OK, I've never had one of these in. Got it from an installation buddy that told me that 'one channel was low in output'. It was installed in a rack in a clothing store for about 5 years. I got it on the bench, and yes, sure enough, one channel was clean, but low in sensitivity compared to the other normal working channel.
The fix was easy: Dirty slide switches on the back of the amp that govern bridging mode and input sensitivity.
The store had already replaced the amp, sol it's now mine.
For those not in the know, the K2 is a digital switching amp that's completely silent as it's convection cooled. It produced a massload of power, with minimal heat, you can stack these in a rack without air space between them, drive the crap out of them, and they don't overheat. This one was powering background music speakers in that clothing store, so it was not driven hard at all. the amp is clean, and was always permanently installed in a rack, never on the road.
The K2 puts out 500 watts RMS into 8 ohms, 800w watts into 4 ohms, and a messload more if bridged mono.
eBay pricing for these runs between $400 in beat up shape to $650 in mint shape. I'm asking $475 plus shipping for this one since it leans towards the mint condition side. The front panel is clean, minor scuffs on the top.
I used DeOxIt to clean the switches, they'll never go intermittent again. Subject to local sale, this one won't last.
Link Posted: Thu Oct 10, 2013 8:53 pm Post subject: Re: YES YOU WANT THIS: Crown K2 power amplifier!
Curt Palme wrote:
For those not in the know, the K2 is a digital switching amp that's completely silent as it's convection cooled. It produced a massload of power, with minimal heat, you can stack these in a rack without air space between them, drive the crap out of them, and they don't overheat.
Sorry to rain on your parade but coming from the switching audio amp industry (Lab.gruppen), I've dissected and lab tested the K2 among others. Yes, it's class D and for home theather applications you will not run into thermal limitation. What Crown have the habit to do is limit the output without indicating it, in the K2 due to thermal and their bigger brother i-tech when you deplete the energy storage in them. So what looks like something that can run all night without overheating is something that is already at its thermal limit and has attenuated the signal a few dB without telling you.
Considering the number of non-fan cooled power amps on the market, the K2 might still be your best option.
Joined: 08 Mar 2006 Posts: 23537 Location: Langley, BC
TV/Projector: All of them!
Link Posted: Thu Oct 10, 2013 11:56 pm Post subject:
Oh trust me, I'm completely disgusted by the whole 'pro' amplifier industry as of late.
QSC and Crown overrate their specs, ditto for everyone now. Labgruppen included. Do you still work for them? I could go on a tirade if you'd like about their amps installed at BC Place, the 60,000 seat football stadium in Vancouver, but I'll do so respectfully, and I'd love your comments if you'd post them.
I got a 30 minute backstage tour, including up on the catwalk, and it was interesting talking shop with their tech.
Link Posted: Sat Oct 12, 2013 8:49 pm Post subject:
Ah, yes, there are these other people, those not not coming from the pro audio industry.
The most striking thing most normal people notice is the output power and compare it with what's available from the the wall socket. Having peak power in terms of stored energy will not make sense for people who are used to big 50/60 Hz transformers + class B output with as many transistors as you can fit. To go from there in order to either increase the output power or reduce the weight of the amplifiers, you need to look at what 99.9 % of the music looks like, which is one big bass punch, 20-30 ms long followed by almost silence for about 500 ms, repeated over and over again to create a 120 BPM song. When I say silent, it's several dB down which is not that audible but represents a huge reduction in power. In comes switching power supplies with low average power (still kW) and high burst/peak power (tens of kW). This will give you ten times the power output since you are not clipping or compressing the music in any way. If you load any radio-friendly music into somethng like wavelab and do an average for the entire track, you end up with something like 8 dB crest-factor, or peak power to average/RMS power. The Crowns, powersofts and QCSs I have measured have all delivered their rated power, just not very long. K2 ran for perhaps 20 minutes. Powersoft K10 did seven minutes if not obstructed by anything else in the rack (ever read the manual for a product which boasts about being 1U in the advertisements but requires you to leave space above and below it in the rack?). This might have been fine if they would have indicated that they had reduced the output by five dB or or so after said minutes but no such thing. i-techs ran all day but didn't have very much power back then.
The only music (remaining 0.1 %) which does not fit in to this where my favorites to destroy equipment with is what will test the various limiter functions. Chemical brothers - under the influence have a bass sweep mixed at 0 dB FS which last for over a second. If you do manage to supply the power, speakers running at their music power rating will survive, just. The power compression at the end of the tone will make you feel sorry for the voice coils. Your power amps will run out of stored energy and unless the power supply try to limit the mains current, you will either brake the mains fuse or give your output transistors a very hard day at work. With well tuned protection, it will either limit the signal or turn on before smoking the silicon heating at perhaps 50 degrees C/second during this event. We tested a copy of our amplifiers with a similar test. Went up in smoke after about 100 ms.
Also, kids of today who only listen to dubstep with a lot of energy between the beats, like grumbling bass, will cause problems for all amplifiers if the DJs run at 0 dB FS. I did a concert last year where I had to EQ out some bass content from the dubstep DJ in order to save the mains fuse (3*25 A 230V IIRC). Other DJs playing more "normal" music where only limited by ear damage/government regulations levels.
No, the economy of '08 took its severe toll on the industry since people already have the kit they need and just won't upgrade when there are fewer/no jobs. The youngest guy had to go, along with a lot of production personnel of course.
Joined: 08 Mar 2006 Posts: 23537 Location: Langley, BC
TV/Projector: All of them!
Link Posted: Sun Oct 13, 2013 1:47 am Post subject:
Thanks for the detailed post. I am tired, my laptiop is acting up, and I've lost my reading glasses, so I can't respond in intelligent detail right now, but I would love to fight (discuss!) with you in the next few days.
I will say this regarding BC Place. Originally apparently, Crown amps were speced into the job, but they failed so often that they were thrown off the job site, and Labgruppen amps were installed. I'll argue with you about the power ratings later, but supposedly so many Labgruppen amps went down right before the Olympics, that their old 1986 Yamaha analog amps had to be pulled out of storage to get the system going in time for the opening ceremonies.
As a contractor, even if I was not involved with this installation, is really frustrating. The design of power amps isn't new, and why one manufacturer has to get kicked off the job, and another one comes in also with unreliable amps, is amazing to me. The overall quality in the design and implementation of said design is exceptionally poor nowadays. I don't care whether the amp has enough digital intelligence in it to control my kitchen sink at home (), I want the stuff to work. I've had issues with Peavey, Crest, Crown, TOA and Bose electronics as well, more so in recent years than 20 years ago.
So there's a start. Care to comment? I will be more concise and will bring up other issues down the road...
Link Posted: Sun Apr 08, 2018 3:28 pm Post subject: K2 switches
You said that you cleaned a K2's switches. I too have a K2 and I think one of my sensitivity switches is getting a little dodgy.
How did you clean/lubricate those switches? They are enclosed in their little rectangular cases. How did you get Deoxit inside the switch cases so as to get the cleaner onto the contacts?
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