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DarTZeel, Stereophile's 2005 Amplification Component...
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Old 16th December 2005, 12:51 AM   #1
Ultima Thule is offline Ultima Thule  Europe
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Default DarTZeel, Stereophile's 2005 Amplification Component...

Hi,

just noticed for some day ago in MikeB's thread (Terry Demol's post) a link to Stereophiles awarding of 2005 Amplification Component, DarTZeel NHB-108 Model One.

Well, I'm not so interested in "ready made products" and what Stereophile thinks, but nevertheless I got a bit curious to what is so "special" with this amplifier so I dug up the patent (issued as late as last year..) and grabbed the principle schematic.

The designer tells the amplifiers input and output stage is outside the NFB loop which is only around the second stage, which to me looks like effectively being more or less a CFP with Q5 inbetween.

The principle schematic is attached below.

Cheers Michael

BTW, the Swiss designer Hervé Delétraz says NHB stands for "Never Heard Before"...
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Old 16th December 2005, 12:58 AM   #2
lumanauw is offline lumanauw  Indonesia
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From his site, I read something, that the DC offset drifts quite some mV, sensitive to temperature. Is this not dangerous?
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Old 16th December 2005, 01:04 AM   #3
Ultima Thule is offline Ultima Thule  Europe
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..and here's the review BTW..

20 W Class A for ridicoulus 18,200 US$!

Lumanauw,

I haven't read that carefully, but if it's some mV at output then it's not much of course, or where did you read the temp drift should be?

Cheers Michael
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Old 16th December 2005, 01:48 AM   #4
lumanauw is offline lumanauw  Indonesia
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I think it is in one of pdf in the manufacturer's site.
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Old 16th December 2005, 02:35 AM   #5
serengetiplains is offline serengetiplains  Canada
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Quote:
Originally posted by Ultima Thule
20 W Class A for ridicoulus 18,200 US$!
Price is of course relative to what you can afford relative to how much you value the art coming through your speakers relative to ___________ [beer, a BMW .... ]
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Old 16th December 2005, 07:58 AM   #6
Ultima Thule is offline Ultima Thule  Europe
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Quote:
Originally posted by serengetiplains


Price is of course relative to what you can afford relative to how much you value the art coming through your speakers relative to ___________ [beer, a BMW .... ]

Oh those diyAudio "politition" aspirants...

As a DIY:er I would of course brew my own beer, drink it up, and then drive around in my DIY BMW!

Wellcome back with some more technical related inputs to this thread, or else please spare your energy.

Cheers Michael
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Old 16th December 2005, 08:20 AM   #7
Upupa Epops is offline Upupa Epops  Czech Republic
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They walk from " wall to wall " in this redaction.... One year win Halcro with outstanding parametres, second year this s... ...Yes, probably for " nice distortion "....
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Old 16th December 2005, 08:32 AM   #8
phase_accurate is offline phase_accurate
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It has in fact two NFB loops. Because of the low loop gain of the last loop - THD is a little high. But it is constant over frequency ! Whis is seldom achieved by amps with overall NFB.

So it would probably be wise to listen to it before uttering a verdict.

Is it overpriced ? IMO yes !

Regards

Charles
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Old 16th December 2005, 11:09 AM   #9
Ultima Thule is offline Ultima Thule  Europe
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Quote:
Originally posted by Ultima Thule

20 W Class A...
I should be more clear mentioning that only the bias level of the otput stage admits 20W in class A, else the amplifier delivers 100W RMS into 8 Ohm.

Charles,

I'm not shure where those two FB loops you see are fitted, I thought Q3, Q5 & Q7 being one (and the only) loop where the feedback path is from Q7 through R11, divided down to earth by R9, to Q3.

The diode, D1 & D2, arrangement is a bit peculiar to me, it seem to let Q11 & Q12 move around a bit until it's clamped by those diodes at more demanding drive levels/loads.

Cheers Michael
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Old 16th December 2005, 11:16 AM   #10
Ultima Thule is offline Ultima Thule  Europe
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Quote:
Originally posted by Upupa Epops
They walk from " wall to wall " in this redaction.... One year win Halcro with outstanding parametres, second year this s... ...Yes, probably for " nice distortion "....

Upupa,

Yes it's funny how Stereophile change taste for amplifiers, maybe they don't like "ultra clean" sound reproduction anymore... BTW darTZeel resembles of your "favorite amplifier" Ayre!

Cheers Michael
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