Fender Rumble 500v3 Fan Noise - My Troubleshooting and Resolution Journey

[toughluck]

ICE says efficiency goes UP at higher power (makes sense):

Total power efficiency %
Po = 100W 4 ohm 75
Po = 400W 4 ohm 80,4
Po = 500W 4 ohm 81,4
Po = 250W 8 ohm 86,4

But power at lower impedance is higher.
P=U²÷R
With the same rail-to-rail voltage, output power is doubled at half the impedance.

That means that waste heat is also doubled.

and also up by a couple of %s 4ohm vs 8.
we are still at <30W typical heat dissipation. even doubling their documented average power consumption of 1/8 of rated max.

Okay, so that's not very meaningful for the simple reason that if you're running the amp at 10% power, even if the inefficiency is doubled (i.e., the amp goes from 90% to 80% efficient), you still dissipate less heat. At 1000 W, you dissipate 100 W. At 100 W, you dissipate 20 W.

I don't know of any component or circuit that would lose efficiency so drastically that it would actually dissipate more power as heat at lower input power.

There are two components that emit significant amounts of heat: power supply and power amplifier.

With the environmental regulations, the power supply can be expected to be >90% efficient across the range.
The amplifier can be expected to be >90% efficient at maximum power, perhaps dropping to 80% at low power, as class D amplifiers are wont to do.
I'll assume 91.3% efficiency for both parts.

If the combo is 500 watts RMS into the speaker, the maximum input power would be 600 watts for just these two components.

What that means is simple: 100 watts is dissipated at maximum power and need to be moved away from the amp. 100 watts is a lot.

If you assume 90% efficiency, then it's still almost 60 W at 250 W output power and 30 W at 125 W output power.

Assuming that efficiency drops to 80% at 10% output power and to 70% at 5% output power, we're talking 28 watts waste heat at 50 watts output power and 25 watts at 25 watts output (total input power=50 watts).

Do not underestimate how much heat even a very efficient amplifier and power supply can emit.

also:
View attachment 7499726
RUMBLE 500 = ICEPower 125ASX2
I can see the thermal pin there. Hope it's not just for looks.

@agedhorse already pointed out that it's a basic function that provides an over-temp signal if the amplifier enters protection mode due to overheating.

 

[agedhorse]

have You measured average consumption from wall when playing (not testing with the ususal sinewave signals, but playing)? I did with an r100 cranked up to uncomfortably high levels some years ago. will not spoiler and let You do the same! curious how an r500 does in that regard!
(also note that I was generous and doubled it. for a reason.)

Of course I have, with a very wide variety of signals.

You might re-read the post by @toughluck above as that covers what's going on pretty effectively.

 

[dORSY]

Of course I have, with a very wide variety of signals.

You might re-read the post by @toughluck above as that covers what's going on pretty effectively.

so not like we, that actually play'em. got it!

 

[Guitalia]

Reading this thread, a scene from the Woody Allen movie Annie Hall came to mind for some mysterious reason.

 

[agedhorse]

so not like we, that actually play'em. got it!

Huh?

Of course the amps receive a LOT of play testing prior to being released. In addition to our stable of players based out of the factory group, a couple of TB members are also play testers. Most of these players tour extensively with these amps prior to release to be sure we (and especially I) haven't missed anything along the way.

The amps get played extensively during development and testing, I usually use a variety of bass loops because that allows me to test different dynamics management and thermal control algorithms with a wide variety of signals that can be repeated as the algorithms evolve.

There's also extensive current draw and thermal testing done prior to the safety certification process, this way any unexpected results can be addressed before the test lab begins the certification process.

I don't know your motivation here, but you are seriously under-estimating what goes into developing a robust, reliable, quality bass amp.

 

[toughluck]

so not like we, that actually play'em. got it!

I have a background in EE and I do play bass. Actually runs in the family, my dad is also an electrician by trade and education and was a bass player in his day. Thinking about watts and decibels just comes naturally to me.

Actually, I see that this is something that a lot of bass players pick up along the way. Think about it: bass requires the biggest and heaviest electronics. A guitarist can get away with a 100 watt combo. The diva vocalist expects a microphone and doesn't care about any intricacies. The drummer has bulky kit, but it's not electronic. The pianist might have some electronics with him, but again — if he's not expected to play bass low registers, he can get away with 100-200 watts of amplification and a stereo keyboard cab (or combo).

Chasing that last decibel and going just one hertz lower makes a lot of people do a deep dive into electronics.

With that said: You'd be very surprised at how little power is needed to rumble the house in the 21st century. 300 watts with the internal speakers is plenty.

Suppose that the 210's sensitivity (combo or roughly identical cab) is around 98 dB @1 W @1 m
At 300 watts, SPL is already almost 123 dB. Add a 210 cab and SPL goes up to 128 dB.

That's very serious volume and you'd be very hard pressed to find a venue that doesn't have its own PA and where you'd need more SPL than a Rumble 500 provides.
If you did, then it's beyond what a combo with a reasonable number of extension cabs (or a head with a number of cabs) would provide, and a band wouldn't be expected to play their own gear, unless they have their own sound engineer who carries a huge PA set.

 

[IpseDixit]

Just picked up a Rumble 500 with this exact issue and this is one of the few threads I’ve found that directly addressed things - I can deal with a little fan noise, but the whine is driving me crazy!

I’m trying to decide if it’s worth the trouble to return the amp and play roulette replacing it with another one hoping it doesn’t have the noise (they are out of stock after I purchased mine, so it would mean a special order) or try and source a quieter fan and replace it myself.

Is the process of opening up the amp to get the to the fan difficult? I’ve had to crack open a few amps over the years, but if this one is especially complex or likely to be hard to reassemble, I may hold off.

Again, thanks for this great post.

 

[agedhorse]

Is the process of opening up the amp to get the to the fan difficult? I’ve had to crack open a few amps over the years, but if this one is especially complex or likely to be hard to reassemble, I may hold off.

Again, thanks for this great post.

It depends on your mechanical ability, but once you start messing with it you kind of own it at that point.

 

[S-Bigbottom]

Thank you Mr. Agedhorse for the great read that went way above any customer service requirement for a product you are not obligated to give any service help or information for.

Your information is appreciated by us "silent readers".

Cooling too fast in one zone and not fast enough in another zone, or too cool all around and the balancing act to keep things reliable is neat.

 

[agedhorse]

Thank you Mr. Agedhorse for the great read that went way above any customer service requirement for a product you are not obligated to give any service help or information for.

Your information is appreciated by us "silent readers".

Cooling too fast in one zone and not fast enough in another zone, or too cool all around and the balancing act to keep things reliable is neat.

Providing a little bit of educational material is part of paying it forward. It's also the basis for the patented technology I worked on that allowed increased performance with increased reliability when using one series of ICEPower modules outside of the standard specifications. When I started on this project, other amp manufacturers (at that time) were sure this mode of operation was impossible... not only was it possible, we were able to do this with increased reliability too. That's a win-win result and the reason KMC went down the patent path with this.

Ultimately, ICEPower incorporated some of what we discovered in their later generation modules, so everybody ended up benefiting down the road. It's a lot tougher being a leader, working on cutting edge solutions than it is to be a follower (essentially copying other's solutions, often without fully understanding them).

 

[Never2Late]

Is the process of opening up the amp to get the to the fan difficult? I’ve had to crack open a few amps over the years, but if this one is especially complex or likely to be hard to reassemble, I may hold off.

I did not find the fan replacement especially complex or hard to reassemble. I would compare it to replacing a CPU fan in a desktop computer.

But as @agedhorse stated, it all depends on your mechanical ability. As he has shared, he has had a lifetime of seeing and having to fix botched attempted repairs. And if this is a new amp, this might void your warranty.

These are the steps:

• I've found it's easiest to start with the combo laying with its front side down.
• There are 9 screws attaching the amp to the enclosure: 5 on the back, 2 on top, 2 on the sides. Take them all out.
• Next there's an electrical connector from the amp to the enclosure, for the speakers. Carefully lift the back/bottom of the amp (the edge with the 5 screws) up away from the enclosure. You'll see the white connector close to the center of the amp. Reach in and disconnect it. Then lift the amp out of the enclosure.
• The fan is electrically connected to the amp with a 2-wire connector. The wires from the fan to the amp boards are tie-wrapped. Take pictures of the connector, the wires, and tie-wraps to see how to put them back afterwards. Carefully cut the tie-wraps and disconnect the connector from the board.
• The fan is mechanically connected to an intake shroud, which is connected to the amp chassis. First remove the 6 screws attaching the intake shroud. Now, with the shroud off, you can remove the 4 screws attaching the fan.
• The factory fan has vibration-isolating foam strips on it. Carefully remove those and attach them to the new fan.
• My replacement fan did not come with the connector, so I ordered one with wires attached and soldered them together. This is the connector I ordered, from eBay: https://www.ebay.com/itm/146087311553
• Then reassemble in reverse order.

Caveat, again: please be cognizant of your abilities. If you aren't familiar with electronics, safe practices for anything electrical, etc., this isn't advised.

 

[IpseDixit]

I did not find the fan replacement especially complex or hard to reassemble. I would compare it to replacing a CPU fan in a desktop computer.

But as @agedhorse stated, it all depends on your mechanical ability. As he has shared, he has had a lifetime of seeing and having to fix botched attempted repairs. And if this is a new amp, this might void your warranty.

These are the steps:

• I've found it's easiest to start with the combo laying with its front side down.
• There are 9 screws attaching the amp to the enclosure: 5 on the back, 2 on top, 2 on the sides. Take them all out.
• Next there's an electrical connector from the amp to the enclosure, for the speakers. Carefully lift the back/bottom of the amp (the edge with the 5 screws) up away from the enclosure. You'll see the white connector close to the center of the amp. Reach in and disconnect it. Then lift the amp out of the enclosure.
• The fan is electrically connected to the amp with a 2-wire connector. The wires from the fan to the amp boards are tie-wrapped. Take pictures of the connector, the wires, and tie-wraps to see how to put them back afterwards. Carefully cut the tie-wraps and disconnect the connector from the board.
• The fan is mechanically connected to an intake shroud, which is connected to the amp chassis. First remove the 6 screws attaching the intake shroud. Now, with the shroud off, you can remove the 4 screws attaching the fan.
• The factory fan has vibration-isolating foam strips on it. Carefully remove those and attach them to the new fan.
• My replacement fan did not come with the connector, so I ordered one with wires attached and soldered them together. This is the connector I ordered, from eBay: https://www.ebay.com/itm/146087311553
• Then reassemble in reverse order.

Caveat, again: please be cognizant of your abilities. If you aren't familiar with electronics, safe practices for anything electrical, etc., this isn't advised.

Just wanted to thank you for the EXCELLENT step-by-step disassembly instructions - I had practically no trouble opening up the amp after reading that, and the lack of good info was the thing that had dissuaded me up until now.

I'd managed to track down the quieter fan via Ebay, so all was going smoothly until I was about to mount it to the intake shroud and I noticed how much shorter the included wires were - just slightly too short to reach the connector, frustratingly! I should have checked that earlier in the process, but the eyeball test failed me. I've ordered the part you linked to on eBay and I'll see if that solves that particular problem.

At the moment, it feels optional, however; after re-assembling everything (a bit crestfallen, but wiser) I discovered that something during my dis-assembly process must have helped lessen the vibration that was causing the fan to make so much noise, because it's considerably less noticeable compared to before I started. What once sounded like an ever present whine (I have tinnitus that comes and goes, and at first I thought it was that, just pitched slightly higher than usual) is now closer to standard fan white noise that I have no issues with.

I'm going to keep the new fan (and the connector I ordered) handy for if/when the amp starts acting up again, but for the moment, I'm happy with the outcome. Appreciate this thread and all the help!