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Class D Switching Power Amplifiers and Power D/A conversion

custom Class D for subwoofer
custom Class D for subwoofer
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Old 18th February 2019, 08:00 PM   #11
Khron is offline Khron  Finland
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The sensitivity of the drivers is quoted at 86dB @ 2W (that's what 2.83Vrms into 4 ohms works out to).

89dB @ 4W
92dB @ 8W
95dB @ 16W
98dB @ 32W
101dB @ 64W

Sound pressure - Wikipedia

That list of examples says a jackhammer from 1m (~3ft) away is around 100dB. Yes, there's also the Fletcher-Munson curves that come into play, but still, 100dB's gonna be noticeably loud.

Especially if you happen to live in an apartment building, that's well within the "pi**ing your neighbours off"-area, especially if we're talking bass

Hell, a few years ago, the next door neighbour had to knock on my door to tell me to turn it down.
I was only using two HiVi B3N 3" fullrange drivers, with a couple of ~30w-ish LM3886 amps driving them
And i didn't even have my first (utterly crappy) subwoofer yet, at that point.
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Last edited by Khron; 18th February 2019 at 08:06 PM.
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Old 18th February 2019, 09:22 PM   #12
mga2009 is offline mga2009
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That's a lot of less power that what I have now...

I think I can limit the power on my Behringer 3000DSP and test it with those numbers... giving about 100Watts...

Any special type of measurements you would like me to do?
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Old 18th February 2019, 09:31 PM   #13
Khron is offline Khron  Finland
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I'm not sure the "power limiting" there works the same way as you might think.

The simplest way would be via the volume control. If you engage the on-board limiter, you'll possibly notice the artifacts of that triggering (which will be some form of distortion).

Room Measurement Tutorial for Dummies Part 1 | Audio Science Review (ASR) Forum
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Old 22nd February 2019, 04:14 PM   #14
stocktrader200 is offline stocktrader200  Canada
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Hypex are reasonably priced, I haven't seen prices for ICEpower.
Any switching or linear supply of the correct voltage and power will work with class D.
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Old 22nd February 2019, 04:59 PM   #15
mga2009 is offline mga2009
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I think ICEpower modules are cheaper than Hypex.

Parts Express have 500W with power supply for USD$311 and the additional module (w/o PSU) is USD$101.

Other alternative is Sure Electronics modules, but their power ratings are kind of difficult to understand to someone like me, as they are rated (mostly) @ 2ohm with a THD of 1%, so to get 500W of clean power @ 4ohm I think I need at least a 2000W module, which are close to USD$200 w/o power supply.

HypeX UcD700HG with HxR is €180 w/o psu, which is another €180 (SMPS1200A700). So USD$400 for 700W and USD$600 for another 700W (psu should power 2 ucd700 modules, right?)

IDK, now that I look the numbers maybe Icepower and HypeX they are the same price watt per dollar...

What about the UcD700 modules, is it good/easy to work? Does it accept unbalanced input, coming form an AVR's LFE output? or do I need an input buffer also?
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Old 23rd February 2019, 03:37 AM   #16
mga2009 is offline mga2009
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I just ordered a few amp. modules. I know they might not be enough for my subwoofers, but it's a start.

HYPEX UCD180LP and ICEpower 50ASX2SE. Both are cheap on ebay.

I've read the HypeX need and input buffer, which it's not necesarry on the ICEpower. Recommendations point to Amplifiers | theslowdiyer

But there are only designs, I preffer to buy an assembled one due to my limited knowledge.

Would this be OK?
HIFI NE5534 DC Buffer Stereo OP-AMP Preamplifier Preamp Board support OPA627 699991670646 | eBay

Also, will this modules accept unbalanced input? or only balanced?

Finally, the HypeX needs a power supply, rated around 48V I think. Any recommendation?

Thanks in advance.
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Old 25th February 2019, 03:06 PM   #17
mga2009 is offline mga2009
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I will reply to some of my own questions...

1-. input buffer are not strictly necessary for neither module

2-. the input buffer sold on ebay would work, but it's not the best design nor the best opamp. According to the listing you can replace the NE5534 OPAMP with the OPA627 which offers better performance.

3-. Both modules are designed for balanced input, so... either I convert signal from unbalanced to balanced or use it as is, which won't offer the best performance/gain.

4-. For the HypeX the recommended power supply is the SMPS1200A180 or the SMPS400A180 but any other switching power supply with 48V will reasonably work.

I will buy a Mean Well Lrs-150-48 for starters. It should be enough for one HypeX module and it's reasonably priced, and best of all, can get it locally.
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Old 25th February 2019, 03:17 PM   #18
Khron is offline Khron  Finland
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Regarding opamps...

NwAvGuy: Op Amps: Myths & Facts

NwAvGuy: Op Amp Measurements

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Old 25th February 2019, 04:22 PM   #19
mga2009 is offline mga2009
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Quote:
Originally Posted by Khron View Post
Thanks Khron,

That's good news... so there shouldn't be any substantial differentce between the opamps.

I ordered the one from eBay. It does not have any gain.

The input buffer goes after or before the unbalanced to balanced converter? I assume after, right before the amp input. right?
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Old 25th February 2019, 05:22 PM   #20
Khron is offline Khron  Finland
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Assuming you have / need a volume potentiometer there, yes, the buffer should be the last thing before the amp input.

If you don't need a volume pot there though, the "balancer" will (or at least damn sure should) have the same effect as a buffer.
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