Simplistic NJFET RIAA - Page 778 - diyAudio
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Old 8th July 2012, 07:12 PM   #7771
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It seems near 2mVpp, what do you think?
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Old 8th July 2012, 07:16 PM   #7772
Salas is offline Salas  Greece
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Lets say 1.6mV pk-pk to me because the line is thick to watch such low and looks less than 2 sub divisions, give it some vertical scope tolerance, your#7761 displays look 16mV pk-pk, that's 10 times=20dB, channels look identical, you are A OK.
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Old 8th July 2012, 07:20 PM   #7773
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Never can do without your kind help, today I learned something to use the scope because you helped me, is a pleasure have persons like you in this forum. Kind thanks.
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Old 8th July 2012, 09:34 PM   #7774
Salas is offline Salas  Greece
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Basic instruments practice is something a diyer can't afford to go without...
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Old 10th July 2012, 07:30 PM   #7775
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Hi
where can I look for the source of the sibilance that I have? The rest of the components of my system can be ruled out as there is no sibilance when I play cds, for xmpl. I have Grado black that needs only 47k load according to manufacturer, no loading cap. I tried various loading caps from 10p to 250p but no luck. Instrumental music sounds fine, no extra hi range or it is less noticeable so it is no problem.But on some vocal inclusive vynils it really gets anoying.I'm sure this sibilance is not product of the preamp, yet I don't know where to look for the cure any more. Apart from the preamp, what else can introduce this nasty distortion?
As far as I understand 100n cap in the preamp is not part of the RIAA, it is just DC block?
Thank you

Last edited by Milos P.; 10th July 2012 at 07:32 PM.
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Old 10th July 2012, 09:57 PM   #7776
Salas is offline Salas  Greece
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Its a DC block. The preamp is not tending to sibilance normally. Look for loading the Grado with 15K or mistracking-VTA-wear-dirt.
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Old 10th July 2012, 10:30 PM   #7777
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Thank you. I also think something is going on with Grado. Will try 15k load.
Cheers
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Old 10th July 2012, 11:51 PM   #7778
ide2003 is offline ide2003  Indonesia
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hi, from my experience sibilance can come from poor jfet matching and biasing, I use multiturn pot for R source to play with
try to swap jfets even if matching is good. also some components on psu especially the last cap can be a source
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Old 11th July 2012, 07:17 PM   #7779
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15k load= some improvement, but not much.
VTA looks good.
No dirt.
Grado wear- about 800hrs.
Most of my vinyls are brand new.
Rs tried from 28-100ohm - no change- apart from level.
JFETs are matched well, I've done it several times before, no problems.
I'll try the "psu last cap" thing one of these days.
I'll also change all the psu caps to audio grade (now I'm using Panasonic FC and Nichicon PW for the 16V cap on the RIAA)
Any other ideas?
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Old 11th July 2012, 07:58 PM   #7780
Salas is offline Salas  Greece
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Arm-cart geometry? Antiskating-tracking modulations? Having a test record and a protractor? Do all tests with such.
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