PMG Phono Question

Audio Components
1

I just watched Paul’s video discussing the PMG Phono preamp and expected availability.

I have some questions about the transimpedance application. I have a moving magnet phono stage with a transimpedance step-up amplifier. The step-up unit has a single dial that adjusts resistive loading and gain at the same time. As gain increases, resistance decreases. For a lot of cartridges, when the recommended resistance is set, there is enough gain. Not so in my case. I use a Soundsmith low output Zepher MIMC Star. This cartridge needs a resistive loading between 470 – 1,000 Ohms and a gain of 58 – 64dB. My transimpedance step-up amp only goes up to 300 Ohms at which point it has 9dB of gain. I don’t use this phono/step-up stage for the Zephyr Star. I use my Stellar phono preamp with custom loading set at 750 Ohms and Low Gain.

My question is, since the PMG phono preamp uses transimpedance, will it work with Soundsmith’s low output cartridges.

2

I have the same question since I have the same moving Soundsmith moving iron cartridge.

3

My take from Paul’s comments is that transimpendance is only on the MC input. And I am surmising that those of us fully satisfied with our MM cartridge (Ortofon 2MR LVB Black on a Rega P8) won’t get a big SQ boost from Stellar → PMG. Not sure I want to re-explore the realm of MC, in part because I now discount most reviews as there is no way to know if the cartridge was properly set up. And if you spend a spare Saturday exploring a sub topic, say, anti skate, you might come away wondering if anyone actually knows the optimal set up parameters, even presuming the cartridge itself is “perfect”. Willing to bet an outside “expert” mounted the Lyra on PS Adios VPI turntable.

4

Transimpedance (in the sense mentioned by Paul) is used only with MCs having very low internal resistance - ideally much less than 10 Ohms.

5

As seen on the back panel of the PMG Signature Phono Preamp it has voltage inputs for MM/MC as well as transimpedance inputs for MC. So for MC cartridges it will provide you with the option to use conventional voltage gain or transimpedance (current) gain circuitry. As some have stated transimpedance gain works best with low output impedance MC carts so you’re given a choice.

6

Yes but a Soundsmith Zephyr MIMD Star is a low output moving iron cartridge. On the Stellar phono preamp I run it at 800 Ohms and medium gain.

7

I’d suggest contacting PS Audio’s customer support to ask about compatibility with your cartridge and desired settings.

8

Won’t work (or won’t work well). I’m pretty sure the lowest internal resistance MI cart made at SS comes in at about 10 Ohms. Can’t (or typically won’t) get the best out of such a cart with a transimpedance stage.

9

So it will come down to what loading/gain options are available on the MM/MC inputs.

10

I noticed Paul mentioned no Optical Phono input. The Transimpedance current drive idea sounds cool. I’m sure that Darren’s Design and Bob’s implementation will be different from the Sutherland stuff.

11

@Paul has the cable sensitivity problem , in the stellar phono pre, been fixed in the PMG phono preamp?

12

I haven’t heard of this, do you mind elaborating?

Edit: I searched the forums and found nothing related to cable sensitivity that needed fixing - just some comments about loose RCA connectors causing noise. Now I’m even more curious.

13

Yes, I believe it has if we’re referring to the same one I think we are.

14

with the stellar phono if input or output ICs are close and parallel to AC cables a hum and or static sounds will be introduced into the signal path. They are audible easily at any volume. My rats nest behind my rack was fine until painters move it to paint. They did not know about this condition so it took a while for me to find the culprits. If ICs end up being parallel to AC cables making sure the ICs are at right angles to the power cords. This will cause the distortion signals to cancel out algebraically

15

Great. My rats nest took a while for me to resolve the static issue after the painting contractors moved my rack. Come on December!

16

Thanks for the reply. With MC carts/MC phono stages of just about any type that I have had this is a thing. Thankfully, it is easily solved with short phono cables and good wire management. I am surprised that this problem was attributed to the Stellar phono when it is more of a generalized issue. i.e. → low-output moving coil setups demand meticulous grounding and high-gain front ends because any minor interference or layout flaw gets heavily amplified and turns into audible buzz.

17

NP. I did not encounter the problem when using a Sutherland Insight Phono amp.

18

It’s good that it didn’t occur with the other phono stage, perhaps the cable routing was a bit different with that setup. But I imagine that any phono stage would produce noise when IC’s are parallel to AC cables. Phono IC’s are probably the most susceptible to interference of any cable type in use.

Perhaps I am misunderstanding the issue. Did you still have the hum/noise with the Stellar phono after appropriately separating the cables? Oh, wait - I see that you resolved the issue after rearranging the rats nest. I would wager that the PMG phono would also have a noise problem if your phono IC’s are routed parallel to AC cables. This is not a component issue, it’s a rats nest issue IMO.

Nevertheless, I am rooting for you to get the PMG Phono when it comes out.

19

Isn’t it supposed to be released in August 2025?

20

It was and we failed. It just wasn’t ready. But now it’s done and moving its way through the slow process of leaving engineering and being picked up by production. That takes what seems a lifetime to get through so probably first quarter next year and then we’ll drop more jaws that already are trying to pick themselves off the floor when the few lucky souls who have heard it got a chance.