Simplistic NJFET RIAA

[Salas]

Don't know, I had listened to that machine a couple of months later too and did not notice anything new. It should have been end 2009 when I put them in first time.

[Salas]

Rush, did you use supreme silver oil at all? That one is expensive but not super expensive and its enough upgrade to many.

[Rush]

Originally Posted by Salas

Rush, did you use supreme silver oil at all? That one is expensive but not super expensive and its enough upgrade to many.

Not yet. I haven't bought any "expensive" caps yet. I am obsessing over this right now. I don't want to spend $100 now and wish I spent $200 later, if you know what I mean.
If a small valve cap (.022 to .1 uF) could be at the output of second stage and a DCB1 as the output from the available Hypnotize supply, I would be dollars ahead. I am looking for a cheaper solution that sounds the best.

Rush

[Salas]

Try the trick I suggested then. If you can make the output cap a small cap between 2nd stage and buffer with an adjustable minus supply and DCB1 like buffer then you will be able to spend much much less. Try it conceptually with a regular cap first. And you can optimize the uF value too, before spending.

[Salas]

Or stopping to second stage and coupling to a dedicated 1meg hypno audio part with a small cap as you say.

[Rush]

Originally Posted by Salas

Or stopping to second stage and coupling to a dedicated 1meg hypno audio part with a small cap as you say.

I found a drawing buried in this thread that showed a B1 cap coupled out, so I modified it.
See if this would work.
Question is where to break the ground as the supply for the B1 will also be used for my crossover or it could be from my Mesmerize which ever you think best. Now that I am thinking about it the Mesmerize is closer to the phono and may provide less chance of grounding issue.

Thanks Salas, maybe others will appreciate this exercise as well.

Rush

[Salas]

Yes, that picture shows a riaa completed single supply system handing over to symmetric PSU buffer through AC coupling. It should work. You got many things in one box and me to predict best grounding is impossible, you should just try it and see if it will do best to locally break and star away or not.

[RCruz]

Originally Posted by Salas

Look to the right hand diagram, Rg (trimmer) is on your side. You can use 27K Vref there even. Increasing the ref filtering cap is the main weapon against 1/f noise in general but with the quality components I see in your pic above it can be costly. Luckily rumble filtering response shape suppresses subsonic 1/f also.

Hi Salas

Back to the V12R

I decided to use a 30kr for vref so I will need 1.15mV to get the desired 35Vout.

So if I am correct Rs = Vp/Id * (sqr(Id/Idss) - 1) than admiting I use a 8mA Idss k170 and admiting it's Vp = -0.45V, I will need a Rs = 243ohm.

If my calc is correct, I can use a 500ohm fixed resistor // 20kohm trimmer to set the voltage to 35V.

Please let me know if I am in the right direction....

PS: In reality I would not need a 20k trimmer but that is the only one I have got now.

[kstlfido]

I hope to take my Salas RIAA build to Burning Amp! I just have to get it into a box in the next 3 weeks....

I have a small collection of good load R's so we can tweak on the spot.

I'd like to try the B1 buffer above, too. I'm coupling the Salas to a Lightspeed attenuator. It's input impedance is quite low (8-10Kohm). So any chance to save on big $$ caps is worth trying.

I have a Hypnotize board here- but IIRC the L&R grounds are tied and my Lightspeed's are not. Potential for ground loops. Ahh, if I can make the time, try it and see....

-Kent

[Salas]

As a combo makes sense.