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Old 24th August 2009, 03:43 AM   #1
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Default AD811 Current Feedback Opamps for sale

I just sold a few AD811's to a friend I met on this forum. He said others here might be interested in them. I have about 500 brand new in rails if anyone is interested.

Thanks,

audioman54 / Mark
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Old 24th August 2009, 06:34 AM   #2
Vil is offline Vil
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Hi ,

is it SMD or DIP package ?
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Old 24th August 2009, 06:10 PM   #3
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They are all DIPS.
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Old 27th August 2009, 05:05 AM   #4
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Default 370 AD811's for sale...make an offer!

I counted what I actually had and it was only 320 part...but I found another tube while I was cleaning up my lab for a demo on Friday. So I do have 370 if anyone needs some.

Mark / audioman54
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Old 28th August 2009, 03:34 AM   #5
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Hi

I've often read about how well this op amp works in i/v and buffer circuits. Some time ago I purchased a few 811's to try myself. No matter what type of on pin decoupling/bypassing (film , os con , + to- / both??) , I've never had anything but runaway oscillation. This was more often than not used in a cd player output section. I'm not trying to high jack this offering , just hoping to get a handle on this much recommended(Jung) device.

Thanks
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Old 28th August 2009, 03:39 AM   #6
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Hi Homemade,

These parts do not like caps in the feedback loops and in addition you must use a 1.2k to 1.5k feedback for best results. Because they are high slew rate and bandwidth layout and powersupplies are very important. If you have a schematic I can take a look at it. Are you inverting or non-inverting?

Best Regards,

Audioman54 / Mark
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Old 28th August 2009, 04:15 AM   #7
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Most often my use has been with Philips based 1541 dac players , for i/v , but also as a buffer with voltage out dac chips. My reference for high slew opamps are the LM6171/6172 devices. When these are used with before mentioned decoupling in the same output circuit , I get very nice results. FIRC , most Philips stock i/v use a 1.8k feedback resistor. There may indeed be a cap in the feedback loop. Mostly this device is used a virtual ground. have gone to great length with shielding/grounding of all digital chips and the op amps themselves. I'm certain there is more i need to understand about usng this 811 device.

Paul
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Old 28th August 2009, 08:16 AM   #8
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Default Please buy my never used new/but old AD811 CFB opamps

Hi Paul,

I posted about the AD811's because I had a bunch to sell. I did that because some people on this site asked if anyone had any and I did because of the MSB CD players I designed and sold many, many years ago that used that part. (TDA1541S1 Crown chips were in those players and I sold those chips also for $50 each a couple of months ago! Still have 4 matched ones left by the way) For $4 each I sold a few of my AD811's and since I have been out of work for 10 months (National Semiconductor laid off all us over 50 guys) it was nice to get a few extra bucks. However the parts I helped to design at National Semiconductor, as a Principal Applications Engineer in the Audio Group, are better parts.

The LME49713 CFB in a metal can is the best sounding opamp you can buy right now (in my humble opinion). It beats the 811 in every single audio measurement and it was designed to do that! So if you can afford the extra money get that LME49713's in either SO or Metal cans (that is the only two packages them come in and for sonics the metal cans are the way to go). Or for voltage feedback go with the LME49710's which are built on the same great/unique process and do come in Dip's, SO's and HA metal cans.

But for those that want/need some AD811's I still have 350 of them to sell at $4 each.

Mark / audioman54
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Old 28th August 2009, 11:12 AM   #9
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Sorry if I'm adding more work than you were looking for just to sell some opamps. At least it's good for a 'bump' .
Given that you have used the 811 for i/v with the 1541 , in general terms , what is the proper circuit design for this opamp? I know others my have interest , as I've read several posts indicating the 811 is tough is work with.

Paul
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