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Old 27th January 2003, 10:44 PM   #1
JDeV is offline JDeV  South Africa
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Default Current Gain Calculations

Can somebody please confirm or correct me with the following:
Mad_K asked me about my AC current gain on my Aleph30. After reading through some relevant threads , I tried to measure my gain and came up with the following:

Applied 9V 1K sine wave, to 8ohm load.
Measured across R22-R27, 0.47ohm x 6, got: V=0.086
Measured across R37-39, 0.47ohm on neg. side, got: V=0.069 on each.
Thus: Iout=1.098A ..................(1)
I on neg. =0.44A total ............(2)
(2) is 40% of (1)

According to Mr.Pass, you must have about a 50% split or up to 60% for better bass.
Which way must this 60% be, 60% more to the output or 60% more to the neg. side?
In my case, is my 40% now good or bad?

Thanx for all help.
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Old 27th January 2003, 10:55 PM   #2
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Default Re: Current Gain Calculations

Quote:
Originally posted by JDeV
Can somebody please confirm or correct me with the following:
Mad_K asked me about my AC current gain on my Aleph30. After reading through some relevant threads , I tried to measure my gain and came up with the following:

Applied 9V 1K sine wave, to 8ohm load.
Measured across R22-R27, 0.47ohm x 6, got: V=0.086
Measured across R37-39, 0.47ohm on neg. side, got: V=0.069 on each.
Thus: Iout=1.098A ..................(1)
I on neg. =0.44A total ............(2)
(2) is 40% of (1)

According to Mr.Pass, you must have about a 50% split or up to 60% for better bass.
Which way must this 60% be, 60% more to the output or 60% more to the neg. side?
In my case, is my 40% now good or bad?
Your calculation indicates that you are running about
60% gain on the current source, since 40% of the
output current is being provided by the negative output
devices.

50% provides generally optimum performance and efficiency,
although sonic differences are available by altering this up
or down. I do not advocate any particular value, so the
word "must" doesn't reflect my thinking.
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Old 27th January 2003, 11:16 PM   #3
JDeV is offline JDeV  South Africa
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Location: Cape Town
I appoligise, must must be should, or must should be should.
If I understand correct, one can fit a 2K POT across R21, on Aleph30, and adjust to get closer to 50% - and then fit permanent resistor = this value. When I did this, I could not get my 40% up, only down. Must I now fit POT in series with R21 or is there another way?:
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Old 27th January 2003, 11:47 PM   #4
halojoy is offline halojoy  Sweden
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Quote:
Originally posted by JDeV
I appoligise, must must be should, or must should be should.
If I understand correct, one can fit a 2K POT across R21, on Aleph30, and adjust to get closer to 50% - and then fit permanent resistor = this value. When I did this, I could not get my 40% up, only down. Must I now fit POT in series with R21 or is there another way?:
Make R21 next value higher in resistance,
and then try with 2K pot across again.
Keep on increasing R21 to the value at which you can adjust
to the 50% with 2k pot.

So it have to be over 50% with ONLY R21.
Because 2k pot in parallell can only lower the %,
and so adjust downto 50%.

This is only based on logic, not seen the schematic.
If it is too bad, so please correct me.

/halo
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