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Old 28th November 2012, 08:40 AM   #2241
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Quote:
Originally Posted by RNMarsh View Post
More than 200 years of expertise in just the 4 people mentioned above...
May I suggest a little bed-time (or beach-side) reading?

Amazon.com: The Mythical Man-Month: Essays on Software Engineering, Anniversary Edition (2nd Edition) (0785342835953): Frederick P. Brooks Jr.: Books
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Old 28th November 2012, 09:18 AM   #2242
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Mr. Marsh, finally figured out the thread is Marsh Headphone Amp Linear Audio

May I commend you on keeping this modest (?? ) 50 page thread in good order and contributing loadsa good stuff on PCB layout & PSUs too. I very much like your 'modest base requirements' in #279.

If I may be so bold .. Is the full circuit this one?
Amp & Auto EQ for Headphones

It's not clear if this little pic on the Linear Audio page is just the output buffer or the full circuit. I can't see any provision for 12dB gain. It is indeed examplary in its simplicity & effectiveness.

I believe my own modest effort with FET990 may meet your requirements list but at a cost of nearly double the active devices. In return, all I can offer is a reduced Iq of 3mA for the same performance and a less stringent need for matching devices.

I'm sorely tempted to treat myself to a beach bum's X'mas present as I see Guru Wurcers 'Supa Dupa Mike Preamps pt 2' is in the same issue of Linear Audio ... and I wanna know wat dis Auto EQ for headphones is too.
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Old 28th November 2012, 10:41 AM   #2243
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That DB headphone circuit might be a good candidate for potential VHF oscillator
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Old 28th November 2012, 11:50 AM   #2244
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Quote:
Originally Posted by benb View Post
That brings up a thought/question. Would it help this to take the feedback from the output of the VAS instead of THE output? It would avoid the problem of spreading out low-harmonic distortion into higher harmonics (is there a name for that?) in the feedback loop.
I think it's called spectral growth distortion.
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Old 28th November 2012, 12:23 PM   #2245
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There will be a knife sharpening seminar offered in the lobby... for those who are interested. Tea, coffee and band-aids to follow...



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Old 28th November 2012, 04:08 PM   #2246
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There will be a knife sharpening seminar offered in the lobby... for those who are interested. Tea, coffee and band-aids to follow...



After seeing the commercial for a sharpener on TV, I'm planning on using credit cards for slicing things, henceforth.
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Old 28th November 2012, 04:30 PM   #2247
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Quote:
Originally Posted by RNMarsh View Post
gads. Did I write all that? And, I only came here in May this year. I just wanted to help DIY headphone amp builders make the headphone amp and enjoy it. Now here I am spilling my life's guts out to a bunch of strangers on this social medium! Am I that desperate!? [not really]. Wasnt I breast fed?

Kgrlee--- I'll see if I have any better luck finding it. -RNM
You posted the schematic in this thread instead of your headphone amp thread.
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Old 28th November 2012, 05:29 PM   #2248
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Quote:
Originally Posted by PMA View Post
That DB headphone circuit might be a good candidate for potential VHF oscillator
Which circuit Pavel?

If you are referring to Marshy's circuit, that's easy enough to solve without affect the performance. 2 resistor values.

Quote:
You posted the schematic in this thread instead of your headphone amp thread.
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.

Last edited by kgrlee; 28th November 2012 at 05:40 PM.
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Old 28th November 2012, 05:33 PM   #2249
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I mean the circuit you have linked,

A Headphone Buffer/Amp and Auto-EQ for Headphones
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Old 28th November 2012, 06:20 PM   #2250
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Quote:
Originally Posted by PMA View Post
I mean the circuit you have linked,

A Headphone Buffer/Amp and Auto-EQ for Headphones
Could you elaborate? Have you had a bad experience?

Any circuit with Complementary Feedback / Sziklai Pair followers may oscillate if designed badly but the cure is usually simple. In this case, IF there is a problem, the solution is to change 2 resistor values. In a VERY BAD case, you may have to add 2 resistors.

There are millions of amps with CFB pair O/Ps which aren't VHF oscillators. I'll concede there are thousands, mainly Golden Pinnae, which do oscillate at VHF from time to time.

Last edited by kgrlee; 28th November 2012 at 06:35 PM.
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