SQ Car Audio DAC Advice

[ironchef2025]

I’m looking for recommendations for a specific use case. I compete in automotive sound quality competitions and a potential system layout has landed me in an area that’s new. I have an MOST150 to Toslink converter from my OEM source unit. The DSP/Amplifier requires a 4 volt or higher RCA signal for reduced noise and higher output.

What USB DAC would forum members recommend? Most I’m seeing have 2 volt max RCA’s but can I just use a 4 volt XLR and convert it to RCA with something like a Mogami adapter?

 

[GXAlan]

Have you looked at the Audiotec Fisher DSP amplifiers? I believe they will take SPDIF IN and you get a nice PEQ to adjust.

 

[DVDdoug]

I don't know, but if the car doesn't have to be running during the competition there should be very little electrical noise.

But for your own use while you're driving (or if they are measuring it) doubling the signal improves the signal-to-noise ratio by 6dB IF the noise is coming after the signal (in your EQ, crossover, amplifiers, etc.).

but can I just use a 4 volt XLR and convert it to RCA with something like a Mogami adapter?

Going from balanced to unbalanced can be tricky depending on the equipment. (The other way, from unbalanced-out to balanced-in is almost always OK and you get most of the noise rejection benefits of a fully-balanced connection.)

It can be done with a transformer if you can find the "right one".

 

[staticV3]

What USB DAC would forum members recommend? Most I’m seeing have 2 volt max RCA’s but can I just use a 4 volt XLR and convert it to RCA with something like a Mogami adapter?

A simple, passive adapter cable cannot convert 4V XLR to 4V RCA.

At most, it can convert 4V XLR to 2V RCA, and badly so.

The best way that I can think of, to get a 4V single-ended line signal in a car is with a DACport HD, Apogee Groove, or Topping DX1 combined with a 3.5mm to 2x RCA cable.

 

[ironchef2025]

Have you looked at the Audiotec Fisher DSP amplifiers? I believe they will take SPDIF IN and you get a nice PEQ to adjust.

I ran a Helix P Six and you’re right, they work great for my setup. But now I’m trying to utilize a new to car audio DSP that utilizes a proper upmixer to enable a single seat sound from all seats in the car.

 

[ironchef2025]

A simple, passive adapter cable cannot convert 4V XLR to 4V RCA.

At most, it can convert 4V XLR to 2V RCA, and badly so.

The best way that I can think of, to get a 4V single-ended line signal in a car is with a DACport HD, Apogee Groove, or Topping DX1 combined with a 3.5mm to 2x RCA cable.

How does a passive adapter lose 2 volts of output?

 

[staticV3]

How does a passive adapter lose 2 volts of output?

4V XLR is 2V Hot+2V Cold+GND.

RCA, being single-ended, can only accept GND and one of the two differential signals, ergo 2V.

Splitting XLR like this has other side effects as well, which you can see here:

Topping D10 Balanced Review (USB DAC)

It looks (in my case) ,that the onboard switching power supply + 5.65V / -5.6V, which supplies the output analog circuits (3 OA) behind the DAC, fails / does not start ..). That PSU is powered from 5V inputs. The all other onboard sources (3.3V, 1.2V, 1V) start up normally, they are linear (not...

www.audiosciencereview.com

Topping Pre90 Review (preamplifier)

That cable permanently shorts one Pre90 output to GND. I definitely wouldn't use it. Then I don't understand why XLR to RCA adapters do the same (????) So using something like this would damage Pre90? What devices are the above cables/adapters intended for? What are these devices that have a...

www.audiosciencereview.com

These include increased noise, distortion, and DC offset.

Adapting 3.5mm headphone out to RCA Line in OTOH, like I suggested above, has none of these drawbacks.

 

[ironchef2025]

4V XLR is 2V Hot+2V Cold+GND.

RCA, being single-ended, can only accept GND and one of the two differential signals, ergo 2V.

Splitting XLR like this has other side effects as well, which you can see here:

Topping D10 Balanced Review (USB DAC)

It looks (in my case) ,that the onboard switching power supply + 5.65V / -5.6V, which supplies the output analog circuits (3 OA) behind the DAC, fails / does not start ..). That PSU is powered from 5V inputs. The all other onboard sources (3.3V, 1.2V, 1V) start up normally, they are linear (not...

www.audiosciencereview.com

Topping Pre90 Review (preamplifier)

That cable permanently shorts one Pre90 output to GND. I definitely wouldn't use it. Then I don't understand why XLR to RCA adapters do the same (????) So using something like this would damage Pre90? What devices are the above cables/adapters intended for? What are these devices that have a...

www.audiosciencereview.com

These include increased noise, distortion, and DC offset.

Adapting 3.5mm headphone out to RCA Line in OTOH, like I suggested above, has none of these drawbacks.

Ah, got it, thank you for that! When I checked out the Topping you indicated, I’m seeing that it doesn’t accept an optical/Toslink input. Any other recommendations?

 

[ironchef2025]

It appears that the Topping DX3 Pro + might be able to give me the proper output via the 3.5mm jack. I would just need a step up converter to go from 12 to 15 volts for the power supply. Thoughts?

 

[Doodski]

It appears that the Topping DX3 Pro + might be able to give me the proper output via the 3.5mm jack. I would just need a step up converter to go from 12 to 15 volts for the power supply. Thoughts?

Is that a 12 VDC adapter for the Topping? If so Google, 12 vdc to 15 vdc adapter
A car's usual DC voltage is about 13.4 V DC so it might be enough.

 

[ironchef2025]

Is that a 12 VDC adapter for the Topping? If so Google, 12 vdc to 15 vdc adapter
A car's usual DC voltage is about 13.4 V DC so it might be enough.

Yes, it’s a 12v DC to 15v DC step up:

https://www.amazon.com/gp/product/B097GRZVF5/ref=ox_sc_act_image_3?smid=A3OXSZC8CUOU5G&psc=1

 

[asrsree]

On my Infiniti g37 coupe, I'm running external burr brown pcm63 dac to Topping pre90 to factory amp.. all rca single ended. Plenty of power. As I don't want to change factory Bose Amp and speakers all that, just added 10inch sub in the trunk. Mostly lossless via android tab and uapp. It sounds out of the world. Since I'm bypassing the HU, I'm missing eq for some bad recordings. 90% of the time I don't need eq. Some times I switch different delta sigma dacs for fun. But some says Topping pre90 better with XLR balanced ..I didn't try yet.