I use an analogue oscilloscope with cursors, 1:1 probes and accurate resistive attenuators. Inverse RIAA correction is done afterwards, using Excel or LibreOffice Calc.
The design center matches the RIAA curve nearly perfectly. The capacitors are 2% tolerance and the resistors are 1% tolerance. I can't measure more accurately than that.
Ed
If you split the filter into two parts with an extra buffer stage between the two, you can adjust them separately without interactions.
There are designs which do that. Yes at the cost of an extra tube.
Hi,
in my designs I utilize split EQ and 0.1% resistors and 1-2% Caps, because I want precision at least on my side ... knowing I can't influence on the source side, the vinyl side.
There's no need then to trim anything and still achieve about just 0.1dB of deviation from RIAA.
Things may differ with simple tube and discrete transistor designs, but with OPAmps its non-critical at all.
0.1% thin film resistors (THT0207 size) have come down so much in price, that it really doesn't count.
And I rather spend a few € on a few low tolerance film and caps -or COG/NPOs for SMD ceramics- than wasting time with matching ... might be different, when I know the not used parts will be needed later.
The low tolerance parts not only result in a linear amplitude response but also in a high inter-channel balance, which is positive for staging and focus.
jauu
Calvin
in my designs I utilize split EQ and 0.1% resistors and 1-2% Caps, because I want precision at least on my side ... knowing I can't influence on the source side, the vinyl side.
There's no need then to trim anything and still achieve about just 0.1dB of deviation from RIAA.
Things may differ with simple tube and discrete transistor designs, but with OPAmps its non-critical at all.
0.1% thin film resistors (THT0207 size) have come down so much in price, that it really doesn't count.
And I rather spend a few € on a few low tolerance film and caps -or COG/NPOs for SMD ceramics- than wasting time with matching ... might be different, when I know the not used parts will be needed later.
The low tolerance parts not only result in a linear amplitude response but also in a high inter-channel balance, which is positive for staging and focus.
jauu
Calvin
When I want things to be accurate, I buy 20 of the parts, measure and sort. For resistors it is easy to add that 10 ohm resistor in series with the 10k or what ever value resistor is 10 ohms low. For capacitors it's easy to do the same, buy extra, sort. Add a tiny capacitor in parallel to the cap that is low. I think left to right matching may be more important than absolute perfect RIAA. This year I did a deep dive into record playback. I ended up building a flat phono preamp and then apply the RIAA eq digitally. That is accurate to 0.01% or something. It's not for everybody.