Calibrating Trim Pots, Pots not responding

[D-Street]

I have PTools HD2 Accel, 192 I/O

I have already run a calibration template and can see I am coming out -10db.
I am trying to get to 0db. The problem is that my trim pots don't seem to be changing anything. I have been told to reset the 192 to see if this fixes the problem. I guess I am not sure how to reset this and was wondering if anyone has had problems with their trim pots in the same.

Is there a quick solution to resetting the pots?

[mixboy bob]

What do you mean by "0db" and "-10db"?

On a VU meter? Tell us more about your calibration setup. You should really be using a voltmeter to do this, but if you have some VU's that you KNOW are calibrated, it can work in a pinch.

What reference level are you trying to hit? -20, -18, -14?

We need more info.

Let us know,

Rob Burrell
aka mixboy

[mixboy bob]

And the pots don't have a reset, they are mechanical. YOU are the reset!

Rob B

[D-Street]

Thanks Mixboy.

I was throwing out a vague post to get a hit. I ran an out to the VU meter which confirms my low levels coming out for reference. I was told how to use the voltmeter to test as well, but this also just confirms my low levels out of the 192 I/O (-10db).

The problem is either way I do it, the pots do nothing. Both the manual and the boys at PTools say to reset the I/O. "Hold the 'SET' button down while powering on and off the I/O. Maybe I'm missing something, but nothing seems to reset the I/O either.

What I am doing is running a temp studio until the pro-studio is finished downstairs,
so I'm not exactly sure what reference level I'm trying to hit. I'm just trying to get a higher out to finish a couple projects before we pull cable and test the main control room.

[mixboy bob]

You didn't explain what you mean by "-10". Where is that reading coming from? An analog VU meter? And what WAS the reading on the voltmeter.

If you are following the PT calibration instructions, and you are reading -10 in PT, you have twisted the pots 2-4db hotter than they can go. You will have to turn them down A LOT to start seeing a change.

You also didn't tell me what "0db" equals. If you are trying to hit "0" in PT, you are misunderstanding calibration.

Give me more info, and I can help. But first, I have to know what you know!

peace

Rob Burrell
aka mixboy

[Sean Russell]

As there are a lot of mixed I/O here, I cal all the 192's to -14db. In calibration mode, I cal the outputs from PT (with the signal generator set to -14) to the volt meter and trim the 192 I/O until I see 1.23 on the volt meter.

-14 = 1.23v on the volt meter on outputs. Then you do the same for the inputs. I've seen it where there's a DB25 cable looping the outs back to the in's. That's what all of us are wondering about - what your volt meter says. I've never done it on a VU.

It sounds to me like you're trying to crank the 192 to -10 (from signal generator?) or you're reading the VU/voltmeter wrong. I'm pretty sure I'm just not understanding the post.

Someone else here can verify how hot the 192 can go - but I got one used once that was jacked all the way up, almost!!

So fill is in - how exactly do you have it set and what exactly is your VM saying?

[D-Street]

Ok. On an analog VU, I am coming out -10db. In the Calibration Template i have set everything to 0db like it says. On the volt meter I am reading .775

I was only using the VU to confirm the low levels coming out of the 192.

I am picking up a more accurate volt meter now and will do away with the VU as suggested.

So what I'm dealing with here is a confirmed read out on both meters while the trim pots are not effecting the levels. This is where the boys at PTools told me to try and reset the I/O. ??

So what you are saying is you set the calibration for -14db of headroom while reaching 1.23v (or an equivalent of a +4db out)? or is calibration at 0, 1.23v=+4db?

The manual says while at 0db in calibration, to get to a 0 VU read... which I believe would be .995 on the volt meter. I would prefer to try your method to 1.23v

Do I need to adjust both A and B pots to get a read? Either way the meters don't change.
-10db=.775v

Once I get my pots to work this will be a lot easier and should make more sense.

This is only a temporary calibration out of channels 1-2 until I move the entire rig next month. At that point I fly my tech in and we will configure the whole system.

[mixboy bob]

Ok, getting closer. What piece of gear is the analog VU meter on?

And I'm also worried that your hardware setup may have the wrong set of pots selected as reference. That is to say, you are turning the "A" trim pots, yet in PT's hardware setup, Trim "B" is selected.

If you are doing music, you should think about cal'ing to -18dbfs. If post production, -20dbfs.

A 1k sine wave played at -18dbfs will equal 0vu which is equal to +4dBu.

So when you say -10db, I am assuming you mean -10vu on the analog meter?

Just trying to be clear here... lot's of details to get correct.

Holla' back!

Rob Burrell
aka mixboy

[mixboy bob]

Originally Posted by mixboy bob

A 1k sine wave played at -18dbfs will equal 0vu which is equal to +4dBu.

This is assuming the analog meter is cal'd for 0vu to equal +4dbu. Usually the case, but this is why I ask what meter you are using.

rb

[D-Street]

Sorry for the hiatus. I have tried so many different things to get this to work.
The calibration template is set for the 1K tone out at -18dbfs and my system is set up correctly. I can see the 1K coming out on a digital meter. I can see where it is just under 1 volt on a standard meter (-10db).

The read on the digital meter for volts is way way low though. Barely reading in even micro volts.

I am using 2 and 3 on the XLR out. I think I have done everything right considering I have been at this for a long time.

The pots are not changing anything.

I am contacting PTools and seeing if there is a larger problem here.

I let you know what they say.

Until then, thanks for all your help.

D