There's a DC voltage present on the balanced audio from the head unit. Wondering if anyone knows why. Does this voltage vary with some function of the HU? Is it controlling something in the OEM amplifier? Did they DC couple the amplifier and the voltage is a result of that?
I'm using an aftermarket amplifier and added series capacitors to decouple the DC and using the shield and balanced + into the amp's unbalanced input (RCA in).
I'm using an aftermarket amplifier and added series capacitors to decouple the DC and using the shield and balanced + into the amp's unbalanced input (RCA in).
my friend i dont know something sure about the balance audio but a couple rx8's
i ve work on i have use high to low converter to drive extra amplifiers...of course
it is not the perfect way to drive rca amplifiers but its usually some mess with the balance signal....
i ve work on i have use high to low converter to drive extra amplifiers...of course
it is not the perfect way to drive rca amplifiers but its usually some mess with the balance signal....
Many of the OEM amps use the bias voltage on the signal lines to switch the amps on.
Using a line output converter is a better option than the capacitors. Amplifiers with unbalanced inputs don't generally have any isolation between the shields for the left and right channels. This means that any time the left and right signals differ, the left and right negative output drivers from the head unit are being stressed.
Using a line output converter is a better option than the capacitors. Amplifiers with unbalanced inputs don't generally have any isolation between the shields for the left and right channels. This means that any time the left and right signals differ, the left and right negative output drivers from the head unit are being stressed.
I'm not using the balanced negative. At one point I had balanced negative decoupled and tied to RCA ground but this had too much noise. Now I have the balanced ground (the shield) tied to RCA ground and the balanced positive decoupled and tied to RCA positive. I have less noise and better separation using the second method.
Is there a DIY or inexpensive active bal to unbal converter that you know of?
Is there a DIY or inexpensive active bal to unbal converter that you know of?
I don't know of any DIY LOCs that would be less expensive than what's readily available. They are stocked by virtually every car audio shop for $20 or less. Read the following page if you have not already done so.
Line Output Converters
Line Output Converters
The frequency response of transformer-based LOCs will be "less then ideal". Any other passive ones that use resistors to reduce the voltage don't have DC removal.
I have used them in the past and thought they sounded fine but my expectations of sound are much higher then they were 20 years ago. Still, they lack DC removal which can damage the OEM head unit.
I may order a few of these to play with but it seems to require a +/- power supply. http://www.ti.com/lit/ds/symlink/ina134.pdf
I'm also looking into DSPs to fix the inevitable time alignment problems in automotive environments. A few of them have balanced in but they get pretty expensive.
I may order a few of these to play with but it seems to require a +/- power supply. http://www.ti.com/lit/ds/symlink/ina134.pdf
I'm also looking into DSPs to fix the inevitable time alignment problems in automotive environments. A few of them have balanced in but they get pretty expensive.
I'm not sure I understand what you mean by "they lack DC removal which can damage the OEM head unit". The transformers eliminate DC from the signal.
why dont you try an active dsp unit like Gladen DSP 4to6 for example or another
similar product....?it works with rca input or high level input signal ''it wiil work
in your case''...and believe me it produses really good-natural sound...
similar product....?it works with rca input or high level input signal ''it wiil work
in your case''...and believe me it produses really good-natural sound...
By shorting it.
Do you know the price?
Google = "Your search - Gladen DSP - did not match any shopping results."
BTW - My HU outputs a balanced (differential) line-level signal, not high-level. Both phases contain a DC offset.
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about 350 euros here in greece for example.....its quite expensive but you can make the set up with the laptop or smartphone and you have a very detailed output from your amplifiers....frequency,filters.tim alligments...etc
If you apply DC to a transformer what happens? It shorts the DC with the winding resistance. I know a transformer doesn't "PASS" DC, but, if applied to a winding, the winding shorts it.
I'll explain again... There is a DC voltage present on each phase of the differential signal coming from the head unit. There are 5 channels totaling of 13 conductors. 5 positive, 5 negative, and 3 shields/grounds. The DC varies between 3~6v and I haven't been able to find any relation between the head unit's settings and this voltage. The voltage may be used to control certain functions of the factory amplifier. The factory amp contains the system's DSP and 5 class-d amplifiers.
I'm removing the amplifier to un-fuk the disaster that Bose created in this car. Fortunately for me, the signal from the head unit is flat. Unfortunately, it's a balanced signal with a DC voltage present. It's known to PROFESSIONAL installers to check for this before "slapping on a LOC" which can damage the head unit. An LOC is fine if it's placed on "speaker level" outputs. This is more complicated then that.
If I can not find an affordable balanced to unbalanced convertor (with decoupling) then I'll have to make them.
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The DC voltage on both the positive and negative signal lines is the same. There is effective no current flow due to the DC. The effective DC applied across the transformer winding is 0v.
Correct. But the DC varies between lines. For example. Right front + may be 3.87v while right front - may be 6.43v (in reference to ground). In that example I'd have 2.56v across a transformer winding. I may try placing caps before a transformer-type LOC to remove the DC offset but the frequency response will still suffer due to the transformers.
Passive LOCs are fine for consumers but completely unacceptable for professional audio.
Passive LOCs are fine for consumers but completely unacceptable for professional audio.
Are you saying that the DC changes to the voltages you listed and remains at those voltages?
If they're rapidly changing, it's AC across the transformer, not DC.
If they're rapidly changing, it's AC across the transformer, not DC.
It's not constant. It does vary (under conditions unknown) but is not the audio signal.
It's probably proportionate to -something- but I don't know what. I believe it's used to signal the amplifier's DSP to do something. Maybe the EQ, compression, loudness, volume compensation, etc.. Sort of like multiplexing.
It's probably proportionate to -something- but I don't know what. I believe it's used to signal the amplifier's DSP to do something. Maybe the EQ, compression, loudness, volume compensation, etc.. Sort of like multiplexing.
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