Simplistic NJFET RIAA

Hello, first of all I have to say a big thank you to Salas for his great work and his even greater help.

I am planning to build the phono stage and I have some questions about the capacitors.
I have already ordered some obbligatto caps, but for higher values there aren't any. The values I can't find are 220uf 25v, and 100uf 65v.
Are there any suggestions for them? Similar quality with the obbligatto would be ideal.
And also for the 15.1nf cap I found a 15nf and a 0.1nf from Jensen but they cost about 80 euro in total. :eek:
Do we have any suggestions about them too?

And if possible the shops I can buy them :eek:
 
diyAudio Chief Moderator
Joined 2002
Paid Member
100 & 220 uF are electrolytics obviously. You are obligated to skip obbligatto.
Get some KMH, FC, etc. and you are done, they are not doing signal.
15nF caps will vary on an LCR meter. Some will be 15.1nF. Still 15nF spot on will be a tad brighter but will do. Most overshoot or undershoot for tolerances.
My suggestion is you go buy plain vanilla MKP caps of small sizes so you can control your layout, and when you will know how to make a noiseless high gain circuit silently so for hum in practice, then spend on parts you fancy by making it from scratch in more wit and wisdom. If you start with expensive parts without having made it before its highly possible you will end up destroying more of them legs in experiments or not knowing how to fit them. Tight layout adds detail. Just my 2C.
 
Member
Joined 2009
Paid Member
Hello, first of all I have to say a big thank you to Salas for his great work and his even greater help.

I am planning to build the phono stage and I have some questions about the capacitors.
I have already ordered some obbligatto caps, but for higher values there aren't any. The values I can't find are 220uf 25v, and 100uf 65v.
Are there any suggestions for them? Similar quality with the obbligatto would be ideal.
And also for the 15.1nf cap I found a 15nf and a 0.1nf from Jensen but they cost about 80 euro in total. :eek:
Do we have any suggestions about them too?

And if possible the shops I can buy them :eek:

As sugested by Salas 1st fix the less hum with maximum gain with cheap components & when you know exact values post it & I will let you know where to buy.
 
Hi Stelakis,

there is a ebay resaler who also sales through his web site, his url is : rutubes.com.
Write to him he will sell you 2 of each of the film caps that you need. He has silver mica (14.7nf,14.8nf,46nf)and the teflon FT3-100nf. He also has some smaller values, that you will need to add to the above caps to reach the desired values.
You have nothing to loose by asking him for a quote.
 
Thank you all for the help.

I decided to buy cheap components at first to give it a go (hopefully in the weekend I will have it ready, I found everything in local shops) and then if everything goes right move to "exotic" parts.

rutubes... nice! Thank you very much psgr!

@Merlin

Muchas gracias mi amigo, when I finish the first silent "prototype" I'll contact you for sure.
 
I am building the 56dB gain version. For that I will need 37Volts of regulated DC using the Salas Shunt regulator. I will use a seperate shunt regulator for each channel.

I need to verify my understanding of the regulator regarding the current it would consume.

If I sum the currents in the regulator I find that it will use about 157mA.
I assume that Q2 will pass 6-7mA and Q1 will pass 150mA approximately.

Q4 will then pass about 135 to 140mA.

Is it critical to have the regulator set up for remote sense?
 
I will be determining IDSS tonight. Have 30 2sk177BL's to play with.
I will incorporate remote sense as it is an easy change in the pcb I designed.
The Power Supply for the shunt regulator can provide up to 49Volts with a RCLC filter. I was curious about the current to get the R in the ball park. The trany is from a previously abandoned project is an Avel Torroidal and has two secondaries of 18V which I was going to stack giving 36VAC. It is overkill but I have it on hand.

I'll post the IDSS tonight when I get the measurements completed.

PS I have around 5dB gain in my linestage available.
 
Thanks. WIll get back to you shortly.

Until then, is this reasonable for the shunt regulator with remote sense?
 

Attachments

  • ShuntSchema with sense.png
    ShuntSchema with sense.png
    14.8 KB · Views: 295
Last edited:
Correct, the proper unit is Amps.

I have a pair for each Q1, Q2, Q3, and Q5 at those currents listed above. From the pdf, I thought that Q1 and Q3 should be the highest Idss, Q2 should be between 8-9mA and Q5 should be low somewhere in the neighborhood of 5-6mA.
If Q5 needs to be > than 7mA I have several pairs that match up 7.3, 7.4, 7.6, 7.7mA.

so to type correctly with proper units.
Q1 = 10.2mA matched pair
Q2 = 8.8mA matched pair
Q3 = 10.0 mA matched pair
Q5 = 6.5mA matched pair with options to go higher if needed.
 
diyAudio Chief Moderator
Joined 2002
Paid Member
OK, tomorrow you will have your double jfet cascoded headamp phono with staggered idss pairs and b1 style ac coupled buffer cct with max gain possible to wake up your 103R, plus a properly wired remote sense V1.0 reg with adjustable Norton Vref, not Zener.
 
diyAudio Chief Moderator
Joined 2002
Paid Member
So the new "B1 style" buffer has become official?

Maybe, it plays OK and I had spares to put there. SGregory has spares and needs gain. I used it in my LMC so not to lose a few mVRMS too, since it has almost infinite load. I haven't done an exactly same build with and without so to tell. Since its load is a two legged made device it can be exchanged with a resistor and evaluate in a build.