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Old 11th August 2011, 05:16 PM   #21
vizion is offline vizion  United States
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That's a nice amplifier case, Klaus. Where did you source the item ?
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Old 21st December 2011, 01:52 PM   #22
Soxen is offline Soxen  Denmark
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Did anybody actually build this amp?

If so what are the listning impressions?

How does it sound compared to the standard ?
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Old 4th September 2014, 04:59 AM   #23
raul_77 is offline raul_77  Europe
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Is this useful?

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Old 5th September 2014, 08:27 PM   #24
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Default how about 4780 instead?

Begs for multiple paralleled lm4780..
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Old 8th September 2014, 03:52 PM   #25
AndrewT is offline AndrewT  Scotland
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The 3886 with a ClassA sinking device will run into overheating problems.
Using the dual chip 4780 in that ClassA format will making the overheating problems even worse.
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Old 9th September 2014, 09:13 AM   #26
Mihkus is offline Mihkus  Estonia
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And its not going to live very long...
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Old 12th September 2014, 05:12 AM   #27
gman76 is offline gman76  United States
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Quote:
Originally Posted by AndrewT View Post
The 3886 with a ClassA sinking device will run into overheating problems.
Using the dual chip 4780 in that ClassA format will making the overheating problems even worse.
Yes, an SOA issue most likely. Interesting concept. BTW I was apps support for the 1875, 675, 391, LM12 back in the day. Can hardly believe they are still being used and discussed.
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Old 13th June 2016, 03:17 PM   #28
mcspack is online now mcspack  United States
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Hello, I hate to revive an old thread but has anyone else built this in a while? I have built several gainclone amps after reading the great article/review on the 47 labs gaincard many years ago. The amp was paired up with a set of Lowther pm2a based horn speakers and the combination was seen as a huge plus by the reviewer, mainly because of the high efficiency of the Lowthers. I experimented with inverting topology and biasing into class a via an 8k resistor to -V, also for buffer I used TVC volume control. I can concur that that amp did pair well with high efficiecy speakers. Real magic there!

My question is in this circuit how critical is the value of the 10u caps on the input. and are these needed if there output caps or 0 DC coming from sources? thanks.
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Old 13th June 2016, 07:42 PM   #29
Steven is offline Steven  Netherlands
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If everything is ideal, the input capacitors are not needed. The inputs of the chipamps carry a deliberate offset, but of opposite sign. So they cancel out at the input. But some unbalance somewhere will mess up the output offset, so it is better to keep the caps in, especially when an input transformer is used, as was shown in a working example. Transformers are not good in handling DC.
They can be smaller, though. With 10u the LF corner frequency will be around 1 Hz, so you can take a value of 1u for a value of 10 Hz.

Steven

PS This might be my first reply in 5 years or so; I have no time to follow diyaudio actively anymore. I just got a mail from diyaudio, that there was an activity on this old thread and I thought why not.
Maybe also time to change that photo from 2003 in my avatar.
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Old 14th June 2016, 08:56 AM   #30
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by mcspack View Post
Hello, I hate to revive an old thread but has anyone else built this in a while? I have built several gainclone amps after reading the great article/review on the 47 labs gaincard many years ago. The amp was paired up with a set of Lowther pm2a based horn speakers and the combination was seen as a huge plus by the reviewer, mainly because of the high efficiency of the Lowthers. I experimented with inverting topology and biasing into class a via an 8k resistor to -V, also for buffer I used TVC volume control. I can concur that that amp did pair well with high efficiecy speakers. Real magic there!

My question is in this circuit how critical is the value of the 10u caps on the input. and are these needed if there output caps or 0 DC coming from sources? thanks.
Very high efficiency speakers require very low noise amplifiers. The chipamps are not very low noise. In my view they are not even low noise. Typical Ein of around 20nV/rtHz to 60nV/rtHz for the 3886, compared to 6nV/rtHz to 12nV/rtHz for a good discrete front end.
That's a total variation from best to worst of 20dB, or the difference from 84dB speakers to 104dB speakers. i,e a 104dB speaker on an amp with Ein = 6nV/rtHz will sound like it has the same noise as an 84dB speaker fed from a Ein = 60nV/rtHz
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Last edited by AndrewT; 14th June 2016 at 09:00 AM.
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