9 replies to this topic

[Macca]

Well heres a topic bassed on SQ comps.

I lost a large amount of points on a large amount of hissing on a zero bit track of silence. At the time Cyberpunkie said its most likley poor gain adjustment.

So i went and looked at the Input sensitivity of my amp (200mV - 5V) Then the out put voltage of my PXA-H600 (4v Variable)

So i went out and tried putting the gains on the amp to the 4v setting and volume was very low (Well i just did reduce the gains by 50% nearley)
But was dead silent.

So what would the better way of setting gains for SQ?

Will a score in any comp (AND mainley CAASQ) be reduced by a lower volume due to a lower gain setting?

Can other offer there thoughts to volume/gain settings in this thred

Now in my system the Alpine PXA-H600 clames it has GAIN ADUSTMENT which is only adjusted when you set the unit to automatically adjust gain/phase/time alignment via its MIC. Now this doesnt do a good job (I have done better by ear)

But what is it using a basis for gain adjustment, the input voltage from my HU (30/40 volume) or what it pickes up from the amp.

How can Pre-Out voltage be measured with equiptment for an acurate reading?

If its any help my signal Path is as follows..

Pioneer 3350b HU =SINGLE PRE-OUT==> Alpine PXA-H600 Processor ==F/R/S OUT==> Hertz H535 Amp

[Cyberpunky]

I think you will find the pxa is unity gain and so only puts out 4 v if fed 4 V. If your HU is only 2 V then you will only get 2 V out.

Anyway to set gains you need to adjust HU to its max undistorted volume then adjust gains on amp so you have no hiss, at any volume. As we judge system at moderate volumes, having gains low wont cause a problem. You can always crank it a bit more when not competeting as the hiss, if minor, wont be an issue when driving.
peace
Cyberpunky

[bthology]

hi cyberpunky
i have an alpine h/u (that puts out 4v)
and an alpine mrv-1005
now on this amp there is a switch input level, nom or 4v
for some reason when i use 4V, the gains dont really work, iits preset?
but yea its a LOT LOT LOT louder when i use teh NOM setting so i can set the gains in the middle
and its bloody amazing
=D

[ January 07, 2004, 05:46 PM: Message edited by: bthology ]

[Cyberpunky]

The alpine HU is a non clipping 4 volts meaning you can turn it up to full volume and the HU wont clip at all. The switch on amp bypasses the gain control and so you can, set and forget, and know that even with HU at full volume neither it or amp will clip the signal.

If you use nom setting then you are only making it louder on lower volume setting, and risk clipping amp if you turn HU to full volume. You are also raising noisefloor.

Anyway if you use gain adjustment and you are not careful with volume control (or your mates arent), then you risk clipping. If you use 4v sw then you are safe even if you or your mates turn it up to full volume, and you will still get full power out of amp and at lowest possible noisefloor.
peace
Cyberpunky

[NUTTTR]

You will find with most "4v" headunits you will only get 4v out with a tone at full volume! Normal music is generally lucky to hit 2v, i tested with a scope
I had a clarion DRX-9675z and now have an external processor on my current clarion and exact same thing! If you run a tone then you'll get full use of it...
You will find some amps will hiss when the gains are up, others won't... generally this is due to the quality of the pre-amp
Aaron

[Flipmo]

If hu's are only putting out half or so of there rated v's, then what hu's actually match there claimed volts for preouts?

[NUTTTR]

Well, they DO make the "claimed" power, but not with music, they usually don't get pushed that far... If a h/u put out 4v with music, it'd probably put out more like 8v with a tone
Aaron

[Bassaholic]

Exactly... This is also why 3:1 (10dB) gain overlap is recommended.. (Except at SQ comps when the judges complain about the small amount of hiss )

[Cyberpunky]

I wish I could know when a car leaves that they wont do an SPL run ever and so tones will never be played or that they wont play a low bass disc or some techno etc that all has sine wave based signals.

If you know you will never do any of the above and most ppl wont come close to using 3:1 overlap, as for music, apart from low bass and some techno/experimental music, its perfect.

If you are 100% sure of how loud and what gets played, on your system, then 3:1 overlap is best option but as I cant know that from ppls faces, eye colour or hair colour I have to err on side of safety, and so use a 1:1 ratio for gain matching. I wish I could know who are crankers, or techno phreaks just from appearance but I cant, and so gain setting aint the projected use, arent easy to define via ppls looks. I choose to use safer than maimum possible levels.

Sure if you know all possibilities of system use, then gain overlap is an easier choice, but real world means I have to be conservative regardless of real world use.

anyway if ppl knew gains werent volume adjustments then makers could mark gain settings for a 3:1 overlap, but like me, they cant afford to have poorly educated customers, who blow there systems up
peace
Cyberpunky

[Bassaholic]

Fair enough, I should have said 3:1 is recommended for sensible and experienced people....