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Old 17th July 2008, 09:04 AM   #1
Ted205 is offline Ted205  United Kingdom
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Default stepped attenuator pop

I'm just testing out my 24 step stepped attenuator to the front of my chipamp gainclone. http://cgi.ebay.ie/Attenuator-24-Step-10K-A-Dale-resistor-Stereo-NEW_W0QQitemZ220247489309QQihZ012QQcategoryZ73369Q QtcZphotoQQcmdZViewItemQQ_trksidZp1742.m153.l1262

It's wired up on my bench with crocodile clips and running from a bench supply.

I'm getting a small 'pop' when the pot is turned. Is there anything that can be done to remove this ? (I know it could be just the poor connections - the croc clips)

thanks
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Old 17th July 2008, 09:46 AM   #2
Ted205 is offline Ted205  United Kingdom
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well it turns out it was a dodgy ground

i do have another newbie question though.

I'm using a 10k volume control with a 25Vac input per channel (so around 32Vdc once rectified and with diode losses ?)

The 10k has a very bad scale. The first click is a big step while the other 23 make very little difference to the volume.

Do i simply need a larger input pot resistance to adjust the scale? Or can i use maybe an in series resistance to help set the volume scale ?
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Old 17th July 2008, 01:20 PM   #3
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What amp and other equipment are you using it with?
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Old 17th July 2008, 04:04 PM   #4
Ted205 is offline Ted205  United Kingdom
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Its a chipamp.com lm3886 amplifier kit i'm currently running one channel from a bench supply.

The chipamp manual schematic shows a 25k pot at the input but i couldn't find a step attenuator rated at the same value.
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Old 17th July 2008, 04:04 PM   #5
Ted205 is offline Ted205  United Kingdom
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i forgot to add. Input is from my laptop (which has a volume control of its own) and the output is a 6 ohm hifi speaker
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Old 17th July 2008, 05:57 PM   #6
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Still that attenuator should work OK. Are you sure that you have it wired up correctly? A picture would help!
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Old 17th July 2008, 09:22 PM   #7
Ted205 is offline Ted205  United Kingdom
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well it does attenuate the signal so i'm assuming ( ) it is wired correctly, its just not very linear and most of the 'steps' i can't hear the attenuation (though i can see it on the scope).

A normal 10k pot does a better job to be honest. Would you suggest i try the 50k or the 100k 24 step ?
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Old 17th July 2008, 10:19 PM   #8
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I'm not sure a different value would change things. A lot depends on the steps that the designer of your attenuator chose.
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Old 18th July 2008, 02:34 AM   #9
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Are you sure it's 10k attenuator? Looking at the picture, the resistor values (100k, 140k, 200K) could indicate 250K attenuator (even the pic name says it)
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File Type: jpg attn250kmainb.jpg (40.0 KB, 322 views)
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Old 18th July 2008, 08:43 AM   #10
Ted205 is offline Ted205  United Kingdom
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its Definitely 10k.

A normal 10k pot does the job but the stepped attenuator doesn't. The first step is like an on/off switch. The steps in the middle are inaudible. Its not until the last 3 or 4 steps that you can hear the difference
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