PG QX 900.1d and Alpine Type X

figjam2407 · Post by **figjam2407** » Tue Jun 16, 2009 7:08 am

Hey guys,
I recently purchased a Phoenix Gold QX 900.1D to run an Alpine Type X 12' sub. I installed it today running 4 gauge and all went to plan. Then I went to set the gains. As I cranked it to just over half gain it started clipping (momentarily flicking the sub on/off). The sub is wired at 2 ohms and is rated at 1000wrms and from what i've read, the PG is about the same.
Can anyone tell me what I can do to rectify the problem??
Is this common for this model?
Will there be something wrong with the amp??
It is running off a stock 360cca battery

Post by **fuzzysnuggleduck** » Tue Jun 16, 2009 7:59 am

Gain settings are there to match the input signal to the preamp section of the amp. So if you have a "hot" signal coming from your HU, you should be able to achieve the amp's full output without cranking the gains. In fact, generally speaking higher input voltages are better.

If you're unfamiliar with the DMM method of settings gains, you should probably read this thread:

http://phoenixphorum.com/gain-setting-w ... vt280.html

figjam2407 · Post by **figjam2407** » Tue Jun 16, 2009 10:47 pm

Hey,
I have 6volt preouts on my head unit.
I took it to some guys today to look at and its doing the same thing. Doesnt seem to go into protection as the blue light stays the same colour. I've tried reading the link but to be honest, i still can't understand the jargin. The amp did the same thing on a different head unit and also on a less powerful sub.
When getting it repaired,
What should I be aware of?? What do people think is wrong with it

bretti_kivi · Post by **bretti_kivi** » Wed Jun 17, 2009 12:09 am

there's no jargon in the link, just pure electronics.

You push power out to your subwoofer.
That power has two components, volts and amps; volts x amps = watts.

Using the formula, 900w@2ohms (which is max output of a 900.1d), gives output of 42V.

Using a test tone CD, you should be able to set the gain so that the output is visible as being 42V. Any higher and you're clipping.

If turning the gain down sorts the problem, it's clipping; you don't say where the head unit's volume control is.

"less powerful sub" makes no sense. Sub that can take less power? Which one? How did you wire it? What head unit? How loud is it? Are you sure there are no supply issues?

Bret

figjam2407 · Post by **figjam2407** » Wed Jun 17, 2009 3:35 am

By less powerfull I mean a 400rms dual 4ohm sub wired at 2 ohm.
My current head unit is a clarion 576USB and has 6v preouts and it was tested on an Alpine unit.
I dont understand why its clipping at only just over half gains. The sub is not even getting loud before it decides to switch off. Then as soon as I turn the head unit volume up and does it constantly. I could run the gains lower but if there's something wrong with the amp I dont want it to be putting a bad signal into my sub.
LOL this is so Annoying.
Could it be that my amp is not recieving enough power at higher levels??
Could it be that the amp is already producing the 900rms at 2 ohm at only half gains and then it just clips when I turn the volume on headunit up (still not much bass as my 400rms is producing about the same as my X before it clips)??

bretti_kivi · Post by **bretti_kivi** » Wed Jun 17, 2009 4:20 am

yes, because the amp is trying too hard. Measure the voltage going out, I think you might be surprised. It sounds like it's trying to amplify a small signal (the 6V should mean you can turn the gain ALL the way down...).
Set the gain to lowest level, turn the volume on the head unit up and see if that helps.

Bret

figjam2407 · Post by **figjam2407** » Wed Jun 17, 2009 4:40 am

Thanks Bret,
I appreciate what your saying.
Would a more powerful amp be a better option??
And Does this mean the sub could get damaged if the amp is doing what its doing??
So you believe from whats been going on that its not a problem with the amp??
Thanks
Brayden

figjam2407 · Post by **figjam2407** » Wed Jun 17, 2009 4:43 am

Oh yeah and quickly,
How do I measure the output with a mulitmeter??

dwnrodeo · Post by **dwnrodeo** » Wed Jun 17, 2009 5:08 am

figjam2407 wrote:Thanks Bret,
I appreciate what your saying.
Would a more powerful amp be a better option??
And Does this mean the sub could get damaged if the amp is doing what its doing??
So you believe from whats been going on that its not a problem with the amp??
Thanks
Brayden

A 900 watt amp should be enough power for your sub. When measuring the voltage at the speaker terminals set your DMM to volts AC. Make sure your headunit EQ is set to flat, and turn all processing off i.e. Bass Boost, Loudness, etc... On your amp make sure the bass boost is off and the gain(sensitivity) knob is set to it's mininum (4 volts). Set your headunit to 3/4 of its max volume and test the AC voltage at the speaker terminals (the far left and right terminals since you will have this amp bridged). Slowly turn your gain/sensitivity knob up until you reach the desired voltage output that Bret stated above.

Post by **Jacampb2** » Wed Jun 17, 2009 5:21 am

figjam2407 wrote:Then I went to set the gains. As I cranked it to just over half gain it started clipping (momentarily flicking the sub on/off).

Are you saying that the sub starts to oscillate on its own, meaning, it just starts to move back and forth at some fixed frequency, rather than playing music? If so, that is not clipping. There is likely something wrong in the amp.

Later,
Jason

figjam2407 · Post by **figjam2407** » Thu Jun 18, 2009 1:38 am

The amp stayed at 31.7 volts from zero gains all the way through to full gains. No change whatsoever.
At soon as sub was hooked up it dropped to 1.8volts

bretti_kivi · Post by **bretti_kivi** » Thu Jun 18, 2009 2:41 am

whoops. You know why? It's class D and that's how they work. I don't think it should drop to 1.8V, though....

Deyamn, I'm not sure you can prove the gains on that at all (I have a 900.1d too..)

Bret

figjam2407 · Post by **figjam2407** » Thu Jun 18, 2009 2:48 am

What do you mean Brett?? by "you can't prove the gains". How does your 900.1 d go?? I picked mine up for $300 AUS. Now know why

bretti_kivi · Post by **bretti_kivi** » Thu Jun 18, 2009 3:28 am

Digital amps work by pushing out a voltage and applying that for a certain amount of time. This is then repeated many times a second, so that the "on" window represents the amount of volume.

Example: you're running at half gain: half of the time the amp will be pushing full power, the other half it won't.
At a quarter gain, a quarter of the time full power, three quarters off.
Because this happens very quickly - maybe thousands of times a second - humans don't normally notice it.

I was thinking for a while that there would be always voltage... what were you playing when you got the 31V? That was AC, yes?

Bret

figjam2407 · Post by **figjam2407** » Thu Jun 18, 2009 3:58 am

It was set to 200 on my V part of multimeter. It doesnt actually say AC but the positive plug isnt in the DC hole so I assume its AC

bretti_kivi · Post by **bretti_kivi** » Thu Jun 18, 2009 7:43 am

..,..32 Ohms output and then 2ohms with the sub?

32V is too low. I will have to take a look at mine when it's running, later.

Bret

Post by **stipud** » Thu Jun 18, 2009 8:20 am

Brett, the same multimeter principle applies to Class-D amps as well. The signal they produce also needs to be a sin-wave, regardless of how it is produced.

Since the QX is rated 900 at 2 ohms you need to get
sqrt(900*2) = 42.42 volts

Since Australia has 50Hz power outlets, you will want to use a 50Hz tone in order to get the most accurate measurement. In north america you would use 60Hz.

Post by **fuzzysnuggleduck** » Thu Jun 18, 2009 9:04 am

stipud wrote:Since Australia has 50Hz power outlets, you will want to use a 50Hz tone in order to get the most accurate measurement. In north america you would use 60Hz.

And the reason for that is because normal multimeters will have their A/C voltage measurement calibrated for the frequency of A/C in the country they are being sold, as opposed to (expensive) True RMS meters which can be used against any A/C frequency and remain accurate.

figjam2407 · Post by **figjam2407** » Thu Jun 18, 2009 4:39 pm

Big thanks guys. I'm learning alot about a topic I didnt know much about. WOW this is great learning.
I'll download myself a 50htz from where?? I read it has to be CD format not MP3. Where are these in that format??

Post by **fuzzysnuggleduck** » Thu Jun 18, 2009 6:18 pm

I just created some WAV tones and uploaded them to the phorum download site.

http://download.phoenixphorum.com/Tones/

You'll find your 50Hz tone there.

Burn it to a normal CD. Yes, a bit of a waste of a CD but keep it around as your "DMM gain setting" CD just in case you need it again

The tones are 60 seconds long, you'll likely want to put your HU on repeat.

figjam2407 · Post by **figjam2407** » Fri Jun 19, 2009 1:12 am

Thanks guys. I'll let you's know how the 50htz sin wave measures on my multimeter.

Post by **stipud** » Fri Jun 19, 2009 6:45 am

Hey Ryan don't suppose you wanna make pink noise as well... far more useful than white

Post by **fuzzysnuggleduck** » Fri Jun 19, 2009 7:33 am

stipud wrote:Hey Ryan don't suppose you wanna make pink noise as well... far more useful than white

Sure, but I was using Audacity and they don't include a pink noise generator. Lemme find something...

bretti_kivi · Post by **bretti_kivi** » Sun Jun 21, 2009 11:14 am

there should also be brown noise on realm of excursion...

figjam2407 · Post by **figjam2407** » Tue Jul 07, 2009 3:09 am

Hey guys,
After having a tech look at the amp, turns out it needs an estimated $300 to get it fixed properly.
So i am leaving it unfixed.
Not a great first impression of phoenix gold

PG QX 900.1d and Alpine Type X

PG QX 900.1d and Alpine Type X

Re: PG QX 900.1d and Alpine Type X