yup - MC , as gain stage where noise is veeeeery important and you need finest part specimens
The real McCoy - Wikipedia, the free encyclopedia
The real McCoy - Wikipedia, the free encyclopedia
So you are saying that Toshiba is better than LS. 
Ok, so you are also saying that technically LS is fine for this application, just have you (or anyone) compared them soundwise? (Well.. yes, I would prefer the Toshibas.)
Please bare with me a little here still...
I do have both LS Jfets measuring between idss 10 to 11, but I also have a few 2SK170 with idss 9.5mA. So I'm wondering if a couple of 2SJ74 would be obtainable from somewhare or would the higher idss of LS still tilt the scale towards LS?
Ok, so you are also saying that technically LS is fine for this application, just have you (or anyone) compared them soundwise? (Well.. yes, I would prefer the Toshibas.)
Please bare with me a little here still...
I do have both LS Jfets measuring between idss 10 to 11, but I also have a few 2SK170 with idss 9.5mA. So I'm wondering if a couple of 2SJ74 would be obtainable from somewhare or would the higher idss of LS still tilt the scale towards LS?
K-J match. ( actually called an N-P match, but we know what you mean
Match as close as you can for Idss, it doesn't matter if the Idss of one channel's pair is very different from the other channel, the bias pots will take care of that.
yes 6L6 N-P-N-P or N-N-P-P match what i mean... (my mistake, sorry
)and the answer is NPNP match, okay 6L6 very clear.
thanks.
Here's a question that if I weren't lazy, I could test myself, and I will anyway if ZM or others don't know. I have heard the transconductance of jets can be increased by paralleling them. Is it additive? If so, then it would seem that you could match them by combining them. Let's say you have a 4.3, a 4.5, a 4.7 and a 4.9. Would paralleling the 4.3 and the 4.9 get you the same transconductance (9.2) as the 4.5 and the 4.7 (9.2). Am I way off base? Thanks.
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i have powered up mine...
zero voltage across R10,11 (because trimpot are sets to zero)
as soon i turn the trimpot, there are some voltage here, and i set them all into 0,76v
well, i thought i have a good start, until i set the DCout.
i can set the DC out before the output caps into zero, but there is a swing voltage 0-10mV.
but instead there is a DC after the output caps arround 200-300mV.
i tried to change into other caps, and also tried the polar caps bypassed with mkp.
still a huge DC after those caps.
why is this happen?
zero voltage across R10,11 (because trimpot are sets to zero)
as soon i turn the trimpot, there are some voltage here, and i set them all into 0,76v
well, i thought i have a good start, until i set the DCout.
i can set the DC out before the output caps into zero, but there is a swing voltage 0-10mV.
but instead there is a DC after the output caps arround 200-300mV.
i tried to change into other caps, and also tried the polar caps bypassed with mkp.
still a huge DC after those caps.
why is this happen?
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BA3 FE as preamp - ba3fepre!
Thanks wengteck for passing along that problem and its solution; it is very helpful for we beginners!
I finished up my BA3 FE as preamp today. It is paired with an F4. It is a combination truely marvelous to hear. I was pinned to my seat listening for several hours, just couldn't leave the music to do something so mundane as eat.
I used the AMB Sigma 22 regulated power supply and a 50K stepped attenuator from valab. The extension driving its knob is from a 16" x 3/8" spade drill bit. You can just barely see it on the bottom edge of the e-nudie. Works like a charm.
I built a little trapeze to hang those oversized PIO 10uF caps from and to run extensions for R10 and R11 so setting bias would be easier.
IEC is on the front so that the AC wiring is not in the cramped chassis (only 8 inches wide). The dancer (I was going for a "balance" icon) is made from window tinting film ;-)
I want to thank 6L6 for his outstanding work in assembling and maintaining these guides and of course the man to who humbles any chest thumping designer of audio gear: Nelson Pass, the people's audio champion!
Thanks wengteck for passing along that problem and its solution; it is very helpful for we beginners!
I finished up my BA3 FE as preamp today. It is paired with an F4. It is a combination truely marvelous to hear. I was pinned to my seat listening for several hours, just couldn't leave the music to do something so mundane as eat.
I used the AMB Sigma 22 regulated power supply and a 50K stepped attenuator from valab. The extension driving its knob is from a 16" x 3/8" spade drill bit
. You can just barely see it on the bottom edge of the e-nudie. Works like a charm.I built a little trapeze to hang those oversized PIO 10uF caps from and to run extensions for R10 and R11 so setting bias would be easier.
IEC is on the front so that the AC wiring is not in the cramped chassis (only 8 inches wide). The dancer (I was going for a "balance" icon) is made from window tinting film ;-)
I want to thank 6L6 for his outstanding work in assembling and maintaining these guides and of course the man to who humbles any chest thumping designer of audio gear: Nelson Pass, the people's audio champion!
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It's better than Truly Fugly - it is well executed, well thought out, and has some creative solutions that are totally worth repeating. And that's just the insides -- the chassis is really wonderful as well.
I love the exposed bias resistors (because of the huge caps) Smart!
And don't get me started with your F4, I think it's a simply stunning chassis.
As someone who knows all about the sound of BA-3 and F4, I know ecaxtily what you mean by, " It is a combination truely marvelous to hear. I was pinned to my seat listening for several hours, just couldn't leave the music to do something so mundane as to eat."
My sincere congratulations.
I love the exposed bias resistors (because of the huge caps) Smart!
And don't get me started with your F4, I think it's a simply stunning chassis.
As someone who knows all about the sound of BA-3 and F4, I know ecaxtily what you mean by, " It is a combination truely marvelous to hear. I was pinned to my seat listening for several hours, just couldn't leave the music to do something so mundane as to eat."
My sincere congratulations.