aleph bias, ...

janey

Disabled Account
2001-01-06 1:32 pm
hello

i am building aleph 30 and i have some questions.

1. is it good to bypass 220uF capacitators ?

2. how much VA have transformer in original aleph 30 ?

3. i would like to incrise bias current. if i replace siurce resistrs
from 0.47 to 0.39 the current will be higher. do i need any other
changes in circuit to increse bias. am i correct?

thanks


janey
 
1-Certainly wouldn't hurt.
2-If you were planning on building a stock 30, then I'd say 350-400VA minimum, but since you appear to be planning on increasing the bias, this won't be large enough.
3-Depends on what bias current you're shooting for. If you decrease the Source resistors from .47 to .39 ohms, yes the bias current will increase. But the actual value you end up with will depend on the heatsinking, etc. You may need to adjust R19 to get the exact target value you want.
Again, keep in mind that the VA rating you were asking about in your second question will need to be increased to accomodate the increased current demands.

Grey
 

janey

Disabled Account
2001-01-06 1:32 pm
thanks Grey for your reply.

in original aleph 30 the source resistors are 0,47 ohm
the bias is 0,25V/0,47ohm is 0,53A per mosfet, total 1,6A

if i put 0.4 ohm resistors in circuit
0,25V/0,4ohm there is 0,625A bias current per mosfet so total
1,875A.

am i right?

do i need to adjust R19?

janey