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Discussion Starter · #1 ·
I use a Samson SX 1200 to drive my front two speakers in a home theater. The internal fans seem to be excessively loud. I have read that disconnecting these fans should not be a problem during normal home use. Can anyone point me to instructions as to how to do this? I searched all over this forum and came up empty.


TIA!


leonp
 

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Have you thought about replacing the fans instead with newer whisper quiet ball-bearings? I am very paranoid when it comes to ventilation, especially in a component rack.
 

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Doing the ep2500 fan mod caused me a lot of grief until I returned it to stock.

A regular amp has heat sinks mounted external to the unit. A pro amp with internal heat sinks depends on a certain amount of air, because there is no natural convection.

Disconnecting the fan entirely will reduce the amount of time your amp will work, minutes probably the being the best unit of time to measure it. If you are lucky, (like me!) thermal protection will kick in. If you are not lucky, you may let some of the magic smoke out.

I moved my amp to a different room.
 

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Discussion Starter · #4 ·
I had not considered this. Any ideas as to where to find these and what the cost may be? Are they easy to replace?


leonp
 

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Very easy to replace.

Just keep in mind, if you run it hard, the engineers knew what they were dong when they built it.

For example, the fan in the ep2500 draws (IIRC) more than twice the current of the favorite replacement. Less power means less air moved.
 

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I haven't personally done this on the Samsons before, but you might want to contact the support group and find out the dimensions of the fan (i.e. if they are 90mm, 80mm, etc), and ask what kind of voltage they require. Replacing them shouldn't be that much of a headache, unless the power cord for the fan is engineered specifically for the Samson board.
 

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He would just have to splices the wire. I did replaced fans on my 3 amps that are fan cooled a QSC MX3000A,QSC RMX1850hd and a Crown XLS402B and no problems at all.

Quote:
Originally Posted by SergeantYnot /forum/post/15580280


I haven't personally done this on the Samsons before, but you might want to contact the support group and find out the dimensions of the fan (i.e. if they are 90mm, 80mm, etc), and ask what kind of voltage they require. Replacing them shouldn't be that much of a headache, unless the power cord for the fan is engineered specifically for the Samson board.
 

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Discussion Starter · #8 ·
I'm worried I'm not smart enough to do this without specific instructions. Can anyone point me in the right direction?


Has anyone disconnected the fans all together? What was the result? I know they weren't designed for this, but I rarely push them near their limits, and when I do, it's never for very long.


leonp
 

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Quote:
Originally Posted by leonp /forum/post/15581960


I'm worried I'm not smart enough to do this without specific instructions. Can anyone point me in the right direction?


Has anyone disconnected the fans all together? What was the result? I know they weren't designed for this, but I rarely push them near their limits, and when I do, it's never for very long.


leonp

I have a Samson s1000 and the damn fans are just TOO DAMN LOUD. I happen to have 2 of these amps, 1 which happens to be dead. Out of curiosity I opened it up, which was easy enough, and was able to ascertain that the fans are easy enough to at least take out. It doesn't appear as though it would be too hard to replace the stock fan with a comparable but quieter computer fan. Before I proceed with this, I thought I'd see if anyone has done this before with a Samson amp?
 

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I disconnected the fans in my two crown amps and never had a problem. they don't even get warm even at loud levels.
 

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Quote:
Originally Posted by perpetual /forum/post/18328151


I disconnected the fans in my two crown amps and never had a problem. they don't even get warm even at loud levels.

Hi, perpetual.


I've been tryng to disconnect the fan in my Crown amp - but it seems to have some sort of anti-tampering circuit somewhere: when the fan is off, the amp won't power-up.


The fan has 5 wires that lead into it: 2 black (I assume hot), each on it's own connector to a board, and three leads (red, white, and blue) terminated to a 3-pin plug. I havent cut any of those 3 individually yet, just pulled the three-pin connector from the board, as this would pull the neutral/white.


I don't know what the red and blue leads to the motor do--it doesn't seem to be a multi-speed or sensor activated fan. It's always been one-speed, always on.


Does this config sound similar to yours, and if so, how did you successfully disconnect?


-- Thanks,

-- Mark
 

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Here are what the 5 wires do


pos

neg

sense (i.e. working or not)

tach (RPM output)

PWM (i.e. variable speed fan)


The reason the amp may not work with the sense wire disconnected is to prevent overheating.


Do a search on google there are ways around this too. These are just computer fans.
 

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My god man it's 2 wires!!! Pop the top off your unit, unscrew the fan, cut the 2 wires black/red and connect your new fan black/red and your done. If you can use a tv remote, you can do this. It's easy as easy gets. Your not going to wreck anything, get it done!
 

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Quote:
Originally Posted by N8DOGG /forum/post/21258091


My god man it's 2 wires!!! . . . . get it done!

N8Dogg: Did you read the two posts that you were replying to?

There are FIVE wires connected to the fan motor. Disconnecting either or both of the black wires prevents the amp from powering-up. Disconnecting the red, white or blue wires prevents the amp from powering up. No 2-wire replacement fan is going to work.


Anyone have a comparable convection-cooled pro amp to trade? Mine is a Crown Power Tech 1 - built like a tank.


-- Mark
 

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DO NOT CUT THE FAN!


Usually there is a simple mosfet switch inline with the fan that shorts out a resistor that is inline with the fan. Switch the resistor to a higher resistance and you'll drastically reduce the fan noise. Also, the fans pro amps use are a level up from junk and have fan geometries that are for high CFM and not low noise; they use sleeve bearings and are noisy as heck. Replace it with a nice ball bearing fan with low noise specs and combined with the resistor mod listed above, you'll reduce fan noise to inaudible levels at quieter listening levels while maintaining the ability to cool the amp decently in high heat circumstances (Drunken new years eve party)


Just about every high power, reputable pro-amp design I have seen and worked on within the last decade or so uses a horizontally aligned 'tunnel' heat-sink that relies on airflow from a fan and will not cool effectively by convective currents alone (Even at low output).


**** There is also a VERY important sound quality benefit in our applications by using a quiet/reduced airflow fan, combined with the higher value resister because during low-medium output that is typical of domestic use, the temperature of the heatsink is higher than the stock cooling implementation will allow to happen. This may seam backwards in logic as generally, lower temps equals better; but in lower end & medium end pro amps, the output stage voltage bias is typically a cheap diode poorly attached to the heatsink and this VBias is tuned according to the higher temps seen during max output for the lowest crossover distortion at loud volumes & on the spec sheet. The output stage VBias is no doubt set at at the factory during 'nominal' room temp with no load or minimal load, etc. But the factory value's the service manuals often tell you to set it to are almost always values that make ZERO sense and only fall within a fair margin of typical values for the output stage design only after heatsink temp has been elevated. The poor & cheap output VBias circuits pro-amps use typically do not track actual output device temperature all that well and if they do track temp well, the design of the electronics do not adjust VBias all that well either. Pro-Amps are tuned for max output in output stage biasing and even then, I often see factory VBias settings on the low side to ensure there will be no cross conduction of output devices in extremely hot circumstances that could lead to a further increase in output stage heat. Pro-Amps are a balance of distortion, reliability, output & cost with distortion being on the lower end of priority because most folks really can't tell the difference between 0.05% THD or 10.0% THD in an amp when SPL is 115db or more and the speakers themselves introduce 15% THD or more.


In the pro-amps I have tuned for home use, I do the cooling mods to shut it up in addition to re-adjusting VBias to typical values according to the output stage design but only after gathering data of average heatsink temps I see when placed into my own setup at normal levels. I then use a 1Khz sine wave to heat up the heatsink to the average temp and set VBias to the well known traditional values that make sense according to the output stage design. There is a very slight audible difference but it is purely subjective and the affect is a reduction in the 'harshness/annoyance' to the sound after a while with the corrected VBias setting. Most people call it 'listener fatigue' which I assume is the desire to want to turn down the volume after a while to prevent further un-pinpointed agitation/annoyance in SQ. I'll fully admit this is no real way to judge effect; I'd love to get an Audio-Precision system to quantify this & fine tune my own amp designs someday.
 

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SPL15,


Great info!


I'd love to pad-down the fan a notch, but I might be out-of-luck . . . according to post #6 here: http://www.audioheritage.org/vbullet...l=1#post245344 ,

my amp seems to have a "fanformer" - Fan doubles as transformer to power the boards. Are you familiar with this config? There was some indication that if I add a power supply to power the boards, I could then pad-down the fan . . . Not sure I want to put more money and time into this thing, unless it's cheap & easy to do.


Thoughts?


-- Mark
 

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That fan is an AC induction type, the field (stator) coil also has secondary taps for isolated power output as well. Pretty neat design as it eliminates the cost of another transformer and forces the fan to be in circuit & electrically operational for the amp to turn on. The fan's field coil is supplying 36 Vac output with a center tap for 18Vac per rail which equates to around 24 Vdc unregulated after the 1.0-1.4 volt drop from bridge rectification and ripple voltage leftover from capacitive filtering.


It would be easy to source a small transformer able to do the job of the fan/former. a 36Vac transformer with a center tap is a pretty common value and should be able to be sourced from a lot of sources (Digikey, mouser, allied, Jameco, etc..). Power wise I would best guess you would need at MAX around a 60 VA transformer to power this part of the circuit. There is a 1 amp fuse inline with the fan/former and most of the draw on this circuit is the power needed to startup and maintain fan speed/torque; the electronics side the fan/former is powering shouldn't need anywhere near 60 watts of energy based on the 1000uF caps used for filtering. Keep in mind, this is just speculation on my part, without knowing the rest of the circuitry and what that power supply is powering, I really do not know for absolute certain what is needed. a simple current measurement would help to determine what sized transformer you can swap, but either way, it will be small and with the active cooling of the replacement DC fan, you could overload the transformer pretty significantly without worry of overheating.


Depending on what that fan/former is powering, swapping in a transformer could help to eliminate fan induced noise in the power supply to give a cleaner output to OPAMPS and other low voltage pre-amp stage parts. I'm guessing that this power supply does in fact power OPAMPS and sensitive pre-amp stage components as it is a Bi-Polar power supply with a negative and positive rail set to the common voltages + and - 15 Vdc. The difference you would hear from this could be significant or nothing at all depending on circuit layout and local filtering/conditioning of the pre-amp stages.


EDIT: and to answer your question, it would be a very very easy thing to do. You would simply snip out that huge fan and swap in a small 36Vac center tapped transformer lead for lead. Then tap into one of the 24Vdc sides of the power supply to power a quieter fan. Your biggest cost will probably be the fan, I paid around $40 for an ultra quiet high flow 24Vdc fan in the QSC RMX1450 I use for my subwoofer while small EI transformers can usually be sourced for $30 or less.
 

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Quote:
Originally Posted by SPL15 /forum/post/21261067


Your biggest cost will probably be the fan, I paid around $40 for an ultra quiet high flow 24Vdc fan in the QSC RMX1450 I use for my subwoofer while small EI transformers can usually be sourced for $30 or less.



Wow, $40 for one fan? I replaced those in my QSC PLX amps for my HT system with lower-flow Pansonic/NMB fans and even with a stack of four running I can't hear any fan noise from more than a foot or two away in a quiet room. I think the fans were $10 each from DigiKey. No problems with overheating/shutdown.
 
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