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m4k1s    0

Hello. I own an itech 6000 which I use for my 728 subs. But I wonder for how long is he going to live. What is the lifetime of an amp like that (in operating hours I mean)? Thanks in advance.

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dakos    0

Dear Makis,

I have seen itechs that were installed in churches, turned on from the very first day of install and sold with as much as 40000 hours on them, in great condition. I've also seen amps that had much less hours on them (500) in the worst condition you can imagine. I think such an amp doesn't break by the number hours it has (unless it's super high) but rather by it's condition and the way it was treated over the years.

Avi

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m4k1s    0

Thanks Avi. Is there any way to figure out the condition of an amp or it just has to malfunction first? Mine has about 15000 hours and since I bought it used I don't know how it was treated. What do you think? Also thinking of buying an 8000 for the subs and use the 6000 on the mids of my 725. Is this going to be a relief for the 6000?

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dakos    0

15,000 hours is allot, especially on a touring amp, obviously you don't have a lemon. But, as far as I know there's no way to know if an amp is close to it's end of life, you would need to open up the amp and look for puffy caps, dust accumulation (easily fixable), any burn smelling parts on the board, noise from fans or any irregular operation. These are general maintenance rules not itch specific. All these things should be done every time the amp is serviced, have you ever had it serviced?

The 8000 fits the 728 (one per channel) better then the 6000 but the difference wouldn't be audible, it would just give you a bit more headroom.

Maybe my friend Alain can shed some light on the subject...

Avi

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m4k1s    0

I 've opened him yesterday to see for dust. Not much dust at all, even at corners or somewhere else that cannot be cleaned easily, no puffy caps, just a tiny irritating noise from the fans. In general the interior seems pretty new comparing with an XTI for example I bought new(and now has about 300 hours)

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joust    0

My dear Dakos, thank you for your trust and confidence!

You are correct to state that the lifetime of a product is not necessarily determined by its age! Just look at me! :)

When I receive older equipment, and not necessarily an ITech, the first thing to do is to effect a visual inspection of the unit; It will let you know if certain components are at the end of their life cycle and may need to be replaced. Next, inspect the output module for heat strains, dirt, corrosion or contamination, mounting, etc.

In the case of an ITech, I will disassemble and remove the output module completely. I would then inspect and clean the fans and remove dirt and debris accumulated by the ventilation of the fans. Then I will inspect and clean the output module and heatsinks of dirt and debris.

Remove the output filter board and inspect the mounting rings for wear and tear;

Remove and inspect the BCA coils; Unsolder the coils and inpect the coil leads to make sure that you have 3 to 5 mm to apply solder;

Remove and inpect the BCA clamps on top of the o/p devices; Some clamps will need to be reformed to apply pressure on the o/p devices.and heatsink; Replace the clamps if necessary;

Remove the heatsinks and clean off the thermal compound. Note : two different heatsink are available; (I recommend the heatsink with the recessed ceramic isolator (for the flyback diodes) 'set' in the heatsink and not the heatsink with the ceramic on top. The recessed isolator assures that the transistors and diodes are all level on the heatsink compared to the initial release of the heatsinks;)

Clean both heatsinks and output devices; Add a small amount of thermal compound to heatsink and devices; Remount the clamps and the t-sens foam over the o/p devices. Inspect the mounted devices so that they move as little as possible. (Note : If the devices are not clamped down enough, the device will heat up quicky and destroy itself!)

Notice that on the hi-side half of each output channel, the furthest transistor has a thermal sensor placed under a foamy strip. This needs to be replaced, in most cases, if the foam is rock hard; If there was little pressure on the thermal device the cicrcuit will run hot. Add a drop a thermal compound in the tab hole, where you will locate and set the thermal sensor.

Once the output module has been reassembled mount it back into the amplifier. Power up and adjust underlap/overlap adjustments.

Of course, firmware update is mandatory!

Hope this helps!

Alain

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m4k1s    0

Thank you very much. You were more than helpful. Your answer was excellent, this is what I was looking for. I'll disassemble the unit and let you know if anything occurs. Thanks again!

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joust    0

Hello Peter,

It shouldn't be too difficult. The best way I found was to remove the DSP/input combo cards and then the main board can be removed easily. Note : The carrier screws are located on the top of the amplifier and also need to be removed. Just make sure that the isolator is set back when reinserting the main board. Aslo, before reinserting the DSP/input cards, make sure the display cable is hooked up to the DSP card!

Also, it is advisable to discharge the rails power supply (there's up to 300V between the positive and negative rails!). The main rails connector from the SMPS module is a good place to discharge the psu. Please, do not use a screwdriver to discharge these voltages! :) I constructed my discharge-meter using an old hand held analog meter (to simply view the voltage as it discharges) and a few PTC (positive temperature coefficient resistor) devices in parallel with the meter probes. These PTC devices are around 6 ohms and will increase resistance with temperature. You could use similar devices, like those blue round components used in the crowbar circuit that is located on the SMPS module.

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m4k1s    0

Hello once again my friends.

I would like to have your opinion on an other matter if that's OK with you..

I use an XTI 1002 for the high frequency drivers of my 725s, can you please suggest the right settings of limiter and EQ, because it's a bit tricky since the DSP on the XTI is not sufficient.

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dakos    0

You can download all the tuning files for the SRX725 from the JBLPRO web site under Support->Download then you mark "Tuning tech notes" and scroll down to "SRX700 Tunings", Download and extract its contents. Open the created folder and there will be many subfolders and one .pdf file, open the .pdf file. Scroll down to page four, you will have a column called "SRX725 BI AMP" - HIGH. That's the data you need.

Avi

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m4k1s    0

As I said before I need limiter values which are not provided in this PDF and also XTIs EQ is not very compatible with the PDF's tunings.

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dakos    0

Oops, didn't see that :)

The limiter calculation is just one line long:

10 X Log(P1/P2)=10XLog(75/275)= −5.6427143 dBfs.

That's the number you input the limiter.

Use long attack and release times, 4 seconds attack and 8 seconds release to start with.

Never clip this amp!!

Did you also try the files here:

http://www.crownaudio.com/media/wysiwyg/XTI2_Downloads/Crown_XTI2_SRX_Presets.zip

Any ways, I'm on a linux computer right now and can't open SA to check the EQ settings problem.

Will update later.

Avi

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m4k1s    0

Thanx man. You are the best.. I didn't try the presets cause I didn't know what to expect, but it's my next move. What do yo think about itech's limiters? I have mine set at 145V 1200W for the 725 mids and 160 V 1600W for the 728 plus the peak limiter enabled on both 6000 and 8000. No need for extra headroom besides that 6db of the speakers. What I want is the system to limit just before distortion if none in the signal chain of course..

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dakos    0

I've rechecked the numbers and they seem to be good so could you please elaborate what's not working for you? Or in other words, what is your goal setting up your limiters?

Avi

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m4k1s    0

Well, what I want is to prevent my speakers from damaging, and have all the available RMS and PEAK power I can. I don't want my limiters predefine headroom. That's the sound guy's job. If I want headroom I'll put in the chain a compressor and get done with it. This is my point of view, it may not be perfect but it is worth it f.e when you need more SPL but you don't have more speakers . So what if I have 12db of headroom or more? I don't want it, I want my system play loud enough for everyone to be satisfied and I get payed as promised.

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dakos    0

I believe you're mixing the terms headroom and compression. Compression does not equal headroom!! You try to give who ever is using your rig as much headroom as they need, depending on the dynamics required by the type of music they play. When you run out of headroom and need more SPL, as a compromise you may use a compressor to lower the dynamics in the signal gracefully while lowering the headroom. Also it's much better to compress only the channel that's eating your headroom (a singer with poor technique or kick drum) and not the entire mix. I'll give you an example, if your rig is intended for a rock concert, that needs 15-20dB of headroom, you can choose to lower the headroom, compress the peaks in the music to say 12dB. This works well till a curtain point when the compression gets audible.

If you just want to protect your drivers then I believe you already have the numbers. If you want consistent SPL during your show then you need different numbers.

This is the calculation for having the peak voltage for your speakers for the itech limiters:

Peak Limiting voltage = SQ Root (Peak speaker rating * speaker impedance)

You already have the numbers for the XTi1002 from previous post.

Running your rig this way is very dangerous and I believe will not give you what you want but I might be wrong...

I'm sorry but despite my trying, I don't know what you're trying to do so I'm a bit limited in assisting you.

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m4k1s    0

Obviously I missexplained something. When I'm referring to a compressor I don't mean I'll compress the peaks. I'll have it set up the way you suggest set up limiters (slow attack, slow release) so I'll have pretty much the same result "Headroom". Only in this case I don't need to carry my PC with me to make a change, or change presets on every amp. I just set up a compressor correctly on the digital console's master out or even bypass it on the fly.

As for headroom sometimes where I come from no one cares about. They just want more SPL, volume, noise how can I say it they just want MORE..

And what can I give them? Peak power or continuous power?

As for the pour technique vocals it is a very common thing but how is this going to be solved with this kind of limiters? Yes a compressor on his channel is a good thing but if you have to push his voice upper than everything else and please don't ask why then your limiters will engage and push everything down..There we go again not enough SPL..plus audible limiting. Tough situation but not uncommon.

I decided to have that extra 6db of vocals average and push a bit more my speakers so I won't hear complaints after show.

What would u do?

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dakos    0

This is getting a bit more complex so I'll split my answer into a few parts...

Obviously I miss explained something. When I'm referring to a compressor I don't mean I'll compress the peaks.

My friend, if I'm not mistaking, compressing the peaks (or automatic gain control) is what compressors do. What turns a compressor into a limiter is not the attack and release times but its compression ratio being high (usually above 1:20). Attack and release times differentiate between an RMS/Continuous limiter (long times) as opposed to Peak limiter (short times).

Here are a couple of good basic guides/tutorials:

http://www.doctorpro...essors_en.shtml

http://www.rane.com/note155.html

Compression & Compression Vs Over Compression:

https://www.youtube....h?v=ZqEoTY3vCIM

A great video tutorial about compressors:

I'll have it set up the way you suggest set up limiters (slow attack, slow release) so I'll have pretty much the same result "Headroom". Only in this case I don't need to carry my PC with me to make a change, or change presets on every amp. I just set up a compressor correctly on the digital console's master out or even bypass it on the fly.

As for headroom sometimes where I come from no one cares about. They just want more SPL, volume, noise how can I say it they just want MORE..

And what can I give them? Peak power or continuous power?

Setting up a compressor the way I suspect you plan to, just gives you fake headroom with the unwanted over compressed sound. Any way I think you're looking at this the wrong way, you can only give what you have or less, not more. If they want MORE, my guessing is that you need to GET MORE!!

If you encounter this type of need at more then 50% of your gigs then this might be the time for upgrades, so I'll ask you this:

For how many people do you usually play (80-90% of your shows)? How far is your crowd from the speakers? Indoors or outdoors? What type of music?

If you're using itechs or some other smart amp, that usually means you need a computer near by.

As for the poor technique vocals it is a very common thing but how is this going to be solved with this kind of limiters? Yes a compressor on his channel is a good thing but if you have to push his voice upper than everything else, and please don't ask why, then your limiters will engage and push everything down. There we go again not enough SPL plus audible limiting. Tough situation but not uncommon.

For every problem we encounter there is a right way and a wrong way to fix. For example the problem of a poor technique vocalist, the right way is to put a compressor only on that channel and take out let's say the top 6dB, that would take good care of the problematic channel while keeping your headroom at the amount you need for the rest of the mix. Since now nobody is eating your headroom, you will still be able to make that singer louder compared to the rest just not when he/she is shouting their lungs out. It wouldn't hurt the overall sound/balance of the whole mix therefore everything would sound as musical as it should.

Could it be that those singers just need more SPL on their stage monitors while the mix in the FOH sounds great?

I decided to have that extra 6db of vocals average and push a bit more my speakers so I won't hear complaints after show.

What would u do?

IMHO you will just hear other complaints, the way you plan on doing things you'll cripple yourself sonically, you'll run into power compression a few minutes into the show, every few minutes you'll need to push the faders just a bit more to get the proper volume your clients want, you'll end up hitting the limiters at the same volume you would have if you'd have set them to 9-12dB just with much more energy and allot more wear and tear for your gear.

Avi

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m4k1s    0

1) Fake headroom?

Let's say you have in frond of you a compressor and a limiter besides quality can't you set them up to do exactly the same thing? Limit? I prefer doing the job with an easily adjustable compressor on a console (or should I say limiter to be more accurate?) than buying a laptop to carry with me. I don't find any good reason not to go this way.

2) Get more? Easy to say so, not very easy to buy more or carry more. Especially when you don't need more, cause I don't for 100-200 people either in or out doors. The problem here is what singers THINK of their voice loudness and clarity in foh mix and what sound guys try to do and when they can't do it they will never say it's their fault, it's always the systems or your fault. So I tried this let the system loose, it gets pretty scary when they push a fader up and they never say I don't have enough of this. And it works. The only catch is I have to be twice alerted.

3) The most dangerous part is when they shout their lounges out. This is an all show long problem and I'm not on the console so I'll push the fader down.

As for power compression I think I've experienced this situation 1-2 times and I want to ask you after what point driving those amps and for how long I might have power compression on my speakers with these values on the limiters? How exactly is power compression connected to limit values?

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dakos    0

1) Fake headroom?

Let's say you have in frond of you a compressor and a limiter besides quality can't you set them up to do exactly the same thing? Limit? I prefer doing the job with an easily adjustable compressor on a console (or should I say limiter to be more accurate?) than buying a laptop to carry with me. I don't find any good reason not to go this way.

I'm guessing the difference is conceptual, if you do things correctly then you shouldn't be hitting the limiters but using the compressor continuously isn't a sign you're doing something wrong. BUT, I'll read what I wrote again tomorrow after I sleep a bit, hope I won't punch myself.

2) Get more? Easy to say so, not very easy to buy more or carry more. Especially when you don't need more, cause I don't for 100-200 people either in or out doors. The problem here is what singers THINK of their voice loudness and clarity in foh mix and what sound guys try to do and when they can't do it they will never say it's their fault, it's always the systems or your fault. So I tried this let the system loose, it gets pretty scary when they push a fader up and they never say I don't have enough of this. And it works. The only catch is I have to be twice alerted.

For 100-200 people you don't need more, you should be able to make them half deaf with what you already have.

3) The most dangerous part is when they shout their lounges out. This is an all show long problem and I'm not on the console so I'll push the fader down.

As for power compression I think I've experienced this situation 1-2 times and I want to ask you after what point driving those amps and for how long I might have power compression on my speakers?

If you feed a speaker its rated RMS power, they reach their max temp (impedance) after about 30 minutes, but they reach 90-95% of that temperature after 5-6 minutes. I'm not sure at which point you experience power compression but it's between the two.

I've posted a link to a thread that contains a picture with graphs made for B&C woofer fed pink noise at its rated RMS power so you may see for yourself how fast the impedance raises (scroll down to Bennnett Prescotts forth post):

http://soundforums.net/junior-varsity/9953-matching-amp-speakers.html

Avi, out...

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dakos    0

Dear Adam,

Been thinking allot what to answer you... You are correct in that if you take a compressor and configure it as a limiter and use it both conceptually and functionally as a limiter then there's no problem. If you're more comfortable keeping an additional compressor instead of a laptop than it's a winner for you. For some reason I thought you wanted to compress, not limit, the entire mix. I still wouldn't recommend you configure the limiters using the speakers absolute limitations, you'll be walking on edge with them, having very little thermal reserve in case something does happen.

So did you manage to calculate all the numbers you needed for the limiters?

Avi

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