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Old 11th December 2006, 10:22 PM   #21
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Dear Routhan,

I am not suggesting that any amp is good or bad. In my opinion all amps are essentially good, as you rightly mention some are better than others.

I do know of the LM4702 as we receive early samples of newly developed semiconductors and we got some of LM4702C in TO-3 11 pin package around the middle of 2005.

I have a few left over samples, but I have never used one myself. Maybe one day I will find something to do with them.

I guess I am old school and I love doing things the hard way, that to me is more fun than building something off a data sheet, because if I design it, I can truly claim that it is mine, after all it is a hobby.

If you love your LM4702 based amp then, that is excellent, I cannot comment.

I was merely suggesting that we may be frigthening our friend away instead of helping him.

In my reply I said nothing about any amplifier/chip or otherwise. I am concerned that you attack me for thinking that I may not like what you like only because I said nothing.

If you care to look in previous discussions I suggested he looks at Marks chip amp site.

You do not say which chip you use (A,B or C) or your operating voltage, but I am sure National Semiconductors would be pleased that you have improved their THD by two orders of magnitude.

The quoted THD + N is only 0.005% by no means a magical figure at all.
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Old 11th December 2006, 10:33 PM   #22
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Hi FastEddy,

That is an excellent idea. I have a few of these received as samples some time back but had no use for them until your suggestion now. Maybe we should go the whole hog and do a complete project with 2/3 way electronic cross-over. I am keen.
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Old 11th December 2006, 10:51 PM   #23
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" ... complete project with 2/3 way electronic cross-over ..."

Good thinking. I intend to do a bi-amp job on my main speakers ( http://3dotaudio.com/waterputtyexperiment.html ) ... I'll just build one 4702 into each speaker, turn the bass woofer and middie+tweeter into active crossover control (and use all those great big caps & coils for something else). I'll be trying for balanced inputs to the 4702 ...

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Old 11th December 2006, 11:13 PM   #24
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Hi FastEddie,

I have a pair of old Yamaha NS1000 still in excellent condition and maybe wothwhile putting the amps inside and then design a sleek remote control front end. How about that. Kinda gets the adrenaline cooking.

Are you going to kick this off?
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Old 11th December 2006, 11:17 PM   #25
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How about using the On-Semi MJL4281 and MJL4302 as output. they are 300V 250 watt jobs in flat pack. The power-stuff all mounted under the PCB so the whole assembly can be bolted on through the tranies onto a decent heatsink. Minimum fuss few wires.

Say wat you like...
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Old 11th December 2006, 11:44 PM   #26
routhun is offline routhun  United States
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Dear Nico Ras,

I am not attacking you in any means. My point is that none of them offered a clear solution, but when I offered a simple solution I was accused of coming to conclusion on somebody's behalf. I am afraid that with all the endless discussions floating on the thread we might not give Prorm a simple practical solution as one of the choice as it happens in all high-level discussions.

Hi FastEddy,

I don't have the PCB designs, I've bought my PCBs from www.chip-pcb.cn. Each PCB costs $6 a peace and complete kit costs $32 and shipping starts at $20. The PCBs are double sided and are professional. Please search the chipAmps threads for LM4702 somebody called harvardian also built an 8-channel amp with this kit.

-Routhun
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Old 11th December 2006, 11:58 PM   #27
routhun is offline routhun  United States
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Dear Nico Ras,

THD of 0.0006% is not my number and I didn't improve the National design. Please take a look at the National Semi's application note AN-1490 for LM4702. It looks like that you lost touch with LM4702.

-Routhun
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Old 12th December 2006, 12:25 AM   #28
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Hi Routhan,

This is a page from their data sheet. I do not see erata anywhere. Besides, this is also with no load. Add a load and see how this value drops on any distrotion analyser.

But I don't quote anything, this is from National. If you look at the graphs a little further, then you also see mpre revealing things not just numbers.

Maybe their appnotes have a different specification. If that is the case I doubt if either are correct. I do not always believe what I read. Put it on test and see if this is really the case after the addition of some other components in a real environment driving non resistive loads at elevated temperatures with ripple on the power supply and noisy non lab environments. The results may be far from perfect.

Anyway as you may notice - FastEddy is suggesting a little project and I am keen regardless if THD is 1% or 1 micro%, if it sound good then this is a starting place.

If after I build one, and I don't like it, it goes to the dustbin and I have learned something. Maybe, I also like it and rave about it.

Kind regards

Nico
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Old 12th December 2006, 12:32 AM   #29
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Nico,

you're a welcome breath of fresh air.
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Old 12th December 2006, 12:54 AM   #30
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All: if this complete kit from www.chip-pcb.cn is worthwhile what I will do, get one or two kits for my projects. http://www.chip-pcb.cn/images/47021.gif & http://www.chip-pcb.cn/images/47026.gif & http://www.chip-pcb.cn/images/47027.gif ... looks pretty good and will fit into my speakers just fine (for bi-amping). This appears to conform to National's PCB layout and looks like all I have to add is the '4702B chip, their or my PS & transformer ... and of course a case or chassis to wrap it in ...

Anyone ever dealt with www.chip-pcb.cn ???

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