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Old 10th December 2006, 08:14 PM   #11
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Very proud, yes. Very satisfied with the results, yes. I couldn't believe how easy the whole amp went together, using an old cast off amp case. I used to try to solder all that stuff together, taking much too long to get everything just right. The most satisfying thing is the listening. Subjectively, the amp is far and away superior in every way to the Crown amp board(s) it replaces. The result is now definately a top quality audio amp.

I intend to take it to my office to drive a pair of flat panel planar speakers ( http://www.magnepan.com/model_MMG ). These babys are power hungry (with modest sound pressure level v. power required) but sound very nice with a 60 watt X 2 channel Sony. ... listening report to follow if anyone is interested.

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Old 10th December 2006, 09:53 PM   #12
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I for some reason browsed Mark Hennessy's web page http://www.mhennessy.f9.co.uk and I am really impressed by the amount of trouble and detail he goes to making his projects aestehetically very pleasing.

Mark well done!
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Old 10th December 2006, 10:19 PM   #13
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" ... Mark Hennessy's web page http://www.mhennessy.f9.co.uk and I am really impressed ... Mark well done! ..."

Amen, brother. Great engineering and construction, details and style ... and documentation and web page work = top drawer work.

check this out too: http://www.mhennessy.f9.co.uk/isolating/index.htm

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Old 11th December 2006, 08:18 AM   #14
AndrewT is offline AndrewT  Scotland
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Default Re: Re: Voltage on rails verses power output.

Quote:
Originally posted by FastEddy
Scaling back on the rail voltage from +/- 65 VDC to +/- 56 VDC = 2 channels, 145 watts ... further scaling back is all linear ratios = rail voltage v. clean power output ( As per Anthony Holton at aussieamplifiers.com : "The NX150 will operate on supply voltages as low as +-20 volts very well and as high as +-70volts").
yes, the power varies sort of linearly. but is proportional to the square of the supply voltage and then only after subtracting for losses through the semis and other components/wiring.

I said
Quote:
very little more (than 70Winto 8r) will be available from +-47Vdc and only if all is optimised for maximum power.
and I meant it. One might be able to get 80W or maybe even 90W from +-47Vdc and I still count that as very little more.

But I am still not sure what was being asked.
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Old 11th December 2006, 09:46 AM   #15
djk is offline djk
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"is it possible to get say 47+ 47- 8 ohms more then 70 watts?
without bridge the amp"

The Adcom GFA535 is rated at 60W into 8R and runs on 52V, as does the 60W rated Hafler DH-120.

"+/- 47 VAC secondaries = +/- 65 VDC rails "

If he has 47-0-47 AC that would be about right.

is formed by holding down the 'alt' key while entering 0177
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Old 11th December 2006, 04:29 PM   #16
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djk: " ... is formed by holding down the 'alt' key while entering 0177 ..."

(alt. plus 01777 = ) ... is what I get on my Mac Mini and MacBook laptop ...

I know this works on modern Windont's ... but not on Apples ...
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Old 11th December 2006, 05:50 PM   #17
edl is offline edl  Hungary
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Hi Prorms,

I prefer Lin topology.
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Old 11th December 2006, 07:14 PM   #18
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Hi guys,

did we manage to help Prorms with his problem or are we just confusing the guy more.

I do not even see him reply to any thread, maybe he has given up by concluding that we are only interested in our own ideas.

My answer to your first question is yes, you can get 70W from a 47V supply. How important is it, or is it due to the fact that it is a transformer you already have.

To obtain the power, it must also be capable of a few amps, lets say at least 2 Amps for the argument.

Transistors will swing close to the rails, FET within about 5V from the rails so transistors would get closer to the magical 70 watts.

Would it make much difference if it is 60 or 70 or 80 watts, your normal listening level (pretty loud) seldom exceeds 10 watts average.
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Old 11th December 2006, 09:25 PM   #19
routhun is offline routhun  United States
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Dear Nico Ras,

May be should read Prorm original request and my response carefully. I've not decided LM4702 for him, that is my suggestion only. If you read my post carefully you find the words "may be" in my post, so he can choose that one if he likes. Sure I don't know his capabilities, but LM4702 is offers a wide range of possibilites. Your comment shows that you have not a single clue about LM4702.

It is a national semiconductor IC and it implements the front-end of an highquality amplifier, and you need the discrete output stage to finish the amplifier. It has the compactness and simplicity of the chip-amp and the power drive of the discrete amp. Atleast it can operate at the voltage levels he is looking for. None of the LM series chip-amps can operate at the voltage levels he requested. Again this IC was designed by the real professional audio amp designers not by a bunch of arm-chair designers. Since it is targetted for commercial production it is quite stable. The National-Semi people designed a 100W+100W amp with 0.0006 THD (yes 0.0006!!!) with this chip. I myself built several chip-amps, which has detail but lacks the thump. This one has great detail and enough thump, I am using it with a LM4562 (which is also an LM opAmp with extremely low distortion) based preamplifier. Its performance exceeded than my Luxman R-1120, Luxman R-117, HK's AVR-520, NAD 7020 etc.

The kit that I am talking about is offered as a just PCB, or full un-assembled kit with all parts including the PCB or just for $6 more a completely assembled kit is also offered. This offers him a wide range of options for whatever the capabilities he have.

Atleast I've suggested something that he can made, without so much bickering, but you, after all these posts and questioning my post still don't have a definite answer for him!!!!!

-Routhun
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Old 11th December 2006, 10:30 PM   #20
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Default re: LM4702

routhun: " ... The kit that I am talking about is offered as a just PCB, or full un-assembled kit with all parts including the PCB or just for $6 more a completely assembled kit is also offered. ..."

Several others have expressed interest in this new National chip. It looks like we may have a project thread in the making : http://www.diyaudio.com/forums/showt...95#post1079095

I'm going to try out a tube pre-amp in front of one of my '4702 projects and use another pair for bi-amping a speaker set ... and if you already have the layout of a PCB and road maps, I am very interested ...

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