I was to curious to find out. Generated a test tone with Rightmark Audio Analyser - applied an inverse RIAA-curve in Audacity - played that sample back through the Edirol and recorded the signal back again. Then analysed it using Rightmark. I believe this is what you wanted, RJM?
20Hz to 20kHz +-0.5dB
An externally hosted image should be here but it was not working when we last tested it.
20Hz to 20kHz +-0.5dB
I think your problem is you don't have fine enough sampling.
Try trans 100m 90m and 1u and see what that gives you. This moves the sampling window out to 90 ms from start up (to reach steady state, just in case) and samples 10 ms at 0.0001 ms steps, for 100 000 data points and 10 complete waveforms. Overkill, probably. Increase the step size until you see artifact peaks show up. That gives you your working limit.
20Hz to 20kHz +-0.5dB
Ok, you win this round!
I see you even managed to correctly reproduce the little tip up at 20 kHz from the 4th time constant...To achieve such stellar results, did you measure/match the RIAA caps, or were they the standard kit ones?
Ok, you win this round!
To achieve such stellar results, did you measure/match the RIAA caps, or were they the standard kit ones?
Oh, not about winning - I just love it that DIY-projects can give you great results at a fraction of expensive equipment.
The RIAA caps were not matched, I do not have a capacitance meter. They are Wima FKP2 caps (all of them). All of them 1nF, C2 made of 3 in parallel. The resistors are metal film, matched. Output cap is Wima MKP-X2 - 2,2uF. For the rest, I kept the PCB as small as possible and kept to your construction guide (star ground,...)
"What are values R1, R2, C1 and C2, how to add C2 to R2?"
The Phonoclone RIAA network is expressed as 750k || 110k + 3 nF || 1 nF for
R1 || R2 +C2 || C1. Careful, I may not have been consistent in the parts labeling in the sims.
C2 and R2 add as R2 + 1/(2 pi f C2)i. i is standard notation for an imaginary number, indicating that the reactive term is 90 degrees out of phase from the resistive term.
Suggest you do some reading. "The Art of Electronics" by Horowitz and Hill is my go-to reference.
The Phonoclone RIAA network is expressed as 750k || 110k + 3 nF || 1 nF for
R1 || R2 +C2 || C1. Careful, I may not have been consistent in the parts labeling in the sims.
C2 and R2 add as R2 + 1/(2 pi f C2)i. i is standard notation for an imaginary number, indicating that the reactive term is 90 degrees out of phase from the resistive term.
Suggest you do some reading. "The Art of Electronics" by Horowitz and Hill is my go-to reference.
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Did some further measurements in Rightmark - full results are here.
As seen earlier - frequency response is dead-on like the simulation on rjm's page (seen here):
Noise level is nice and quiet too:
Note that is not an X-Reg version like rjm ships them, this should be even better for his. I'm using an LM317/LM337 combo, using the additional ripple caps on the adjust pin (10uF). 4400uF on each rail before the regulator. 1uF tantal to decouple (like the original National specs say). Each rail has a led indicator to make sure the minimum current draw is reached.
I think this could still be improved by a CRC-style filter feeding the regs (note the small "bump" at 50Hz). Still, dynamic range is at +83.0dB A-weighted, which is already more than what vinyl as a physical media might give you
As seen earlier - frequency response is dead-on like the simulation on rjm's page (seen here):
An externally hosted image should be here but it was not working when we last tested it.
Noise level is nice and quiet too:
An externally hosted image should be here but it was not working when we last tested it.
Note that is not an X-Reg version like rjm ships them, this should be even better for his. I'm using an LM317/LM337 combo, using the additional ripple caps on the adjust pin (10uF). 4400uF on each rail before the regulator. 1uF tantal to decouple (like the original National specs say). Each rail has a led indicator to make sure the minimum current draw is reached.
I think this could still be improved by a CRC-style filter feeding the regs (note the small "bump" at 50Hz). Still, dynamic range is at +83.0dB A-weighted, which is already more than what vinyl as a physical media might give you
If you are feeding the phono stage an input signal from the computer: disconnect it and put a dummy load (470 ohms for MM, 10 ohms for MC) before making the noise measurement. Otherwise you are likely just measuring the output noise of the DAC, amplified through the VSPS.
But, anyway, your results look fine. Nothing to see here...
The one that adds the 4th time-constant.
There is some difference to RJM's quoted values in my VSPS, seeing as I don't have the precision resistors. Some were made by putting them in series/parallel. Though always matched left/right. The 4th time-constant has come into discussion, but I like it that way. Most carts start to roll-off there; so it makes the end-result nice and flat. I also changed the input impedance to match my current Nagaoka cart (running at 79K). Sounds superb.
RJM - good call on the dummy load. I'll have to make some additional plugs for that though. The Nagaoka measures about 560 Ohm; so I'll take that as a dummy load.
Easy - it's the one you can find on RJM's website:
An externally hosted image should be here but it was not working when we last tested it.
As I said earlier - R1 was changed to match the Nagaoka - 79K
Dead link.. OK, working now
I didn't think what RIAA network.. what inverse RIAA you used for measurement?
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Works perfect here - check it out on RJM Audio - The Very Simple Phono Stage
The inverse RIAA is the one that's available in Audacity. It's pretty accurate if you take a look at the XML.
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