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Harman Kardon HK 680 or PM 655 - What’s the better pick for cranking metal & rock?

K

kacperkot477

New Member
I’m using a set of JBL Control 5 speakers from 1988 and thoroughly enjoy cranking some intense metal and rock—think Megadeth, Pantera, along with some iconic Zeppelin or Sabbath. My room measures about 20 square meters, and I’m searching for an integrated amplifier from Harman Kardon to really make these speakers shine. I'm torn between the HK 680 and the PM 655 (or 655 VXi if I can locate one).

I’ve heard that the HK 680 (from the mid-90s, around 85 watts per channel) delivers incredible bass and sharp mids and highs, making it ideal for fast-paced riffs. The PM 655 (from the mid-80s, about 60 watts per channel) has a warmer and punchy sound, but it may not have the same power for driving my JBLs. Has anyone tested these two against each other? How do they manage heavy riffs—do they have tight bass, clear vocals, and powerful guitars? Are there any reliability issues or other peculiarities to be aware of? Also, is the 655 VXi worth pursuing instead of the standard 655?
 
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The power differential between the two is negligible. (Remember, you have to double the power to increase the SPL output by 3db... noticable, but not significant). 15 watts will hardly even be noticed.

Never heard the HK 680. But, I do have a HK 655xvi (90 watts/8 Ohm's) and once the known issues* are sorted it's an extremely capable amp well suited for any genre. I'm an old Metal Head from the 80's and when I'm feeling nostalgic the only disservice it does to my old favorites is expose how poorly some of those old recordings were mastered. It doesn't make bad recordings sound worse, but it doesn't soft peddle them either. Great recordings are rewarded though! I wouldn't hesitate to recommend. I've heard some say they prefer the older lesser powered 655 to the more powerful 655vxi, but I can't comment. I do know the engineering was supposed to be really good on both and HK supposedly really focused on getting perfect square wave response at rated frequency and power levels. My understanding is that's what's partly responsible for their accurate without being fatiguing sound signature.
I find the vxi version to really do rock well! Guitar riffs are excellent. Of course speaker pairing will be a major factor.

* These series have 2 main flaws that are pretty much required servicing for continued use:
1) they are known for bad solder joints that need to be reflowed if they haven't already.
2) the tiny push button switches are NLA, and prone to getting dirty. They can be cleaned, but it is a pain in the butt. I've done it and didn't find it that hard. But, my experience level as a DIY hobbyist prepared me for the hassle.

Also, plan on a re-cap. At 40+ years it's due. There's one in particular in the protection delay that goes bad and can really mess with the start up.
 
I don't have either, but I do have a PM650.

I think it sounds quite nice and it seems fairly, if not conservatively, rated.

That said, it's not set up in a "for ear-blistering cranking" setup. Most amps I have are much more powerful.
 
I'm gonna be the fly in the ointment here and say that if you want to really crank some metal, you might just want to get a real amp and capable speakers. Unless you are rockin' out in a phone booth or something, a pair of bookshelf speakers and a 60-80 wpc amp isn't gonna be very impressive. IMCO, of course.
 
tarior said:
I'm gonna be the fly in the ointment here and say that if you want to really crank some metal, you might just want to get a real amp and capable speakers. Unless you are rockin' out in a phone booth or something, a pair of bookshelf speakers and a 60-80 wpc amp isn't gonna be very impressive. IMCO, of course.
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But he's in a room the size of a phone booth lol.
 
Welcome to Audiokarma @kacperkot477 . I see you're a new member. I don't know if you're new to this hobby or not, but if so you'll soon discover in this testosterone filled field there are plenty of people that will tell you your gear is not good enough. That's just BS. 50-90 watts through decent bookshelves (or in this case, what JBL is calling "Control Monitors") is more than enough to thoroughly enjoy ear shredding levels in an equivalent 14'x14' room (20sq. Meters). Even blasting yourself out of the room I doubt you would ever get above 10 watts sustained constant output. The rest is just for headroom and dynamic swings. Considering most people really only listen to the first few watts of any amplifier for average listening.
 
dogwan said:
I don't know if you're new to this hobby or not, but if so you'll soon discover in this testosterone filled field there are plenty of people that will tell you your gear is not good enough. That's just BS. 50-90 watts through decent bookshelves (or in this case, what JBL is calling "Control Monitors") is more than enough to thoroughly enjoy ear shredding
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The real point here is the wide variance in what people consider "ear shredding" levels.

In any given case, your opinion or my opinion of ear shredding levels may or may not be aligned with others or the OP in that regard.
 
@spark1

Since you don't allow private messages I'll ask openly.

Curious why you find the comment about differing opinions of what loud means deserving a "Sad" reaction?
 
OP, if you are determined to run one of these amps with those JBLs, you might want to consider either a powered subwoofer with speaker level inputs and a built in passive high pass crossover or, since both have pre-out/main in, some sort of active crossover (or DSP)/powered sub combo.
It will relieve those small speakers of having to make bass, which they won't do, and it will greatly increase the headroom of the system.
 
tarior said:
OP, jeśli jesteś zdecydowany na podłączenie jednego z tych wzmacniaczy do głośników JBL, możesz rozważyć albo aktywny subwoofer z wejściami głośnikowymi i wbudowaną pasywną zwrotnicą górnoprzepustową, albo, skoro oba mają wyjście przedwzmacniacza/wejście główne, jakiś rodzaj aktywnej zwrotnicy (lub DSP)/aktywnego subwoofera.
Uwolni to małe głośniki od konieczności generowania basu, czego i tak nie potrafią, a także znacznie zwiększy zapas mocy systemu.
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I could buy jbl sb5, subwoofer made for Control 5
 
tarior said:
I'm gonna be the fly in the ointment here and say that if you want to really crank some metal, you might just want to get a real amp and capable speakers. Unless you are rockin' out in a phone booth or something, a pair of bookshelf speakers and a 60-80 wpc amp isn't gonna be very impressive. IMCO, of course.
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Haha, yo, I hear ya—big amps and monster speakers would be sick! But man, I’m just a teenager without some Russian oligarch’s bank account, ya know? My JBL Control 5s and a 60-80W Harman Kardon are what I can swing for my little 20m² room. Gotta work with what I got to crank Megadeth and Pantera without pissing off the neighbors too much. You think the HK 680 or 655 can still bring enough punch for that metal vibe on a budget, or am I dreaming?
 
dogwan said:
Welcome to Audiokarma @kacperkot477 . I see you're a new member. I don't know if you're new to this hobby or not, but if so you'll soon discover in this testosterone filled field there are plenty of people that will tell you your gear is not good enough. That's just BS. 50-90 watts through decent bookshelves (or in this case, what JBL is calling "Control Monitors") is more than enough to thoroughly enjoy ear shredding levels in an equivalent 14'x14' room (20sq. Meters). Even blasting yourself out of the room I doubt you would ever get above 10 watts sustained constant output. The rest is just for headroom and dynamic swings. Considering most people really only listen to the first few watts of any amplifier for average listening.
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Yo, @dogwan , thanks for the warm welcome and the solid advice! I’m pretty new to this audio stuff, just trying to build a killer setup for my Megadeth and Pantera sessions without breaking my piggy bank, lol. Good to know my JBL Control 5s and something like the HK 680 or 655 can still shred in my 20m² room. Makes me feel better about not needing some crazy 500W beast to have fun. So, between the 680 and 655, which one do you think would give me that extra kick for metal—tighter bass or clearer riffs? And any tips for keeping these old HKs from crapping out? Appreciate the backup, man!
 
I restored PM655 years ago. There was a bad cap in the protection circuit when I got it which was preventing the amp portion from working. And as was already mentioned, numerous poor solder joints. Though not bottom of the barrel, TK caps were used in most places, so it could use fresh caps. And the tiny pushbutton switches are a bit of a pain to clean. But once done, it is a high current design, and sounds really good. No experience with the 680.

H/K PM-655 Integrated Amp Recap

Just got mostly finished this amp, but once again, like with the TU-915 I recently completed, I was short 2 caps which I want to change from 'lytics to film (0.22uF/50V). I found a couple caps had copper corrosion on the legs, with one or two having bad traces once the solder blob was removed...
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