# Pro/DJ amps instead of multi channel amp



## Mitcon (Aug 24, 2008)

Hi all,

I'm sure it's not a new idea but I was wondering how many (if any) folks use a couple of Pro AMP's (DJ like amps) instead of expensive multi channel HT AMPs to increase the power in their home HT set-up. Have many done this ? How suitable are they to the task, what are the ups and downs of this idea. Is fan noise a huge issue ? Is heat an issue when you have 3 of these stacked together, do they help improve the end sound quality much ?

I've got a half decent AVR (Pioneer VSX-AX2AS-s one of the Pioneer Elite range in USA I think) that I'm thinking of using just the pre-outs from. MY mains, centre and rears/surround sides are rated for 300w @ 8ohms (centre rear/surrounds only rated 150w @ 8ohms) so I was wondering how this might work out as a HT multi-channel AMP with 7 x 300w @ 8ohms is expensive to say the least.


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## bobgpsr (Apr 20, 2006)

A lot of people's DIY subwoofer projects end up using a pro amp to drive it.

Some users use a two channel pro amp to drive their Left/Right main speakers. Threads about doing so started about 6 years ago on another home theater forum. It has also been brought up before here on HTS. Things you have to deal with are fan noise (many put a resistor in series with the internal fan to quiet them down) and also the difference between consumer electronics line level versus pro audio line level which sometimes requires using a device like the ART Cleanbox to go from -10dBV to +4dBA.


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## tonyvdb (Sep 5, 2007)

Mitcon said:


> Is fan noise a huge issue ? Is heat an issue when you have 3 of these stacked together, do they help improve the end sound quality much ?


This has been discussed alot on here and the jury is still out on the answer. My personal opinion is that using an external amp to drive at least your main channels is a very good idea as it lowers the demand on the receivers power supply. Receivers are rated driving only two channels at full watts for an extended period of time and can not drive all 7 or 5 channels simultaneously at its full wattage due to the fact that in most receivers the power supply can not maintain all the amps running that hard so it will start to distort.
Most Pro amps have fans in them and can be somewhat noisy particularly if you have more than one of them. They are designed to be stacked as the ventilation is front to back not through the top in most cases. You would be required to have at least two dedicated 15 amp circuits to power 3 external amps and your existing equipment. Some amps even require a dedicated 20 amp circuit.
I use a Samson amp that is convection cooled so there is no fan but requires about 3" of space above so it can cool. The amp also has a Toroidal Power supply so that is also an advantage as it produces cleaner power and is more efficient, they can be had for as little as $150 each.


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## thxgoon (Feb 23, 2007)

Mitcon said:


> Have many done this ?


A few people have done this with good results. There seems to be a stigmata hanging over these amps that because they are built for the road, they are not 'hi fi', but this is far from the truth.



Mitcon said:


> How suitable are they to the task, what are the ups and downs of this idea. Is fan noise a huge issue ? .


They work just fine in a home theater environment. They are built to take a lot more abuse than they will see in home theater. As such, in your living room you are virtually guarenteed of their reliability, and with most good pro gear the warranties are fantastic. I know that Crown will send you a unit to use while yours is being repaired. This is a result of the demands of the pro sound industry where a broken amp can hurt a show. The fans are loud, but this can be modified as mentioned above or the amps can be placed out of site.



Mitcon said:


> Is heat an issue when you have 3 of these stacked together, do they help improve the end sound quality much ?


As Tony said, the amps are designed to be stacked in a road case or rack so are designed to stay cool in this application. Another benefit of good modern pro amps is their high efficiency. This is important on the road when tons of watts are needed but you are limited to a certain amount of power. This means less heat is dissapated from the amp and less power pulled from the wall. As Tony says you'll need to run a lot of power into your listening room if you want to run the amps at full throttle, but with the efficiency of most of these amps you can probably get away with listening at reference with them all on a single 15 amp breaker.

Do they improve the sound? This is a hot debate. An amp is an amp is an amp. It is designed to do one thing. Take a signal and make it bigger. Unless an amp suffers from a bad design or it is being asked to perform outside of its normal operating range they are going to sound the same. There has never been a scientificly conducted blind listening test which has confirmed a difference in sound quality between a cheap amp and an expensive amp when both are operating within their design constraints.

If you're looking for more power, pro amps cannot be beat for watts/price.


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## Mitcon (Aug 24, 2008)

Thanks folks, I suspected as much.

Multi channel HT amps with passive cooling start for the cheapies around $3k here and thats just way out of my budget but I still want to set things up best I can. I'd post a link of the units I was thinking of buying to get peoples thoughts and advice but the forum wont allow it yet untill I have more posts. They are a Biema W330ii 450w + 450w (300w + 300w @ 8ohms) and look to be what I'm after though I'm worried about fan noise. I may have to mod them as suggested. I will have a look to see if we can get those Samson amps here as space is not an issue so passive colling would be even better.


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## tcarcio (Jun 27, 2007)

I run pro amps for my HT and I wish I did it sooner. I have much more power and fidelity than before and plenty of headroom. I run 2 Crown cts 600's for my mains and surrounds and a JBL mpc 200 for my center. As stated fan noise can be an issue but it depends on your set up and if they will be close to you when in use. The Crowns I have have temp sensitive variable speed fans and don't even come on most of the time and if they do I don't hear them. T he jbl is more noticable but only if you listen for it so in my instance it is not an issue. They usually are able to have a cheap mod done to the fans to solve the problem if you get one that is noisey. Best bang for the buck as far as wattage and like mentioned are very reliable. I use a few Rolls MB15's to balance the signal from my Pioneer Elite and increase input. If you try it I think you will be happy with the result.:yay:


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## Mitcon (Aug 24, 2008)

A thought, will I have a problem with balance (I've no idea if my Pioneer has balance or unbalanced pre-outs) or pre outs sensitivity compared to the amps input sensitivity


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## thxgoon (Feb 23, 2007)

No, you can just purchase a cheap RCA to XLR adapter from radio shack (or equivalent downunder). As mentioned above you may have level setting troubles between the receiver and the amp but this is solvable.


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## Mitcon (Aug 24, 2008)

Great, sounds like the way to go then. I can't see why people would go with a more expensive HT AMP other than the bonus of passive cooling and bragging rights lol. I mean I'm looking at 1.8 to a 2.7Kw system for under $1k and I'm also told that the AMPs will prolly last longer/be more reliable because in a consumer use they will have an easy life. I wonder what a 2.7kw Multi-Channel HT AMP would cost though to be honest I've not seen one lol.

Still I have to be honest I would like a HT AMP because they do look nicer and passive cooling is just easier right from the get go but I have to live within my buget as most people in a real world do.

Any other things I should know about ? It just sounds a little too easy, I thought there would be more drawbacks and problems than this.


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## WmAx (Jan 26, 2008)

As for noise of fan: the Yamaha Pxx00S series(P2500s, P3500s, etc.) have fans, but these fans will never come on in any domestic application that I can imagine. I have several of these on my main 2 channel rig(fully active, so I require several amps) and the only time I have able to get a fan to come on is when purposely testing a driver and dumping several hundred watts into it for several minutes with test signals. Also, these amps have a very low noise floor, the same that would be expected from any top quality home hi-fi amp. The only issue is feeding them proper pro-level input signal, which you need to use something like an ART Cleanbox, or other output with sufficient voltage level to feed the pro-level inputs of the Yamahas.

-Chris


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## Mitcon (Aug 24, 2008)

How do I go about finding out what the line level output is on my AVR's pre-outs ? The AMP I'm thinking of using has a input sensitivity of 0.77V.

I shouldn't need to get RCA to XLR adaptor as the AMP has RCA inputs also anyway. It also has a ground/lift switch for ground loop/hum problems. Also the fans are thermally cued so they only run when/if needed. Has soft start and a few other features as well.

Doesn't say if the RCA input are balanced or not, how do I know/find out if my Pre-outs from the AVR are balanced and what the line level is also ? I guess thats all I need to work out now so I know if I need to buy something like the Art Cleanbox or not.


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## tenzip (May 4, 2007)

If the amp you're thinking of using has RCA inputs, those will likely be at -10bB, so you won't have to worry about the level matching. The TRS and XLR connections will be at +4. Download a manual and take a look.

What equipment are you thinking of using?


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## Mitcon (Aug 24, 2008)

This is the AMP I'm looking at http://cgi.ebay.com.au/BRANDNEW-BIE...photoQQcmdZViewItemQQ_trksidZp1742.m153.l1262

I also have the manual for it


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## thxgoon (Feb 23, 2007)

Wow, that amp even has RCA inputs on it. I would have to venture a guess that those would be properly calibratred for consumer level (-10db) as I can't think of any pro gear using RCA. If that's the case it would be literally plug and play. Nice


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## tenzip (May 4, 2007)

Mitcon said:


> This is the AMP I'm looking at http://cgi.ebay.com.au/BRANDNEW-BIEMA-450W-450W-RMS-PROFESSIONAL-POWER-AMP_W0QQitemZ360081284614QQihZ023QQcategoryZ58718QQtcZphotoQQcmdZViewItemQQ_trksidZp1742.m153.l1262
> 
> I also have the manual for it


What does the manual say about input levels? Are the RCA -10dB?


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## tonyvdb (Sep 5, 2007)

RCA are standard -10 if it has them then your are good to go :T I have noticed that companies are seeing a trend to using amps in home theater use and are taking notice several manufacturers are now incorporating RCA inputs into there designs. Samson has been dong this for several years now already.


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## Mitcon (Aug 24, 2008)

Manual is extremely basic and doesn't really say much

http://www.altronics.com.au/download/Instructions/Audio/A4154.pdf

I could ask the company that makes them but from what you guys have said it looks like it's good to go. Just have to speak to the Minister of War & Finance to work out when I may get my hands on one to give it a go. Will most likely just get one unit first and see how good it woks out and then grab more after.


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## Mitcon (Aug 24, 2008)

Well SWMBO says the budget doesn't allow right now so may have to wait a month or two :explode:


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## Mitcon (Aug 24, 2008)

Just thought I'd mention it if there are any other Aussie's or folks looking at these that I spoke with a local dealer and the RCA are standard -10db consumer lvl unbalanced, the other connections are balanced. Also asked about the fans and noise and was told again that they are thermally cued and only come on as needed.

So I'm certainly going to get at least one first to try it out and most likely another 2 after that if all goes well. Have already started sweet talking the wife so with some luck I'll have one sooner rather than later hehehe


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## salvasol (Oct 31, 2006)

Mitcon said:


> Have already started sweet talking the wife so with some luck I'll have one sooner rather than later hehehe


Sweet talking??? ... you need some raying: . :kiss: . :hail: . :crying: . :innocent: . :dancebanana:


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## Mitcon (Aug 24, 2008)

Well I bought 2 of these Biema W330II (3rd will come later) and upon having a look over them now that I have them I'm a little disapointed. They look quite ok (better than I had expected) are really heavy and seem to work quite well. In HT use for movies the fans don't seem to come on at all but for demanding/loudmusic the fans do run.

The problem is now I have them and have checked them out I don't think the RCA inputs are consumer level of -10dBv and the manual for it just says the input sensitivity is .77v which in my mental math is equal to the +4dBu. 

So I'm not getting anywhere near the volume I should am I, though with the volume/gain on the AMPs at full they still drive my speakers quiteloud & better than the internal amplification of the AVR. I can't help but think I'm pushing the noise floor and the sound would be better if the line level was matched correctly and thus the AMPs wouldn't be pushed so hard (with loud demanding music they get very hot and reach almost 50c).

So that brings me to what wondering peoples thoughts on line level shifters/drivers. I know the Art Cleanbox is one often talked about but it must be a pain having several of them. Would something like the Behringer Ultralink Pro MX882 be ok for using as a line level shifter to bring the unbalanced -10dBV upto +4dBu for a 6 channel (3 x these stereo amps) set-up ? Also then there is thepain of finding cables that go from RCA to both XLR and TRS


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## tcarcio (Jun 27, 2007)

You can use anything that will produce a balanced signal whether that is a mixer or a cleanbox. Also, cables are easy to find just google them or google Hosa as they manufacture them. Also places like music stores or musicians friend have them.


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## Colorburst (Feb 4, 2009)

Hello all 

I just wanted to say great thread you all seem to have alot of good info. I just wanted to add a point of interest here. I have used pro audio amps for my home theater system for years. The difference in input gain from your non pro audio preamp does make for weak input signal to the balanced pro audio amp. The way to get around this is to use a device called a Direct Box. This is a box that changes an unbalanced signal to a balanced signal. The normal connections you will see on this is two 1/4 inch jacks on one side and an XLR connection on the other. This allows you to take an RCA to 1/4 inch jack cable to go from your home theater receiver to the pro audio amp. This device has a transformer in it to take the unbalanced signal to balanced level. It also has a ground lift switch on it to get rid of pesky ground loop noise. Your levels will still be a tad weak but are at this point just below reference. So this is a way to get around maxing speaker levels and reducing distortion. I can not say enough to how helpful the ground lift switch is in getting rid of that bone jaring HUM you sometimes get from a weak or poor ground. The reason you would want to go this route is because if you only change the connection type and do not match signal reference your signal level will be very low and you will not get a reasonable volume level. I hope this helps people on there way to using pro audio amps. I mean come on if you can not feel the bomb blast in your chest then whats the point of having a home theater system LOL.. Take care all.


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## Guest (Feb 26, 2009)

thxgoon said:


> No, you can just purchase a cheap RCA to XLR adapter from radio shack (or equivalent downunder). As mentioned above you may have level setting troubles between the receiver and the amp but this is solvable.


Ok, I have a behringer ep2500 amp and I want to run a subwoofer off of it. If I have an xlr to rca adapter and if i connect the rca from my receivers subwoofer preout to the amps rca input I have to put the gain on the subout all the way up and the gain on the amp all the way up and it still only barely moves the sub the bass is so inaudible. The only thing I can think of is cutting an rca and splicing it into the speaker level outputs of my receiver and with a low pass filter on the end of the rca connected to the amp to filter out everything except the lows...Any other suggestions??? Please help, Ive been hitting my head against my computer desk for hours trying to get this to work. :dizzy: :hissyfit: :wits-end::crying: :gah::duh:


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## salvasol (Oct 31, 2006)

mazdamiata210 said:


> I have a behringer ep2500 amp and I want to run a subwoofer off of it. If I have an xlr to rca adapter and if i connect the rca from my receivers subwoofer preout to the amps rca input I have to put the gain on the subout all the way up and the gain on the amp all the way up and it still only barely moves the sub the bass is so inaudible...


Just buy an ArtCleanBox to match the line levels between consumer products and pro products ...most of the time that's the problem.

Here is a link to one http://www.sweetwater.com/store/detail/CleanBox/


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## Guest (Feb 26, 2009)

salvasol said:


> Just buy an ArtCleanBox to match the line levels between consumer products and pro products ...most of the time that's the problem.


OK, would the Samson S-convert - Bump Box also work besides the cleanbox?


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## salvasol (Oct 31, 2006)

mazdamiata210 said:


> OK, would the Samson S-convert - Bump Box also work besides the cleanbox?


If I recall correctly yes, you'll need to use a RCA to 1/4" adapter or cable :yes:

That's what I like about my Samsom Servo 600...it has RCA connectors, so I don't need to use any box to match levels :whew:


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## Guest (Feb 26, 2009)

I was looking at an amp with rca inputs but it wasnt enough wattage I need atleast 750w per channel at 4 ohms...I would need a female to male xlr to use the cleanbox correct? Also, If I use a 3.5mm to rca cable and connect it to the line out on my ipod dock and the rca to the xlr to rca adapter the amp gets more then enough signal and it works fine so why wouldnt it work from my sub pre out?


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