Dedicated phono-pre for MM only?

Hi Mark - FWIW, my experimentation with discrete JFET MM stages included both the 2SK389 dual, and a pair of 2SK369 singles. I cascoded them with 2N5089 NPN bipolars, and loaded the collectors with 1K . . . there was also a single 2N5089 used as a simple current source for the tail. Rails were +/- 20V, and I put about 8mA through the tail (4mA through each JFET). VDS across the JFETS was about 5V.

I used this circuit in an unbalanced-input feedback amplifier, in the classic "hybrid-amplifier" (JFET-frontend feeds opamp) topology. Instead of a monolithic, I used a 990 discrete opamp, driving a low-impedance EQ network for the 318uS and 3180uS time-constants, with about 20dB of gain at 1KC. This fed a passive 75uS network and another 990 for 20dB more gain, same as my MC design.

I never really put in the time to fully optimize the circuit, but it was very low-distortion, and CRAZY quiet . . . like greater than -90dBV at the output when looking at a 1K source impedance. I think that the 2SK269s had a little better 1/F noise, and even though the offset on the 2SK389 was much better, it didn't really matter for my application. Of course, YMMV.

Hi Lewm - I will add my vote as well to the higher-loading approach, I think that 100K with minimal capacitance is much better (with virtually every cartridge that I've tried) than the common 47K/150pF.

But as far as commercially-available phono stages go . . . I don't really see enough of them anymore to have really strong opinions. I do think that in general, getting the subtle details right makes more difference than any generalisations about whether it uses JFETs, tubes, bipolars, opamps, etc. etc. There are certainly an unlimited number of ways to screw things up, or to avoid doing so.

I'm currently using my Beogram 4002/MMC20CL with a little phono preamp that's an opamp design, made on a Vectorboard . . . and the case and power-supply from a Lehmann Black Cube. Its a two-stage topology like my MC phono unit, with active 318/3180 in the first stage, passive 75uS, then more gain in the output stage. Opamps are AD745 (input) followed by AD797 (output), both of them use complementary discrete JFET buffers for high-current output, within each feedback loop.

Daer Axel: I can speak about that switch subject. During our researh and tests on the deign of the Esential 3160 and due that this PHonolinepreamp was/is designed for our ( José and I. ) specifics need in one of the prototypes ( the one battery powered. ) we have six phono inputs through a switch that I use it for several months till I decided to hear the same cartridges with out that switch where every change on tonearm/cartridge means disconnect/connect in manual way each time, well there is a quality improvement with out that switch and we decided to go in this " fashion ".

But the Essential 3160 is not a product thinking on commercial subjects ( facilities for the customer: using switchs instead that manual changes, switchs for impedance changes instead solder resistors, etc, et. ) but with targets of absolut quality performace where less means more and with no trade-offs or trade-offs at minimum. Many times this approach ( no trade-offs on quality performace. ) means that the Essential user has less facilities: switchs.

Regards and enjoy the music,
Raul.

Raul, Do you mean to say that every time you change from an MC that likes to see, for example, ~100R to one that needs significantly higher R, you actually take the 3160 to the workbench and solder in the required higher R? Or do you use some plug-in system that obviates the need for a switch but still puts mechanical (i.e., unsoldered, pressure-based) contact points in the signal path? Or do you still have a switch for load resistance? (Your post suggests you eliminated switching between input jacks, rather than between load resistors. Even with a single pair of inputs it would be desirable to be able to switch load resistors.)

Kirkus, I just paid too much for a B&O MMC20CL off eBay. I hope I will be happy. The AD797 is one of the ICs I had in mind when I noted that the op amp-based schematic that was posted above might be upgraded with later, better chips. (The schematic used TL072, I think.)

I just paid too much for a B&O MMC20CL off eBay. I hope I will be happy.

I think that I was looking at that one too . . . glad you got it. If it's in good shape, then you didn't overpay. Stellar cartridge.

On the AD797 - this opamp is capable of extremely high performance, but it's definately NOT one to swap into an existing circuit without careful consideration, especially if it originally uses TL072s! The AD797 really shines with low source impedances (not MM cartridges), but on the other hand, it can be limited in its useable output current . . . so it doesn't necessarily do the best job of driving the low-impedance feedback network that suits its low eN characteristics. That's why I used the discrete JFETs as a buffer, and why I used it in the second stage, where it can be driven from the low source impedance of the first. The AD745 is FET-input, so it works great with an MM cartridge . . . but it's not stable at lower gains, so stability and phase margin have to be carefully considered in application. Then there's the fact that the TL072 is a dual, and AD797 and AD745 are singles.

For general TL072 replacement, try OP249.