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Author Topic: QSC SPA series install amplifiers?  (Read 831 times)

Frank Koenig

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QSC SPA series install amplifiers?
« on: May 01, 2020, 11:43:36 am »

I have a little home-audio project for which a QSC SPA4-100 four-channel amp looks like a perfect fit. I like that it's small, no-fans, efficient and has auto-standby and single-pot remote volume. (It looks nice, too.) Curiously, QSC does not provide performance specs for noise and distortion, but I assume that these are beyond reproach.

I'd love to hear of any experience that any of you may have had with these. Thanks.

--Frank

https://www.qsc.com/systems/products/power-amplifiers/energystar-amplifiers/spa-series/spa4-100/
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Robert Healey

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Re: QSC SPA series install amplifiers?
« Reply #1 on: May 01, 2020, 02:44:40 pm »

I have a little home-audio project for which a QSC SPA4-100 four-channel amp looks like a perfect fit. I like that it's small, no-fans, efficient and has auto-standby and single-pot remote volume. (It looks nice, too.) Curiously, QSC does not provide performance specs for noise and distortion, but I assume that these are beyond reproach.

I'd love to hear of any experience that any of you may have had with these. Thanks.

--Frank

https://www.qsc.com/systems/products/power-amplifiers/energystar-amplifiers/spa-series/spa4-100/

I've had them go in a few recent auditoriums for BOH monitoring and paging speaker systems in 70V mode. No issues reported but I am not sure you could judge fidelity on a 4" Atlas ceiling speaker.

I am hoping for a "Q" version that is a native device in a Q-Sys system.
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Caleb Dueck

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Re: QSC SPA series install amplifiers?
« Reply #2 on: May 01, 2020, 04:37:07 pm »

I'd love to hear of any experience that any of you may have had with these. Thanks.

Not much to share other than - if you need a small/cheap amp and are using a lot of QSC anyway, such as QSys and background speakers and/or conferencing - they seem to work well.  If you're looking to drive small subwoofers or studio monitors - there are better options.  They're a price point option.
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Frank Koenig

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Re: QSC SPA series install amplifiers?
« Reply #3 on: May 02, 2020, 11:57:22 am »

...there are better options.  They're a price point option.

Thank you both for the replies. It sounds like there is no particular reliability problem with these and that they're out there being used which is a big plus. Having said that I'm in no way wed to this model and am very happy to hear alternatives.

My requirements are, roughly:

3 channels for stereo full-range and one sub. I expect this to be achieved with 4 channels 2 of which are bridged for the (8 Ohm) sub. This is for use with a TV on which I'll primarily stream movies (TV series) about people with problems. I expect to use a MiniDSP 2x4HD for processing.

>100 W into 4-8 Ohms. More is better.

Low-power standby with auto power-on in the presence of signal. This is a hard requirement.

Preferably no, or very low, fan noise and a compact package is a plus as it would allow me to locate it in the listening area rather than having to run wires to another room.

Freedom from dead-zone ("crossover") distortion that is audible at low power levels. I'm less concerned about THD near clipping.

Noise low enough that it won't bother me in a 200 sq ft room with, say, 95 dB sensitivity speakers. Pretty much anything beyond a crappy car-stereo amplifier should be able to meet this.

Budget $1500 tops. I feel that I should be able to get what I want for less, maybe a lot less. The QSC is ~$900. If I go to $1700 I can get into a Quattrocanali, for example, which is a nice piece, but it has a fan and is really more than I need. It costs more than the damn TV! But I would prefer a brand I've heard of :)

Many thanks.

--Frank
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Caleb Dueck

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Re: QSC SPA series install amplifiers?
« Reply #4 on: May 02, 2020, 10:20:20 pm »

It sounds like you're looking for a studio-focused amp, which I'm not as familiar with.  Otherwise the lower powered amps seem to be consumer focused or budget focused.

Powersoft Mezzo are worth a look.
Lab.Gruppen Lucia
Stewart as well, but most are lower power.
LEA, the new brand with ex-Crown guys.

I think there are some older Crown, Crest, Ashly, and Rane options targeted for this.

If there isn't an auto-stand-by - what about a relay, like a Furman PS-REL and CN-20MP?
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Frank Koenig

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Re: QSC SPA series install amplifiers?
« Reply #5 on: May 04, 2020, 12:22:11 pm »

Powersoft Mezzo are worth a look.

Caleb, thanks. I had overlooked the Mezzo. It appears to be directly competitive with the QSC SPA and costs only a little more. It ticks all the boxes for me. It has the interesting property that all channels are capable of utilizing the full output of the power supply over a wide range of load impedances so it makes efficient use of the supply for asymmetric loads. It also has some built-in DSP which could be useful for other projects. Alas it does not include FIR filters.

When it comes to power management, of course I could rig up a relay and remote switch (or get out the conduit bender), but auto-standby is really nice for me. I like that you can just turn off the TV with the remote and forget about it, especially since others may be at the controls.

--Frank
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Lee Douglas

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Re: QSC SPA series install amplifiers?
« Reply #6 on: May 04, 2020, 01:20:39 pm »

Otherwise the lower powered amps seem to be consumer focused or budget focused.

That's what I was thinking.  Frank, just curious; why not use consumer stuff?  For the cost of any of the amps suggested you could get a decent surround amp and a powered sub that would have a decent amount of DSP and use next to nothing in power when the TV was off.  They would certainly be quiet enough and would not need an outboard crossover.  I have two Yamaha surround amp in my house rack and they are on 24/7 and idle most of the time.  Hell, with the right remote, you could set up a macro to put them in standby with the TV.
« Last Edit: May 04, 2020, 03:26:50 pm by Lee Douglas »
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John Roberts {JR}

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Re: QSC SPA series install amplifiers?
« Reply #7 on: May 04, 2020, 01:32:52 pm »

I have a little home-audio project for which a QSC SPA4-100 four-channel amp looks like a perfect fit. I like that it's small, no-fans, efficient and has auto-standby and single-pot remote volume. (It looks nice, too.) Curiously, QSC does not provide performance specs for noise and distortion, but I assume that these are beyond reproach.
Don't ASSume... there is a spec sheet at the link you provided.  ::)

Install amps are generally cost effective (cheap) but these spec 100dB S/N and flat 20-20k response.

The amplifiers are modern class D so don't look for crossover distortion or other false bogeymen.
Quote
I'd love to hear of any experience that any of you may have had with these. Thanks.

--Frank

https://www.qsc.com/systems/products/power-amplifiers/energystar-amplifiers/spa-series/spa4-100/
I have no first hand experience but modern amplifiers, even these inexpensive install amps generally don't suck.

JR
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Frank Koenig

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Re: QSC SPA series install amplifiers?
« Reply #8 on: May 04, 2020, 02:48:12 pm »

Don't ASSume... there is a spec sheet at the link you provided.  ::)

Install amps are generally cost effective (cheap) but these spec 100dB S/N and flat 20-20k response.

The amplifiers are modern class D so don't look for crossover distortion or other false bogeymen. I have no first hand experience but modern amplifiers, even these inexpensive install amps generally don't suck.

JR

Thanks JR, I did find the noise spec, just missed it the first time. But so far as I can tell there really is no distortion spec, which just strikes me as odd. Even if it's  kind of useless it's a spec that consumers have expected to see since time immemorial. The frequency response spec is weird, too. +/- .1 dB, really? Even an $8000 Powersoft specs to -.5 dB, which is good enough for me, and everyone else it appears. I guess if you got it, flaunt it, and I know that these sheets are written by marketing folks after pressing the engineers for numbers.

As for distortion at low power, I was really only listing requirements as they came to mind. And while I agree that it should be a thing of the past I find it curious that some modern amps only spec THD above some power level, typically .1 or 1 W. Do you suppose that distortion really does go up, beyond the ability of the negative feedback to correct, as the on-time of the output switch goes to zero, or is it just a measurement problem, or something else? I have this superstition that my big Powersoft K-series are a little fuzzy sounding at very low power, but it may be just that. I could try to measure but it might be tricky with all the switching hash on the outputs. I don't know how my old HP Audio analyzer or the ADCs on my computer interface (for Smaart, etc.) would handle that. I might have to build and qualify proper filters, which is a bit of an undertaking.

Anyway, thanks for indulging me.

--Frank
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John Roberts {JR}

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Re: QSC SPA series install amplifiers?
« Reply #9 on: May 04, 2020, 08:16:18 pm »

Thanks JR, I did find the noise spec, just missed it the first time. But so far as I can tell there really is no distortion spec, which just strikes me as odd. Even if it's  kind of useless it's a spec that consumers have expected to see since time immemorial. The frequency response spec is weird, too. +/- .1 dB, really? Even an $8000 Powersoft specs to -.5 dB, which is good enough for me, and everyone else it appears. I guess if you got it, flaunt it, and I know that these sheets are written by marketing folks after pressing the engineers for numbers.

As for distortion at low power, I was really only listing requirements as they came to mind. And while I agree that it should be a thing of the past I find it curious that some modern amps only spec THD above some power level, typically .1 or 1 W. Do you suppose that distortion really does go up, beyond the ability of the negative feedback to correct, as the on-time of the output switch goes to zero, or is it just a measurement problem, or something else? I have this superstition that my big Powersoft K-series are a little fuzzy sounding at very low power, but it may be just that. I could try to measure but it might be tricky with all the switching hash on the outputs. I don't know how my old HP Audio analyzer or the ADCs on my computer interface (for Smaart, etc.) would handle that. I might have to build and qualify proper filters, which is a bit of an undertaking.

Anyway, thanks for indulging me.

--Frank
Class D amps are different animals with different behaviors... I don't have the time or energy to explain where their flaws may be hiding, but it is not crossover distortion.

JR

PS: FWIW I am using 6x class D amps for my living room TV surround system... Sounds good enough for me... (not QSC but I expect they are OK too).

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Re: QSC SPA series install amplifiers?
« Reply #9 on: May 04, 2020, 08:16:18 pm »


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