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Old 5th June 2010, 03:20 PM   #151
generg is offline generg  Germany
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..... one answer I found from Nelson, corresponding to Mini-Aleph, I suppose, (correct Tea-Bag?) was

...."The R100 has a lower Vgs than the IRFP240, so you need to
lower the value of the resistance from the Drain of Q1 to V- in
to bias it correctly. I use a potentiometer there...."

things go on!
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Old 5th June 2010, 04:10 PM   #152
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Not sure here about the IRF610,
but based on other statements, lowering value of P201 might bake the output sound better. This is based on his recommendation on the Aleph-J of lowering R7 on Aleph-J schematic. The lower Vgs of the R100's means that we dont need 5v across it, can be lowered down a bit. Of course keep checking offset when changing. Get it lower and listen, see if it sounds better.
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Old 5th June 2010, 04:38 PM   #153
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Old 5th June 2010, 05:07 PM   #154
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hmm.......

"If the gate voltage is above the threshold voltage (lower figure), the transistor is turned on, due to there being many electrons in the channel at the oxide-silicon interface, creating a low-resistance channel where charge can flow from drain to source. For voltages significantly above threshold, this situation is called strong inversion. The channel is tapered when VD > 0 because the voltage drop due to the current in the resistive channel reduces the oxide field supporting the channel as the drain is approached.

hm,hm ...
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Old 7th June 2010, 02:58 PM   #155
generg is offline generg  Germany
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Vgs is 1v for the SSR100 I put on the place of the IRF610 now and the Vgs of the SSR100 implemented in the outputstage is 1,1V for each SSouth.
I suppose these values are O.K. for SSR100 in action.

Is there anybody who can confirm that.....

or tell me what is else important?

happy generg

Last edited by generg; 7th June 2010 at 03:07 PM.
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Old 7th June 2010, 03:02 PM   #156
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you'll have to wait 'till tonight ...... at least to me
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Old 7th June 2010, 03:04 PM   #157
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... it will be a good night!
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Old 7th June 2010, 03:28 PM   #158
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hi BA-1 experts,

do I understand Nelsons hint right, when I cancel the 10uF cap (for trial) I have to omit the positiv branch of biasing, but keep the negativ and I use the gainstage pot to put the output to zero?
The problem for me is to reverse Nelsons statement logically correct for the opposite case he mentioned.


"Assuming you use C203 as recommended, you will also want the positive bias network consisting of R212, R213, R214, Z201, C209, and P202. C203 and all these parts are absolutely essential if you decide to use the output stage as a stand-along power buffer. The purpose of this circuitry is to provide a positive constant bias voltage to the input of the bank of power Mosfets which sets their output to 0 volts DC. P202 is used to adjust
this value.
There is also a bias system for the negative half of the output stage formed by R216, R217, R218, R219, C207 and Q204. Q204 is a generic NPN transistor which sees the voltage appearing across the 1 ohm Source resistors of the negative half of the output stage and sets their value at about 0.6 volts,
locking them in at a constant current value of 0.6A each.." (BA-1 manual)
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Last edited by generg; 7th June 2010 at 03:30 PM.
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Old 7th June 2010, 04:10 PM   #159
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Generg, all my SemiSouth R100 science projects have had lower VgS operationally. Your number sounds right.
They need less voltage to conduct.
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Old 8th June 2010, 09:31 PM   #160
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nobody answers ...... so I will try at own risk without cap and only negative half of bias

i hope to survive....
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