Simplistic NJFET RIAA

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chalkandtalk

Member
Joined 2006
What is the best way to arrange 0V connections?

I have two separate DC supplies (kept in a separate PSU case). The RIAA circuit is in it's own case with the shunt regs. Both cases are connected to earth. The catridge 0v wires connect to the 0V of each side of the RIAA.

Should 0V of each supply be connected? If so would it be best to connect them in the PSU after (or maybe before) the smoothing caps?

Should the earth wire from the deck be connected to mains earth and the common 0V connection?

Thanks for your help.
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
I usually reference the regulators to their box at their 0 Force out points. I usually connect the TT ground wire to a non insulated post on the box which is grounded itself. I have seen in two box builds that best hum performance may vary for best grounding scheme depending on how the circuit segments are separated and boxed. I usually try a few schemes when watching harmonic noise on the FFT.
 
keantoken

keantoken

Member
Joined 2006
I adjusted the VTF. I am amazed at how sensitive this adjustment is. I added a self-cleaning attachment for the pipe cleaner brush... When the tonearm swings off the record, the brush falls onto a pipe cleaner track and drags across it to the rest. This way the brush is cleaned automatically after each playing.

Unfortunately all my records seem to suffer from excess distortion at loud volumes. After glueing records, the quality starts to get near the youtube clips, imaging is usually better than youtube (but I guess that's no surprise). VTF adjustment was very important for the soundstage depth. I used "Pavanne (Gould)" from "Pops goes the trumpet".

I think I will try to make a recording. Unfortunately it will be using my soundblaster, which was a way overpriced rip-off. So it will probably be 48KHz 16-bit. I hope to get an M-audio 192 in the future.
 
keantoken

keantoken

Member
Joined 2006
I would be greatfull if you would help me to determine what some of the noises in this one are. This is what I used to tune the VTF. I don't have records with a lot of bass, I will try to find one. This one will be next in line for glueing.

Also I'm not sure how to tell if playing a record will damage it or the stylus.

I have Switched-On Bach, which has suitable bass, but these are synths, not real instruments.

http://www.mediafire.com/?jd0mk4uqfcx9t8d
 
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chalkandtalk

Member
Joined 2006
Have made a little progress. I've joined the 0V of each channel to the earth point. However, there is still a loud hum. What I'm tempted to try now is a star earth. So 0V in , 0V out, 0V of RIAA and 0V of shunt (not sure about 0V of force and sense) all meet at the earth connection post.

When the deck is disconnected from RIAA there is no hum whatsoever from the RIAA.:rain:
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
You can AC short from RCA (in) gnd ring with 1nF directly near it to chassis. That should short RF. But it can be resonance of the generator and the wiring/gate capacitance. Can you scope the output as it hums? Is there the Rock arm and chassis grounding scheme available to see?
 
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chalkandtalk

Member
Joined 2006
I'll get on to that Salas. I have a scope so will post some pics of whats on the output of the RIAA. I have an old amp which has a MM stage. When the rock (with MC) is plugged into that there is no hum (volume low obviously). So I suspect there is a problem with my DIY unit. Should get some pics by the weekend. Thanks for your help. :)
 
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