Emerald phono stage

Chops54

Junior Member
I've been a valve man for a long time but I'm not too entrenched that I won't try something else if I think I may benefit from it. I'd read good things about RJMs Emerald phono stage and I was curious as to whether ICs and their implementation had improved any since my last dalliance some twenty odd years ago. I contacted Richard Murdy and bought a complete kit and when it arrived I then had to decide how I was going to do it. He advises two enclosures, one for the stage, the other for the power supply. I did try to fit it all into a single Naim box but Richards suggestion stuck in my mind and I thought what the hell and cut the Naim box in half. I've welded a new piece of aluminium to each cut end of the sled so I now I have two boxes.

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That's all for now, I need to try and get some sleep!
 

Chops54

Junior Member
Richard Murdy, the chap responsible for designing and marketing the Emerald suggests a two box approach with simply a transformer and two bridge rectifiers in the power supply box. The phono stage has excellent filtering and regulation on board so the power supply doesn't need smoothing caps etc but I personally don't like feeding rippling dc to something like a phono stage. All the ac artefacts etc end up in there too so I included basic smoothing and filtering in my power supply.

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This power supply board can do five stages of filtering but I thought four caps, two per side would be more than sufficient given the generous filtering and on board regulation already available.
Here's the power supply built and tested. I used xlr plugs and sockets and bog standard three core cable for the dc umbilical.

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Now all I had to do was finish the other cut down case and mount the boards. After wiring it looked like this.

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So how does it sound? Well it sounds pretty good but I'd have to say that because I built it! But yes it does sound extremely good. I started out with a 2M Red simply because it was to hand on a deck I'd built for someone. I'm very familiar with this cartridge and whilst it can sound a bit rough round the edges its not offensive at all. Those rough edges seemed to vanish and it was so enjoyable to listen to. I said to a friend that if this phono stage could make a Red sound good then the world would be our oyster!

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Here's my Lenco plonked on my workbench with the 2M Red. On the opposite shelf sits my Empire with Spacearm and Benz 0.4. A quick shift around and I had the Benz playing through the Emerald. Now I hadn't used this deck in a while because I was under the impression that the Benz was past its best and needed retipping. However playing through the Emerald you just wouldn't think so. It's the best I've ever heard this cartridge in five years of ownership. It was so clear and detailed with just the right amount of sweetness. I've always found Benz carts to be a touch full at either end but there was none of this here. It was bloody brilliant. Here's my Empire turntable. I had turn the phono stage onto its front to get it in a workable position.

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I decided to take the Emerald downstairs along with the Lenco and slot it all into our main system. Took me about an hour to get it all sorted and I thought I'd press the Jolidas into service as they hadn't been on for a while. My own turntable has a Goldring Eroica fitted to my own arm and whilst it not an expensive cartridge it's quite a pleasant device. This wasn't as successful as I'd hoped for though it did perform well enough. I felt it was lacking something and I think that was because the loading was wrong. I have put extra sockets on the phono stage for loading plugs but tbh I didn't have any plugs make up so it was back to the Lenco and the 2M Red for the rest of the day.

Here's our main music system.

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Two days after finishing the Emerald I lent it to a friend. I've just had a phone call asking me if I'll build him one.
 
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Chops54

Junior Member
I'd just like to add that when I get the Emerald back I'll post some pics of the finished article as I neglected to take any before lending it out. Future improvements will included external switching for mm/mc and possibly gain too. I'll also get a modest selection of loading plugs made up.
 

Chops54

Junior Member
I was mulling over the circuit diagram again last night and after looking at the image posted by Wntrmute2 I realised that I only need to include a gain switch on the rear panel. The 47.5K input loading resistor for moving magnet stays in circuit all the time and all loading resistors for moving coil are put in parallel with this. When no moving coil loading resistors are plugged in the phono stage simply defaults to moving magnet. Now if I wanted to I could make the moving magnet input impedance switchable between 47.5K and say 38K to accommodate AT carts like the 440Mlb. A 440 correctly loaded is a real ear opener I can tell you. They also benefit from a low input capacitance too and this was one of the reasons for my interest in the Emerald.
 

Chops54

Junior Member
Since I last posted here I've built another Emerald phono stage for my other system. I didn't want to cut another Naim shoebox in half so I ordered a couple of cheap aluminium enclosures. Because of delays caused by Covid and because I was feeling impatient I thought I'd build it all into the one shoebox and rehouse the boards later once the new enclosures were here. Well I have to say I'm surprised. I've made no attempt to shield the transformer or the psu and all the wiring is unshielded yet this phono stage is as quiet as a mouse.

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