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Old 28th November 2012, 06:26 PM   #2251
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I have documented the problem in another thread (250MHz oscillations, Agilent spectrum analyzer measurement). Output CFP of DB is prone to UHF oscillations triggered by RFI impulse sent to the output.
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Old 28th November 2012, 06:39 PM   #2252
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Quote:
Originally Posted by kgrlee
Got a link homemodder? I'm exhausted from looking through 50 pgs of the Headphone Amp thread.

Do you know if the small pic on the Linear Audio website is the full circuit?

Apologies to those who would have me buy the book. I am counting my pennies.
Go back to August 30th, post #522
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Old 28th November 2012, 06:40 PM   #2253
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Quote:
Originally Posted by PMA View Post
I have documented the problem in another thread (250MHz oscillations, Agilent spectrum analyzer measurement). Output CFP of DB is prone to UHF oscillations triggered by RFI impulse sent to the output.
Got a link?
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Old 28th November 2012, 06:48 PM   #2254
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Somewhere in last days BT thread posts.
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Old 28th November 2012, 07:14 PM   #2255
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Default compl push-pull topolgy as line stage -

I would be happy to discuss the compl- push-pull and the output stage and rfi etc over in the Marsh headphone amp section.... the guts and gore departmment. -RNM
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Old 29th November 2012, 12:04 AM   #2256
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Quote:
Originally Posted by PMA View Post
I have documented the problem in another thread (250MHz oscillations, Agilent spectrum analyzer measurement). Output CFP of DB is prone to UHF oscillations triggered by RFI impulse sent to the output.
Pavel, I could only find this
http://www.diyaudio.com/forums/analog-line-level/146693-john-curls-blowtorch-preamplifier-part-ii-2996.html I can't believe I've just looked through more than 350 posts to find it.

But Marshy's headphone amp, neither the pic at http://www.linearaudio.net/index.php?option=com_content&view=article&id=161:a-headphone-bufferamp-and-auto-eq-for-headphones&catid=44:volume-3&Itemid=108
OR
#522 on this thread
are standard 'Diamond Buffer".

So are the Agilent plots of some other evil Golden Pinnae device?
__________

As Mr. Marsh is at pains to point out, he is not putting forward this design to compete with SW-OPA. But for it's intended purpose, and also for a simple buffer or amp, it's elegantly effective if you can select devices and don't mind running 50ma Iq.

I for one am impressed and jealous cos he gets his performance with half the active devices that I need.
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Old 29th November 2012, 12:41 AM   #2257
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Well on firing up my input stage there was some 100MHz fuzz, so a little work remains. In general it all looks ready, the breadboard is a "little" sketchy I admit.
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Last edited by scott wurcer; 29th November 2012 at 01:04 AM.
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Old 29th November 2012, 01:39 AM   #2258
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cool
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Old 29th November 2012, 05:54 AM   #2259
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Quote:
Originally Posted by RNMarsh View Post
Output 'buffer' circuits vary in their isolation ability to minimize the affects.
...
But it clearly can affect performance .... such as, power amp and loudspeaker reflecting back any nonelinear Z.

...which topology in the output stage has the greatest isolation from output to Av stage...
Though developed as a power chipamp, the Mauro Penasa MyRef uses a nested Howland Current Pump within a global voltage-series feedback loop to address precisely this issue - the effect of a nonlinear load-Z on audible sonics.

There are huge active threads in the chipamps forum on the MyRef and its derivatives. I've built several, and can attest to its outstanding sonics.
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Old 29th November 2012, 06:21 AM   #2260
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Quote:
Originally Posted by kgrlee View Post
...
unlike certain pseudo Messiah's that shall remain nameless ...
Lol - bad-hair day?

BTW, I've preferred simplicity from the beginning of this thread, which is why I picked up on the Kaneda initially, and later played around with the single-ended versions of SWOPA, with various output stages.

IMHO, all have various pros and cons, but if I had to build yet another line-level discrete-opamp to actually listen to music, I'd probably go with a Kaneda/Constellation derivative, despite the fact that it's not an ultra-low THD contender. Why? Because it's simple and only requires a few parts to be matched, and by most accounts, has clean wide-open soundstage and resolution.
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