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Can you connect powered speakers to a dac + amp ( Topping MX3 ) ?

Cartola

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#1
Hello everyone! First time poster here, I've been lurking this forum for the past few months and am a big fan of this forum's objective and friendly environment [many thanks to Amir]

I'm sure a few people are in a similar situation as I am, so help would be greatly appreciated!

Primary question: Can I control my powered speakers (JBL LSR305 mk ii / 305P) using the speaker amplifier output of a dac + amp (e.g. Topping MX3) ?

I'm thinking of using banana plugs to TS cables to connect the devices and set the MX3's speaker out to 0 db which should equal line out (?) Will this setup have unwanted consequences (affect audio quality) other than the possibility of blowing up your speakers if the MX3 is set too loudly?

Topping MX3 Specs:
1551084046343.png


JBL LSR305 mk ii specs:
1551084122429.png


Alternatively: If I use a 3.5mm jack splitter from the MX3's headphone out to power both earphones and speakers, will they interact with each other in such a way that will degrade audio quality? I'm aware that I will have to match volume levels with the speaker's built in gain.

Context: My computer suffers from severe interference/ground loop. Therefore, I need a dac and/or amp with a separate power source i.e. not powered by the computer's USB. I also have 16 ohm impedance earphones (Tin Audio T2). I would like to control both, ideally with physical buttons/knobs. Budget is up to ~$150 USD.

The Topping MX3 is the (almost) perfect solution for me because:

- It has low impedance for the earphones
- I can afford it
- It has a good volume knob
- It can remember the different volume levels that you've set for your speakers and headphones
- It can switch between outputs

The slight let down is that the nominal THD + N of the MX3 speaker out is only %0.05 which should mean it only has 66db of undistorted signal. But I doubt this matters in my application since I'm listening in a small room and my computer's fans aren't particularly quiet so I probably won't turn it up past where the distortion is appreciable. Plus I don't think my speakers are high quality enough to make the MX3's distortion a matter.

I think the 'proper' solution to my problem is the Topping DX3 Pro but that product is unfortunately riddled with problems apart from being expensive (relative to my setup). Alternative solutions are of course wekcome.

Thank you for whoever takes their time to read this and reply! If you need further information do ask and please feel free to correct any gaps/misunderstanding in my knowledge.
 

Krunok

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#2
Your active JBLs have amps in them so they require XLR (balanced) output from a suitable DAC/preamp, not an output from another amp.

Toppind DX7s would be a good choice to pair with your speakers.
SMSL SU-8 V2 is a good alternative but no headphone amp there.
 
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Cartola

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#3
Your active JBLs have amps in them so they require XLR (balanced) output from a suitable DAC/preamp, not an output from another amp.

Toppind DX7s would be a good choice to pair with your speakers.
SMSL SU-8 V2 is a good alternative but no headphone amp there.
I know that they have an amp in them and by my understanding a balanced connection isn't a must so they can take make mono TS plugs as long as the cables aren't picking up interference. Topping DX7s would be a good choice if price wasn't a concern but I do think it's very overkill for my use case.

But back to my original question, do you know for sure that you can't attenuate the speaker out of a dac + amp like the MX3 so that it outputs an equivalent to line level? I've looked up this topic on the internet and most answers seem to be 'powered speakers already have amps' without actually addressing my main question directly. I just want a definitive answer from someone knowledgeable. I understand basic electrical theory (up to things like transformers, basic 3 phase implementation, basic op amp analysis etc.) so an explanation along those would be great for my knowledge.

The only alternative I have come up with is to use a 3.5mm y splitter cable from the headphone output to both my speakers and my headphones because the MX3 is specified to act as a DAC + pre amplifier in that setup. The only drawback I see in this configuration is that switching off my speakers would require manual disconnection or a separate switching component such as the 'Mackie Big Knob Passive'. What are your thoughts?

Thanks for replying btw :)
 

dreite

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#4
You want what's called a speaker-to-line-level converter. (This sort of thing is pretty common in the car-audio world.)
That will drop the voltage down by 20db or so and make it compatible with typical line-level inputs. However, it's possible you could incur some hum/noise issues with this sort of interfacing.

The simplest version of this would be just a two-resistor L-pad with about a 10:1 ratio. Some of the converters use transformers for the voltage drop and to provide galvanic isolation.

Dave.
 

solderdude

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#5
I recommend to not use the speaker outputs, also not using attenuators.
The reason is the speaker outputs are coming from a class-D amp (balanced at that) and need a good load to work properly.
You would thus have to load the amp with an 8 Ohm dummy load and apply the attenuators.
Also there will be HF switching energy (class-D) which won't damage passive speakers but can cause trouble in the amps of the LSR.
When you look at the specs of the amp you will notice the output voltage difference is a factor 4.6 but the noise levels a factor 28 !
So the outputs are not simply an amplified version of the analog headphone output.

You can use the headphone out.
As the output resistance is very low chances are you can use the splitter and drive the HP's and speakers at the same time.
I would not recommend to leave sensitive IEM's connected while using the speakers.
 

NTomokawa

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#6
I think what you really need here is a USB audio interface with a balanced output, something akin to this.
Or even better.

For the longest time I couldn't figure out how to interface a USB DAC with powered monitors... so I went with passive speakers instead.
 

Krunok

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#7
But back to my original question, do you know for sure that you can't attenuate the speaker out of a dac + amp like the MX3 so that it outputs an equivalent to line level?
it can be done but I don't recommend it.
 

Cartola

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#8
Thank you all for your replies! I've decided to bite the bullet with a Topping DX3 since there is a certified supplier near me so returns shouldn't be a hassle if problems arise with that unit.
@dreite, I am wary of using transformers because transparent ones are apparently expensive if they even exist. @solderdude I didn't think about the high frequency issue. But you've convinced me with the 'signal isn't a simple amplified version' so turning the volume down would probably introduce too much noise if it's even possible. @NTomokawa ahaha selling my speakers isn't an option :p
 
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#9
i have same problem with you..I have this powered bookshelf speaker and i just bought Topping MX3 because i wanted to use it for my speaker and headphone. Can we use the active subwoofer out for the speaker to connect the powered speaker instead? would the sound quality effected?
 

Attachments

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#10
Thank you all for your replies! I've decided to bite the bullet with a Topping DX3 since there is a certified supplier near me so returns shouldn't be a hassle if problems arise with that unit.
@dreite, I am wary of using transformers because transparent ones are apparently expensive if they even exist. @solderdude I didn't think about the high frequency issue. But you've convinced me with the 'signal isn't a simple amplified version' so turning the volume down would probably introduce too much noise if it's even possible. @NTomokawa ahaha selling my speakers isn't an option :p
i saw the spec on ur speakers yes.. you should keep those babies.. SPL and frequency range is noice~.. you should share us a videos of the outcome from your topping + JBL.
 
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