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Old 26th October 2011, 07:49 PM   #1071
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Quote:
Originally Posted by juma View Post
R5 and R6 have wrong values in that sch.
R6 overloads the JFET (you can keep it but make it 100k) and R5 needlessly increases the output impedance (22R is enough to isolate cable capacitance).
R5 and R6 are from the original schematic.

But when I did the 310's mod, I tried R6 with 50K, and 100K as well (I didn't change the R5 value).
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Old 26th October 2011, 07:51 PM   #1072
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Quote:
Originally Posted by tmblack View Post
Does it work with 12V power supply?
If you have a adequate Idss on the K170's, yes
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Old 26th October 2011, 09:06 PM   #1073
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OK I can make it 16V optimal for 2SK170 as NP intended.
Why go with U310?
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Old 26th October 2011, 09:44 PM   #1074
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Quote:
Originally Posted by tmblack View Post
OK I can make it 16V optimal for 2SK170 as NP intended.
Why go with U310?
In this post, you can get a idea about the relationship between Idss and V for the K170.

The U310 have less gain than the K170
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Old 27th October 2011, 03:02 AM   #1075
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For the original circuit, why are there two 2.2k load resistors one to Vcc and other to ground after the output C?
Can we just use say 1.1k resistor (1k should be close enough) as drain resistor connected to Vcc?
This probably means Vcc must be adjusted for sweet spot.
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Old 27th October 2011, 05:55 AM   #1076
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OK I get it, all I have to do is build one again.
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Old 13th November 2011, 01:46 PM   #1077
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Default BOZ-J - A listening Impression - Replaced Attenuator

For sometime now I was using a P.E.C. pot in the BOZ-J.
Althought it the P.E.C. pot sounded good, it was noisy/scratchy from the minute it was installed. It never cleared up and rotating the pot back and forth to clear the scratchiness was usless.

It was replaced with a parallel 24-stepped attenuator from 8Audio.com.
It uses 1% metal film resistors of an unknown brand. They look like standard Xircon color coded 1% metal film resistors. I suspose an email to the pot manufacture would reveal the brand of resistor. The attenuator is well built and small enough to fit inside a 1.5" high case with some clearance for small, flexible wiring for the in, out, ground connections.

From a cold start of all equipment, there was an improvement. After warm up, it was evident that stepped attenuators are the real thing. To describe the sound: everything was more fluid, had bit more resolution and had a bit deeper soundstage and it made most music more involving. The layers of instruments was better defined. I also noticed a bit wider sound stage beyond the speaker's outer edge.

For a small, simple, easy to build pre-amp, it continues to deliver better sound when upgrading components. It's hard to believe.

Vince
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Last edited by vdi_nenna; 13th November 2011 at 02:07 PM.
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Old 13th November 2011, 09:21 PM   #1078
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Did you use the 500k or 24k attenuator?
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Old 13th November 2011, 11:16 PM   #1079
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Quote:
Did you use the 500k or 24k attenuator?
Used 25k.
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Old 15th November 2011, 05:43 PM   #1080
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How does BOZ-J sound compared to BOZ?
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