I would like to see a pre-amp done on here with SMD, some are using SMD, but the circuit size reduction and minimised circuit parasitics must help... here is a notch filter channel I re-did for someone to show how small it can be (it could be smaller and tighter but got to allow for DIY, it is 4 layer, two of them are just contiguous ground planes)
http://www.diyaudio.com/forums/equi...z-notch-filter-project-pcb-4.html#post4582973
With SMD and the correct layout you can optimise circuit size and thermal interactions, especially with DACs and class D, I see so many with a little SMD chip and then its surrounded by acres and acres of PTH components including the biggest sin PTH decoupling capacitors.....
Amstrads, Binatone, Fidelity, Hinari. All the good stuff
I see. Those brands never been seen/heard here
Would it not be much simpler to type Parasound JC-1 in google ?
(what I do for high biased output stages is superposition class AB peak dissipation on class A steady state. The heatsinks of the JC-1's are not undersized for 9 pairs of MT200 devices, according to my calculation at the time of their release. Not really a surprise, as the JC-1 was preceded by the HCA3500 stereo model, close to identical case/heatsink dimensions, 1 pair of the same output devices less per channel)
My datasheets of the J50/K135 are in paper, and likely have more pages and graphs than yours.
(I must have been doing it for too long
)
GBW of 55 MHz and 140dB OLG means all the things you can do with a 5532/34 are suddenly rendered obsolete.
However, this does not explain why the AD797 is ok - it also has very high OLG and IIRC high GBW.
Since the 4562 is pretty quiet, in its own right I would assume the 1st stage is running at quite a high current (SW metioned 500~900uA per side in the AD797 by way of some guidance) with Ib compensation.
The mystery remains - what is causing this in these opamps?
However, this does not explain why the AD797 is ok - it also has very high OLG and IIRC high GBW.
Since the 4562 is pretty quiet, in its own right I would assume the 1st stage is running at quite a high current (SW metioned 500~900uA per side in the AD797 by way of some guidance) with Ib compensation.
The mystery remains - what is causing this in these opamps?
Sorry, I'm not familiar with this old gear. Besides, Mr. Curl said this is a new amp, not a JC-1 reloaded.
I see the JC-1 is specified up to 1200Winto 2ohm, was it ever tested at these levels for more than short bursts? I guess not, since Stereophile testing says:
A reflect of our period... I keep my big books of datasheet from AD, PMI etc. like Gold and Diamonds as well: Information seems to be lost forever by the marketing departments of big companies...My datasheets of the J50/K135 are in paper, and likely have more pages and graphs than yours.
(I must have been doing it for too long
10 pages of measurement numbers and graphs replaced by some "Get the best, use our J50/K135 parts, the best on the market".
;-)
Some habits are hard to change.
(I monitored the JC-1 on Quad ESL's, no complaint on my part. Mr Hansen's Trakkies as well, btw. Besides, what's a few degrees under or over fifty C between friends)
Waly, I don't publish my latest designs. However, the JC-1 was designed for HOME USE, not PA, so there is no fan. If I had designed the JC-1 for the Grateful Dead, I would have added a fan for sure. When the heatsinks get too hot for safety, there is a thermal cutoff that shuts the amp down until it cools off.
Good for you.
The web has it's merits though, e.g. the hard-copy book on semi package design by Michael Pecht cost me plenty $$, several of his publications and other stuff he was involved in are freebee downloads on the internet.
(I have no faith in modern technology, in case I don't toss myself into the ocean, I prefer a traditional burial on top of large stacks of burning paper. For science sake and/or mankind.
)
Given the 12dB crest factor on nearly all sensible music is there any good reason why one would need the amp to support those power levels continuously for home use? Not like you are jump starting your car with it.
As JC says, PA is a different case.
The Chinese one now!
'Bout this time last year I was 20 floors up in my apartment in Shanghai watching the fireworks go off.
both Cordell and Self go into the theory of peak currents that could be drawn with reactive loads such as multi-way loudspeakers - require special waveforms to pump the reactances and a then reverse the phase of the drive
estimates go up to 5X over the nominal resistive speaker impedance calc
and there have been infamous "Audiophile" speakers with odd XO choices that dipped that low below nominal impedance for sinewave drive at some frequencies
full range electrostat panels driven thru a step-up xmfr also see pretty much an Ohm or 2 of the xfmr winding series R by 20 kHz with ~10uF reflected C at the primary being near 1 imaginary Ohm
estimates go up to 5X over the nominal resistive speaker impedance calc
and there have been infamous "Audiophile" speakers with odd XO choices that dipped that low below nominal impedance for sinewave drive at some frequencies
full range electrostat panels driven thru a step-up xmfr also see pretty much an Ohm or 2 of the xfmr winding series R by 20 kHz with ~10uF reflected C at the primary being near 1 imaginary Ohm
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And as John owns said speakers I suspect he makes sure his amps can drive those all day. To me the JC-1 looks like its thermal management is designed to handle all real world domestic cases. There might be one or two loons in this world with serious edge cases like apogee scintilla owners who like overcompressed pop music in huge rooms but they are rare even in our world.
The Chinese one now!
'Bout this time last year I was 20 floors up in my apartment in Shanghai watching the fireworks go off.
Its cold and wet here..... I think I will wander back over to Asia early next month. Checking on a ride at this time. But too late for the New Year's party. Next year I'll be in sync with the good weather places. Will bring some more test equipment with me and set up an office/test room in always sunny and warm Thailand. Just have to stay away from popular tourist areas... least I get myself blown up.
-RM
I understand that, although I believe 12dB or more headroom may lead to an underestimating of the thermal load. That is, a 100W/8ohm amplifier (40Vp at the output) can be designed to support an average power dissipation of only 12.5W continuous (10Vp at the output)? That sounds like a stretch, even if you double it to 25W.
And wasn't the 1 hour @ 1/3 power a mandatory test for certification?
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