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Old 19th March 2013, 02:46 PM   #2861
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Where is this thread please?

I see Mike is back. I have two weeks to a tapeout and then I should get time to rev my boards and take more measurements.
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Old 20th March 2013, 01:19 AM   #2862
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Hi Frank,

Does this go for the Intel/AMD chip and socket in your PC.
Perish the thought of ever using a valve in a socket !!
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Old 20th March 2013, 01:38 AM   #2863
fas42 is offline fas42  Australia
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Which is why I would approach the concept of a valve amp very, very carefully ... things are very different in the latter world, lots of heat, temperature cycling is ferocious, chunky connectors, high voltages - like going from a chamber music performance to a disco, electrically speaking ...

Frank
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Old 20th March 2013, 04:44 AM   #2864
benb is offline benb  United States
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I think I've found a test signal:
WALTER MURPHY- A Fifth of Beethoven (extended version) - YouTube
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Old 21st March 2013, 06:47 AM   #2865
fas42 is offline fas42  Australia
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How so? Fairly straightforward mix of classical and light jazz acoustics, shouldn't be too hard ...

Now, if I want a decent stress test I would try some 90's Joe Cocker, "You Can Leave Your Hat On" era material: big, big acoustics, full on big band sound -- this is sound that can subjectively grab your house and threaten to crush it like a cardboard box if it's reproduced well at high volume ...

Frank
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Old 27th March 2013, 11:40 PM   #2866
fas42 is offline fas42  Australia
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Scott's still on to it, but not a single other person has hacked one of these to see what they think of it ... ?

Frank
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Old 28th March 2013, 05:55 AM   #2867
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Scott's still on to it, but not a single other person has hacked one of these to see what they think of it ... ?
SWOPA is a bit too complicated for me, so I went with a Class-A folded Kaneda with 7 actives in 11mm x 14mm SMD. I've built over a dozen prototypes with slight tweaks and parts changes, and it's now stabilized with tight offsets.

I also did a Class-AB FET990 derivative in 15mm x 15mm, and the first batch of boards is in transit to me. These can use BF862 or 2sk209 inputs, and SOT89 outputs like the 2sa1213/2sc2873.

I also have an updated schematic and layout for the FET990 with jcx's clamp-diode bootstrap idea, also in 15mm x 15mm, but I'll hold off on fabrication those boards until the existing board is fully validated and auditioned.

I'm still searching (in simulation) for a simple topology with low transistor count and acceptably good performance. Nothing beats the FET990 derivatives to date.

For the output-stage, Ken Peter's non-switching Class-B with Schottkys is a very strong contender for low-bias current applications - it works reasonably well down to 1 mA bias and maybe lower. However, it does best with a high-performance monolithic opamp as the gain stage driving it.
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Old 2nd April 2013, 12:01 PM   #2868
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For the output-stage, Ken Peter's non-switching Class-B with Schottkys is a very strong contender for low-bias current applications - it works reasonably well down to 1 mA bias and maybe lower. However, it does best with a high-performance monolithic opamp as the gain stage driving it.
Have you a link to this please.
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Old 2nd April 2013, 12:35 PM   #2869
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I'm going to risk sounding off as a audiophile who is not an EE, but why hasn't someone advocated an all npn Class A output stage. I thought that pnp transistors typically had much higher c-b capacitance which slows their switching speed for Class B-AB stages. I read that the Burr Brown OPA604 had an all npn output state. So why in a no holds barred design are we possessed with efficiency? Please be kind! Cordially, Ray
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Old 3rd April 2013, 02:15 AM   #2870
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If your going to use Joe Cocker as a test use 1985's Shefield Steel with Sly and Robbie as the rhythm section. Not a commercial hit, but Joe doing great dynamic music instead of the commercially viable Musak he's been stuck with for decades.... Now back to our program

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