Simplistic NJFET RIAA

[merlin el mago]

1Khz sine wave, probe x1 left channel

 

[merlin el mago]

1Khz sine wave, probe x1 right channel

 

[merlin el mago]

Both measurements done with scope ampl. 2V/cm timebase 0.5ms

 

[Salas]

What is this? What chain you measure? MC in pre-pre to MM Rotel to tape out?

 

[merlin el mago]

I'm measureing only MM Rotel, MM input to tape out

 

[Salas]

So both your transformer and pre-pre feed no signal? Is the cart, arm & TT wiring OK?

 

[merlin el mago]

I try with Simplistic NJFET RIAA.

 

[merlin el mago]

Simplistic NJFET RIAA is going OK solid as a rock with my EB line amp/headphone amp.

 

[Salas]

There is a mystery then? TT plays confirmed, pre-pre measures confirmed, Partridge is a confirmed passive component, Rotel works from MM confirmed, but when you chain TT either from pre-pre or Partridge to Rotel you get nothing. I can't find logic in this. There is something done wrong.

 

[merlin el mago]

Is really strange

 

[vgeorge]

Try to put your scope on your hole amplification chain.
Do you still get a healthy sine wave?
If still yes, then maybe there is either a ground loop or you are missing a ground somewhere.

 

[merlin el mago]

In the Low MC pre-pre the signal ground isn't connected to chassis, TT ground is connected to chassis ground.

In the Partridge step-up the TT ground is connected directly to Rotel MM.

 

[merlin el mago]

Try to put your scope on your hole amplification chain.
Do you still get a healthy sine wave?
If still yes, then maybe there is either a ground loop or you are missing a ground somewhere.

I connected the Low MC pre-pre to Rotel MM and I have a perfect sine wave

 

[merlin el mago]

I suspect is a ground loop in the Low MC pre-pre so I will do proper wiring gnd to avoid it.

 

[merlin el mago]

Good & bad news.

Good news: channel left is sounding with a big buzz

Bad news: channel right don't sound nothing as is not connected

I reversed the channels at the input Rotel MM and....only sounds always left channel with big buzz so Low MC pre-pre is sounding both channels thi make sense because the same problem was with the step-up combo, I have to wait until I have finished the Itch

 

[vgeorge]

Something is not connected properly. If you have a sine from the scope you should have music. Maybe post a picture of all the cabling, so if somebody with a sharp eye can help.

 

[merlin el mago]

Pics

 

[vgeorge]

For start, I would remove all ground wires from the rca to the chassis and check.
Then one wire from the star of your circuit to the chassis.
These are just suggestions, I would recomend to try various grounding arrangements and see.

 

[studeb]

Why are both input and output gnds tied to the star gnd?
Would it not be better if they were both floating?

 

[merlin el mago]

For start, I would remove all ground wires from the rca to the chassis and check.
Then one wire from the star of your circuit to the chassis.
These are just suggestions, I would recomend to try various grounding arrangements and see.

I have to ground stars one for each channel, have I to connect the two ground stars togheter & after one wire to chassis or have I to connect two wires (one of each channel) to the chassis?