Dan d'Agostino MOMENTUM: Sonic Character like pure ClassA/SE despite low Idle Power ?

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#121
LineSource said:
Can any expert in output error correction circuits describe how to improve the basic circuit in the attached schematic for 12 pairs of 60Mhz Sanken output transistors? The Spice simulation shows 0.015% THD for 300 watts into an 8 ohm load.

What is the best output error correction circuit for 12 pairs of 60Mhz power transistors?

As a reference, a fully symmetrical design with global negative feedback using the same output transistors simulates at 0.00008% THD for 300 watts into 8 ohms.
Click to expand...
Mr. Bob Cordell actually must have the most knowledge in this case - check out this thread:
http://www.diyaudio.com/forums/solid-state/89023-bob-cordell-interview-error-correction.html
 
#123
Nico Ras said:
I am sorry to say, it is really ugly with that meter on it - bathroom scale looks better.
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The amp is gorgeous in person, pics don't do it justice....

LineSource said:
Can any expert in output error correction circuits describe how to improve the basic circuit in the attached schematic for 12 pairs of 60Mhz Sanken output transistors? The Spice simulation shows 0.015% THD for 300 watts into an 8 ohm load.

What is the best output error correction circuit for 12 pairs of 60Mhz power transistors?

As a reference, a fully symmetrical design with global negative feedback using the same output transistors simulates at 0.00008% THD for 300 watts into 8 ohms.
Click to expand...

Can you drive that many outputs with such a small driver stage ...?
 
#127
I think so too, probably the same topology used by pioneer in their high end amps of the 80s. Highly tweaked or for better words much improved Diamond buffer + driver (consists of smaller and faster transistors with high Ft in paralel) + many output devices in open loop. Note it is a 4 stages circuit, the outputs of the diamond buffer is not the driver stage. Best THD figures for an outputstage without feedback or error correction Ive seen and it sounds very good too.
 
#128
I'm sorry about the necro, but I've discovered this amp and thread a week ago.

tiefbassuebertr said:
Are there any news concerning listening tests and the topology ?
Click to expand...

It seems the output transistors are 2SC6145, and (highly) probably 2SA2223

Do you really believe such horizontal hfe vs. Ic curves?

AKSA said:
Diamond buffer output stage in open loop, I understand?
Click to expand...

AKSA... Why do you say that about a diamond buffer?
 
#131
nRm said:
I'd been thinking about your reply and may be you doubt about my 2SC6145 assertion.

Look here, at the sixth page, the first image at the right side.
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Good pictures from inside on URL
http://dagostinoinc.com/documents/356_Dan_cover.pdf
Thank you for this advice.
more pics from german's magazine "AUDIO"
http://www.audio.de/bildergalerie/bilder-dan-d-agostino-momentum-1368187.html

It is only a matter of time until a clone turns up. Circuit topology must actually be easy to clone, because there are no SMD parts in use. If one drawn all transistors in parallel mode as one pcs in the reverse engineered schematic diagram, one get an "easy to bild" and good to understand circuit - so I think.

The main flaw in this device are at first glance the Panasonic electrolytic capacitors, which have no chance against this from follow URL for example:
http://www.ftcap.de/index.php/screw-terminals-read-more/items/serie-gw-40c-105c-5000-h-92.html

OTOH this amp is a very low cost amp in comparison to the following models:
HigherFi-Ultimate - The Worlds Best and Most Expensive Audio Amp and Amplifiers
Thus no more expensive caps can be use (but the advice on the rear panel "no user serviceable parts inside" therefore is wrong).

BTW - who can provide a translate from this test review?

other URLs:
http://www.whatsbestforum.com/showt...rience-with-Dan-D-Agostino-Momentum-Amplifier
http://www.youtube.com/watch?v=vXLaTWbS5SQ
 
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#133
"It seems the output transistors are 2SC6145, and (highly) probably 2SA2223"

If the on-line Sanken datasheets are accurate, this NPN - PNP complementary pair are not very well matched.

Sanken 2SA2223 PNP fT=35Mhz, Cob=500pF
Sanken 2SC6145 NPN fT=60Mhz, Cob=250pF
 

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#135
LineSource said:
"It seems the output transistors are 2SC6145, and (highly) probably 2SA2223"

If the on-line Sanken datasheets are accurate, this NPN - PNP complementary pair are not very well matched.

Sanken 2SA2223 PNP fT=35Mhz, Cob=500pF
Sanken 2SC6145 NPN fT=60Mhz, Cob=250pF
Click to expand...

No Bjts are really, the same matching diversity is found from onsemi pairs and for that matter from all manufacturers. This not only applies to output transistors but also small signal transistors.
 
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