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The Phonoclone and VSPS PCB Help Desk
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Old 6th December 2017, 12:21 PM   #3811
hajj is offline hajj  Lebanon
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Could the emerald be used as a high gain MM phono stage?
The idea is to use it with the infamous B&O low output MM carts
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Old 6th December 2017, 12:52 PM   #3812
rjm is offline rjm  Japan
Richard Murdey
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Sure. What gain/load combo is required?
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Old 6th December 2017, 01:58 PM   #3813
hajj is offline hajj  Lebanon
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B&O MM carts usually hover around the 2-2.15mV output with the typical 47Kohm load.

I was hoping to get around 1V RMS output or thereabout, which is a long stretch but would be great for the gain structure downstream.

Thanks
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Old 6th December 2017, 10:35 PM   #3814
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I've attached the Emerald BOM here, though it's already uploaded to the website. There's a worksheet which lets you experiment with resistor values R1-5, for customized load and gain options.

Re B&O cartridges, I've got a couple of things to say on that and I'll have to be careful in my bullet point ordering so as not to derail the thread.

Okay.

1. To keep 47.5k load, JP1-1 is left open, while closing JP1-2 will increase the gain to 60 dB in stock configuration. The high gain setting would bring a 2.2 mV cartridge to 2.2 V, which is close to your stated goal. You can change R3 to 150 to reduce the high gain output to 52 dB, giving an output closer to 1 V and leaving the low gain setting unchanged, or you can change R4 to 150 ohms to increase the low gain setting to 52 dB, leaving the high gain about 60 dB.

Actually though, what you really want is 46 dB and an output level of about 300 mV.

.deep breath.

2. The sensitivity of a cartridge in mV does not follow the same standard as the line level output of a CD player. Multiplying a cartridge with an listed sensitivity of 1 mV to 1 V rms (0 dB) line level standard doesn't mean the sound level will be the same as a CD player. Consumer audio line level is closer to -10 dB, and 300 mV is closer to the number you want to "hit" when multiplying the cartridge sensitivity by the phono stage midband gain. The traditional phono stage gains of 36 dB MM and 56 dB MC give the correct output with "typical" cartridge sensitivity of 5 mV and 0.5 mV respectively. The B&O is only 6 dB lower than typical MM. In my experience it's not worth worrying about 6 dB one way or another in a phono stage. That level of difference is easily mopped up by your preamp's volume control. To the ear the difference in signal loudness is not especially great. Indeed that's the general thinking in preamp design: 36 dB covers 2.5-10 mV range of MM sensitivities, 56 dB covers 0.25-1 mV. B&O is just in the middle ground where, if these things bothered you, you might find yourself wanting about 46 dB. If you were building the Emerald specifically for this cart, maybe set it up to have "MM-LO" 36 dB and "MM-HI" 46 dB gain positions [R3 475 ohms, R4 1.5k]]. That would give 440 mV with your B&O and a similar output level with MM carts hovering around 5 mV. As a bonus, the MM-HI setting would also be good with high output MC which often hover around 1-2 mV output.

I'd also set R2 to 1k, so the loading options were 47k5 and 1k.

The more I think about what I wrote here, the more I think this (i.e. MMLO MMHI, 47k/1k) would be a pretty sweet setup for a high end MM phono stage.
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File Type: zip pcb-emerald-10s-bom.zip (406.0 KB, 19 views)
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Last edited by rjm; 6th December 2017 at 10:48 PM.
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Old 7th December 2017, 12:23 AM   #3815
rjm is offline rjm  Japan
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This hopefully gives a better idea of the numbers involved.

People do seem to want to overthink this, making a problem out of something which really isn't one. Just build your phono stage 40 dB (MM) and 60 dB (MC) ballpark figures, and you'll be good to go.

I recommend the vinyl engine cartridge database for lookup info.

As far as I can see only a few "problem" cartridges exist in the grey area around 1.0 mV lying about mid way between MM and MC centerpoints. Examples include the Benz Micro Glider, some of the high end Grados, and one or two models from Roksan and Van den Hul. A similar number of cartridges fall into the "ultra low output" class 0.10 mV and below, where a gain higher than 60 dB could be rationalized. Audio Note, some Denon, Benz again, and Fidelity Research. Taking the grand prize is the Ortofon MC 10 mkII at 0.024 mV and few similar 0.05 mV and below which would indeed require a special setup.

The difference in gain between traditional and modern circuits is a combination of average cartridges outputs getting smaller over the years, the increased availability of cheap op amps with low noise and high voltage gain, and the increase in standard line level outputs coinciding with the introduction of digital audio.
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File Type: png phono stage gain.png (95.2 KB, 165 views)
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File Type: zip Phono cartridge gain worksheet.zip (9.6 KB, 5 views)
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Last edited by rjm; 7th December 2017 at 12:51 AM.
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Old 11th December 2017, 07:02 AM   #3816
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Default Emerald BOM 1.0s2

cleaned up and expanded the BOM a little, no major changes or fixes

- default BOM electrolytic caps are now Nichicon Muse UKZ.
- default BOM R3,4 are 56.2R and 750R, so gain is 40/60 exactly rather than a more awkward but perfectly reasonable 39/59 dB obtained with 68.1R/1k. The reason I prefer the latter is they fall in my list of standard resistors I keep around in stock, but so many of the other resistors in this circuit need to be bought specially there's not really a big deal about adding a couple more.
- added some worksheets to explain the relationship between gain and cartridge sensitivity re. post 3815 above, for interests sake only.
- added workable alternative versions of the Emerald circuit: 40/50 dB, 50/60 dB, and 60/70 dB.
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File Type: zip pcb-emerald-10s2-bom.zip (413.0 KB, 9 views)
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Last edited by rjm; 11th December 2017 at 07:05 AM.
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Old 11th December 2017, 11:39 AM   #3817
ALPUY is offline ALPUY  Uruguay
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Richard. I'm confusing. As I mentioned, I must buy the components to assemble the VSPS400 outdoors.
I want to assemble it with the best components, that's why I'm delaying in completing it.
But I see that you are assembling with electrolytic Nichicon Muse UKZ. Are they better than FG ?. What electrolytic would you recommend ?. For the RIAA capacitors I will use Cornell Dubilier 1%. It's okay?. Resistors DALE 1%. There are other recommendable ?.
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Old 11th December 2017, 11:45 AM   #3818
kffern is offline kffern  Australia
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Hi RJM,
My second phonoclone3 has also stopped working. One channel died first which seemed to be caused by the ground cable on one board lifting off the solder. Looks like I wasnít making good joints with my old 20w iron.
I connected the ground but now am getting nothing from either board. I am getting 9v across pins 3 and 7 of the first and second 8pin dip socket. Are there any other measurements I can do to check what is going on? I'm sure you have mentioned it somewhere in the thread but its hard to find.

I havenít ordered the parts for the Emerald as yet but would like to get this one working as well.
Thanks,
Kffern
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Old 11th December 2017, 10:29 PM   #3819
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@Jose

My comments and notes about the Emerald circuit do not apply to the VSPS400, and vice versa. For the VSPS 400, please use the BOM or equivalent parts.

I do not in any case recommend FG or KZ or whatever, but since people want to use these "audio grade" electrolytic capacitors I have modified the latest boards (Emerald and Phonoclone) to make this possible.

I actually have ordered some FG and KZ from Mouser, and will see if I can imagine they improve the sound. They aren't very expensive, so its not a big deal either way.

@Kevan

That's the first time I've ever heard of one of my boards which was working stop working. With 9 V on all op amps (correct!), and no output from either board, I suspect everything is fine and it's something very simple ... (was your amplifier turned on? Preamp set to the right inputs? when you did the repair did you connect IN+ and IN- correctly and not backwards? input RCA connected to output by mistake??)

Still, you suspect a bad connection can double check continuity (zero ohms) between all the grounds (COM, IN-, OUT-, GND)
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Old 12th December 2017, 06:07 AM   #3820
gigigirl is online now gigigirl
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Default Using phonoclone from batteries.

Hi, I am very interested in building your Phonoclone boards up. can you use the kit with +18 / -18 VDC battery supply.

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