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RJM Audio Emerald Phono Stage Help Desk
RJM Audio Emerald Phono Stage Help Desk
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Old 18th April 2019, 11:20 AM   #1
rjm is offline rjm  Japan
Richard Murdey
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RJM Audio Emerald Phono Stage Help Desk
Default RJM Audio Emerald Phono Stage Help Desk

Emerald Phono Stage

"A two stage op amp circuit, the Emerald has switchable voltage gain and loading options and features an active-passive hybrid RIAA with exceptionally accurate response. Single channel, dual-layer 10 cm x 8 cm board. The S-Reg voltage regulator circuit is built in to the boards, no additional regulation or filtering required."

Help desk and build thread. I've had a couple of people asking me to separate it from the (now 14 year old) VSPS and Phonoclone help desk. So here you go...
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Old 21st April 2019, 09:21 PM   #2
WntrMute2 is offline WntrMute2  United States
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Hello, I'm about to fire up my Emerald with switch-board input. I am planning on starting with a Hi-output Sumiko Blackbird. If I'm reading your instructions correctly, I should leave both jumpers out. Does that seem correct? All the switch-board switches are off for starters. I built it with the stock BOM parts.

Sumiko Blackbird
Output - 2.5mV
Internal Impedance - 135ohms
Load - 47K
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Old 21st April 2019, 10:42 PM   #3
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Richard Murdey
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RJM Audio Emerald Phono Stage Help Desk
Quote:
Originally Posted by WntrMute2 View Post
If I'm reading your instructions correctly, I should leave both jumpers out. Does that seem correct? All the switch-board switches are off for starters. I built it with the stock BOM parts.

Sumiko Blackbird
Output - 2.5mV
Internal Impedance - 135ohms
Load - 47K
Yes, High Output MC carts are treated as MM carts for this purpose. You want to have the Emerald set to 47 kohms input impedance, and the MM level gain (about 40 db).

The switchboard would be left disabled (all switches open) for this cart, you don't need it.

/R
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Old 22nd April 2019, 01:31 AM   #4
Mark Tillotson is offline Mark Tillotson
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I'm intrigued by the low gain of the first stage for MM of only x2, given the importance of keeping noise under control...
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Old 30th April 2019, 10:09 PM   #5
WntrMute2 is offline WntrMute2  United States
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Quote:
Originally Posted by rjm View Post
Yes, High Output MC carts are treated as MM carts for this purpose. You want to have the Emerald set to 47 kohms input impedance, and the MM level gain (about 40 db).

The switchboard would be left disabled (all switches open) for this cart, you don't need it.

/R
Next cartridge will be the Sound Smith Paua. Should be here in a few weeks.
I'm assuming I'll need changes to the switchboard of the Emerald itself.

Output 0.4mv.
Load 470 ohms to 2,800(or so) ohms
Capacitance not specified

Suggestions as to changes to the Emerald or the switch board to accomplish the range of load resistance?
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Old 30th April 2019, 10:45 PM   #6
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RJM Audio Emerald Phono Stage Help Desk
Set the Switchboard to Position 1 ON (100000) to give 980 ohm load. Optionally Position 6 ON (100001) to add 100 pF capacitance.
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Old 30th April 2019, 10:52 PM   #7
WntrMute2 is offline WntrMute2  United States
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Quote:
Originally Posted by rjm View Post
Set the Switchboard to Position 1 ON (100000) to give 980 ohm load. Optionally Position 6 ON (100001) to add 100 pF capacitance.
I'm assuming I'd remove the load and gain jumper in the Emerald. If I wanted a range of load values, any way of accomplishing that? I socketed R1 thru R5 in the Emerald so I could easily swap resistors BTW.
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Old 1st May 2019, 12:33 AM   #8
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RJM Audio Emerald Phono Stage Help Desk
Think of the Switchboard as an alternative to your on-board socketed resistor R1. Of course you can just swap out R1 or R2 for a different value, but when using switchboard you leave JP1_1 open to set the board input to 47kohms, then select the parallel resistance value on the switchboard to set the load. The gain setting is switched via JP1_2 as always, it is unaffected by the switchboard.
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Old 2nd May 2019, 02:10 AM   #9
WntrMute2 is offline WntrMute2  United States
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Got that. I think I'll need to replace some or all of the resistors if I want a load variation from say 4k down to just below 1k. I'm assuming the sweet spot may be around 2,800k. Suggestions on what to populate the board with?
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Old 2nd May 2019, 10:24 PM   #10
WntrMute2 is offline WntrMute2  United States
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I spun a variety af records today with excellent results. Adderly to Coltrane to Cowboy Junkies and finally a rocking' session with Humble Pie. Seemed perfect all around! This is with a HOMC Sumiko Blackbird. Pretty happy at this point.
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