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Old 25th November 2003, 01:45 AM   #11
jwb is offline jwb  United States
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I will state for the record that by listing my changes to the circuits of Mr. Pass & Mr. Jung, I do not mean to imply any deficiency or lack in the originals. Indeed, I selected these designs because of my high regard for both of them.

So, If I say that I have improved the Jung regulator with a better current source for the pass device, I mean to say only that my current source has a higher Z (about a megohm, by my reckoning) than the original. Strictly speaking, you may not think this makes any difference in the final product, and you may not think it rises to the level of "improvement".

Furthermore if I say that I've improved the Aleph amplifier with a monolithic JFET pair and a higher-impedance current source, I only mean to say that I've calculated and measured lower DC offset and higher CMRR with my changes than without them. I do not mean to diminish the qualities of the original design.
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Old 25th November 2003, 02:24 AM   #12
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JWB

The circuit look nice and should sound good. However, you can't claim a high CMRR with out having a balanced input, maybe you meant PSRR. Anyway, I am sure it sounds nice. So what kind of phones are you using?
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Old 25th November 2003, 04:28 AM   #13
jwb is offline jwb  United States
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I hope, sir, you are not implying this amp is single-ended!

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Old 25th November 2003, 04:29 AM   #14
jwb is offline jwb  United States
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Default I hope you are all quite ready for more bad photography

This is her innards. That's the attenuator hanging out of the case.
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Old 25th November 2003, 04:30 AM   #15
jwb is offline jwb  United States
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A little more assembled
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Old 25th November 2003, 04:32 AM   #16
jwb is offline jwb  United States
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All ready to go, with my Grado SR 80 cans. Plans to upgrade to SR-1 are underway.
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Old 25th November 2003, 04:38 AM   #17
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Quote:
Originally posted by jwb
I hope, sir, you are not implying this amp is single-ended!


Well, one end looks single.

I'm admiring a new design, following how it's constructed, but not reading how good it sounds...



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Old 25th November 2003, 05:10 AM   #18
jwb is offline jwb  United States
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It sounds amazing of course.

Imagine combining an amplifier you can't afford (say, a Pass Aleph 5) with a speaker you can't afford (e.g. Wilson), and listening to it in a room your house doesn't have. That's what I feel listening to this little amp.

Right now I'm listening to Homeless from Paul Simon's Graceland. When those throaty African gentleman say he-EH he-EH he-EH, I might as easily be in the recording hall in South Africa. The impact is of the proverbial velvet hammer variety: a representation of the original power of the performance, rather than something injected by the equipment. The clicking of tongues, something ommitted almost entirely by the opamp headphone output of my receiver, is reproduced faithfully.

Previously I was listening to Dire Straits' Sultans of Swing. The bass sounded very nice. I don't want to say "it has good bass", for fear of invoking images of kids in Hondas with Kickers in the trunk. But this is a song with the bass turned up to 11, and I can hear it properly now. Knopfler's ending solo has great staccatto attacks.

This amp basically never runs out of power. I might even reduce the idle current to spare myself some heat problems.

But I never trust equipment reviewed by the builder. You might as well be reading Bose sales literature.

Instead I'll mention that initially the amp had a bit of a buzz. I thought the 1/2" run of .1" wide PCB trace would be low enough impedance to avoid the problem, but apparently not. Luckily I included a giant via right next to the filter caps, and by moving the main ground there, I eliminated the buzz. The real problem isn't, I don't think, that the grounding scheme was so bad, bad rather that I didn't design for so large a Vrip: 1Vpp.

Also it's running kinda hot. As long as the sink temperature stays under 140C, I'm within the specs. Right now the sink is running at about 60C. That would be good except it's making the plastic case smell.
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Old 25th November 2003, 05:15 AM   #19
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Old 25th November 2003, 10:04 AM   #20
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Nice work jwb,

With my old Niam amps, I've never had the luxury of headphone output. Very compact arrangement too.
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The bill of materials. Only $150 worth!
Very attractive!

Paul
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