I've had my Genzler mg350 head about two years and couldn't be happier. Just curious why it has a cooling fan? I thought class D doesn't generate much heat and it's never got warm to the touch in addition I have a similar wattage stereo class D amp with no fan or vents. So why the fan and vents with Genzler? The other funny thing is the stereo amp weighs 25 pounds and the Genzler is super light. Just curious about this class D stuff.Thanks
Enjoy the benefits of a premium membership!
Upgrade Account
-
TalkBass has been independent since 1998. Add your voice.
Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
Join free Log in
Want zero display ads or expanded classifieds tools? Compare plans.
Class D amp question, you amp techs will know.
- Thread starter MrRiff
- Start date
- Feb 12, 2006
- 61,075
- 5
- 221,153
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
It's a design choice, in part because the amp is good for a higher than average duty cycle and in part because it's rated to drive a 2.67 ohm load.
Not sure how relevant this is to your specific comparison, but a large amp can space its components farther apart so the generated heat isn't concentrated in a small spot.
Lack of fan does not necessarily mean a lack of cooling, just a different method. The Trickfish B1K, for instance, does not have a fan, but does have a heat sink to deal with the generation of heat from the amplifier.
Something that's popular will have at least one fan.
Something that's popular will have at least one fan.
Those two facts are (partially) related.
You could take the Genzler, put it in a much larger enclosure and add a passive heat sink, and you would not need a fan any more. We've had these in the past.
When you shrink something to the minimum of what is feasible, among the first things you'll have to do away with is passive cooling because that needs room for the components and extra room because those components need air around them.
Even with class-D being highly efficient, when you make a 350 watt amp, you will have to anticipate that people will run it on full, and it needs to survive that.
Constructing a worst case scenario,
let's say the Genzler has a true power rating, and at full, it puts out 350 watts, and you play a piece that completely consists lots of long, low notes played legato, so there is very little dynamic content, it's basically full-on all the time.
Grabbing a number out of thin air, I assume the amp has an efficiency of 90%,
then it'll pull 388 watts from the socket and those extra 88 watts will mostly turn to heat that needs to be taken care of.
I haven't designed bass amps but have been involved in designing equipment with built-in electronics. The counterintuitive thing is that a small amount of heat in a tight space can have a noticeable effect. Even a highly efficient amp generates some heat, and it doesn't take a lot to raise the internal temperature. After all, a 15-Watt soldering iron can melt solder.
What a lot of designers have noticed over the years is that even a small amount of air flow (or even just stirring the air within an enclosure) can greatly improve the margin of error for whether an amp can survive the extremes of its operating conditions. My own hunch is that if an amp has a 2 speed fan, it will probably operate on the lower speed most of the time, and will be essentially silent. My GK MB200 head is that way.
The stereo may be bolting the heat generating components to a heavy chassis so they can be cooled passively from the outside. But also, a lot of electronic products have been deliberately designed to be heavy because it feels more substantial.
What a lot of designers have noticed over the years is that even a small amount of air flow (or even just stirring the air within an enclosure) can greatly improve the margin of error for whether an amp can survive the extremes of its operating conditions. My own hunch is that if an amp has a 2 speed fan, it will probably operate on the lower speed most of the time, and will be essentially silent. My GK MB200 head is that way.
The stereo may be bolting the heat generating components to a heavy chassis so they can be cooled passively from the outside. But also, a lot of electronic products have been deliberately designed to be heavy because it feels more substantial.
All Walter Woods amps, whether Class A/B or Class D, regardless of power rating, used the same small case and heatsink, and all are passive cooling. Some had more vent holes on the top than others, that is the only difference I have noticed between them. None of the three that I have owned (two Class A/B and one Class D) got very warm at all.
Here is an older example showing the case size and heatsink Walter used on all models.
Last edited:
My old Peavey MKIV head has a massive heat sink on the rear for heat management.
I burned my finger on one of these when reaching over, searching for the off switch.
I never did, but I burnt the location of the on/off switch in memory just in case loll The power cable wraps around the entire heat sink for storage or traveling. Great head and I still use it occasionally with the Peavey 1820 cab.
This could be a problem back in the day when rack mounting gear was far more common. Guys would NOT read the fine print in the manual and leave empty rack spaces above or below as recommended, so you'd see these crammed racks, often with a box room fan in front or behind to try and get around the proper spacing. Some stereo power amps had internal fans, some didn't and had heat sinks, but still required the proper venting.
I never understood why paying another 20 or 30 bucks for the right height rack was cheaper than cooking a big power amp . . . or the other processors above or below them.
I never understood why paying another 20 or 30 bucks for the right height rack was cheaper than cooking a big power amp . . . or the other processors above or below them.
I have a tiny Warwick Gnome 200W Class D head that arrived with a noisy fan that didn't actually move much air (I bought it used). The amp got hot to the touch very quickly. A replacement £5 fan made it quiet and now it stays cool.
- Feb 12, 2006
- 61,075
- 5
- 221,153
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Walter's amps did not need a fan to keep them cool. The package is similar to modern, current Class D amps, and even the older designs that are Class A/B don't need a fan to keep them cool.
