Simplistic NJFET RIAA

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#6,922
Bksabath said:
I have not made much progres
Life sems to be trowing same big spanners in the works latley.

I have started the design of the new PCB with the uge Mundorf capacitors.

I have aded a 12 way dip switch for cartridge loading and I am going to use
5 resistors and 6 capacitors for cartridge loading.

I am planning on switchable values from say 40 Homs up to 1K and capacitance from 10 to 200 Pf. (the capacitance bit is easy as values sums by parralel connection).

Is all in my brain at the moment so ne real values so far.

The big question is how much it will impact on the 0.2 mv signal from the cartridge as more tracks more PCB area exposed and so on.
Idealy once found the best values by listening
I am planing on the first switch to thake the rest out of thecircuit and provide board space for components to be soldered on permanentley.

Another alternative is to solder the components inside the phono plugs.

To be continued...
Click to expand...

Many put complex stuff on signal input to have loading options. I could understand if in commercial, catering for the unknown. In diy I would avoid contacts and distances at the signal's most delicate. I.e. when exits shielded and goes to first gate. A bulk foil trimmer could do it all. For capacitors I personally would not bother at all.
 
#6,924
Tanks Salas and Ricardo

Fair point and much on my line of thinking dip switches and extra signal pats are bad especialy at such low levels.

Thing is there is not a real standard for cartridges outputs and loading and same time manufacturer reccomandation may not be ideal.

So I will try to get te thing set up with the possibility to take the Dip switch out of the signal pat and solder the best sounding combination on the imput pins once I have found it, + Elite today and tomorow? may be sometink else.
 
#6,925
One step forward 2 back

Got a batch of CIF boards from Farnell and .....Crap photosensitive layer living bad stracks and acid working its way troug.

So still shopping for parts

Found very nice post about resistor noise on the part forum
Quote

Originally Posted by Ron AKA
Have a look at the test circuitry, and test results in this paper, and in particular the Vishay S102K.

https://dcc.ligo.org/public/0002/T0900200/001/current_noise.pdf
The author Frank Seifert is a research engineer working on the development of a quantum-noise limited power stabilization for a high-precision laser system.

End quote

worth a look IMO sorry if out of topic
 
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#6,926
The Reflektor went even less parts meantime. After Ricardo's subjective experiments and some suggestions by me it looks that its 1000uF ref filter can work in nice tone without its PP Cap + small R bypass, if the output cap will go 0.47u and every stopper resistor be 120R. So make it like this if you will ever add such regs, which I highly recommend. I have read the resistors current noise article BTW.
 

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#6,936
Tanks Salas
Going to order a few tomorow.

I can get Multycomp current gain 100
Or On semy current gain 200 (2N4403G)

Do the transistors need matching?

And how?

Ops Sorry just realised this should be on the Power suply forum.
Maybe for continuity sake may be worth moving the SCH there?
 
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#6,940
troubleshooting one channel

I got my salas riaa built but it is not working. I am using the Salas 1.1 bib as the regulator and I am measuring 25.1 volts. I am trying to build the Salas Simplistic NJFET Riaa Version 1.0 PDF(MM or MC High version) not the most current PDF version 11.02.F0

The leds are powered on but I am getting no sound or hum on one channel. My other channel isn't working either and is in worse shape.

From reading some of the thread there is mention of measuring the drain to ground voltage so I think I measured these correctly.

Q6 - 24.9 volts
Q3 collector - 15.65 volts
Q1 drain - 7.16 volts
Q2 drain - .961 volts
Q5 drain - .443 volts

Compared to recent PDF
Q6 is Q5
Q3 is Q4
Q5 is Q3

Any help is appreciated.

Kerux
 
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