Willem
I find it works much cheaper in the long run to order from Mouser or Digikey. I usually build up my orders till they are more than $200 so that I get the shipping for free. I also order more of each to build up my local stock to save on later having to order. For example I order 50 of the Dale resistors each when I have to order a value. RS here locally has been useless of late.
I find it works much cheaper in the long run to order from Mouser or Digikey. I usually build up my orders till they are more than $200 so that I get the shipping for free. I also order more of each to build up my local stock to save on later having to order. For example I order 50 of the Dale resistors each when I have to order a value. RS here locally has been useless of late.
Hi Guys, 6l6 Jim has convinced me to build the F4 as it seems he really likes it, and have started ordering parts.....
I found a small supply of original 74BLs from a friend and he will try to match, he asked me to find out how they should be matched tolerance, as matched quads or matched pairs.
What would be the proper matching levels for these fets? I assume only a pair per channel need to be matched, not a quad.
Thanks again to Jim for his help in helping me sort out my F5 bias....
Cheers, John
I found a small supply of original 74BLs from a friend and he will try to match, he asked me to find out how they should be matched tolerance, as matched quads or matched pairs.
What would be the proper matching levels for these fets? I assume only a pair per channel need to be matched, not a quad.
Thanks again to Jim for his help in helping me sort out my F5 bias....
Cheers, John
For the F4, the Idss of the J74 should match the Idss of the K170. Idss of 7.0-9.0 would be about ideal.
There is no place where you need a matched pair of J74 in that circuit... If you were building an Aleph J you would, as the input stage uses a matched set of J74 as a differential pair.
What preamp will you use for the F4?
There is no place where you need a matched pair of J74 in that circuit... If you were building an Aleph J you would, as the input stage uses a matched set of J74 as a differential pair.
What preamp will you use for the F4?
Thanks Jim 6l6, of course, for the F4 will ask for matched idss of 7 to 9 for the j74 and k170 is noted. He told me he thought he could match to idss of 3.
I will use the BA3 as a preamp for the f4 as discussed and will ask for similar matching as above for that.
I meant to say earlier for the Aleph J as a differential pair, what matching would I need?
Have ordered parts for all these projects now, F4 BA and Aleph J.
I will use the BA3 as a preamp for the f4 as discussed and will ask for similar matching as above for that.
I meant to say earlier for the Aleph J as a differential pair, what matching would I need?
Have ordered parts for all these projects now, F4 BA and Aleph J.
I hope he means .3
The Idss on the Aleph should fall in about the same range; 7-9 being ideal, although the range is not as critical as the tight matching of the two J74's - they should be within about .1
So with a BA-3 front-end preamp,and F4 and Aleph J you will need (4) K170/J74 sets and (2) J74/J74 sets.
The Idss on the Aleph should fall in about the same range; 7-9 being ideal, although the range is not as critical as the tight matching of the two J74's - they should be within about .1
So with a BA-3 front-end preamp,and F4 and Aleph J you will need (4) K170/J74 sets and (2) J74/J74 sets.
At long last, I am ready to order parts and build an F4.
About the power transformer. Of course the Antek AN-4218 is discontinued, replaced by the AS-4218. But the AS-4218 is perpetually out of stock.
Is anyone aware of a suitable substitute from another brand? Or would it be a good idea to use the grossly oversized AN-6218?
About the power transformer. Of course the Antek AN-4218 is discontinued, replaced by the AS-4218. But the AS-4218 is perpetually out of stock.
Is anyone aware of a suitable substitute from another brand? Or would it be a good idea to use the grossly oversized AN-6218?
