Can you use DAC in a vehicle?

[bmwe39528i]

So I'm coming from having issues with my audio system and I really worked very hard to fix everything.

There's still some issues like static, minor whine etc. that I just can't get rid of.

I understand that going the way of balanced (differential) instead of unbalanced (single ended) audio at least gets rid of ground loops.

So I understand that DAC produces balanced audio output.

I understand that I feed DAC from my headunit. Then from DAC, cables go to the amp, which now produces balanced output?
However the question is, aren't the amps also rated balanced vs unbalanced?

I.e. if I have an amp made for rca (single ended) audio, does it mean I cannot make sound in my vehicle balanced?

Sorry for a noob question

 

[AdamG]

Yes, I use this inexpensive one and it also gives you a port for charging your phone. They have various models for different connection types.

https://www.amazon.com/dp/B089XXL3YD?ref_=cm_sw_r_ud_dp_T17THH87QA1A93D5KVW5

USB C to 3.5mm Audio Headphone Adapter and Charger, 2 in 1 USB-C to Aux Headphone Jack Adapter with 30W PD Fast Charging, Compatible with Samsung Galaxy S21/S20/Note20/Note10, Pixel 5 4 4XL, iPad Pro

I may have missed your specific situation completely as you have not told us how you want to put the DAC in the Audio chain. The above assumes your using an iPhone as the source and your car amp has a 3.5mm input Jack plug.

This one is Apple lighting adapter DAC:

https://www.amazon.com/dp/B09KRNKS36?_encoding=UTF8&psc=1&ref_=cm_sw_r_ud_dp_ST0CFVSY1H6AE1HXDGWN

 

[Lambda]

I.e. if I have an amp made for rca (single ended) audio, does it mean I cannot make sound in my vehicle balanced?

Yes.
You can use a unbalance source with an balanced input but not the other way around.

Have you tied a isolation transformer?

 

[bmwe39528i]

I bought 2 Jensen transformers, they set me back $500 CAD with shipping, duties and taxes lol.

The problem I'm having right now, which I believe I might have solved 5 minutes ago, is the static in my speakers/tweeters.

Now you'll be surprised to hear the following:

- car is not running
- headunit is completely disconnected
- only one speaker is being powered by the amp
- if I connect rca cable to the amp, I hear static in that tweeter and speaker
- the other end of the rca cable is not even attached to anything!
- if I disconnect rca cable from the amp, the noise disappears!

Now this situation is very bad, because transformers go between headunit and amp, however in my case one rca end is not connected anywhere.


Ideally, I would like to not use the headunit, and only use my phone (android) as audio source. And I'd like to connect to DAC wirelessly through Bluetooth, and then input signal from the DAC into the amp. Would it then become balanced?

Or is it better to get a DSP, such as this?

Dayton Audio DSP-408 4x8 DSP Digital Signal Processor for Home and Car Audio https://a.co/d/5sid9VX

 

[bmwe39528i]

Or if there's a better solution? Maybe there's a 4 channel bluetooth amp, at least 75 rms per channel?
Or DSP+amp in one unit that has Bluetooth connectivity?

 

[AnalogSteph]

- if I connect rca cable to the amp, I hear static in that tweeter and speaker
- the other end of the rca cable is not even attached to anything!

If you leave the end of the cable open, it acts as sort of an antenna, with impedance levels being dominated by amplifier input impedance, so noise levels are inherently up as well. Improvise a shorting plug and see what that does. This may still indicate an issue like the amplifier not grounded properly or having issues with switch-mode converter noise getting into the input, or just poor cable shielding.

 

[Zek]

- if I connect rca cable to the amp, I hear static in that tweeter and speaker

Don't connect rca cable to the amp when amp is switced on, you can damage speakers.
Maybe rca cable have bad shielding, if it have any.

 

[DVDdoug]

Of course, a DAC needs a digital input. Does your head unit have a digital output?

the other end of the rca cable is not even attached to anything!

That's unusual for a shielded cable.

Maybe the whole problem is an RCA cable with a broken shield? Have you tried a different cable?

The transformers should solve any ground loop problems, if it's actually a ground loop problem and if the transformers are "correct".

Sometimes noise can get into the head unit and/or the power amplifier through the 12V power so it's not necessarily a ground loop problem. And a higher power amplifier with more gain will amplify any noise more than a low-gain amplifier.

There are filters for the 12V, but if you have a high-power amplifier a high-current filter may be hard to find. I'd try a filter on the head unit first.

 

[DVDdoug]

Dayton Audio DSP-408 4x8 DSP Digital Signal Processor for Home and Car Audio https://a.co/d/5sid9VX

It says there is a Bluetooth adapter available so that should work with your phone. If that unit is located near the power amp you shouldn't get ground loop issues so you shouldn't need transformers or a balanced connection.

Or, you might just look for a Bluetooth receiver.

 

[bmwe39528i]

You guys are all right. I grounded the disconnected side of rca and there was no more noise. The only problem, whenever I plugged that end into headunit, grounded to same ground as amp, I'd still have some noise.
So I removed the headunit and rca cables completely and used a $30 USB dongle to provide signal to my amp from my phone. Now everything is perfect.
The only thing I don't know is what's my limitation with sound quality?
I mean bluetooth dongle probably can only do 320 kbps?
But if I'm streaming from YouTube, it doesn't matter as YouTube is not higher anyways?

 

[bmwe39528i]

Of course, a DAC needs a digital input. Does your head unit have a digital output?

That's unusual for a shielded cable.

Maybe the whole problem is an RCA cable with a broken shield? Have you tried a different cable?

The transformers should solve any ground loop problems, if it's actually a ground loop problem and if the transformers are "correct".

Sometimes noise can get into the head unit and/or the power amplifier through the 12V power so it's not necessarily a ground loop problem. And a higher power amplifier with more gain will amplify any noise more than a low-gain amplifier.

There are filters for the 12V, but if you have a high-power amplifier a high-current filter may be hard to find. I'd try a filter on the head unit first.

I tried like 5 different cables, amazon basics, 2 models of blue jeans, MonoPrice and something else.
I think people who are saying if rca is unattached it acts as an antenna are correct.

I already have 150 amp filter on the alternator.
People suggest buying filters for the amp, so I bought a 50 amp one. Only problem is, amp is supposed to be fed with 4 gauge power wire and these filters have like 10 gauge wires max.

Well now that I removed the rca cables and the headunit, sounds seems to be working without issues.
I wonder if I can connect to a DAC via Bluetooth from my phone, and then connect DAC to the amp, would there be any benefits?

 

[antcollinet]

You guys are all right. I grounded the disconnected side of rca and there was no more noise. The only problem, whenever I plugged that end into headunit, grounded to same ground as amp, I'd still have some noise.
So I removed the headunit and rca cables completely and used a $30 USB dongle to provide signal to my amp from my phone. Now everything is perfect.
The only thing I don't know is what's my limitation with sound quality?
I mean bluetooth dongle probably can only do 320 kbps?
But if I'm streaming from YouTube, it doesn't matter as YouTube is not higher anyways?

If you can hear the difference between bluetooth and uncompressed redbook in a quiet room, you are doing well. In a car - forget it. Don't worry about any limitations of bluetooth.

 

[poxymoron]

Is there really any benefit to balanced input in a vehicle? I use a Helm Bolt USB DAC in the car, 2017 Jaguar XE. Thankfully the car has a jack input, but most newer cars as far as I can see do not. The current XE model doesn't, as far as I know. I've not done blind ABX tests but it's far better than the SBC Bluetooth in the car and the car has a very good sounding Meridian system. The lack of distortion at higher volume is immediately obvious, if nothing else. I would consider a jack input in a car one of the most important features unless it had LDAC bluetooth.

 

[bmwe39528i]

I'm not sure what codec I'm using but apparently best one now is aptx HD.
If my phone had aptx hd, I'd need to find a BT receiver with aptx hd, which I don't seem to find looking in amazon
But if my phone had aptx hd and the receiver BT module had same, I'd be able to plug that received into the amp with 3.5mm jack or rca cables and that would be the top Bluetooth quality available right?

 

[poxymoron]

I'm not sure what codec I'm using but apparently best one now is aptx HD.
If my phone had aptx hd, I'd need to find a BT receiver with aptx hd, which I don't seem to find looking in amazon
But if my phone had aptx hd and the receiver BT module had same, I'd be able to plug that received into the amp with 3.5mm jack or rca cables and that would be the top Bluetooth quality available right?

LDAC is better than Atptx HD but whether you'd notice the difference is a different matter, particularly in a car. As I said in my earlier post, for me the biggest difference in finding an alternative to the car's SBC Bluetooth is the reduced distortion at higher volumes.
This seems to be one of the better units and should work well in a car:

TOPPING BC3 ES9018Q2C Digital to Analog Convertor (DAC)

TOPPING BC3 is a compact Bluetooth decoder that supports Bluetooth 5.0 and LDAC transmission, while outputting digital optical fiber, headphone jack and Line Out interface, and built-in battery. It can be used as a complement to the Bluetooth input of the decoder, can be used as a portable...

shenzhenaudio.com

 

[bmwe39528i]

Thanks for the link. I've seen this device suggested before. My stupid phone galaxy s21 only supports SBC and that's all!
Only two tablets on the market support aptx HD....
Maybe more tablets support ldac. At least I got the receiver figured out, the one you suggested!

 

[bmwe39528i]

My bad, android had ldac forever, it's just that it can only be selected once connected to Bluetooth device

 

[bmwe39528i]

Ended up ordering this unit...

Audison - Car Audio Amplifiers, Speakers, Processors

Car audio DSP amplifiers, speakers, and subwoofers. Go beyond the ordinary solutions that are where our instinct comes in.

www.audison.eu

I'm just too apprehensive of Chinese stuff, especially after dealing with a bad install, I didn't want to take anymore chances...