Guys with aftermarket amps, how did you set your gains?

[808MGuy]

Since the OEM HU does not have a volume level display, how do you set the volume so you can set the input gains on your amps. Do you just crank it all the way up assuming eventually it gets to max and set it that way or do you crank it all the way up and then down a few clicks before you set it?

[Technic]

Originally Posted by 808MGuy

Since the OEM HU does not have a volume level display, how do you set the volume so you can set the input gains on your amps. Do you just crank it all the way up assuming eventually it gets to max and set it that way or do you crank it all the way up and then down a few clicks before you set it?

Personally, my amps gains are always set to minimum if possible to minimize hiss. The gains of either the processor or/and a line driver if used are the ones that I adjust.

For example, for a base analog OEM system I don't use a direct to amps/processor connection, I use a line driver at the OEM HU/Nav outputs first, then to the aftermarket processors/amp and that's what I adjust for the best signal to noise ratio. That's what I did in my E46 M3 Harman Kardon OEM system, no hiss at all.

In the case of my current Premium setup, because of the issues of the bit one high level inputs being saturated with the OEM amp, I was forced to adjust only the underseat subs amp gain because I have to reduce a lot of the input level of the processor to avoid the saturation. At least the OEM mids and tweets amp gain can remain at minimum, so hiss is almost non-existent.

However, once the digital preamp device shows up then I will be able to set the bit one built in line driver to its maximum levels and set all my amps gains to minimum.

[808MGuy]

Originally Posted by Technic

Personally, my amps gains are always set to minimum if possible to minimize hiss. The gains of either the processor or/and a line driver if used are the ones that I adjust.

For example, for a base analog OEM system I don't use a direct to amps/processor connection, I use a line driver at the OEM HU/Nav outputs first, then to the aftermarket processors/amp and that's what I adjust for the best signal to noise ratio. That's what I did in my E46 M3 Harman Kardon OEM system, no hiss at all.

In the case of my current Premium setup, because of the issues of the bit one high level inputs being saturated with the OEM amp, I was forced to adjust only the underseat subs amp gain because I have to reduce a lot of the input level of the processor to avoid the saturation. At least the OEM mids and tweets amp gain can remain at minimum, so hiss is almost non-existent.

However, once the digital preamp device shows up then I will be able to set the bit one built in line driver to its maximum levels and set all my amps gains to minimum.

Even if you're setting line driver gains or DSP input gains instead of amp gains, you still need a baseline input signal to set them with which would be the output of the HU. I assume you'd have the same problem with the premium sound system and the BitOne. You'd have to set a baseline reference level for the BitOne to De-EQ and set its input gains. What did you use as your baseline?

[badfish]

If you just have an amplifier with no processors, you can just turn your system on, turn the volume down on the head unit and adjust the gains to where you can hear hiss and then turn it down so you don't hear any hiss. It's been several months since I set mine and I'll double-check but I think the head unit puts out a fairly nice line voltage so you don't have to turn the gains up too much. The area where I had to adjust is the front/rear levels because the OEM speakers I left in the back were much more efficient.

[Technic]

Originally Posted by 808MGuy

Even if you're setting line driver gains or DSP input gains instead of amp gains, you still need a baseline input signal to set them with which would be the output of the HU. I assume you'd have the same problem with the premium sound system and the BitOne. You'd have to set a baseline reference level for the BitOne to De-EQ and set its input gains. What did you use as your baseline?

That's different from what you are asking for... the amp gains are irrelevant in setting the bit one input level for calibration/de-EQ when using either the low or high level inputs. In my particular case, once I went thru the bit one calibration set up that was it with my OEM volume. I'm not using the bit one DRC remote nor any Master volume, just the OEM volume. The bit one max output level is 4V, so it matches prefectly the PDX input level just for the front and rear speakers; the underseat subs cannot be set for the full 4V output for the reasons already stated, so I make up that deficiency by increasing the PDX gain of those channels only up to the point that I cannot hear any bass pops/distortion up to my max volume.

Your max volume (because there is no way of measuring that in our OEM systems) is set by you, so it can be higher or lower than mine. In my case I just play certain bass notes or certain heavy bass songs and crank the volume up to a level that I consider enough and then I listen for any pops/distortion. If any pop is heard then I lower the gain until I don't hear it any more. With a processor this can be done in too many ways, output level, EQ or even crossover type and not adjust the gains at all at any volume. So there is no one single correct way of adjusting gains.

Regardless of using a processor/line driver or not, the amp gains are normally adjusted either based on how high you can turn the volume up without distortion (by ear) and then adjusting the gains to just below that distortion threshold or by following the JL Audio more technical process of measuring amp output voltages (page 10, http://mobile.jlaudio.com/pdfs/14997.pdf).

The great thing about the BMW OEM HU/CCC/CIC is that the analog outputs are 5V differential. So it could be possible to just leave the gains at minimum if those outputs are connected directly to an amp that have a max input level in the 4-5V range.

[808MGuy]

Originally Posted by Technic

That's different from what you are asking for... the amp gains are irrelevant in setting the bit one input level for calibration/de-EQ when using either the low or high level inputs.

Regardless of using a processor/line driver or not, the amp gains are normally adjusted either based on how high you can turn the volume up without distortion (by ear) and then adjusting the gains to just below that distortion threshold or by following the JL Audio more technical process of measuring amp output voltages (page 10, http://mobile.jlaudio.com/pdfs/14997.pdf).

I was thinking of it in more general terms and not specifically to the BitOne. The reason this question came about is because a lot of DSPs or amp have clipping indicators that help you set the gain. The process is also done without the speakers connected so you can't do it by ear. You would have to set the output of the head unit to some pre-determined level and then set the gains based on that reference level using the clipping indicator. I guess the other way to do it would be like what you said and just listen for distortion which is typically how I've done it in the past but I was just looking for a way to take advantage of the clipping indicator provided.

[Technic]

Originally Posted by 808MGuy

I was thinking of it in more general terms and not specifically to the BitOne. The reason this question came about is because a lot of DSPs or amp have clipping indicators that help you set the gain. The process is also done without the speakers connected so you can't do it by ear. You would have to set the output of the head unit to some pre-determined level and then set the gains based on that reference level using the clipping indicator. I guess the other way to do it would be like what you said and just listen for distortion which is typically how I've done it in the past but I was just looking for a way to take advantage of the clipping indicator provided.

Yes, you can use a clipping indicator if the amp have one, but most often than not clipping indicators are found in processors and in line drivers and not in amps. So we are back to square one: adjust all you can the gains/levels at those devices before the amps , i.e., get the highest low level input possible before the amps. That will give you the cleanest sound possible without any added hiss, IMO.

[808MGuy]

Originally Posted by Technic

Yes, you can use a clipping indicator if the amp have one, but most often than not clipping indicators are found in processors and in line drivers and not in amps. So we are back to square one: adjust all you can the gains/levels at those devices before the amps , i.e., get the highest low level input possible before the amps. That will give you the cleanest sound possible without any added hiss, IMO.

OK. I get the idea of how you've approached this now. I guess if you wanted to be on the safe side and be sure that no devices would ever clip the signal, you could turn the amp gains to min, crank the volume to max, and set everything else in between using the clipping indicator.

I've never used a DSP with a built in line driver so I've never actually used one of these indicators. The only DSP I ever used was the Alpine H701. The amps that I was looking at that started this whole thing was the Kenwood Excelon X4R. Built in DSP with clipping indicators but I'm starting to think that only the crossovers would be useful because the parametric EQ bands are not really infinitely adjustable. So I would probably end up getting an outboard EQ anyway.