# Pro Amp for home use.



## Peter Stoffregen

Has anyone found a solution for fan noise from Pro Amps. After "shopping it to death", I have purchased a Crest CA-18 to drive RCF 18" subs in a 3-way electronically crossed over system. Someone here explained that some fans have windings that are used as transformers, But the schematic for this amps seems to show just 2 wires to the fans. I do not want to 'butcher' the amp, and thought that a series resistor with the fan motors would be the least obtrusive mod. Has anyone done this? The amp will not be driven hard for any extended periods, but the Phase Linear 700 has run out of head room with my new, less efficient subs


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## AudiocRaver

Peter Stoffregen said:


> Has anyone found a solution for fan noise from Pro Amps. After "shopping it to death", I have purchased a Crest CA-18 to drive RCF 18" subs in a 3-way electronically crossed over system. Someone here explained that some fans have windings that are used as transformers, But the schematic for this amps seems to show just 2 wires to the fans. I do not want to 'butcher' the amp, and thought that a series resistor with the fan motors would be the least obtrusive mod. Has anyone done this? The amp will not be driven hard for any extended periods, but the Phase Linear 700 has run out of head room with my new, less efficient subs


I am "in the process" of modifying my Crown to quiet the fans (2). I chose to purchase a pair of fans that are designed for super-quiet operation. They are DC fans, the same size as the original, but the originals were 24V designs and the replacements are 12V. So I have also purchased the appropriate power resistors to wire in series with the fans. The amount of power to be dissipated is 2.4 W, and I don't want it to run hot, so I purchased 10 W power resistors, definitely over-sized, but they will be cool and reliable.

With less power spinning the fan, air flow will be less. As in your case, the power levels the amp will be used at will be a fraction of the design/spec level, so I do not expect that to be a problem. It would be nice to be able to compare "before" and "after" airflow, but that is difficult to do other than ballparking.

I have the parts, just need to get back to the project.

In your case, you are hoping you can find a happy medium fan speed where it runs quietly and still cools adequately. Hard to say if that is possible or not. Some fans, depending on bearings, are noisy even at slower speeds. Also, at lower spin rates, the fan might stop spinning altogether. You might consider replacing with low-noise fans.


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## Wayne A. Pflughaupt

The Yamaha PxxxxS amps are known to have virtually no fan noise. If you don’t want to void the Crest's warranty or do the “butchering” yourself, you might consider a swap.

Regards, 
Wayne


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## Peter Stoffregen

Thanks Wayne and Wayne;
I will consider your suggestions. I will check the fan speed to insure there is no risk of stalling. Your mention of 12 and 24 volt fans, gave me another (crazy) idea; why not use existing fans and connect them in series. The fans are driven by individual temp controlled regulators, but since bass is mostly balanced between Left and Right, could I use one channel fan driver to power both fans (in series) to reduce speed?
I would appreciate your thoughts, this mod does not require power resistors and the problem of placing them in the amp in a non critical area. 
Thanks again for your advice so far, Peter


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## AudiocRaver

Actually, not a bad idea. The problem with many amps is that they will have fan rotation detection circuitry for each fan, so it is possible you will get a fault condition for not having a fan driven by each the 2 fan drivers.


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## NBPk402

i run the Yamaha Pro amps and they have zero fan noise in my setup., and I have 3 of them stacked right on top of each other between 2 shelves. :T:T


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## tonyvdb

I have two Samson servo amps that have fans but they are inaudible 5 ft from where I sit. The Samson amps are nice also because they have both rca unbalanced inputs and TRS balanced inputs.


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## etroze86

I have Crown XLS amps and I haven't heard any fan noise but I also am not driving it very hard at all.


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## AudiocRaver

A number of pro amps use a dual-speed cooling approach. At low temperature, the fans run at a slow, quiet speed. At some temperature threshold, the fans kick up to full speed. In our home applications, it is probably rare, if ever, that the higher temperature threshold would be reached, so that higher fan speed might never even be heard, say when an extended high-volume audio passage suddenly drops to silence... any fan noise???

This would not apply to all pro amps, but many.


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## prerich

AudiocRaver said:


> A number of pro amps use a dual-speed cooling approach. At low temperature, the fans run at a slow, quiet speed. At some temperature threshold, the fans kick up to full speed. In our home applications, it is probably rare, if ever, that the higher temperature threshold would be reached, so that higher fan speed might never even be heard, say when an extended high-volume audio passage suddenly drops to silence... any fan noise???
> 
> This would not apply to all pro amps, but many.


I've found that the inexpensive Crown X-xxxx series runs very quiet. As far running mains with them - I haven't attempted that yet. I know that the S/N level on the XLS -1000 series is too noisy for main channel use (but good for subs). Just something to think about if you are looking for quiet pro amps. :T


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## xtinkshun

I use Crown X1000 and xls1500. both are very quiet. I also use Inukes, they are NOT quiet and require a fan mode. Very easy to do. You can use a $5 - $30 fan. Depends on your preference and where you purchase. Once the new fan goes in, its whisper quiet.


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## Almaric

Hi,
One option may be to use more quiet fans. I've read about that in the past. The fans in those amplifiers are build for rough use and long durability. Maybe a matching fan from a computer store would be a lot quieter. 

If that's not working you can only modify the amp or rather the circuit driving the fans. Or you place the amp in another room, or you build a "hush box" like some guys do for projectors. You could also use a "silent rack" which is mainly a 19" rack in varying heights, mostly for server use. But those are rather expensive and (of course) have fans themselves to get the air in and out. 

As other members suggested you could also use a different amplifier, but I wouldn't swap a CA-18 for one of those modern amps the others listed. Least of all when the CA-18 is used for subwoofers.

Marcel


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## NBPk402

Don't forget if the amp is new, and you change the fan there is a good chance you voided the warranty.:T


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## whitey019

+1 for Crown XLS series at least as far as fan noise goes.


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## Coytee

Yeah, old thread...

What I've done is bought three Crown K2's. Convection cooled and quiet as a mouse (ask me how I know, my cat brings home a wayward mouse about every other night)

Regarding a fan (which I currently don't have) what I envision is putting a vent at the top of my closet (which is next to the garage and the garage is open studs)

Put some ducting into the garage, between the studs. I can go out maybe 20 feet or so. Put at the end of the duct or inline, a small fan to create some movement OUT of the closet and dump it into the garage. Attach the power to the fan to the power of the system (I've dedicated four circuits and have a bunch of switched outlets)


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## Almaric

Coytee said:


> What I've done is bought three Crown K2's.


Yeah, I totally forgot about those, that's definitely a good recommendation. Over the years I've seen some of them on Ebay but the european models sold in germany were still quite expensive. I don't know how much money you have to spend in the US for a used K2. Too bad Crown didn't continue this series.


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