Pro/DJ amps instead of multi channel amp

[Mitcon]

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.

[bobgpsr]

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.

[tonyvdb]

Mitcon wrote:

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.

[thxgoon]

Mitcon wrote:

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 wrote:

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 wrote:

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.

[Mitcon]

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.

[tcarcio]

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.

[Mitcon]

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

[thxgoon]

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.

[Mitcon]

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.

[WmAx]

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