Deleted
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Post by Deleted on Jul 2, 2018 9:42:17 GMT
Can someone explain this to me please? I have attached two images. One shows the inside of a NAD 214 PA and the other my old Quad 99 PA.
The NAD layout makes sense to me - one side per channel, FETs (I presume) are sitting on the heatsinks. I can how it amplifies, as it were.
The other piccy is my Quad 99 Poweramp. I can't see anything of the sort here. No heatsinks (apart from those two tiny ones), yet it runs cool (the transformer gets warm after a few hours).
So, what is the deal with the Quad? It is described as a "a conventional transistor amplifier" in a review. The Quad blurb says it uses "dual complementary feedback circuits" and I have read they do bandwith limitation, but that seems beside the point.
Thanks in advance for the education.
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Bigman80
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Post by Bigman80 on Jul 2, 2018 9:51:48 GMT
I think the heat sinking on the Quad is provided by the case. I’m not technical so I can’t really help with circuit layout though. Hopefully someone else can have a better look.
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Post by Deleted on Jul 2, 2018 10:24:29 GMT
If you design or build or repair amplifiers as a business or hobby, for everyone else all they need is their music and their ears. The explanations to you would be meaningless or bullshit. I might understand and it may not be BS to me.
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Post by dsjr on Jul 2, 2018 11:58:31 GMT
The Quad 77 and 99 amps are Class AB, so conventional and by this time the so-called advantages of Current Dumping had been evolved out I'm told (better matched output stages and higher current devices apparently). I suspect a lot of that circuitry is the supply and probably protection. You'd need to start at the speaker terminals and work backwards to find where the amp stops and external gubbins begins...
Naim amps were supposedly well laid out and look how Sh#t they usually sound, especially when you push 'em?
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Post by Deleted on Jul 2, 2018 14:57:04 GMT
Haha. I have only heard Naim amps at HiFi shows or in shops but never really got a chance to listen critically. Too expensive for me anyway.
Working back from the speaker terminals on the the NAD schematic it is definitely an AB amp. I can't find the service manual for the Quad 99 Power amp yet.
Maybe NAD just added those heatsinks to bring it up to 12KG so that it felt expensive?
No worries - I'll do some digging around. It is intruiging me.
Cheers!
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Post by dsjr on Jul 2, 2018 20:46:05 GMT
The Quad is definitely AB, as I was around when the internally similar 77 series came along and we discussed it at the time and were amazed how 'sweet' the sound was. I loved them...
For whatever reason, the 99 board isn't symmetrical, but you can see the two amp blocks, with one seemingly rotated compared to the other. The couple of inches difference in the wires to the speaker terminals isn't an issue really, but the Quadlink stuff in the top middle of the board was a bit, although I never found it audibly intrusive.
NAD amps have specialised in massive peak outputs I remember, so the large heatsinks may well be a part of this. Maybe this gets round the thinner? casework panels over the solid Quad casing...
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Deleted
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Post by Deleted on Jul 2, 2018 21:13:22 GMT
The Quad is definitely AB, as I was around when the internally similar 77 series came along and we discussed it at the time and were amazed how 'sweet' the sound was. I loved them... For whatever reason, the 99 board isn't symmetrical, but you can see the two amp blocks, with one seemingly rotated compared to the other. The couple of inches difference in the wires to the speaker terminals isn't an issue really, but the Quadlink stuff in the top middle of the board was a bit, although I never found it audibly intrusive. NAD amps have specialised in massive peak outputs I remember, so the large heatsinks may well be a part of this. Maybe this gets round the thinner? casework panels over the solid Quad casing... I think you are right there. I didn't look long enough did I?
Plus, NADs at the time were still flaunting their "soft-clipping" feature which you could turn on and theoretically somehow even out the squared off waves to prevent your speakers getting ruined. If you used that feature it would get hot, no doubt.
I remember when all the magazines were raving about the NAD 3020 which also had this soft-clipping thing. It was designed in Britain but - built in China - unheard of at the time. Now they are Canadian and their cheaper range is all class D. Whatever next?
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Bigman80
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Post by Bigman80 on Jul 3, 2018 7:32:10 GMT
The Quad is definitely AB, as I was around when the internally similar 77 series came along and we discussed it at the time and were amazed how 'sweet' the sound was. I loved them... For whatever reason, the 99 board isn't symmetrical, but you can see the two amp blocks, with one seemingly rotated compared to the other. The couple of inches difference in the wires to the speaker terminals isn't an issue really, but the Quadlink stuff in the top middle of the board was a bit, although I never found it audibly intrusive. NAD amps have specialised in massive peak outputs I remember, so the large heatsinks may well be a part of this. Maybe this gets round the thinner? casework panels over the solid Quad casing... As ever, Dave. The time and care taken to answer genuine interest in hifi is very much appreciated, |
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