In this case cart internal R becomes Rg. Just plug it in INA gain formula and that is it, no adjustments possible. If internet is correct, Hana Sl has 30R and DL103R has 14R coil resistance.
Many modern amps like $$$ Sutherland Loco series use this kind of set up, Hans Polak did it in his brilliant preamp, we discussed it a lot on my thread "Fully balanced MC phono preamplifier thoughts"
Regarding input termination;
Input 470p cap sees only 14R source impedance from cart (DL103R)..... Dont thing it is ok to do.
I made sketch considering cartridge R and ground referencing, if you follow it, Impedance as seen by INA input is not same any more, degrading CMR...., lower picture is what I think is better....
Hi all,
some background to the design an calculation of the RIAA network of my phone stage, in post #1 i was a little short on this.
the type C configuration is concerning capacitor use more economic thn the "classic" type A with to capacitors in series.
http://waynestegall.com/audio/riaa.htm is a very helpfull documentation on calculating various RIAA networks. i started, as mentioned in post #1, with the capacitors.
i think it is not necessary to be accurate to the last digit, capacitor tolarance is 2% best case, available values are based on the E6.
the ratio C1:C2 = 2.916, slightly less than 3, inspired me to look for combinations of one small capacitor and two larger ones with equal value.
i found empirically the following combinations and calculated the deviation:
calculating the resistors is straight forward, ratio is R1:R2 = 6.877358491
i started to calculate R1 based on C1 as well as C2 and took a standard value between the two results. for R2 i decided to use two resistors in parallel to find a value near the ratio to R1, there are tables in the net for that.
lt spice simulation for the calculated values:
the 3dB corner frequency of the 6 dB high pass before the RIAA equalisation is 15Hz
anyway: capacitors are 2%, resistors 1%,, and don´t be smarter than your ears ;-)
some background to the design an calculation of the RIAA network of my phone stage, in post #1 i was a little short on this.
the type C configuration is concerning capacitor use more economic thn the "classic" type A with to capacitors in series.
http://waynestegall.com/audio/riaa.htm is a very helpfull documentation on calculating various RIAA networks. i started, as mentioned in post #1, with the capacitors.
i think it is not necessary to be accurate to the last digit, capacitor tolarance is 2% best case, available values are based on the E6.
the ratio C1:C2 = 2.916, slightly less than 3, inspired me to look for combinations of one small capacitor and two larger ones with equal value.
i found empirically the following combinations and calculated the deviation:
- 1.5 : 2.2 || 2.2 +0.59%
- 6.8 : 10 || 10 +0.86%
- 4.7 : 6.8 || 6.8 -0.77%
calculating the resistors is straight forward, ratio is R1:R2 = 6.877358491
i started to calculate R1 based on C1 as well as C2 and took a standard value between the two results. for R2 i decided to use two resistors in parallel to find a value near the ratio to R1, there are tables in the net for that.
lt spice simulation for the calculated values:
the 3dB corner frequency of the 6 dB high pass before the RIAA equalisation is 15Hz
anyway: capacitors are 2%, resistors 1%,, and don´t be smarter than your ears ;-)
your lower picture is more ore less my first version, complete symetrical. i had slight issues with picking up hum in combination with the unsymetrical coaxial connection to the record player. the screen of the cable is with the second version more ore less connected to ground.
You can use 2 RCA pins to connect + and- cart signals, and run gnd through shield separately by GND bolt. I converted to XLR long ago.
i have to admit that my opamp choice documented in post #1 was not optimal. over the weekend i had plenty opportunity for listening tests.
final choice ist the LM4562. i think the first impression was the same mistake i made when designing speaker crossovers: don´t make design choices to early, give things time to burn in, listen to broad material. otherwise you end up with a optimal solution for each single record ;-) also noise is reduced, the phonostage is very silent now.
i also swapped the input capacitor to 100 pF from 470pF as suggested above. honestly i couldn´t hear a difference. i think the requirement for low input capacity is primaly essential for MM Pickups. this phonostage is definitely dedicated to MC pickups.
next points i will try out with this prototype are reducing C6 to 1u5, moving the bass rolloff from 15Hz to 20Hz, as well as using a real split power supply.
final choice ist the LM4562. i think the first impression was the same mistake i made when designing speaker crossovers: don´t make design choices to early, give things time to burn in, listen to broad material. otherwise you end up with a optimal solution for each single record ;-) also noise is reduced, the phonostage is very silent now.
i also swapped the input capacitor to 100 pF from 470pF as suggested above. honestly i couldn´t hear a difference. i think the requirement for low input capacity is primaly essential for MM Pickups. this phonostage is definitely dedicated to MC pickups.
next points i will try out with this prototype are reducing C6 to 1u5, moving the bass rolloff from 15Hz to 20Hz, as well as using a real split power supply.
Hi, a question as I'm interested; in which way did LM4562 contribute to better sound vs OP27? Did you notice any noise increase (probably not, but I'm asking as OP27 has much better current noise performance)?
I know this is about subjective observations, hardly anyone can measure differences between 2. Any other opams tried and discarded?
Thanks,
Drazen
I know this is about subjective observations, hardly anyone can measure differences between 2. Any other opams tried and discarded?
Thanks,
Drazen
Hi Drazen,
i prefer the LM4562 over the OPA2134, not the OP27. I use the OP27 model in LTSpice, in the blue text at the button of the schematics i have mentioned the concrete used parts:
i prefer the LM4562 over the OPA2134, not the OP27. I use the OP27 model in LTSpice, in the blue text at the button of the schematics i have mentioned the concrete used parts:
- THAT 1510
- LM 4562
- OPA2134
- TLE 2142
- LM 4562
- NE5532 (oscillation, i was suprised here)
- OPA627 (oscillation)
Thanks for detailed reply, it's generally interesting IMO.
Sorry, I read first and all posts, but forgot 🤔 Picture of OP27 stayed in my head. By the way, I think OP27 would be fit for this purpose.
OPA2134 I have in differential amp , after first MC gain stage and passive RIAA, and don't like the sound neither, before I had Pass balanced Zen with my mods (occupied 2H chassis) and it was different story to listen, just deeper and clearer, more presence of musicians in the room (even thd of that is most horrible comparing to opamp).
In your not good opamps camp I can add OPA2604, same kind of digitalized sound....
I'm bit surprised that 5532 and 637 oscillate in this circuit...
It is funny (but in reality it happens) that you find more defined bass from different op-amp, All opams have huge LF gain and there they should be best at... But than again in bass THD doesn't matter anyway. However I found the same, without reasonable explanations some things sound better..... As my experience with 2 switching mosfets (zen amp above) vs 2 opamps,
What I found is very important (and measurable) is to get rid of 50 (or 60 depends on country) Hz mains introduced noise, this one really changes the timbre of bass, and everything else due its harmonics. Your choice of differential input solves that (IMHO) main issue, but it doesn't explain why bass is better with different opamp..... Doesn't matter, it is not easy one to answer for anyone..
I also like to pump up gain in first stage, my long bellowed MC preamp is 66db gain to start with (about that gain many turn their heads around, but it works without overload issues) , than passive riaa, than 20db to compensate for passive riaa.
Sorry, I read first and all posts, but forgot 🤔 Picture of OP27 stayed in my head. By the way, I think OP27 would be fit for this purpose.
OPA2134 I have in differential amp , after first MC gain stage and passive RIAA, and don't like the sound neither, before I had Pass balanced Zen with my mods (occupied 2H chassis) and it was different story to listen, just deeper and clearer, more presence of musicians in the room (even thd of that is most horrible comparing to opamp).
In your not good opamps camp I can add OPA2604, same kind of digitalized sound....
I'm bit surprised that 5532 and 637 oscillate in this circuit...
It is funny (but in reality it happens) that you find more defined bass from different op-amp, All opams have huge LF gain and there they should be best at... But than again in bass THD doesn't matter anyway. However I found the same, without reasonable explanations some things sound better..... As my experience with 2 switching mosfets (zen amp above) vs 2 opamps,
What I found is very important (and measurable) is to get rid of 50 (or 60 depends on country) Hz mains introduced noise, this one really changes the timbre of bass, and everything else due its harmonics. Your choice of differential input solves that (IMHO) main issue, but it doesn't explain why bass is better with different opamp..... Doesn't matter, it is not easy one to answer for anyone..
I also like to pump up gain in first stage, my long bellowed MC preamp is 66db gain to start with (about that gain many turn their heads around, but it works without overload issues) , than passive riaa, than 20db to compensate for passive riaa.