Pro Amp Input Voltage question - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 16 Old 05-17-2019, 09:00 AM - Thread Starter
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Pro Amp Input Voltage question

Hi folks,

I am building a Dayton Ultimax 18 sealed and i've moved to power. I had though about getting a plate amp of 1000w RMS and can ask the manufacturer to remove the HPF.

I can't get the amp for a could of months so looking at other options. I'm interested in the crown 1502 range or possibly NX3000D or 6000D with a fan mod. I'm worried about purchasing the pro amp but my HT Amp (Onkyo 5010) says it's rated RCA level and impedance is 1v/470 (PRE OUT) and maximum RCA output level and impedance of 5.5v. The Crown takes 1.4v to reach full power but has a high sensitivity switch of .775. What will this do to the power levels if I drop the input sensitivity?

Also, there is a HPF on the amplifier, does anyone if it's set at 20Hz at 6db roll off? Will this affect the bottom end? Does it have a variable HPF? Do other amps out there provide HPF flexibility?

Would you also recommend that I get a mini DSP to 'fine tune' the sub or can I do without it and add later? Where does the mini DSP sit in the chain?

Thanks

Stewart
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post #2 of 16 Old 05-17-2019, 11:58 AM
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If you get an amp with DSP already, you don’t need a minidsp. The minidsp sits between the AVR and the amp. I’ve seen posts here on AVS explaining ways to “hack” a lower HPF on those amps like the nukes that only go down to 20.
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post #3 of 16 Old 05-17-2019, 12:16 PM
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Quote:
Originally Posted by sassuki View Post
If you get an amp with DSP already, you don’t need a minidsp. The minidsp sits between the AVR and the amp. I’ve seen posts here on AVS explaining ways to “hack” a lower HPF on those amps like the nukes that only go down to 20.

The only DSP that's contained in an amp that is useful is the one in the Behringer amps. All of the others are pretty much useless. Crown, etc. And even though the DSP in the Behringers is capable, the MiniDSP will give you even more control. It all comes down to your setup and needs.
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post #4 of 16 Old 05-17-2019, 01:35 PM
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Just speaking from my own experience, the Crown set at the 0.775V setting shouldn't even be an option. It doesn't work as well as they say. I have a Marantz SR5010 and had difficulties driving my XLS1502 at the 0.775V setting. I added an ART Cleanbox Pro with an XLR cable and set it back to 4V, and it worked quite well after that. It's a great amplifier, and shouldn't be overlooked, but it did take more input voltage than my Marantz could put out to drive it to max output.
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post #5 of 16 Old 05-17-2019, 01:44 PM
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If this is a standard 4.0 cu ft sealed build, no need for a HPF which means the Crown is in the mix. However, if you decide to get the most from a sealed setup, you'll want to add boost which requires boost from a capable DSP like the mini. Or if you switch to ported, you'll need DSP that is stronger than the Crown offers. For me, the inukes have too many things to work around to make them work good for HT. I like the Crown/miniDSP idea more, personally.
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post #6 of 16 Old 05-18-2019, 04:25 AM
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Quote:
Originally Posted by samhain1 View Post
I'm worried about purchasing the pro amp but my HT Amp (Onkyo 5010) says it's rated RCA level and impedance is 1v/470 (PRE OUT) and maximum RCA output level and impedance of 5.5v. The Crown takes 1.4v to reach full power but has a high sensitivity switch of .775. What will this do to the power levels if I drop the input sensitivity?
Where did you get that? The specs say the RCA output is 5.5 volts. That’s like three times more voltage as the Crown needs.

https://www.onkyousa.com/Products/mo...class=Receiver

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post #7 of 16 Old 05-18-2019, 04:47 AM
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Quote:
Originally Posted by notfastenough View Post
If this is a standard 4.0 cu ft sealed build, no need for a HPF which means the Crown is in the mix. However, if you decide to get the most from a sealed setup, you'll want to add boost which requires boost from a capable DSP like the mini. Or if you switch to ported, you'll need DSP that is stronger than the Crown offers. For me, the inukes have too many things to work around to make them work good for HT. I like the Crown/miniDSP idea more, personally.
It is my understanding the mini dsp also corrects for the consumer audio to pro audio voltage gain.
Your always better off driving pro audio amplifiers with the full required pro audio signal.

Whatever your rca actual output is.................. you can be sure it will be 4 times higher once
corrected for the expected pro audio input. Therefore I will have to second the notion about the usefulness of the mini dsp, and also the usefulness of match boxes, like art, aphex,124 ati mm 100 etc,

If you have a mini dsp, you can use any amp without dsp built in, which will give you many more options.

https://discuss.avscience.com/index.php?topic=459.60
A Good amplifier requires a adequate power supply, It does not matter what the amplifier is capable of if the power supply will not provide the power required. Most amplifiers have under rated power supplies. It is up to you to make sure you get the ones that are least under rated if at all.
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post #8 of 16 Old 05-18-2019, 04:55 AM
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Quote:
Originally Posted by Wayne A. Pflughaupt View Post
Where did you get that? The specs say the RCA output is 5.5 volts. That’s like three times more voltage as the Crown needs.

https://www.onkyousa.com/Products/mo...class=Receiver

Regards,
Wayne A. Pflughaupt
I think it can produce enough voltage to drive the amp when not loaded but the problem is that the input of the amp has an impedance that's low enough that the RCA output can't produce enough current to get the voltage high enough to drive the amp's input. It's a loading issue and using something like a direct box between the source and the amp should fix the problem.
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post #9 of 16 Old 05-18-2019, 05:30 AM - Thread Starter
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Yes sealed 4cuft. In terms of the voltage I’ve heard many stories about home theatre amps not pushing enough voltage to drive the pro amps so this might be an issue.

Great help though guys
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post #10 of 16 Old 05-18-2019, 06:55 AM
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Quote:
Originally Posted by johnplayerson View Post
It is my understanding the mini dsp also corrects for the consumer audio to pro audio voltage gain.
Your always better off driving pro audio amplifiers with the full required pro audio signal.

Whatever your rca actual output is.................. you can be sure it will be 4 times higher once
corrected for the expected pro audio input. Therefore I will have to second the notion about the usefulness of the mini dsp, and also the usefulness of match boxes, like art, aphex,124 ati mm 100 etc,

If you have a mini dsp, you can use any amp without dsp built in, which will give you many more options.
As far as miniDSP stepping up signal voltage, you have to be a bit observant of the model being discussed. The output voltage isn't the same across the board.

I don't recall from memory but you have to check the specs for the different models to make sure you are actually getting enough output to match your amp's input sensitivity.
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post #11 of 16 Old 05-18-2019, 06:57 AM
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Quote:
Originally Posted by drewp29 View Post
Just speaking from my own experience, the Crown set at the 0.775V setting shouldn't even be an option. It doesn't work as well as they say. I have a Marantz SR5010 and had difficulties driving my XLS1502 at the 0.775V setting. I added an ART Cleanbox Pro with an XLR cable and set it back to 4V, and it worked quite well after that. It's a great amplifier, and shouldn't be overlooked, but it did take more input voltage than my Marantz could put out to drive it to max output.
+1000
I had this issue too. It was the main reason I bought the crown too. It was very frustrating. The cleanbox works great but if you turn it off prior to the amp you’ll get a heck of a thump!
I actually got a home amp and bridged it so I didn’t need the cleanbox but it takes up more
SPace and has heat.

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post #12 of 16 Old 05-18-2019, 10:54 AM
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Is the issue the Marantz or the Crown amp?

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post #13 of 16 Old 05-19-2019, 01:15 PM - Thread Starter
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So the options I seem to have;

1. Get a plate amp (but I have to wait for a couple of months on production). The good thing about the plate amp is that it will give me a true 1000w RMS into a 4 ohm load. I can also ask the manufacturer to remove the HPF and as I am going 4 cuft sealed this won't be a problem for damaging the sub. I still need a DSP (not essential but worth having to boost where there is a null for a smooth response curve)

2. Get a Crown amp that can output the power level's required but buy a cleanbox pro (not expensive) with an XLR cable and this will increase the nominal voltage from my Onkyo RCA (1v) to the power requirement of the crown amp. Got to watch out for thumps from the subwoofer if I switch off the cleanbox pro before the amplifier. I still need a DSP (again probably not essential but the crown doesn't have a proper DSP so would need to look at the minidsp, which is quite expensive. The crown doesn't seem to need a fan mod in the same way as the iNukes. The Crown amp has a HPF which limits output below 20Hz, which is not bad, however, if there a way to defeat the HPF for Crown pro amps?

3. Get a iNuke with a DSP, so no need to get a minidsp and carry out a fan mod. I'm also guessing that I would still need the cleanbox pro to feed the inuke? I would then also need to look to defeat the HPF of the iNukes below 20Hz but there does seem to be a workaround.
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post #14 of 16 Old 05-19-2019, 02:14 PM
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I have a pile of crown amps and mix/match the 1.4 and .775V settings to suit my particular needs in each setup, and the settings (at least on my amps) definitely work correctly. I have seen some issues where the sub out on various receivers is a relatively low signal and the .775V setting just isn't enough gain to get you where you want to be, particularly if you like the low end hot (you should), you do a lot of boosting (you should), and the speakers driven by the receiver are relatively sensitive. Most plate amps have ridiculous gain capability, so in general this isn't an issue when using them.
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post #15 of 16 Old 05-20-2019, 09:12 PM
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Quote:
Originally Posted by samhain1 View Post
So the options I seem to have;

1. Get a plate amp (but I have to wait for a couple of months on production). The good thing about the plate amp is that it will give me a true 1000w RMS into a 4 ohm load. I can also ask the manufacturer to remove the HPF and as I am going 4 cuft sealed this won't be a problem for damaging the sub. I still need a DSP (not essential but worth having to boost where there is a null for a smooth response curve)

2. Get a Crown amp that can output the power level's required but buy a cleanbox pro (not expensive) with an XLR cable and this will increase the nominal voltage from my Onkyo RCA (1v) to the power requirement of the crown amp. Got to watch out for thumps from the subwoofer if I switch off the cleanbox pro before the amplifier. I still need a DSP (again probably not essential but the crown doesn't have a proper DSP so would need to look at the minidsp, which is quite expensive. The crown doesn't seem to need a fan mod in the same way as the iNukes. The Crown amp has a HPF which limits output below 20Hz, which is not bad, however, if there a way to defeat the HPF for Crown pro amps?

3. Get a iNuke with a DSP, so no need to get a minidsp and carry out a fan mod. I'm also guessing that I would still need the cleanbox pro to feed the inuke? I would then also need to look to defeat the HPF of the iNukes below 20Hz but there does seem to be a workaround.
A separate dsp unit will give you greater control over your bass, and even if you bought the cheapest amplifier on the planet with DSP, you now can buy the model without dsp and have a great single place to accomplish all your dsp tasks. Even the mini dsp has 4 extra outputs,
so expansion is possible down the road. Personally I like spending more money on units like this popular Ashley processor clone.
https://www.ebay.com/itm/4-8SP-4in-8...3e67%7Ciid%3A1

I also prefer to step up the voltage before the processor. Aphex 124 Samson s convert,
Art mm 100, Symetrix 303 etc.

Take your time, and don't make money the whole purchasing decision. Unfortunate is the fact amplifier availability is not what it is used to be. The behringer ep 4000 still works great bridged into 8 ohm final speaker loads.

https://discuss.avscience.com/index.php?topic=459.60
A Good amplifier requires a adequate power supply, It does not matter what the amplifier is capable of if the power supply will not provide the power required. Most amplifiers have under rated power supplies. It is up to you to make sure you get the ones that are least under rated if at all.
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post #16 of 16 Old 05-20-2019, 09:41 PM
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Quote:
Originally Posted by johnplayerson View Post
It is my understanding the mini dsp also corrects for the consumer audio to pro audio voltage gain.
Your always better off driving pro audio amplifiers with the full required pro audio signal.

Whatever your rca actual output is.................. you can be sure it will be 4 times higher once
corrected for the expected pro audio input. Therefore I will have to second the notion about the usefulness of the mini dsp, and also the usefulness of match boxes, like art, aphex,124 ati mm 100 etc,

If you have a mini dsp, you can use any amp without dsp built in, which will give you many more options.
MiniDSP does not raise the output voltage unless you add gain somewhere in your filter settings.
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