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Old 26th February 2011, 11:05 AM   #5841
Salas is online now Salas  Greece
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Quote:
Originally Posted by smpkje View Post
I solved the problem with temperature; by reduce the current from 2X175mA to 2 X 130mA. Now the temperature is 50C on heat sink and 40 inside the case near the elements. Also I reduced the value of C2 from 15.33nF to 15.10nf. The equalization now is more accuracy and the stage more wide.
But I think that it needs more gain. My old phono has 63dB and the 56dB sounds a little weak. Sometimes I think is better to convert it to MM with 43dB plus low MC pre-pre (total 63db according PDF). Do you believe that will have problem with noise or anything else? My cart is Shelter 501 (0.4 mV)
Send me the exact circuit with idss values you got and drain to earth voltages you can measure to see if we can easily convert it to 60dB with not much hassle first.
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Old 26th February 2011, 01:28 PM   #5842
smpkje is offline smpkje  Greece
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Thanks Nikos
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Old 26th February 2011, 01:41 PM   #5843
smpkje is offline smpkje  Greece
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And 3 more photos.
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Old 26th February 2011, 01:52 PM   #5844
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This is very well reading for voltages and currents. Well done. Do you have some extra 8-8.5 Idss K170, so I know what is in hand?
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Old 26th February 2011, 02:06 PM   #5845
smpkje is offline smpkje  Greece
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Yes i have 3 more. i will tell you the idss in a minute
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Old 26th February 2011, 02:12 PM   #5846
smpkje is offline smpkje  Greece
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8.00/8.10/8.08
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Old 26th February 2011, 02:14 PM   #5847
smpkje is offline smpkje  Greece
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I have also 18(6.50-7.00)
7(7.00-7.50)
8(7.50-8.00)
10(8.50-11.00)
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Old 26th February 2011, 02:30 PM   #5848
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Do you have some 220R resistors and do you have margin for rising B+ to 40V?
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Old 26th February 2011, 02:49 PM   #5849
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Yes I have
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Old 26th February 2011, 02:58 PM   #5850
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OK then. Before we perplex it with extra Jfets or whatever, short each R2 with a parallel jumper wire, parallel 220R to each R6, and go 40V B+ on both channels. That will boost the gain to about +2.5dB without any real hassle. Lets see, maybe it will do the trick. Its like your cart becomes 0.53mV with the gain you now got. About +30% on line output. Is there gain in your preamp by the way? 63dB is for 0.2mV LowMC carts usually.
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