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Old 18th December 2015, 01:24 PM   #1
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Default phono sp16

hello there would be ways to modify the circuit by removing refeeding as it has
much gain and the input signal is overloaded
thanks


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Old 18th December 2015, 02:13 PM   #2
rayma is offline rayma  United States
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[QUOTE=miguelnoda;4551953it has much gain and the input signal is overloaded[/QUOTE]

This phono stage has 55dB midband gain, and is intended for low output cartridges. It can't be easily modified for less gain.
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Old 19th December 2015, 12:27 PM   #3
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Default phono sp16

I just wipe the needle with the volume when the volume falls by
one backfiring on the speakers not saying it can be.
all shots are fine lands
salu2
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Old 19th December 2015, 03:36 PM   #4
Koonw is offline Koonw  Malaysia
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The sim show you can add a 100-200K volume pot to output to adjust the gain with no side effect.
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Old 19th December 2015, 03:40 PM   #5
rayma is offline rayma  United States
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Originally Posted by Koonw View Post
The sim show you can add a 100-200K volume pot to output to adjust the gain with no side effect.
He says the cartridge signal is too large for the 55dB gain, and is overloading the input,
so that a volume control at the output would not help.
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Old 19th December 2015, 03:47 PM   #6
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I have a solution if decide against the 100k pot, you could install 12at7's disconnect the trim feedback, and install a 27k resistor between the cathodes of the gain stages. Below is the spiced schematic, good results and between 42 and 45dB gain. The PF resistor can be tailored for an even better response.
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Old 19th December 2015, 04:41 PM   #7
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I removed the three resistors in series of 10 M brings factory and I've put a 1M as in the scheme and now goes well (TRM!) on feedback
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Old 19th December 2015, 05:10 PM   #8
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I spiced the 1M resistor into the feedback, the AC sweep isn't very smooth, I'm not sure why ARC did this, I've spiced out several of their phono designs, and they aren't that great! at least their all tube designs! I'm not sure if their current designers use spice programs to test their new schemas or not, would be a helpful tool!
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Old 19th December 2015, 05:20 PM   #9
Koonw is offline Koonw  Malaysia
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Quote:
Originally Posted by denny9167 View Post
I spiced the 1M resistor into the feedback, the AC sweep isn't very smooth, I'm not sure why ARC did this, I've spiced out several of their designs, and they aren't that great!
With just 1M, the response is not straight (dip down 2.5dbs) after 150Hz or so. So I also change feedback resistor 137Kto 62K and cap 2276pf to 5nf in addition to TRM 1M, now appears smooth and gain down to -2 db.
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Old 19th December 2015, 05:29 PM   #10
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Quote:
Originally Posted by Koonw View Post
With just 1M, the response is not straight (dip down 2.5dbs) after 150Hz or so. So I also change feedback resistor 137Kto 62K and cap 2276pf to 5nf in addition to TRM 1M, now appears smooth and gain down to -2 db.
B2 Spice confirms similar results!
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