjp; 01-30-2019 at 08:44 AM.
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post #14 of 98 Old 01-30-2019, 10:18 AM - Thread Starter
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I think the CR-445 does have an RCA sub output, so you should be able to connect it directly. Or are you already doing that and you just aren't happy with the sound in that configuration?
Yeah, I'm already doing that.

The CR-445 really isn't bad. I just got an upgrade itch, and researching if there is anything on the low budget that could potentially help drive the bookshelf speakers better / with more headroom. I'm OK with using speaker-level connections to the sub if the new amp doesn't have a dedicated RCA pre-out.

At this point, I feel like the Fosi TB10A with dual TPA3116D2 chips would be my best route, but it's currently out of stock on Amazon. But I'm not in a rush.

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post #15 of 98 Old 01-30-2019, 06:53 PM
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In the cheap department the Lepai t-amps aren't too bad. I've owned one a while back and found it works pretty good, but they peter out fast at higher volumes. A step or two up and the Topping amps are pretty decent. I've never owned or heard one, but there are a lot of favorable reviews online.

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post #16 of 98 Old 01-31-2019, 02:11 PM
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Alt. Source for Fosi TB10A Mini-Amp with 100+100W into 4-ohms...or 2x60W into 8-ohms....which is REAL POWER: 20 Hz - 20 kHz at less than 0.04% THD:
https://fosiaudio.com/collections/2-...h-power-supply

Alt. Sources for Fosi BT20A [adds Bluetooth Receiver] with 100+100W into 4-ohms...or 2x60W into 8-ohms....which is REAL POWER: 20 Hz - 20 kHz at less than 0.04% THD:
https://fosiaudio.com/collections/fr...-home-speakers
https://www.amazon.com/dp/B07BQC7GNL...rum-convert-20

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post #17 of 98 Old 01-31-2019, 02:31 PM
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Quote:
Originally Posted by Pete7874 View Post
Yeah, unfortunately, reading the owner's manual of my Velodyne VX-11 sub, I don't believe that is the case. It still sends full frequency spectrum to the speakers.
Manual for Velodyne VX-11 doesn't really SAY whether it RE-DIRECTS Low-Freqs from L/R to S-W....and for sure it does NOT say that they are unfiltered either. Connect Amp L/R Outputs to Velodyne Speaker Inputs and Speakers to Outputs....and then adjust LOW PASS FREQUENCY knob on VX-11 while you listen to L/R Speakers. I'm pretty sure that you will hear the Low-Freqs disappear from the Main L/R Speakers as you increase the [LFE Crossover] Frequency, verifying that Bass Re-Direction in indeed working as it is SUPPOSED to:
http://velodyneacoustics.com/pdf/vx-...anual_revb.pdf
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post #18 of 98 Old 01-31-2019, 02:44 PM
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I'm confident the sub's speaker level outputs are full range. The test to confirm this is incredible easy: temporarily connect it to a full range speaker and see what you get out of it: just highs or high frequencies + bass too.
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post #19 of 98 Old 01-31-2019, 02:59 PM
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Quote:
Originally Posted by pjp View Post
In my opinion, with small main speakers, it's much better to drive the sub with the amp's speaker-level outputs because the sub's speaker-level output will typically have the low bass filtered out, which offloads the main speakers from trying to produce bass signals than can't produce anyway.
Is this actually true? I didn't think any sub did this because the components needed to filter a high level signal vs line level are cost prohibitive and the outputs are just bridged with the inputs on the inside of the enclosure.


EDIT: I should have read zillch's post first
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post #20 of 98 Old 01-31-2019, 04:35 PM - Thread Starter
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Originally Posted by holl_ands View Post
Manual for Velodyne VX-11 doesn't really SAY whether it RE-DIRECTS Low-Freqs from L/R to S-W....and for sure it does NOT say that they are unfiltered either. Connect Amp L/R Outputs to Velodyne Speaker Inputs and Speakers to Outputs....and then adjust LOW PASS FREQUENCY knob on VX-11 while you listen to L/R Speakers. I'm pretty sure that you will hear the Low-Freqs disappear from the Main L/R Speakers as you increase the [LFE Crossover] Frequency, verifying that Bass Re-Direction in indeed working as it is SUPPOSED to:
http://velodyneacoustics.com/pdf/vx-...anual_revb.pdf
That sub only has a low-pass crossover. It would have to also have a high-pass crossover to do what you're describing above.

But yeah, easy enough to verify.

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post #21 of 98 Old 01-31-2019, 04:53 PM
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Originally Posted by CrusherW9 View Post
Is this actually true? I didn't think any sub did this because the components needed to filter a high level signal vs line level are cost prohibitive and the outputs are just bridged with the inputs on the inside of the enclosure.
That's an interesting question. The reason I believed many subs do this is from an article a long, long time ago, I think from "Stereo Review" before they changed the name to "Sound & Vision", where they said it was better to use speaker-level connections to subs to offload the mains. That article stuck in my head, so I've never really given any thought about the internals of speaker outputs on subs since reading it. Now I'm curious to know if, or how many, subs do high-pass filtering on speaker outputs.
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post #22 of 98 Old 01-31-2019, 04:56 PM
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I kind of skimmed through this video, but it seems to discuss amps with subwoofer outs (not favoring amps that have sub outs for 2-channel) and it discusses speaker level connections. I didn't have time to watch the whole thing, so I won't try to summarize, but it might be interesting viewing for this topic -> https://www.psaudio.com/askpaul/the-...t-a-subwoofer/

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post #23 of 98 Old 01-31-2019, 06:39 PM - Thread Starter
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Quote:
Originally Posted by holl_ands View Post
Manual for Velodyne VX-11 doesn't really SAY whether it RE-DIRECTS Low-Freqs from L/R to S-W....and for sure it does NOT say that they are unfiltered either. Connect Amp L/R Outputs to Velodyne Speaker Inputs and Speakers to Outputs....and then adjust LOW PASS FREQUENCY knob on VX-11 while you listen to L/R Speakers. I'm pretty sure that you will hear the Low-Freqs disappear from the Main L/R Speakers as you increase the [LFE Crossover] Frequency, verifying that Bass Re-Direction in indeed working as it is SUPPOSED to:
http://velodyneacoustics.com/pdf/vx-...anual_revb.pdf
Just rewired it and tested. The speakers are receiving full bandwidth. No filter is being applied to them, and turning the crossover knob on the sub makes no difference to the sound of the speakers.

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post #24 of 98 Old 01-31-2019, 06:40 PM
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Quote:
Originally Posted by pjp View Post
That's an interesting question. The reason I believed many subs do this is from an article a long, long time ago, I think from "Stereo Review" before they changed the name to "Sound & Vision", where they said it was better to use speaker-level connections to subs to offload the mains. That article stuck in my head, so I've never really given any thought about the internals of speaker outputs on subs since reading it. Now I'm curious to know if, or how many, subs do high-pass filtering on speaker outputs.
Very few if any filter their speaker level outs.

It's good to filter away the taxing (hard to reproduce) bass from the main speakers at the line level stage [pre-amplification] so neither the speakers nor the main speaker's amp have to reproduce it and to re-direct this deep bass off to the more capable, built specifically for it, powered sub. This is "bass management".

It's also theoretically best to get the deep bass sucked off pre-amplification becuase it is technically "cleaner" at this point since it hasn't gone through the main amp [unnecessarily, since it needs to be brought down to pre-amp level first before the sub amp can deal with it] where it can only pick up additional hum, hiss, distortion, and frequency response skewing [although this is usually innocuous].
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post #25 of 98 Old 01-31-2019, 06:46 PM
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Quote:
Originally Posted by Pete7874 View Post
I'm looking for a small (narrow) mini amp (Class D is OK) to power a set of bookshelf speakers on my computer desk. I also want it to have a subwoofer pre out. Can you suggest anything out there under $100 that fits the requirements?

Or should I forget the subwoofer pre out and just use speaker level connections to feed the subwoofer?

I am currently using a little Onkyo mini-receiver from a small executive system, but I feel like it's rather weak and not doing my bookshelf speakers justice.

So far, I found this:
https://www.parts-express.com/smsl-q...2x40w--230-210

But I was hoping to spend less, plus this one is only 2x20W at 8 Ohm, but maybe it's enough?


Thanks!
Sounds like the Leppai / Lepai / Leppy (brand names vary) 168-HA is exactly what you need. $35 or so, 20 watts per channel stereo, 68 watts for sub with crossover and separate sub volume. I use several of these in video game conversions. They'll probably be perfect for you.
https://www.amazon.com/dp/B0070Z87YO
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post #26 of 98 Old 01-31-2019, 07:19 PM
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Originally Posted by m. zillch View Post
Very few if any filter their speaker level outs.

It's good to filter away the taxing (hard to reproduce) bass from the main speakers at the line level stage [pre-amplification] so neither the speakers nor the main speaker's amp have to reproduce it and to re-direct this deep bass off to the more capable, built specifically for it, powered sub. This is "bass management".

It's also theoretically best to get the deep bass sucked off pre-amplification becuase it is technically "cleaner" at this point since it hasn't gone through the main amp [unnecessarily, since it needs to be brought down to pre-amp level first before the sub amp can deal with it] where it can only pick up additional hum, hiss, distortion, and frequency response skewing.
I don't know how common it is, but this article (https://audiophilereview.com/subwoof...ubwoofers.html) makes reference to some subs having a high pass filter, but they indicate it's typically a very simple fixed filter (just a single capacitor). I guess if it did have this type of circuit, the test of moving the crossover knob wouldn't indicate whether or not it had a filter because it sounds like the high-pass filter is typically fixed (independent of sub crossover setting). The only way to test if there is a high-pass filter would be to compare bass output between direct speaker connection to the amp against connection to sub speaker-level outputs.

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Originally Posted by Relevant excerpt from article above:
By the way, this method works whether you connect an extra set of speaker cables to the subwoofer's speaker-level inputs, or use a line-level connection to the sub from your preamp or integrated amp. Some subs have high-pass-filtered speaker-level outputs you can run to your main speakers. You can try using these, but the effects are unpredictable because they just use a single capacitor in series with the speaker to do the filtering, and its effects will vary depending on the speakers you're using.
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post #27 of 98 Old 01-31-2019, 07:28 PM
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Sounds like the Leppai / Lepai / Leppy (brand names vary) 168-HA is exactly what you need. $35 or so, 20 watts per channel stereo, 68 watts for sub with crossover and separate sub volume. I use several of these in video game conversions. They'll probably be perfect for you.
https://www.amazon.com/dp/B0070Z87YO
I use also use one of these in a home-built arcade. It works great in that capacity, but I don't think it works too well as a standalone amp because the volume controls are weird. I can't remember the details exactly, but I think it has independent volume knobs for the sub output and the mains, so you use those amp volume knobs to balance the mains and sub, but then must control the overall volume on the input to the amp if you want to maintain main/sub balance. So it acts more like a 2.1 amp rather than an integrated amp. Also, he has a powered sub, so I'm thinking he doesn't need the .1 amp.

It's very cool to see somebody else using these in a video game -- perfect application for it.
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post #28 of 98 Old 01-31-2019, 07:32 PM
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Originally Posted by pjp View Post
I use also use one of these in a home-built arcade. It works great in that capacity, but I don't think it works too well as a standalone amp because the volume controls are weird. I can't remember the details exactly, but I think it has independent volume knobs for the sub output and the mains, so you use those amp volume knobs to balance the mains and sub, but then must control the overall volume on the input to the amp if you want to maintain main/sub balance. So it acts more like a 2.1 amp rather than an integrated amp. Also, he has a powered sub, so I'm thinking he doesn't need the .1 amp.

It's very cool to see somebody else using these in a video game -- perfect application for it.
The knobs are:
Bass
Treble
Volume
Sub Volume
Crossover

Sub volume is the volume of the sub but once set, the volume turns both sub and volume up and down. So it should be ok as an integrate amp in my opinion.
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post #29 of 98 Old 01-31-2019, 07:40 PM - Thread Starter
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Originally Posted by markmon1 View Post
Sounds like the Leppai / Lepai / Leppy (brand names vary) 168-HA is exactly what you need. $35 or so, 20 watts per channel stereo, 68 watts for sub
What if my sub already has an amp built-in?

I think I still like the Fosi one better, but thanks.

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post #30 of 98 Old 01-31-2019, 07:40 PM
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The only way to test if there is a high-pass filter would be to compare bass output between direct speaker connection to the amp against connection to sub speaker-level outputs.
That sounds like a good test. Why don't you do it? Here's a test signal:
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