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Old 1st March 2012, 08:09 AM   #2021
PauloPT is offline PauloPT  Portugal
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Quote:
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Can anyone please look at my simulation files on post #2011 and tell me what I'm doing wrong? Thank you.
R6
The problem is if I increase R6 I get huge distortion. 300 Ohms gives me (only) about 1%...

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Old 1st March 2012, 09:29 AM   #2022
MiiB is offline MiiB  Denmark
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can you post a schematic not a sim file..??
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Old 1st March 2012, 10:37 AM   #2023
PauloPT is offline PauloPT  Portugal
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Yes, this is the schematics. R6 should be a 5k trimpot but 300 ohms is for the lowest distortion I can get from the sim and that is 1% (a lot!)

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Old 1st March 2012, 11:01 PM   #2024
Salas is offline Salas  Greece
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Try V3=2.2V R6,8,11,12=510 Ohm
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Old 1st March 2012, 11:17 PM   #2025
Salas is offline Salas  Greece
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Also R13,16,23=375 Ohm for ~3mA bias in the drivers and ~100mA in the Lats.
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Old 2nd March 2012, 12:12 AM   #2026
Sheldon is offline Sheldon  United States
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Will do. But might be a couple of weeks before I can get to it.
Gave it (CCS under top driver) a quick try with LSK170. Shows some promise. I had overshoot before, but clean rise and fall now on square waves. Some HF noise, but no time to track that down. The 170 is not ideal, because current doesn't level out until about 10V G/S. Need better part, or wait a see what LC's fix is.

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Old 2nd March 2012, 12:33 AM   #2027
PauloPT is offline PauloPT  Portugal
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Default Thanks!

Thank you, Sheldon and Salas!

Perfect!
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Old 2nd March 2012, 06:52 AM   #2028
Salas is offline Salas  Greece
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Quote:
Originally Posted by Sheldon View Post
Gave it (CCS under top driver) a quick try with LSK170. Shows some promise. I had overshoot before, but clean rise and fall now on square waves. Some HF noise, but no time to track that down. The 170 is not ideal, because current doesn't level out until about 10V G/S. Need better part, or wait a see what LC's fix is.

Sheldon
With K30ATM and BF245A had tested only. But mine's LAT and low driver bias suffices. Check if your input BJTs still run about the same Ie, and if the amp's output tracks sine wave well symmetrically when cranking it up on the scope. Say at 30V pk-pk. About HF noise, see if its acting up so to revisit comp caps or input filtering 'cause the CCS boosts its speed. Will some NTC find enough temp to react when bundled with two small BJTs running 30mW each? We must get to know which exact type works for LC first. Still the CCS is fixing the drivers bias stability not the input drift. But in a bridge everything interacts non the less.
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Old 2nd March 2012, 08:52 AM   #2029
MiiB is offline MiiB  Denmark
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why is R-6 and R-8 so differnt..???
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Old 2nd March 2012, 09:02 AM   #2030
Salas is offline Salas  Greece
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Not in the spice working example #2025. In reality one gets to be a trimmer to counteract the output bias imbalance and offset.
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