Simplistic NJFET RIAA

Hi, and Happy New year to all.

I purchased a mini kit and boards for this project about 12 months back and now (after moving house) I'm finally getting around to building it.

I want to build the MM version for use with the new AT700 series cartridges.

As I live in the UK I wonder if you could advise me please on where I can purchase a 36V transformer for it. I have a 30V but I fear this would not be enough (Mr Sakis ?)

Also Mr Sakis, (just slightly off topic) did you make a circuit for a MC Pre-preamp ?
If so could you direct me to it please?

Many thanks in advance,
Royville.
 
diyAudio Chief Moderator
Joined 2002
Paid Member
Who's Mr. Sakis? :)

Connect a 330 Ohm 10W resistor across the secondary of that 30V AC nominal trafo you got. See if at that load on your mains gives anything like 32-33 VAC in reality. If it does so, use it.

In post#1 press first link "build guide MC & MM older version". It will lead you to the 2010 paper that also has a standalone MC pre pre circuit in page 7.
 
diyAudio Chief Moderator
Joined 2002
Paid Member
Has anyone used a Ortofon Cadenza Black with the FSP yet? I will be helping a friend assemble his soon and was wondering if there was any cartridge loading details I could learn. Cart details below:

Output voltage at 1000 Hz, 5cm/sec. - 0,33 mV
Compliance, dynamic, lateral - 16 µm/mN
Tracking force range - 2,0-2,5 g (20-25 mN)
Tracking force, recommended - 2,3 g (23 mN)
Internal impedance, DC resistance - 5 Ohm
Recommended load impedance - > 10 Ohm
Cartridge body material - Stainless steel Aluminium

Thanks,

KC

As 6L6 said. For gain I would build the guide's highest sensitivity option of course. As for loading I would populate 100 150 200 250 Ohm resistors for the DIP switch selection options provided on the FSP's board.
 
If only I could read !!!

Who's Mr. Sakis? :)

Dear Mr Salas,

Please accept my apologies for getting your name wrong. :guilty:
Thankfully you knew I meant yourself. :eek: and thanks for replying so fast, I will try what you have suggested regarding the 30v transformer, and checkout the link you mentioned. I just want to try it on an old Dynavector 10x5 HOMC fed into the phono stage of my old NAD 3020
integrated amp.

Much appreciated Sir,
Royville.
 
230:30Vac are commonly available in the UK.
Some have dual primaries but that does not affect UK users/Builders.

Typically we have 240Vac to 245Vac outwith the high demand times and that leads to a 30Vac transformer putting out ~5% extra voltage i.e. 31.5Vac

If you then take account of transformer regulation, you find that 33Vac is probably more typical for UK outputs from a 230:30Vac transformer.
 
diyAudio Chief Moderator
Joined 2002
Paid Member
Dear Mr Salas,

Please accept my apologies for getting your name wrong. :guilty:
Thankfully you knew I meant yourself. :eek: and thanks for replying so fast, I will try what you have suggested regarding the 30v transformer, and checkout the link you mentioned. I just want to try it on an old Dynavector 10x5 HOMC fed into the phono stage of my old NAD 3020
integrated amp.

Much appreciated Sir,
Royville.

Hi

I have an older Dyna 10X4 mk.II model that I tried on a Systemdek IIX 900 with a Rega arm and it played very nicely. Certainly different but not a let down when switching from the DL-103R. The ZYX Bloom was above both though. I suggest that you should follow the 43dB gain configuration values for HOMC as described in the guide.

Regards
 

Attachments

  • Picture 002.jpg
    Picture 002.jpg
    348.4 KB · Views: 305
  • DSCF2856.JPG
    DSCF2856.JPG
    379.6 KB · Views: 297
  • IMG_Dyna.jpg
    IMG_Dyna.jpg
    815.5 KB · Views: 290
Hi Salas,

I too had a 10x4 a few years ago which I traded in for the 10x5 and I recall that the 10x4 sounded better to me. The 10x5 always sounded a little softer as though it had a slightly rolled off treble.

Anyways I am just curious how it would sound using your pre-pre between it and a mm phono stage (nad). Maybe it would open up the sound a bit more.

I want to build your RIAA to use with an AT745 MM I hope to be purchasing soon, so you see I was talking about two separate issues really.

Kind regards
Roy.
 
diyAudio Chief Moderator
Joined 2002
Paid Member
Hi Salas,

I too had a 10x4 a few years ago which I traded in for the 10x5 and I recall that the 10x4 sounded better to me. The 10x5 always sounded a little softer as though it had a slightly rolled off treble.

Anyways I am just curious how it would sound using your pre-pre between it and a mm phono stage (nad). Maybe it would open up the sound a bit more.

I want to build your RIAA to use with an AT745 MM I hope to be purchasing soon, so you see I was talking about two separate issues really.

Kind regards
Roy.
Roy, better use 47K Z-Foil R1 and no other Rx load options so the 10x5 will sound at its most open in the highs. Use Z-Foil for R14 too if the budget permits.
 
diyAudio Chief Moderator
Joined 2002
Paid Member
Has D1x shorted? Its the only way it could keep the rail up, if it had failed open it would have cut any current running in the reg's Vref. Replace it of course.

Also load the output with a 10-50K resistor to simulate its connected to a preamp, see if it still shows any DCmV. Leaking modern output capacitor is unlike.
 
diyAudio Chief Moderator
Joined 2002
Paid Member
AC is another thing. Means some signal or noise. Is the 80mV AC on the same channel that has the dead D1x? Better fix that first and check that Q3x Q4x Q5x are good also. By normal circa 0.6V Vbe in Q4x and by normal RDS Ohms in the others (JFETS). Few decades of Ohms. Not shorted, not open, not just few Ohms not hundreds of Ohms or kOhms.
 
AC is another thing. Means some signal or noise. Is the 80mV AC on the same channel that has the dead D1x? Better fix that first and check that Q3x Q4x Q5x are good also. By normal circa 0.6V Vbe in Q4x and by normal RDS Ohms in the others (JFETS). Few decades of Ohms. Not shorted, not open, not just few Ohms not hundreds of Ohms or kOhms.

Pulled D1x, it measured fine and lit up??? Though after replacing, all is back in working order. Making great music! Thanks Salas.