RJM Audio Emerald Phono Stage Help Desk

[rjm]

@Carlos,

Looks good. Glad you found the problem. It's curious to me that a bad connection on the primary side of the transformer caused hiss, I would have thought that loss of power (no functionality) would have been the result. Bad RCA cables, on the other hand can and do cause noise.

 

[enterk]

I finally completed my first Emerald project. After a few initial issues and with Richard's help I got there eventually. The result is quite impressive, the Emerald has replaced a Linn Linto phono stage in my system featuring a Dynavector XX2 cartridge. I have to say the Emerald performs really well and my first impressions are that it is superior to the Linto. Probably needs a few weeks of settling in before I can make final conclusions. The only changes to the original spec are: Mundorf MCap ZN Capacitor as a replacement for C3 and Van Damme balanced cable for the internal signal wiring - this helped with some RFI I was experiencing

 

[fakeall]

You are absolutely right, thank you. What speaks against it now is that it will take at least one month to get here., and that i would like it accessible from the outside
However, it gives me the values i was looking for so i can start figuring out the switches.

Guess i could have waited for a switchboard anyhow, because i still did not do a load switch for MC.
Re-reading what i could find, i am not sure now whether the load resistor (R2) should roughly match the DC resistance of the MC cartridge or have a higher value? It seems that e.g. SPU's have a much lower DC resistance in the region of 2 to 4 Ohms, and i wonder whether such a value would be safe and desirable for R2?

Thank you for your help.

 

[rjm]

Sorry I skipped over replying to your earlier post, I though it was answered by someone else.

The Emerald is a straightforward voltage input amplifier, the load resistor for the MC stage is whatever is the recommended value suggested by the cartridge manufacturer. Typically 100 ohms is fine, but if you want to fine tune it you'll either have to substitute another value for R2 or use the Switchboard, or, you know, just wire a load resistor across the RCA jack in combination with the jumper set to the MM load of 47k.

 

[fakeall]

Thank you Richard, all clear now. I will have a three position switch so i can use three MC cartridges.

 

[brinker]

1½ years after ordering the PCBs, I finally have all components in. Single chassis layout tested. Will put in a small division between the PSU side and the PCBs. Now I just have to find the time to actually solder everything up.

 

[janpo]

I'm so inspired by all the beautiful work being done here.
The mailman better hurry up and deliver.
Hifi2000 enclosure and silkscreening equipment is ready to go.

I was wondering, did anyone ever consider making a balanced version of the Emerald ?
That would mean 4 boards, right ?

 

[rjm]

It can be done with 4 boards, but remember the signal to noise is 3 dB worse in balanced mode. (Since the input to each side is half of the original signal)

A se-bal converter circuit at the emerald's output might be a better option.

 

[brinker]

Not sure if this has been asked before - but is there any particular reason for R10 to be Carbon Composition, and not Metal Film like the rest?

 

[rjm]

@brinker

Carbon composition are noisier than metal film, but are less inductive. The noise contribution from a 47 ohm resistor on the circuit output being negligible, I prefer to use carbon comp at this position.

 

[KeLLoGsX]

I have my boards for the Emerald and psu on its way. Super fast service! Thank you Richard

Now I'm going through the BOM for parts and there is one part out of stock: 660-MF1/4DC1001F.

I found a replacement that looks fine but it's 3 times more expensive, still not much but I need to know if it will suit as replacement 660-MF1/4DL1001F

 

[sq225917]

https://www.mouser.co.uk/ProductDetail/Vishay-Dale/RN60D1001FB14?qs=vEZPefDgUPkcBU7jWJvieQ==

you might have to bend the legs a little.

 

[rjm]

Now I'm going through the BOM for parts and there is one part out of stock: 660-MF1/4DC1001F.

That's a 1/4 W 1k metal film resistor. At first thought, it's pretty hilarious that Mouser would run out of something like 1k through-hole resistors, though it may be Covid-related in which case not so funny.

In any event, any 1/4 1k 1% metal film resistor will do fine. Recommend Vishay or KOA

This one for example, if cost is a concern.

 

[KeLLoGsX]

Thank you both!


It's not really the cost that's my concern. But this will be my first electronic diy project and I'm really uncertain how things work. I just want to get the right components. The replacement I found was much more expensive and I couldn't understand why so I wasn't sure if I could use it.

 

[rjm]

The one you had picked was more expensive because it was not RoHS compliant. Resistor prices at Mouser are a bit weird. Some special resistors are more expensive because they have 0.1% or 0.5% tolerance or rated to high voltage or have especially low temperature coefficient, but a lot are expensive just because Mouser wants to sell you something else.

 

[KeLLoGsX]

First order from Mouser is placed. Only items missing are the Nichicon KZ capacitors which were out of stock and the C3 capacitor were I'll probably go for a Mundorf M-Cap Supreme.
The psu will be next, and I'll probably look for an enclosure to fit both, maybe a Hifi 2000 Galaxy GX383 330x230
This will be fun... maybe not so much for all of you when I start asking stupid questions.

 

[brinker]

Boards have been populated - just need to wire up the PSU and finish up the back plate, so that input/output can be wired up! Hopefully I will have it ready in a couple weeks.

 

[rjm]

It looks to be coming along nicely.

 

[WntrMute2]

Nice work! I've wanted to try those caps as well.

 

[dwinstonwood]

New Emerald project under way

Hello all, I've decided to build an Emerald. I'm excited about it.
So, I've ordered my boards from Richard and I'm finishing up my Mouser order.
But, I've hit a snag...

I'm trying to buy standard circular connectors for the DC umbilical and I have no idea what I need. I've spent over two hours clicking through Mouser's website, filtering by manufacturer, number of pin positions, price, material, etc. But, I'm no closer to knowing what to buy. There are literally hundreds of types.

I'm guessing I want 6-position connectors, but I'm not really sure.

Will two of these work:
6-Pin Chassis Connector - Panel Mount (male and female) - PRT-11475 - SparkFun Electronics

Thanks in advance for any help, and sorry if my frustration is showing through in my post!

David