I just received my Hartke KB15 and I absolutely love it, but the fan seems to be way too loud. I've read that Hartke amps have loud fans, but this is kinda annoying. Does anybody know if this is normal?
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Hartke KB15 fan noise.
- Thread starter bordinco90
- Start date
Well I just played 4 or 5 live shows with the Hartke and let me tell you it is the best amp that I have ever played through. I can actually hear myself on stage with drums, keys, vocals, guitar, ect... and this is with everyone with their own PA mix and monitors. I can't hear the fan noise at all when playing or even in between sets when we are not playing.
Just picked up a new KB12 today for some specific uses; great sounding rig. I knew the tonal offerings, and its versatility having played through them, also little else out there in that price range....most of class D combos are toys, they manipulate the phasing on lower frequencies to convince folks it is louder, yet they ultimately sag with uneven responses. KB is very nicely voiced, and lightweight. The fan noise however it more than annoying....rather it is unnecessary in form & function, sounding like a front radiator fan on a Kenworth semi truck, yet moving low CFM velocity of air. Should have been a better fan impeller, lower RPM motor, and thermally timed for load and duty cycle. Going to think this one over a bit....hoping it won't be a deal breaker.
My KB15 is really great, but had that loud hairdryer sound....annoying.
But it's not the fan itself....thats actually quite quiet.
There are several things causing the noise:
The area for the intake is too small.
The intake consists of narrow slots with square edges. (turbulent flow=noise)
The slots are too close to the blades of the fan. (more 'pulsed' turbulence)
The total effect is that the fan flows a small fraction of its rated capacity, and is noisy.
This amp (see pic) has had the intake completely opened out, and a computer-style round-wire grill
installed (they have a stand-off built in). All this means the airflow is much greater than standard, and is much quieter.
Even better, the speed can now be reduced, making it even quieter. The amp supply is about 9.5v (the fan is 12v, 2 wires), but a 10 ohm resistor knocks it down to a bit over 7v. Still more air than standard, but much quieter. The resistor and wiring need to be secured against vibration.
Great for use in quiet bands as well, now!
A point to watch: you could buy a premium fan (such as Noctua) and try to get it even quieter (though the standard one is pretty good). But....there may be a problem with that....when switching on the fan, the amp slowly ramps up the voltage , starting from about 4v. Some fans (like the one I tried) will not start at 4v, and until they start, the amp does not ramp up to the higher full voltage.....so it stays 'off'!
If you need any other details, please get in touch. And of course, safety first...remember there are dangerous voltages in the amp...
But it's not the fan itself....thats actually quite quiet.
There are several things causing the noise:
The area for the intake is too small.
The intake consists of narrow slots with square edges. (turbulent flow=noise)
The slots are too close to the blades of the fan. (more 'pulsed' turbulence)
The total effect is that the fan flows a small fraction of its rated capacity, and is noisy.
This amp (see pic) has had the intake completely opened out, and a computer-style round-wire grill
installed (they have a stand-off built in). All this means the airflow is much greater than standard, and is much quieter.
Even better, the speed can now be reduced, making it even quieter. The amp supply is about 9.5v (the fan is 12v, 2 wires), but a 10 ohm resistor knocks it down to a bit over 7v. Still more air than standard, but much quieter. The resistor and wiring need to be secured against vibration.
Great for use in quiet bands as well, now!
A point to watch: you could buy a premium fan (such as Noctua) and try to get it even quieter (though the standard one is pretty good). But....there may be a problem with that....when switching on the fan, the amp slowly ramps up the voltage , starting from about 4v. Some fans (like the one I tried) will not start at 4v, and until they start, the amp does not ramp up to the higher full voltage.....so it stays 'off'!
If you need any other details, please get in touch. And of course, safety first...remember there are dangerous voltages in the amp...
Do you have the specs/size for the replacement metal fan grate? Is it as simple as unscrewing the one that's there and replacing it with the grate you mention?
Well thought-out and completed mod! Never a problem at gig time, but I was just wondering what my options were on this noisy little bastard when using at the house.
Sorry for my extremely late reply....for some reason I haven't received notifications, until now.
Anyway....for the mod you have to undo the 6 retaining screws on top of the unit, unplug the speaker and carefully slide out the amp, ensuring you don't guillotine the speaker cable, which was a squeeze on mine.
The pic shows the interior.....you can see there its a bit awkward to remove the fan, but its do-able.
Once the fan was swung out of the way, I made a sort of sticky 'coffer dam' where the fan was, out of wide duct tape, to trap filings as they were removed. Then working from the exterior, I used a Dremel tool with various attachments, to grind out the slatted grill to make a large plain circular hole about the diameter of the fan blades, or a bit wider. Round off the edges of the hole....this helps with noise too. I removed the duct tape and used a soft brush and strong vacuum to remove any hidden filings from the inside.
You can get a suitable wire fan guard from ebay (or similar) very cheaply. The size is '60mm'...that's just over 70mm diagonally across the screw holes. Get one with a slight 'stand off' that holds the grill away from the panel (though I think most are like that). I think I was able to use the original screws to re-mount the fan with the grill on the outside.
Inside, I soldered in a 10ohm resistor into one of the leads and secured everything against vibration with a hot glue gun (very difficult to be neat with that stuff!). Reassemble into case. Check the fan cuts in (as before) after 5 to 25 mins of operation.
These class 'D' amplifiers are extremely efficient and produce very little heat, so the requirements for cooling are minimal....but this fan, even running slower than intended, provides greater cooling than the original installation.
I've been using it for over a year now.....including at a fairly large gig where the power was fully utilised.....and the air temp was up around 38C......absolutely no cooling issues then, since, or ever!
Good luck if you try this, its not all that difficult, but obviously there is a small risk of damage!
I'm very pleased it's so quiet on the odd occasion we are 'acoustic'.
F
Thank you for the guide!
I just got my KB15, and it too sounds like a jet engine. I'm looking to try this as my first amp-mod ever.
Please help out a total noob here. When looking at resistors, they are specified in ohms but also watts. What do I need here? And where exactly do you connect the resistor in this mod?
I am a clockmaker by trade, so the mechanical work won't be an issue, but I am pretty green on the electrical part.
Hello! I would like to ask you a question. Does the fan turn on immediately when the amplifier is turned on? Or does it have to reach a temperature to light up? I bought a used Hartke KB 15 and when I turn it on the fan doesn't move. I don't know if it's broken or normal.
At Sweetwater, there's a 1-star review by "Russell A. from Dallas" that implies the fan powers on only when the amp warms up.
https://www.sweetwater.com/store/detail/KB15--hartke-kb15-kickback-500w-1x15-inch-bass-combo/reviews?stars=1
https://www.sweetwater.com/store/detail/KB15--hartke-kb15-kickback-500w-1x15-inch-bass-combo/reviews?stars=1
I have the KB15 and love it for a lightweight gigging option. The fan is noticeable at home and I probably wouldn't enjoy it in a quieter practice room. But, for gigging, it's not noticeable. I see a lot of comments about the fan noise in Class D amps and am guessing its probably a common thing for keeping them cool. Probably a trade off for a light weight high powered amp. I wouldn't lose my mind over it. For my practice room, I have heavier class a/b amps because I don't need to move them and I like the quieter fans.
- Feb 12, 2006
- 61,047
- 5
- 221,002
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Fan noise doesn’t have to be an issue with class D amps, and it’s been my experience that fan noise in general is much higher in the equivalent power class AB amps.
It’s all about the design, packaging and execution, and nothing to do with the class if the amp.
Makes sense. If we isolate to just the Hartke gear, I can say for sure their Class D’s are quite loud and the Class A/B’s are very quiet. I can speak from experience on that as I have 2 LH1000’s, 1 LH500, 1 KB15, 1 KB12 & owned a 8500. I sent back the 8500 intended for my home practice space bc of the of fan noise. There’s now an LH500 in it’s place.
- Feb 12, 2006
- 61,047
- 5
- 221,002
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
