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The Kuartlotron - keantoken's simple error-correction superbuffer
The Kuartlotron - keantoken's simple error-correction superbuffer
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Old 24th March 2014, 02:34 AM   #171
keantoken is offline keantoken  United States
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That's fairly normal, so it seems something else is the problem.

What are the differences between your build and the current schematic? I'm guessing TP is very high right now. The problem with a 250R resistor is that your input transistor is running very low current.
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Old 24th March 2014, 03:28 AM   #172
Joachim Gerhard is offline Joachim Gerhard  Germany
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Instead of R6 i have a J-fet CCS.
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Old 24th March 2014, 03:28 AM   #173
Joachim Gerhard is offline Joachim Gerhard  Germany
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I will test the TP.
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Old 24th March 2014, 03:34 AM   #174
Joachim Gerhard is offline Joachim Gerhard  Germany
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I have shorted the input. TP is at 4.5V with 2 x 9V batteries as supply.
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Old 24th March 2014, 05:35 AM   #175
keantoken is offline keantoken  United States
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If TP is at 4.5V right now, then R5 must have been too low to begin with.

Try making R1 39R, then adjust R5 to make TP 4.5V. Then trim R1 for distortion.
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Old 24th March 2014, 06:23 AM   #176
keantoken is offline keantoken  United States
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OOPS. Your BC5x0C seem to be much like mine. Leave R1 and R2 at 56R and just adjust R5 so TP=4.5V. Then trim R2 for distortion.

If this doesn't work, then I'm not sure what's going on.
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Old 24th March 2014, 12:47 PM   #177
Joachim Gerhard is offline Joachim Gerhard  Germany
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R5 in my build is 4.7kOhm.
I wanted to trim that value but i never did, sorry.
Nevertheless the buffer measures great now.
I will listen and make the changes later.
Then i know the difference.
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Old 25th March 2014, 12:41 PM   #178
Joachim Gerhard is offline Joachim Gerhard  Germany
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I have put the trimed buffer ( with 270 Ohm ) in my system and it works.
I do not know why i got that odd value of the distortion trim resistor.
I am also very busy with other things but i plan to look into this further when time permits.
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Old 27th March 2014, 05:22 AM   #179
baswamin is online now baswamin  India
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Kean,

Can you tell me what is the purpose of output resistor R10 (47 ohms)? Can it be of different value? I broke my 47ohm leads and hence am looking at my parts bin for alternative.

Thanks
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Old 27th March 2014, 06:34 AM   #180
taisho_daniel is offline taisho_daniel  Philippines
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From Kean's article :

Reduce output impedance
Output resistance at the emitter of Q4 may be negative or positive, and it's important to keep it from going negative or else you risk oscillation. For this reason I would recommend at least a 4.7R output resistor. The 47R output resistor was chosen for best compatibility with signal cables. Transmission lines are reactive by nature and without the right termination impedance, become a cascade of series and parallel resonators. Without termination, the cables become antennas for RFI. 22R-47R is a good range for damping cable resonances. Without termination, any buffer will resonate with the cable's series resonance mode; the 47R resistor was chosen to prevent this.

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Originally Posted by baswamin View Post
Kean,

Can you tell me what is the purpose of output resistor R10 (47 ohms)? Can it be of different value? I broke my 47ohm leads and hence am looking at my parts bin for alternative.

Thanks
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