Dan d'Agostino MOMENTUM: Sonic Character like pure ClassA/SE despite low Idle Power ? - Page 3 - diyAudio
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Old 18th October 2011, 06:44 PM   #21
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Quote from hi-fi News:

Any flies in the ointment? Hum and noise is fractionally high in this early sample (yielding an A-wtd S/N of 78dB re. 0dBW, 104dB re. 300W



Is A-weighting S/N standard practice, or is it marketing?

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Old 19th October 2011, 12:53 AM   #22
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It looks a lot like an amp without a global loop feedback - or one that is not the usual 20+db or more... thus the rather high output impedance and the way it looks in the distortion specs/graphs. The paralleled output devices will help drop the output Z and distortion... not a bad way to make a bipolar amp, all things considered. Very "tube like"??

_-_-bear

PS. think I will just pick one up so that we can open the case and see what is inside!

PPS. wouldn't it be funny if there were maybe 6 transistors per channel in there on a tiny 1" square SMT board?? HA HA!
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Old 19th October 2011, 01:46 AM   #23
adason is offline adason  United States
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bear, there is supposedly 24 output transistors, do not know if total or per side
you can see how it looks inside from the link jacco posted
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Old 19th October 2011, 02:24 AM   #24
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FWIW: At RMAF, I overheard D'Agostino mention that global feedback is 6db, and the differential input stage has no gain.

Last edited by thune; 19th October 2011 at 02:27 AM.
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Old 19th October 2011, 07:29 AM   #25
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Quote:
Originally Posted by thune View Post
FWIW: At RMAF, I overheard D'Agostino mention that global feedback is 6db, and the differential input stage has no gain.
This topology seems to be close to that topologies from Anders Thule.
There is no global feedback (only local feedback despite low idle current through the output) through virtual Class-A. Check out this threads:
Ultimate ECC for Class B from Thule Audio? Topology also used by Teac
What happen to thule audio?
Thule Audio Vintage Integrated Amplifier IA-120 (IA120) Schematic wanted

Last edited by tiefbassuebertr; 19th October 2011 at 07:33 AM.
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Old 19th October 2011, 02:16 PM   #26
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Quote:
Originally Posted by adason View Post
bear, there is supposedly 24 output transistors, do not know if total or per side
you can see how it looks inside from the link jacco posted
Oh! Yep. I missed that little pic down on the bottom of the page the first time!

Ok... now I see...tnx.

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Old 19th October 2011, 02:28 PM   #27
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Judging by the hurd of TO92s in parallel, there's a fair bit of KAV300i heritage in there.
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Old 19th October 2011, 02:57 PM   #28
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Quote:
Originally Posted by tiefbassuebertr View Post
This topology seems to be close to that topologies from Anders Thule.
There is no global feedback (only local feedback despite low idle current through the output) through virtual Class-A. Check out this threads:
Ultimate ECC for Class B from Thule Audio? Topology also used by Teac
What happen to thule audio?
Thule Audio Vintage Integrated Amplifier IA-120 (IA120) Schematic wanted

Maybe someone can explain it to me - I seem to be drawing a blank.
How can the current mirror that is floating on the speaker output cause the output devices to NOT switch off?? I can see it MAYBE on one rail, but on both??

Clearly I am missing something in this design as to how it works... then too, how does the DC offset correction work, if one rail is being hauled away from zero/ground potential? I can see that the DC correction would cause the opposite polarity OPs to have to turn on in response to the other side being hauled high to prevent switch off. But then you have a tug of war between the two circuits, with the difference manifesting itself because of the time constant differences between the two (current mirror vs. DC offset servo)??

Seems interesting.

I'd bet that Dan D'A has something similar or identical going on... seems likely anyhow...

So, tiefbassuebertr, you've had ur hands on some of these Thule amps, how do they sound??

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Old 19th October 2011, 03:19 PM   #29
Jozua is offline Jozua  South Africa
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Hi

As a long time Krell owner and enthusiast I am somewhat perplexed by the absence of reviews re this amp. What is going on?

Jozua
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Old 19th October 2011, 04:31 PM   #30
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Quote:
Originally Posted by bear View Post
Maybe someone can explain it to me - I seem to be drawing a blank.
How can the current mirror that is floating on the speaker output cause the output devices to NOT switch off?? I can see it MAYBE on one rail, but on both??

Clearly I am missing something in this design as to how it works... then too, how does the DC offset correction work, if one rail is being hauled away from zero/ground potential? I can see that the DC correction would cause the opposite polarity OPs to have to turn on in response to the other side being hauled high to prevent switch off. But then you have a tug of war between the two circuits, with the difference manifesting itself because of the time constant differences between the two (current mirror vs. DC offset servo)??
Seems interesting.
I'd bet that Dan D'A has something similar or identical going on... seems likely anyhow...
So, tiefbassuebertr, you've had your hands on some of these Thule amps, how do they sound?? _-_-bear
This amps sounded very good inside of the category of Class AB amp (from my view one of the best). But Anders Thule don't conjure. Thus the sound is very bad compared to each good constructed Single Ended and Push-Pull pure class A amplifier.
Therefore I want to know a Class AB topology with low idle current through the output power stage, that sound is close as possible to class A and have start this thread:
Collection of Class B topologies <100mA Idle and Sound closest by Class A
The only amp, that sounds like pure class-A is the HCA power amp MX-10000 from Yamaha about
Yamaha's Hyperbolic Conversion Amplification (HCA) Circuit
Concerning the DC offset topology I haven't made any investigations concerning the correction behaviour, because I haven't until now discover unwanted effects.

Last edited by tiefbassuebertr; 19th October 2011 at 04:42 PM.
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