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Old 3rd February 2013, 01:56 PM   #71
gk7 is offline gk7
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Quote:
Originally Posted by tinitus View Post
I was looking for a j310
could only find it as SMD

I guess all new jfets are SMD
probably not designed to drive ClassA power amps
Mouser still has some J310 in TO-92.

j310 Transistors | Mouser

But who knows for how long, the Fairchild version is already "end of life"...
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Old 18th April 2013, 01:12 AM   #72
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hi everyone. I will revive this thread.
I do think now that my b1 has a problem, probably because of my fault

musical coherence is simply not there, and after changing my speakers and source, and now my preamp, I know that the b1 is seriously having a problem.

Left side plays louder then right side, slightly, but its confirmed. I have switch to no preamp at all, and well music is back. I have no musical coherence with the b1, its as if some things are slow and some thing are fast, or whatever, hard to explain really, but it almost makes me dizzy listening to the thing. All I hear is a bunch of sound and no music coherence.

I just want to take back my comments about the B1 and also ask for help, I now think that its how I build it that is the problem. I will measure the LSK389 to see if they match, or maybe they are fake? I met the guy in montreal in a parking lot for the LSK389. but I reached him via the distributor site and he gave me all the documentation and everything, seems legit, but I will measure...

Then, if they measure right, I will just order a board from Mr. Pass because I hardwired the pre amp, maybe I made a mistake, but ouf, its been a year I use the pre amp and I just realize that all this time, that was the problem, nothing else. I feel stupid.

One question about the boards. If I buy the board, can I still have two outputs and add a simple crossover for one of the outputs?
this is how I did my pre:
e will have two times C101 and C201, which we shall call C101a/201a
for the "Full Range" or better "Full Bass Range" output and C101b/201b
for the "High Frequencies" or better "Limited Bass Range" .

C101a/201a will be 2.2uF, C101b/201b will be 33nF.

R104/204 and R105/205 will also have an 'a' and 'b' incarnation.

For 'a' we will have R104a/204a being 1K or lower (uncritical) and
R105a/205a being 1M.

For 'b' we will have R104b/204b being 1K or lower (uncritical) and
R105b/205b being 1M plus switchable resistors of 100K & 33K to adjust
the at which frequency the low frequencies are cut out for this
output.

I guess I cannot implement many outputs if I buy the boards?

Last edited by murphythecat8; 18th April 2013 at 01:23 AM.
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Old 18th April 2013, 03:11 PM   #73
AndrewT is offline AndrewT  Scotland
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Compare the outputs as you currently have them.
Swap the outputs and compare again.
swap the inputs and compare again.
Which component has the fault?
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Old 19th April 2013, 09:32 PM   #74
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Quote:
Originally Posted by AndrewT View Post
Compare the outputs as you currently have them.
Swap the outputs and compare again.
swap the inputs and compare again.
Which component has the fault?
the sound is so bad, I thought the channel were off. I used a mono source, channels seems to be okay. I also tested to be sure. both channel outputs are the same.
Howver, my crossover is problematic. when the crossover is on, I have a a different signal. the input and output does not picture the same on a oscilloscope.

Last edited by murphythecat8; 19th April 2013 at 09:35 PM.
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Old 23rd April 2013, 05:34 PM   #75
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high pass filter close measured at J3
then, I adjusted the out signal at 1volt rms @ 1Khz.
4- Switch S2 open (hipass open), same output, 1 volt rms @ 1Khz.
5- I have adjusted the signal generator to 0.707volts rms (-3db) @ 106Hz (cut off frequency



High Pass Filter circuit were RT= 47Kohms
Channel #1 >>>Input, Channel #2 >>>Output


Without High Pass Filter (S2 close) >>>Output at J3 >>>1volt rms @ 106Hz
With High Pass Filter (S2 open)>>>Output at J3 >>>0.707volt rms @ 106Hz (-3db).

However, its clear with the pictures that something is wrong

The two picture has the same signal shown. the upper signal is the same and the input
#1 , and the output #2 is the down signal...
Attached Images
File Type: jpg Preamp High Pass Filtre.jpg (326.3 KB, 329 views)
File Type: jpg Preamp High Pass Filtre_00.jpg (332.1 KB, 329 views)
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Old 8th April 2014, 03:28 PM   #76
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ill update. the problem on my B1 was a faulty pot. The pot was the problem all along. I simply swap the pot and voila, musical coherence was all back.

Crazy. Ive done blind test with my girlfriend and the difference was not subtle. The good pot sounds totally transparent while the other one really messes up the sound.

so after rewiring everything with premium wires, changin the Fets, the problem was only the pot!

cheers
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Old 9th April 2014, 07:08 PM   #77
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by murphythecat8 View Post
The pot was the problem all along.
I simply swap the pot and voila, musical coherence was all back.
lets bend that in neon
that sure was a long ride
and just to find a shitty pot
glad you got it solved, at least

can I ask, why was the pot faulty ?
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Old 9th April 2014, 09:46 PM   #78
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no clue seriously. I didnt need a preamp for a long time so didnt bothered fixing it, but now I needed one so got to it.
Its a noble pot, genuine, but for some reason its definitely problematic sounding. its hard to explain really, but the sound was uncoherent, not naturel at all, unmusical, clinical it almost seems as if it was slow. Anyways, that was the problem for sure since as soon as I changed it, both me and my girlfriend we were like wow, music is back.
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Old 9th April 2014, 09:50 PM   #79
weskoki is offline weskoki  Europe
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What kind of pot did you use?
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Old 9th April 2014, 10:15 PM   #80
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by weskoki View Post
What kind of pot did you use?
I was going to ask that

prices may go sky high
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