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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

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Old 12th July 2011, 09:48 AM   #11
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I guess not. I've tried with one DS1802 and two DS1807 (similar chip but uses I2C instead of SPI/push button interface). The results were always the same.
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Old 12th July 2011, 12:09 PM   #12
Leon08 is offline Leon08  Germany
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What is your input and output device ?
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Old 12th July 2011, 09:43 PM   #13
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The input device is a line input of an ordinary amp. As output devices I've tried a CD player with a line out, as well as an mp3 player with its headphone output.
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Old 12th July 2011, 10:01 PM   #14
Leon08 is offline Leon08  Germany
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But you said that there were no distortion as you tried it.This is imposible with only 5v supply.A Cd-player output is 2volt. There is not enough headroom for this.I think the problem is that your input signal is too strong.
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Old 12th July 2011, 10:15 PM   #15
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There was no distortion, at least none that was audible and I am pretty sure I would have noticed distortion caused by clipping. Why would that be impossible with 5 V? The opamps are configured to run with unity-gain, so there is no voltage amplification. Also, with the MP3 player I have tried with various output levels. It makes no difference at all (except for the absolute volume which is of course lower if I reduce the mp3 player's output level).
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Old 13th July 2011, 12:07 PM   #16
Leon08 is offline Leon08  Germany
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You have a difficult problem.Sorry, but I don't know why it does not work.
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Old 13th July 2011, 01:42 PM   #17
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Yeah, I guess. Thanks for your help, though. I appreciate it.
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Old 4th August 2011, 05:38 PM   #18
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I just completed the prototype for a basic cmoy type amp with the DS1802. I used this circuit for the ds1802. Though with this a 2V source would be too high.
http://circuit-zone.com/ediy_blog/70/ds1802_sch.gif

I tried the bridge approach like in the app notes but I had some noise problems and some other problems. I cant remember if I had other issues because this little chip gave me alot of problems initially.

No audible noise or zipper noise using push buttons (Im about to start coding a uC for IR control)

Just thought I might pop in if you are still having problems.
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Old 18th April 2012, 04:27 PM   #19
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Talking solution (probably)

some0ne: this may be a tad too late, but i've faced the same problem recently and i think i finally managed to crack it:

the circuit is similar to this one: http://www.maxim-ic.com/images/appno...1/161Fig05.gif except the buffer is made with a different ic (lm4562 powered from +/-9V in my case). the problem appears to be the wheatstone bridge. the high side of the pot is connected to the R1s' common and the lower side to the R2s' common. so, there is actually a 50k resistor pulling the lower side of the pot as the high side swings due to input signal (Rpot in the attached picture). consequently, when the pot is set to its lowest position a lot of the signal bleeds through Rpot and passes to the buffers.
161Fig05_modif.gif
This could be mitigated by reducing the R2 values, bridging the R2s with large (and low ESR) capacitors or by creating a tough virtual ground.

For me a 33uF low-esr cap placed across the lower R2s and reducing them to 1k solved that problem (mute function really mutes). I am still going to try replacing the upper R2s with a constant current source
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File Type: gif 161Fig05.gif (15.8 KB, 93 views)
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