I think I was a little rude not introducing myself before asking for anything.
I've read a lot on the different forums on Diyaudio and try to contribute when I think I could be helpful. I have to say this is the
best hobby I've ever gotten into. I'm not a techie or even very smart but there is enough info on these forums where if anyone "really wanted" to achieve building one of Mr. Pass's kindly donated schematics it is truly achievable with in that persons capabilities. There is so much to learn and understand(this one might take a while) but the end result is very satisfying. I'm constantly browsing the sight and studying on what I would like to build next or just read. I'm very thankful to all who contribute to Diyaudio because with out this site I would have never had the confidence to get into this wonderful hobby. I don't talk much but I'm on here almost every day. I usually don't speak because if I do, it will most likely be questions and 99% of the time it has been ask already. Thank you in advanced for any help.
Eric
I've read a lot on the different forums on Diyaudio and try to contribute when I think I could be helpful. I have to say this is the
best hobby I've ever gotten into. I'm not a techie or even very smart but there is enough info on these forums where if anyone "really wanted" to achieve building one of Mr. Pass's kindly donated schematics it is truly achievable with in that persons capabilities. There is so much to learn and understand(this one might take a while) but the end result is very satisfying. I'm constantly browsing the sight and studying on what I would like to build next or just read. I'm very thankful to all who contribute to Diyaudio because with out this site I would have never had the confidence to get into this wonderful hobby. I don't talk much but I'm on here almost every day. I usually don't speak because if I do, it will most likely be questions and 99% of the time it has been ask already. Thank you in advanced for any help.
Eric
Oh! didn't realize... thank you generg and thank you Tea-Bag for pointing that out to me.
Well, the reason I am curious is I'm purchasing some naked vishay resistors from a gentleman on the swap meet. This would be my main reason why I wanted to know. Well since I'm here, would it be almost as critical to have quality resistors on R6, P1 and R4? I was also curious about turn-on thump. For my F5 I used thermistors on both the hot and neutral for turn-on surges(works great by the way). He mentions this in the Zen 5 article but would this work for the F2J? Thanks again
Well, the reason I am curious is I'm purchasing some naked vishay resistors from a gentleman on the swap meet. This would be my main reason why I wanted to know. Well since I'm here, would it be almost as critical to have quality resistors on R6, P1 and R4? I was also curious about turn-on thump. For my F5 I used thermistors on both the hot and neutral for turn-on surges(works great by the way). He mentions this in the Zen 5 article but would this work for the F2J? Thanks again
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Hello,
Sorry to bring up an old post, but I just got out my old SemiSouth F2 amp and was checking things on it..
Basically, isn't the bias supposed to be exactly 1/2 the voltage of the amp? So, for me, I've got exactly 22v coming from the PS feeding the amp, and I've got my bias at 11v.
I thought it had to do w/ keeping the signal square and balanced.
Or, am I wrong, and the bias is only adjusting how hot we're running things, so a bit more, if the heatsinks can take it, might be better?
I'm wondering because I've got huge heatsinks, and can definitely run things hotter. The amp barely gets warm the way it is. I like the idea of running things hotter if it could help.
(I don't have test equipment for this, so I want to go for whatever is generally considered best practice)
Thanks
Bump, for above question. I let it go for a while 'cause I thought maybe it was just a dumb question.. but I re-read this thread and there is conflicting info it. One of the early pages says to do it the way I have it.. exactly 1/2 the input voltage (I usually work w/ tubes, so 1/2 b+).
But later in the thread there is talk about pushing it to run hotter, implying higher bias is better if your heatsinks can take it.
Which is it?
Thanks
But later in the thread there is talk about pushing it to run hotter, implying higher bias is better if your heatsinks can take it.
Which is it?
Thanks
Two kinds of bias.
1) The amount of current running through, generally set by the constant
current source
2) Voltage output bias, the voltage across the Drains.
I set the former as high as I think the circuit will take.
I set the latter at 1/2 supply for these transistors. Maybe I vary it a bit
if I have a distortion analyzer.
1) The amount of current running through, generally set by the constant
current source
2) Voltage output bias, the voltage across the Drains.
I set the former as high as I think the circuit will take.
I set the latter at 1/2 supply for these transistors. Maybe I vary it a bit
if I have a distortion analyzer.
Value for R6 in F2J
I built an F2J clone a while back when the value of R6 was said to be 46K and it sounded great. Now I found that Mr Pass has posted the schematic for F2J on firstwatt.com and the value of R6 is 8.2K. Should I make the change?
Also I've just changed the speakers that this amp was driving from Sachiko with FE206E to
Alpair 7 in OB. Should I leave the 3 47ohm resistors across the output or remove them?
I built an F2J clone a while back when the value of R6 was said to be 46K and it sounded great. Now I found that Mr Pass has posted the schematic for F2J on firstwatt.com and the value of R6 is 8.2K. Should I make the change?
Also I've just changed the speakers that this amp was driving from Sachiko with FE206E to
Alpair 7 in OB. Should I leave the 3 47ohm resistors across the output or remove them?
Why not?
I've been asking me the same question about the altered resistor value. I suppose, that it's because the rolloff is now at ~1.8Hz (calculated with 11uF), which brings it more in the range of ~1.6Hz (the value of the first F2). Would be interesting to know if this is due to any "distortion fingerprint" considerations.
Why not?
I've been asking me the same question about the altered resistor value. I suppose, that it's because the rolloff is now at ~1.8Hz (calculated with 11uF), which brings it more in the range of ~1.6Hz (the value of the first F2). Would be interesting to know if this is due to any "distortion fingerprint" considerations.
It's a DC consideration.
The lower value is to make allowance for the Gate leakage current of the
Jfets. This varies from less than 1 uA to more than 100 uA. Generally I
select them out at < 10 uA at 20V / 2A conditions after a brief warm up.
I don't assume that the DIY crowd is going to have that luxury, so I lower
the resistance.
Something I can chew on the next time.
Edit: Something I can chew on in the coming days.
(English and German may have some similarities, but these "false friends"...)
I am lost in the current crossover piece.
I want to do a 2-pole setup for a tweeter, but I don't undestand how the following scales.
L = R1 / (6.28 * F) and C = 1 / ( 6.28 * R2 * F)
I want to cross the tweeter in at 10K
So for a single pole I would use
L=8/6.28*10000hz I get .000127 which I think is 128 henries. (Big wire).
Of course I want to put a cap into it, because I fear for the tweeter. So the two pole solution I just dont understand.
But if I run the cap equation
c=1/(6.28*8*10000) = ~ 2uf
Lost...
I want to do a 2-pole setup for a tweeter, but I don't undestand how the following scales.
L = R1 / (6.28 * F) and C = 1 / ( 6.28 * R2 * F)
I want to cross the tweeter in at 10K
So for a single pole I would use
L=8/6.28*10000hz I get .000127 which I think is 128 henries. (Big wire).
Of course I want to put a cap into it, because I fear for the tweeter. So the two pole solution I just dont understand.
But if I run the cap equation
c=1/(6.28*8*10000) = ~ 2uf
Lost...
They dont work according to the basis of this article.
http://www.passdiy.com/pdf/CurrentSourceCrossoverNetworks.pdf
I start losing the basis of it at page 4-5.
http://www.passdiy.com/pdf/CurrentSourceCrossoverNetworks.pdf
I start losing the basis of it at page 4-5.