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Old 23rd January 2013, 02:11 PM   #1141
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Default reply resistors

Thank you guys for the answer, I will use the 1 watters from shinkoh and takman and hear if it will influance the sound. GTrtz Teake
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Old 23rd January 2013, 02:53 PM   #1142
6L6 is offline 6L6  United States
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The most influence you will have on the sound is if you use no resistors... there would be no sound!!! :P
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Old 23rd January 2013, 04:14 PM   #1143
ittien is offline ittien  Viet Nam
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@Buzzford: i did it everytime, but that day just hurry to show it up, and make it until late midnight, too tired maybe...:lol.
Anyway, i also work hard tonight but just only can bring back 1 channel to work, another got fired that i still don't know reason. but one channel is good enough to show you all about narrow bandwidth.
Following Images series is what i measured for that channel.
Power Max: 19VAC ~45W
1KHz at output 3.342VAC.
1KHz.JPG

10KHz, output is 3.305VAC, slightly reduce
10KHz.JPG

15KHz, output is 3.257VAC, more reduce
15KHz.JPG

25KHz, output is 3.107VAC, reduce faster
25KHz.JPG

40KHz,output is 2.876VAC, too much reduce, look at the OSC you can see the sinewave much smaller than 1KHz
40KHz.JPG

So do you think that it has very narrow bandwidth?

Last edited by ittien; 23rd January 2013 at 04:24 PM.
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Old 23rd January 2013, 04:21 PM   #1144
ittien is offline ittien  Viet Nam
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I also did test with square wave.
1KHz, square wave is good
1KHz Square.JPG

10KHz, i don't know it is good enough or not, but it can show up not good as HF
10KHz Square.JPG

For Low Frequency, 100Hz
100Hz Square.JPG

And 25Hz
25Hz Square.JPG

So the Low Frequency is not bad.

This time do test i used 500VA transformer for 1 channel, so it should not the underpowered issue.
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Old 23rd January 2013, 04:22 PM   #1145
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Bad FE Jfets, is most likely cause. I dont see any correlation to the mosfet bias offset, but I could be wrong. I think Nelson says original F5 can go out to 1Mhz. The mosfets were approved by Fairchild, through major ordeal, so their validity is not an issue.
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Last edited by buzzforb; 23rd January 2013 at 04:24 PM.
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Old 23rd January 2013, 04:31 PM   #1146
ittien is offline ittien  Viet Nam
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Bias at 350mV/1R, and the difference between output FET <10mV. it is too good i think. i'm not bias as 400mV as Manual, because my heatsink is not good enough. i got smoked for lot of IRF when trying.

@buzzford: can you tell me where i can buy genuine JFet?
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Old 23rd January 2013, 04:37 PM   #1147
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Old 23rd January 2013, 05:03 PM   #1148
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by sangram View Post
Or, probably 1% when resistors are in parallel and 4% when they are in series. If it was only one resistor it would be 2%.........
No.
You still have not got how tolerance works.
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Old 23rd January 2013, 05:11 PM   #1149
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by ittien View Post
Power Max: 19VAC ~45W
1KHz at output 3.342VAC.


10KHz, output is 3.305VAC, slightly reduce


15KHz, output is 3.257VAC, more reduce


25KHz, output is 3.107VAC, reduce faster


40KHz,output is 2.876VAC, too much reduce, look at the OSC you can see the sinewave much smaller than 1KHz
25kHz is +-0.6dB ref 3.342Vac @ 1kHz
40kHz is ~ -1.3dB ref 1kHz.
Not great.
But, did you check your input signal?
Is it constant at those spot frequencies?
Or does it too vary as you sweep the frequency?
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Old 23rd January 2013, 05:16 PM   #1150
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by ittien View Post
I also did test with square wave.
1KHz, square wave is good
Attachment 325883

10KHz, i don't know it is good enough or not, but it can show up not good as HF
Attachment 325884

For Low Frequency, 100Hz
Attachment 325886

And 25Hz
Attachment 325885

So the Low Frequency is not bad.

This time do test i used 500VA transformer for 1 channel, so it should not the underpowered issue.
Square response is not good IMO, that much low frequency tilt is unacceptable ..
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