Can your DMM show steady mV on AC if you will touch its probes across the 220R input resistor as it is driven by that signal? Lets see how much it actually is.
I'm sorry Salas I don't have DMM for mV on AC, could you recommend me DMM true RMS to measure low level AC signal?
Just use the scope's probe across pre's 220R as it receives signal so you confirm what attenuation it really gets. What is your generator model?
Seems it gives more signal for 600 Ohm source impedance to 220R load. Measure the applied signal as in #7764 Maybe the gen spec is that it can drive 600 Ohm audio terminations in essence.
Give it shorter displayed period with the time scale scope button so to watch the peaks easier.
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.
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.
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
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
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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.
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
try to swap jfets even if matching is good. also some components on psu especially the last cap can be a source
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?
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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