Updated: Oct 8
Here's a look at a custom phono stage I made this summer, intended only for low output moving coil cartridges and made to match the visual design of one of my Legendarium 2A3 amps.
The main circuit uses a 12AX7 first stage, all-in-one passive RIAA network, 6DJ8 second stage and another 6DJ8 buffer for the output. Since it is for moving coil only, I integrated a pair of Lundahl step-up transformers on the input to bring the low level signal up to a suitable level for the main phono stage, and there are control dials to set the input impedance load between 40 and 400 ohms, allowing for adjustment to a wide range of phono cartridges. (As a side note, this load is calculated in combination of the phono stage input impedance settings and the step-up transformer ratio, so I think the best way to handle a step-up transformer is to integrate it into the amp, instead of using an external unit with a standard phono stage that would be unlikely to have the best load options.)
The measurements and sound quality are excellent, and I really enjoyed a test period before sending it on to the buyer who commissioned it.
I think I've mentioned before I do have some plans to add a pre-amp to my standard lineup, and hope to have an option for a phono stage. I'm probably still several months away (have I said that before?) A tube phono stage does have some challenges in keeping it quiet and high performing relative to what's possible with a solid-state phono stage, but done well it can be a great system.
This particular project took me in a few new directions. I already mentioned above about using step-up transformers, and I was so impressed with the quality of the Lundahl brand that I'm going to be trying a few of their other products to consider for other amps. Second, I designed a custom printed circuit board (PCB) for the main circuit. This allows very careful and tight layout to minimize wiring distances and keep the amp relatively small. I'm starting to use more PCBs in certain ways. I am not a purist about point-to-point wiring, though it is very flexible and the most direct expression of the builder's craft, but not right for all situations, and there are some nice benefits to a well designed PCB. Finally, you will notice I'm using a toroidal power transformer, which has a sleek look to it and also seems to have good performance in terms of minimizing hum and noise from the power supply. I am trying a few more of these in potential new products for my lineup.
On a personal level, I've been hesitant to go full steam into vinyl for my own listening--taking time to build a collection, the cost and physical space it needs, and having the right equipment for the high quality sound I expect.* Still, I have taken the path far enough into the woods to say it really is an enjoyable experience and certainly in line with my analog ethos! Taking an album from its cover, dropping the needle to the surface, listening with intention and not just changing around quickly as I might do with a streaming source, then pausing for a moment when the side is done. It's a pleasure, and the sound quality of vinyl absolutely can compete as a high fidelity source--or at least, I can say I don't mind the authenticity of hearing just a bit of surface noise or an occasional click of imperfection. The analog sound has made a long journey from recording the artist, engineering and production of the record, and then playback in my system. I'm hearing the artistry of the music and the ecosystem, and it feels quite real. Give it a try if you are inclined!
* I am lately using a Riga Planar P3 table and a Hana EL cartridge, both of which I am finding excellent.