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Old 13th December 2019, 06:12 AM   #111
Adams_Leo is offline Adams_Leo  China
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One more question,in the document of Volume 4 of Linear Audio Figure 6, I can see the D1 and D2 in the Figure,but it show empty there?does it a switch to control the C5 and C6?

Thanks
Leo
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Old 13th December 2019, 06:42 AM   #112
jan.didden is online now jan.didden  Europe
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With all respect, you should read the article. Or do a 'find' on D1 for instance.

The absence of NFB allows the 75us RIAA time constant to be implemented with a hand-selected combination of 2 polystyrene shunt capacitors totaling 0.02uF at the high-Z VAS node. This means that the amplifier need not ever swing the amount of voltage that would otherwise occur at high frequencies if the amplifier had a flat gain of 10. Nodes D1 and D2 are connected to ground through relay contacts for conventional equalization. The contacts are opened for damped EQ, inserting a zero at 8kHz via R19.

Jan
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Old 13th December 2019, 08:50 AM   #113
Adams_Leo is offline Adams_Leo  China
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Quote:
Originally Posted by jan.didden View Post
With all respect, you should read the article. Or do a 'find' on D1 for instance.

The absence of NFB allows the 75us RIAA time constant to be implemented with a hand-selected combination of 2 polystyrene shunt capacitors totaling 0.02uF at the high-Z VAS node. This means that the amplifier need not ever swing the amount of voltage that would otherwise occur at high frequencies if the amplifier had a flat gain of 10. Nodes D1 and D2 are connected to ground through relay contacts for conventional equalization. The contacts are opened for damped EQ, inserting a zero at 8kHz via R19.

Jan
Yes,yes,find it.thanks Jan again
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Old 13th December 2019, 10:04 AM   #114
Adams_Leo is offline Adams_Leo  China
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Can I use the 2sk489 to replace for BOTH the 2sk389 and LS844?
But check the datasheet the 2sk489 noice is 1.8nv and 2sk389 only 1.3nv,still better than 2SK489.

Which grade 2SK389 should be used.A,B or C?
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Old 13th December 2019, 10:25 AM   #115
Adams_Leo is offline Adams_Leo  China
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I have checked Linear system for the 2SK389,seems like EOL,no stock and can not put the order.
is there any other parts to replace for 2SK389? I have almost 200pcs 2sk170GR ,can I use this one to replace 2sk389?
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Old 13th December 2019, 11:20 AM   #116
jan.didden is online now jan.didden  Europe
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Leo I am not familiar with FETs, but ask EUVL, he's the FET czar here ;-)

Jan
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Old 13th December 2019, 11:59 AM   #117
Adams_Leo is offline Adams_Leo  China
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Dear Jan,thanks. Do you know which grade will be used ?2SK389A,or 2SK389B,I guess It should be B grade.
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Old 13th December 2019, 04:05 PM   #118
Bob Cordell is offline Bob Cordell  United States
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Quote:
Originally Posted by Adams_Leo View Post
Can I use the 2sk489 to replace for BOTH the 2sk389 and LS844?
But check the datasheet the 2sk489 noice is 1.8nv and 2sk389 only 1.3nv,still better than 2SK489.

Which grade 2SK389 should be used.A,B or C?
The LSK389 has significantly lower voltage noise than the LSK489. They are both very good parts, but optimized for different applications. The LSK389 is a large die with high transconductance that leads to very low noise. However, as a result, its capacitances are larger. The LSK489 is a smaller die with quite low capacitances and smaller transconductance, and yet still achieves low noise performance, just not as low as that of the LSK389. Use of the LSK389 is particularly important in the MC part of the preamp. The LSK489 can and should generally be used instead of the older LS844.

These parts are readily available from Linear Systems. Look for the LSK parts rather than the 2SK parts. The old Toshiba 2SK389 is no longer available. I usually recommend using the B version of the LSK389.

Cheers,
Bob
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Old 15th December 2019, 11:40 PM   #119
Adams_Leo is offline Adams_Leo  China
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Quote:
Originally Posted by Bob Cordell View Post
The LSK389 has significantly lower voltage noise than the LSK489. They are both very good parts, but optimized for different applications. The LSK389 is a large die with high transconductance that leads to very low noise. However, as a result, its capacitances are larger. The LSK489 is a smaller die with quite low capacitances and smaller transconductance, and yet still achieves low noise performance, just not as low as that of the LSK389. Use of the LSK389 is particularly important in the MC part of the preamp. The LSK489 can and should generally be used instead of the older LS844.

These parts are readily available from Linear Systems. Look for the LSK parts rather than the 2SK parts. The old Toshiba 2SK389 is no longer available. I usually recommend using the B version of the LSK389.

Cheers,
Bob
Bob,thanks for you detail input.that is clear
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Old 8th January 2020, 12:43 PM   #120
Adams_Leo is offline Adams_Leo  China
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is there any way to remove the Figure 7 OP IC?and update to use fully passive EQ
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