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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Salas hotrodded blue DCB1 build
Salas hotrodded blue DCB1 build
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Old 24th February 2012, 12:23 AM   #1661
necplusultra is offline necplusultra  Canada
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thanks Salas

R measures about 1.6 and 1.8 V
Vgs about 4 on one side and and 3.8 on the other
dc offset at .9 and -.7 mv

I thought that hotrod would get much warmer. The mills 3.3R are hot though

sounding great. bass is nice an tight.
using bib to power ldrs and arduino controller
thanks again
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Old 24th February 2012, 12:46 AM   #1662
Salas is offline Salas  Greece
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Salas hotrodded blue DCB1 build
A 0.5A median CCS value then. Quite potent. A nice quality line control system configuration also. Enjoy.
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Old 24th February 2012, 07:50 AM   #1663
syklab is offline syklab  United States
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Hi,
I have just received 2 sets of matched quads 2SK170BL:

7.6x mA
7.1x mA

Which one should be better for the DCB1?
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Old 24th February 2012, 07:56 PM   #1664
evanc is offline evanc  United States
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Salas hotrodded blue DCB1 build
OK... A couple observations and a question. I adjusted the current setting resistors to 3.9ohm from 10ohm and yes there is a subjective improvement. All of the good is a better. My system at this point sounds the best it ever has. Thank you all so much for helping me get here.

Now the question. I measure 1.33volts across one 3.9 and 1.72volts across the other. So there are different amounts of current. Across the 1ohm I get 5.78mv and 6.39mv. Should I simply adjust the 3.9 resistors to get even current, or is it more then that? The offset at the output is 1.4mv and 1.7 mv.

Thanks, Evan
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Old 24th February 2012, 08:08 PM   #1665
Salas is offline Salas  Greece
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Salas hotrodded blue DCB1 build
Just adjust the resistors. Its due to Vgs differences between PMOS, NMOS and random by part.
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Old 24th February 2012, 08:09 PM   #1666
Salas is offline Salas  Greece
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Salas hotrodded blue DCB1 build
Quote:
Originally Posted by syklab View Post
Hi,
I have just received 2 sets of matched quads 2SK170BL:

7.6x mA
7.1x mA

Which one should be better for the DCB1?
Either, no big difference.
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Old 24th February 2012, 10:01 PM   #1667
evanc is offline evanc  United States
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Salas hotrodded blue DCB1 build
Well now I'm confused...I know, what's new..... I added resistance parallel to the 3.9 ohm resistor and did not get the expected result. The reading across the 1ohm resistor changes a lot less then I expected. I was able to get the current up to about 590 ma but that was with 2.7ohms in the set position. I quit while I was ahead and hooked the thing back up...Any thoughts?
Evan
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Old 24th February 2012, 10:18 PM   #1668
buzzforb is offline buzzforb  United States
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What was the resistance you added. What is the Vgs of each fet. You should be able to figure out exactly what you need. Mine didnt match exactly, but i havent found that it affects performance. You do beautiful work, btw.
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Old 24th February 2012, 10:21 PM   #1669
Salas is offline Salas  Greece
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Salas hotrodded blue DCB1 build
Quote:
Originally Posted by evanc View Post
Well now I'm confused...I know, what's new..... I added resistance parallel to the 3.9 ohm resistor and did not get the expected result. The reading across the 1ohm resistor changes a lot less then I expected. I was able to get the current up to about 590 ma but that was with 2.7ohms in the set position. I quit while I was ahead and hooked the thing back up...Any thoughts?
Evan
The power resistors you change value are to set/balance the main CCS currents between rails, have nothing to do with the indications on the 1 Ohm little resistors. Those are reflecting the IDSS differences of the Jfets serving the 5 LEDs strings and a little difference plays no role in the LEDs stability of forward drop.
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Old 24th February 2012, 10:22 PM   #1670
evanc is offline evanc  United States
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Salas hotrodded blue DCB1 build
thank you. I thought I worked out that I needed to go to 3r3, but I must have made a mistake....I'll work more on it tomorrow. For now we listen....
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