IT8000 Update & Input gain question

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Vinny D'Agostino

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Jan 12, 2011
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Warwick, Rhode Island, United States
Itech 8000 update & input gain question
I worked my first show with my newly aquired IT8000 running my complete system:
(2-QRX218s & 2-QW3f)
My first noticeable improvement was how much easier it was taking the amp rack out of the truck with just the single IT8000 in it!
Overall I liked how the system sounded, the subs were noticeably improved from how they were being run previously (RMX4050HD & Ashley XR1001 crossover)
I don't know if it was just from the amplifier switch to the Crown or the way how I have the IT crossover and filters set, but it was a big difference.
The amp chugged along all night with ease but there was only one minor issue that I need to correct/adjust.
From just testing in my basement with an ipod it seemed like I had the input gains set correctly and getting all the power I needed would be easy.....well, not so much.
With finally getting to play around with a live band I noticed something needs to be changed in the gain structure as I was really having to drive my A&H MixWiz hard to get enough output from the amp.
Way harder then I have ever had to (were talking flashing red lights on the output meter).
I haven't pulled the amp out of my truck yet but I just checked System Arch. to see how the amp was set.
Here it is:
Input Sensitivity 1.40volts
Input Gain 39.4db
What should I look at changing so this amp see's a stronger input voltage?
The amp was certainly loud enough when I was pushing the board hard, it was still only flickering the -20db lights, so there is plenty more power in there for me to get at.

Thanks,
Vinny
 
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Re: IT8000 Update & Input gain question

I doubt it's an input sensitivity issue, as your previous amp was only about 1 dB more sensitive. I suspect you were making up gain either at the input or outputs of the XR1001.

How hard were you driving the desk compared to before? Did you change any drive cabling or other gear?

For our VerTec rig, the amp input sensitivity varies between 5.x volts and 6.4v depending on speaker model preset. Since most* of the BEs out there like to see red clippy lights all the fuck over, it works out well. On an analog desk, that mean the VU meter needle is consistently above -4 and frequently hitting the +4 stop. On digital mixers it means we see peaks of -8DBFS, too... but we don't have amp inputs set for 1.4v for FTB, or we'd be buying $700 HF diaphragms and reconing everything else.

Based on what we know right now, I'm standing by my guess that your analog crossover was supplying additional gain.

Have fun, good luck.

Tim Mc

* the lone BE who runs his desk "cool" is Frank from Ted Nugent. We brought down system drive levels for the support acts and gave Ready Teddy's show more console headroom, which Frank appreciates and uses to his advantage. Everyone else would have more and brighter red lights if console makers would put them in...
 
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Re: IT8000 Update & Input gain question

Tim McCulloch said:
I doubt it's an input sensitivity issue, as your previous amp was only about 1 dB more sensitive. I suspect you were making up gain either at the input or outputs of the XR1001.

How hard were you driving the desk compared to before? Did you change any drive cabling or other gear?

For our VerTec rig, the amp input sensitivity varies between 5.x volts and 6.4v depending on speaker model preset. Since most* of the BEs out there like to see red clippy lights all the fuck over, it works out well. On an analog desk, that mean the VU meter needle is consistently above -4 and frequently hitting the +4 stop. On digital mixers it means we see peaks of -8DBFS, too... but we don't have amp inputs set for 1.4v for FTB, or we'd be buying $700 HF diaphragms and reconing everything else.

Based on what we know right now, I'm standing by my guess that your analog crossover was supplying additional gain.

Have fun, good luck.

Tim Mc

* the lone BE who runs his desk "cool" is Frank from Ted Nugent. We brought down system drive levels for the support acts and gave Ready Teddy's show more console headroom, which Frank appreciates and uses to his advantage. Everyone else would have more and brighter red lights if console makers would put them in...
Click to expand...

The LOW out on my XR1001 was set at 12oclock and the HIGH out was dialed back quite a bit:
P2230484.jpg

Nothing else has changed cable wise, XLR from mixer to EQ to Itech.
 
Re: IT8000 Update & Input gain question

Then we're back to where you've set limiters in the ITech. Were you able to monitor them with SA during the show, or were you performing?

Edit info... after reading Jonathan's reply, I guess I should have asked about how you have the crossover set up in the ITech, too. FWIW, in the VerTec presets, the 4880 subs have a band-pass output gain of +10dB, the 4889 LF is also +10dB, and the mids & highs are both +2dB (all figures were extracted from the v4 VerTec processing in SA).

You're losing heat somewhere... we just need to find it.

Have fun, full output. ;)

Tim Mc
 
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Re: IT8000 Update & Input gain question

It would seem to me that your mixer should be performing the opposite with the amps input sensitivities at that setting. I originally had sensitivities set there and then changed to 32db for better signal/noise. Last night I had 12db of headroom at my disposal and the system was rocking.

Were you still cutting your tops 15db? Have you tried cutting at the bandpass rather than the attenuators?

I have also just barley begun my journey with this amazing piece of equipment. Keep me posted Vinny!
 
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Re: IT8000 Update & Input gain question

I have been getting good results with +6db on my 718's and -3 db on my tops.

Vinny. I tried one of my presets with a steep HP 36But slope like you did. I ended up liking the HP 18But slope better.
 
Re: IT8000 Update & Input gain question

jonathan betts said:
It would seem to me that your mixer should be performing the opposite with the amps input sensitivities at that setting. I originally had sensitivities set there and then changed to 32db for better signal/noise. Last night I had 12db of headroom at my disposal and the system was rocking.

Were you still cutting your tops 15db? Have you tried cutting at the bandpass rather than the attenuators?

I have also just barley begun my journey with this amazing piece of equipment. Keep me posted Vinny!
Click to expand...


I had the same issue. Console didn't need much to drive the rig very hard. Switched to 32 and all is good.

Vinny, looks like your XR1001 was set at +3db at the crossover point. Was each knobs at full tilt boogie?
 
Re: IT8000 Update & Input gain question

Tim McCulloch said:
Edit info... after reading Jonathan's reply, I guess I should have asked about how you have the crossover set up in the ITech, too. FWIW, in the VerTec presets, the 4880 subs have a band-pass output gain of +10dB, the 4889 LF is also +10dB, and the mids & highs are both +2dB (all figures were extracted from the v4 VerTec processing in SA).

You're losing heat somewhere... we just need to find it.

Have fun, full output. ;)

Tim Mc
Click to expand...

This may be were another issue is that I created....
After finding a crossover freq. that I liked with my setup ( 80hz ) I originaly had a +6db setting on the lows.
In testing in my basement only I felt it was too much and dropped it to 0db.........I should probably go back and reset it to +6db and take another look at how hard my mixer is driving the amp with that much of a boost in the low freq.
 
Re: IT8000 Update & Input gain question

Okay, did a little more testing now that I have a lap top and can easily connect it to my IT8k.
I setup my FOH rack & IT8k, i did not connect any speakers as I wanted to watch System Architect and see what was really happening with my input signal.
I have come to the conclusion that the input signal not being strong enough is not my issue!
From watching what was happening when the output meters on my MixWiz flashed the +3db yellow indicator SA was showing that the input source on Ch1 & 2 were clipping.
So it would seem to me that I may need to reduce the input gain on the IT8k to avoid this, does that make sense?

I also must add that I did change the peak voltage limiters and the RMS power limiters to reflect a continuous RMS level x 1.5
So I had the Subs set at 85v 1800w @ 4ohms (3600w @ 2ohms)
The Tops set at 110v 1500w @ 8ohms (3000w @ 4ohms)

I did set the band pass gain on the subs back to +6db

So without having speakers tied into the amp there is no way to tell if the system is loud enough, my main goal was too see what was actually happening with the amplifier and my setup.

So besides firing up the speakers and hearing whats going on what should I do about the input gain?
I should also mention that while watching what was happening I never saw the output clip on either channel.
 
Re: IT8000 Update & Input gain question

Vinny D'Agostino said:
This may be were another issue is that I created....
After finding a crossover freq. that I liked with my setup ( 80hz ) I originaly had a +6db setting on the lows.
In testing in my basement only I felt it was too much and dropped it to 0db...
Click to expand...
Don't forget that a 6dB increase equates to a doubling of the voltage. So, even if you were driving the amp inputs at an adequate level, you may have decreased performance by making that cut in the digital realm.

Thoughts/comments/corrections gladly welcome...:)~:)~:smile:
 
Re: IT8000 Update & Input gain question

I think we're getting closer... When you did your testing, did you observe any peak voltage limiting? How hot was the MixWiz output running at the gig?

I'd change the input sensitivity to 2.8v to start with, and if that doesn't fix the input clipping, go to 5.6v. Raise your bandpass outputs +3dB/+6dB to compensate. And check your limiters, particularly the subs as I think you have the peak voltage set too low.
 
Re: IT8000 Update & Input gain question

Tim McCulloch said:
I think we're getting closer... When you did your testing, did you observe any peak voltage limiting?
Click to expand...
I did not think to check the peak voltage during my test, I can check it tomorrow.

Tim McCulloch said:
How hot was the MixWiz output running at the gig?
Click to expand...
At the gig I was running the MixWiz very hot, the output meters were flashing the red led's (which I think are +26db?)

Tim McCulloch said:
I'd change the input sensitivity to 2.8v to start with, and if that doesn't fix the input clipping, go to 5.6v. Raise your bandpass outputs +3dB/+6dB to compensate. And check your limiters, particularly the subs as I think you have the peak voltage set too low.
Click to expand...
I can try the input sensitivity tomorrow also, I already have the bandpass output on the subs at +6db so I will leave it there and see what happens.
I set the peak voltage to 85volts for the subs, which should be 1800w @ 4ohms if I calculated correctly.
I went with x1.5 the continuous RMS rating (1200w @ 4ohms), I just know that I have read of many failures with the EV QRX subs when feeding them too much power so I am cautiously staying a bit safe until I figure this amp out.

Thanks for the help!
 
Re: IT8000 Update & Input gain question

Hi Vinny-

If you were running the mixer at Full Tilt Boogie, I suspect you were very much into your limiters. How was the balance between the tops and subs?

Peak voltage limits for the tops sounds about right, but the subs seem about 25 volts low.

The other thing to consider is that limiters are limiters, and they don't know anything about the program material. Commercially released recordings will not hit your limiter (the peaks have been removed already) the same way live music will.

Have fun, good luck.

Tim Mc
 
Re: IT8000 Update & Input gain question

Okay, I had a chance to play around a little bit tonight and I think I am getting closer......I think

I ended up changing the input sensitivity to: 2.8v
The Input gain stayed at 33.3 db
The Input range also stayed at +15dbu
(the Gain & Range are defaulted to there at that input sensitivity that I selected, they can be changed but I figured that amplifier is smarter then me at this point!)

With this change I can get the MixWiz output meters to hit the second yellow LED which is +6db without making the input clip, a little more output from the MixWiz and it would slightly hit the input peak/clip indicator.
I will normally hit the +6 LED on the MW when I am mixing a live band.
So to me this setting seems like I am close to were I want to be.....

I then had to change the Bandpass gain on the channel outputs of the IT8000.
On channel 1 running the subs I ended up with +9db
On Channel 2 running the tops I ended up with +3db
With these settings if I cranked up the MixWiz with my Ipod so that I was hitting the +6db level I would see some output *limiting* (not clipping) on Channel 1 (it was around -5db it was limiting)
Channel 2 would not get into the limiters or clip

I have the RMS limiters on channel 1 (subs) set to: 3600w @ 2ohms (1800w per cab, which is 1.5x there continuous rating)
The RMS limiters on channel 2 (tops) are set to: 3000w @ 4ohms (1500w per cab, 1.5x there continuous rating)

I also changed the crossover slope to -24db/Butterworth @ 80hz.
Electrovoice had emailed me and suggested -24db/LR @ 80hz but when I listened to the subs I prefered the BW filter, the subs had more output and hit much better.

I only actually connected the speakers for a quick listen as running the rig that hot in my basement causes too many things to vibrate off walls & shelves
So most of this testing was done just looking at meters and my laptop running System Arcitect.
I won't actually have a chance to use this rig live until the beggining of next month, so for now I think I will leave it as is until I get a chance to hear it out in the real world.

Thanks again,
Vinny
 
Re: IT8000 Update & Input gain question

I think your rms limiters are set too high. You also shouldn't have a problem getting those subs loud, they have an input sensitivity of 102db.
The IT8000 only does 3500W @ 2ohms.
 
Re: IT8000 Update & Input gain question

Vinny- EV recommended LR because that's what's usually used for symmetrical crossovers, to ensure the phase stays complimentary. By switching to BW, you have 3dB more output at the crossover knee, but your phase is now screwed. You probably should stick to what EV says unless you can measure it yourself.

You will never hit the RMS limiter of 1800 watts at 2 ohms, unless you play a sine wave. And if you do, the woofers are still going to die. As Steve said, and Bennett said, and I said previously, you might want to make the RMS limit half of the driver's RMS rating.
 
Re: IT8000 Update & Input gain question

Silas Pradetto said:
Vinny- EV recommended LR because that's what's usually used for symmetrical crossovers, to ensure the phase stays complimentary. By switching to BW, you have 3dB more output at the crossover knee, but your phase is now screwed. You probably should stick to what EV says unless you can measure it yourself.

You will never hit the RMS limiter of 1800 watts at 2 ohms, unless you play a sine wave. And if you do, the woofers are still going to die. As Steve said, and Bennett said, and I said previously, you might want to make the RMS limit half of the driver's RMS rating.
Click to expand...

If I make the RMS limiter half of the RMS rating the amp will be hitting the limiters all night long.
I have asked for help and even offered to pay to have someone help me with this and so far nothing.

So if anyone really wants to tell me were I should be setting everything for my cabinets I am hear to listen, but so far everytime I mention what I have stuff set at it's wrong.
When I calculate for peak voltage everyone says it's too low.
Whats the right way, what am I missing?

If anyone is local too me I will pay you to come take a visit and help me.
 
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