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Topping D90/A90 with Power Amp and Subwoofers

EdTice

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Aug 18, 2020
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OK, so my two cases are:

A90 via XLR -> first sub -> second sub -> speaker amp

A90 via XLR -> speaker amp
A90 via RCA -> first sub -> second sub

In that case multiple subs need more power than one sub. I was wrong about "taking a copy". Yes it sounds obvious but I thought it was possible it worked differently. The output on the sub is the remains of the input.

Interesting, I didn't know subwoofers' input sensitivity was so low.

Forgive a newbie question:

My power amp has an input sensitivity of 4.0V. I need to supply more voltage to the power amp, so how do I know I won't supply too much to the subwoofers (more than 0.75V for SVS)? In both cases at the top of this reply.

I know I won't exceed 4.0V on the power amp because it would be extremely loud (I'm probably getting 2x JBL LSR6332), and I could measure the voltage with a voltmeter if I really wanted to (I have done this in the past with a preamp that has a lot of headroom).

To make an extreme example, suppose I supplied 3V to power amp and I have just one sub. That means in the second case above, surely the sub will be receiving 1.5V, which is too high.
This is why the SVS has a volume control! The "maximum" volume is 0 which means that 0.75V will drive it to full power. If you set the volume to -10dB, it will attenuate the input signal by 10dB which means you now need 0.75V/(1-0.32) ~ 1.1v to drive it to full power. If you sent the attenuation at -20dB, you would need 0.75V/( (1-0.32)^2) ~ 1.6v to drive it to full power. Et cetera. This is why, when you set things up, you have to "level" the subwoofer (set the volume). Start with a volume of like -30dB and then bring it up until its loud enough, not the other way around (unless you hate your neighbors).

The volume control on an SVS subwoofer is actually a variable gain control not an input attenuator so my example above is not completely accurate but good enough if you don't want to read more. Amplifiers multiply the voltage. So with the volume turned down, the input voltage is multiplied less before its sent to the speaker. Putting 4V into the SVS (with the volume turned down) won't hurt it one bit. I can't find a spec for maximum input voltage (with the gain set correctly) so it can probably handle as much as really high-end preamps put out (in the 10 volt range). On the other hand if you put 4V into it at maximum volume the output would be a painfully loud, distorted mess, that would risk damaging the speaker if it weren't for the built-in protection mechanisms. (Don't try this at home).

I may have over-explained that. The input sensitivity is 0.75V *at maximum volume*. It's higher at lower volumes. Again the key to almost all things in audio is that almost all devices can put out more voltage than the next device in the chain can accept at full rated power. It sounds scary but its not. It's actually necessary for good audio fidelity. There are built-in protection mechanisms so that minor mishaps don't cause thousands of dollars of damage. But the *primary* protection mechanism is your ears. Start with things at low volume/low gain and turn them up slowly. If you can hear audible distortion, turn it back down. That solves pretty much every voltage issue imaginable as long as you aren't using insanely incmpatible equipment combinations.
 
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concorde1

concorde1

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Mar 15, 2021
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I just returned to my question and found a helpful and simple schematic on page 20 of the Arendal 1723 subwoofer product handbook.

It shows the electronic stages are:

Analog inputs -> Programmable gain amplifier -> A/D Conversion -> DSP -> D/A Conversion -> Amplifier For Subwoofer

A/D Conversion draws infinitesimally small power, so the original signal is unaffected.

So it's not like passing into a power amp which will actually draw power from the preamp.

I asked Arendal support a question about passing a low voltage to the subwoofers and concern with noise floor, I will post the correspondence back here if could be helpful.
 

Dasbeerboot

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Feb 8, 2022
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I just returned to my question and found a helpful and simple schematic on page 20 of the Arendal 1723 subwoofer product handbook.

It shows the electronic stages are:

Analog inputs -> Programmable gain amplifier -> A/D Conversion -> DSP -> D/A Conversion -> Amplifier For Subwoofer

A/D Conversion draws infinitesimally small power, so the original signal is unaffected.

So it's not like passing into a power amp which will actually draw power from the preamp.

I asked Arendal support a question about passing a low voltage to the subwoofers and concern with noise floor, I will post the correspondence back here if could be helpful.
Hey, have you been using this setup, and if so, how's it going?

I've been using this setup:

Topping D90 ->
Topping A90 ->
XLR -> Topping LA90 -> Arendal 1961 Monitors
RCA -> Arendal 1961 Subwoofer 1S

It's worked well for me for quite a while. Unfortunately, my A90 lost its right channel last week. If I leave the A90 off for a few hours and turn it back on, it will function again for about an hour then the right channel will go out again. I'm wondering if outputting through both the XLR and RCA is putting too much strain on the amp. Maybe it would be better to run the RCA -> Subwoofer -> Stereo Amp -> Speakers. Thoughts?
 
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concorde1

concorde1

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balanced

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Aug 19, 2023
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Hey, have you been using this setup, and if so, how's it going?

I've been using this setup:

Topping D90 ->
Topping A90 ->
XLR -> Topping LA90 -> Arendal 1961 Monitors
RCA -> Arendal 1961 Subwoofer 1S

It's worked well for me for quite a while.

Did you forget to mention an hipass filter for the monitors or you used it with the full range on the monitors dispite the subwoofer in place there?
 
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