which shortcommings/disadvantages are to expect by the use of only one RIAA network (instead a splitted RIAA network in two parts together with additional OPA STAGE) in the feedback loop as realized by NAD PP2 or Musical fidelity "The Preamp" ?
Go to post #5 about
http://www.diyaudio.com/forums/analogue-source/155449-head-pre-denon-dl-103-a.html
I have heard, that only this kind of equalizing avoid or reduce at least unwanted clipping effects in case of low supply voltage, if the records have scratches resp. if dirty records are in use.
Is this true? Until now I though, that unwanted clipping effects are only absence by the use of tube phono input stages, because here the supply voltage is usual 200-300 VDC.
Go to post #5 about
http://www.diyaudio.com/forums/analogue-source/155449-head-pre-denon-dl-103-a.html
I have heard, that only this kind of equalizing avoid or reduce at least unwanted clipping effects in case of low supply voltage, if the records have scratches resp. if dirty records are in use.
Is this true? Until now I though, that unwanted clipping effects are only absence by the use of tube phono input stages, because here the supply voltage is usual 200-300 VDC.
Last edited:
The reason therefore could be the fact, that opamps run usually with only -/-15V and the gain factor from the first gain stage produce a clipping signal by occur of a sratch-pop.
Tube stages don't produce a clipping signal due much more supply voltage.
Which other approaches exist to avoid clipping signal by exist record scratches (except high supply voltage) ?
Maybe a NFB riaa network in the first gain stage like there:
RJM Audio - The Very Simple Phono Stage
resp- in the mentioned URLs from my previous post?
Take a look at the Philips NE5532 opamp application notes. On page 10 there's a rumble/scratch filter for opamp based riaa stages. http://www.nxp.com/documents/application_note/AN142.pdf
Hi,
a all-in-one RIAA, though technically elegant, may not give as a precise RIAA-EQ as a split network.
The splitting offers the advantage to design the networks independant of each other.
This can reduce losses and improve on noise.
With regard to clipping headroom matters depend on circuit topology.
A inverting stage would be probabely best in this regard, due to low parts number count and lowest commonmode voltage swing at the input.
But since the (non-constant) pickups impedance would define the gain and would add considerable amounts of noise with rising frequency.
Such a single inverting stage would rather be found as second gain stage with a linear noninverting input stage ahead.
Single gain stages are almost always of noninverting configuration.
A non-inverting RIAA-gainstage would not tend towards a gain of 0 with rising frequency as required by RIAA, but to a gain of 1.
Such a stage would require an additional lowpass to achieve the RIAA response.
This lowpass may either follow behind the RIAA-stage or may be between a linear gain stage and the RIAA-stage.
The latter offering the highest flexibility. Since the linear input gain stage would take over most but not all amplification, clipping is rather a no issue with standard +-15V supplies.
A all passive RIAA-EQ would require two linear gain-stages and 20dB more gain than split RIAA with 210Hz passive and 50-500Hz active RIAA-EQ.
jauu
Calvin
a all-in-one RIAA, though technically elegant, may not give as a precise RIAA-EQ as a split network.
The splitting offers the advantage to design the networks independant of each other.
This can reduce losses and improve on noise.
With regard to clipping headroom matters depend on circuit topology.
A inverting stage would be probabely best in this regard, due to low parts number count and lowest commonmode voltage swing at the input.
But since the (non-constant) pickups impedance would define the gain and would add considerable amounts of noise with rising frequency.
Such a single inverting stage would rather be found as second gain stage with a linear noninverting input stage ahead.
Single gain stages are almost always of noninverting configuration.
A non-inverting RIAA-gainstage would not tend towards a gain of 0 with rising frequency as required by RIAA, but to a gain of 1.
Such a stage would require an additional lowpass to achieve the RIAA response.
This lowpass may either follow behind the RIAA-stage or may be between a linear gain stage and the RIAA-stage.
The latter offering the highest flexibility. Since the linear input gain stage would take over most but not all amplification, clipping is rather a no issue with standard +-15V supplies.
A all passive RIAA-EQ would require two linear gain-stages and 20dB more gain than split RIAA with 210Hz passive and 50-500Hz active RIAA-EQ.
jauu
Calvin
Record surface scratches (usually) do not overload a properly designed phono stage having +/-15V power supply. Once I tried two passive RIAA phono amplifiers of the same topology. The gain stages were opamps in the first case (TL071), and tubes in the other (SRPP Anzai circuit), but the passive RIAA network between the stages was the same. Needless to say they sounded much different, the tube version did not exaggerate the record surface noise, and it was not due to HF rolloff.
in this case follow URLs are of interest:
http://hifisonix.com/wordpress/wp-content/uploads/2010/10/RIAA-Equalization-Amplifiers-Part-One1.pdf
http://www.angelfire.com/az3/dimitri/images/riaa.pdf
Inverted input stages with RIAA are to find there:
A Paul Kemble web page - John Linsley Hood preamp designs.
The Class-A Amplifier Site - Modular Pre-Amplifier Design
Musical Fidelity A1 - Technical
URL is death. check this URL:
https://web.archive.org/web/20131013005547/http://www.nxp.com/documents/application_note/AN142.pdf
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.