Measuring RIAA

Onvinyl · 4th April 2005, 12:56 PM

While measuring my riaa with a sine, I see the resulting sine wave waving around the axis. Like this: ~~~~~~~~~, where ~ is the envelope of the sine.

Why is this, and what can I do about it?
rüdiger

peranders · 4th April 2005, 01:36 PM

Hum?

Try to fix an anti-RIAA network infront of the vinyl amp.

Onvinyl · 4th April 2005, 03:03 PM

Hi Per,
I have an anti-RiAA sweep and fed it to the riaa-preamp.
the resulting output 'waves' around. This is a screenshot (@400Hz):

Mr Evil · 4th April 2005, 03:13 PM

The superimposed low frequency is about 50Hz. You could be picking up some radiated fields from the mains.

Onvinyl · 4th April 2005, 03:19 PM

Hm, the phono stage runs from batteries.
the reference signal (same route, but no riaa inserted does not show this radiated signal. But 50Hz may be correct, because it is the only stable freq. in the resulting sweep.

So I think it's the signal-source feeding the amp.

Thanks,
Rüdiger

4th April 2005, 12:56 PM	#1
Onvinyl diyAudio Member Join Date: Aug 2002 Location: Germany	Measuring RIAA While measuring my riaa with a sine, I see the resulting sine wave waving around the axis. Like this: ~~~~~~~~~, where ~ is the envelope of the sine. Why is this, and what can I do about it? rüdiger

4th April 2005, 01:36 PM	#2
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	Hum? Try to fix an anti-RIAA network infront of the vinyl amp. __________________ /Per-Anders (my first name) or P-A as my friends call me

4th April 2005, 03:13 PM	#4
Mr Evil diyAudio Member Join Date: Aug 2004 Location: Behind you	The superimposed low frequency is about 50Hz. You could be picking up some radiated fields from the mains. __________________ https://mrevil.asvachin.eu/

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4th April 2005, 03:03 PM	#3
Onvinyl diyAudio Member Join Date: Aug 2002 Location: Germany	Hi Per, I have an anti-RiAA sweep and fed it to the riaa-preamp. the resulting output 'waves' around. This is a screenshot (@400Hz):

4th April 2005, 03:19 PM	#5
Onvinyl diyAudio Member Join Date: Aug 2002 Location: Germany	Hm, the phono stage runs from batteries. the reference signal (same route, but no riaa inserted does not show this radiated signal. But 50Hz may be correct, because it is the only stable freq. in the resulting sweep. So I think it's the signal-source feeding the amp. Thanks, Rüdiger

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