Simplistic NJFET RIAA

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maxpou said:
Hi Salas,
do you have tried the CCS with green and red leds? what do you have preferred? thank you! Maxpou

The reds are just a very little bit less noisy, yellow are the least noisy. Green I recommend because if you measure their Vf they tend to hold near nominal. Get yellow ones and make two identical Vf strings of 5.2-5.6V total, by matching. That's the academically best for the psu ccs voltage ref.
 
Hi,
Thanks for the quick response.
I’m not an Engineer, just a hobbyist. Does Q6 need to have the same Idss as Q1, or can I use a lower Idss Jfet.
Also, regarding the pair Q2-Q5, which one should have the higher Idss jfet(there is a Delta of 4 tenths of mA in my pairs).

Thanks
PS
 
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-I am not an engineer as well, just a DIYer. Welcome to the club.;)

-Q6 is just a constant current source for the LEDs. The LEDs are happy between 5-10mA. Its not an amplifying JFET. So use non matched between channels there, +/- 1-2mA difference between them is OK. So to keep similar characteristics for the Vref.

-Use your a bit higher one for Q5.
 
An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

Well, that's for a days work :)
The nasty part is to follow, making a neat casing.
 

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ikoflexer said:
Wow, that's beautiful! Thanks for sharing!
Salas said:
3D! I like!

Would be nice to let us know more about parts choices (interesting resistors BTW), pcb design and sound impressions when you listen.
Being both nice guys ... ;)
An externally hosted image should be here but it was not working when we last tested it.

The Evox series SMR is a low loss capacitor. Its dielectric is PPS (poly phynel sulphide) and has lowest absorption of all modern film capacitors. For what that's worth they sound like a piece of wire :D when it comes to coupling signals. I guess in the filter we only want to loose what's intended to be lost.

Erie Resistor UK made from the late thirties on High Stability Resistors from cracked carbon. Hermetically sealed (waxed!), non-magnetic, low-inductive. On show are 0.25W, 0.5W and 1W. For tube audio . . . . :hbeat:
The smaller ones tend to become a little noisy in the high values, so I took a nice 0.5 for the 1M resistors. Mind you, although these little critters are 40 to 50 years old I've matched the pairs to 0%.

The 16000pF in the filter is made from a Soviet silver mica and a modern silver mica. Selected from a large stock of 8.2nF 10% :D

The coupling caps at the output are ASC, nothing fancy. It's open for experiment as the Silmic II seems to be a nice coupler too.

Some resistors are tin-oxide, R3 is CC, Rload is a non magnetic Holco. Voltage references are 10mV apart. The purple caps are Panasonics because I ran out of something nicer in that value.

The PCB has separate ground returns for front ends and back ends, so four (or two) regulators can be used. I'll start with just one cuz the biggens are quite expensive.

Listening will be no sooner possible than next weekend I'm afraid.
 
Salas said:
Nice info. A much promising build. What sensitivity you made, and for what cart model?

Promising maybe, the proof ... etc. :yummy:

I took your MM-version. Last year I sold the Gyro and now I've downgraded to an obscure plastic Philips with a humble catridge. Nice elliptical needle though, rumour has it that Van den Hull made the design in the eighties. Its denomination is '406'. In the Netherlands it has been sold in large quantities on the best players Philips delivered.

For Q1 I matched a pair of 10.2mA FETs, for Q2 8.6mA, for Q5 10.9mA and for Q6 7.0mA.
 
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PCBs

Crt, the guy who did my symmetrical psu capacitorless Pass B1 version PCB, made a PCB for the Simplistic NJFET RIAA too.
He made it compact (must print at 86X50mm) and accepts only modern small polypropylene filter and interstage capacitors. I have seen enough builds with no specialized NOS big parts by now, so I guess there is a use for the not that fanatic builder with less than a stellar TT and cart. It can be used for all 3 sensitivities of the final schematic that can be found on page 73 of this thread. Has a nice layout with centralized ground and it is single channel.

Thanks La Ode.
 

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And his build. He used 2X12V Zeners in series, you can jumper one position and use the proper Zener for your Voltage version.

*Thanks to Disco as well! I believe that his 3D big NOS parts accepting RIAA build shown higher in this page, will be especially attractive to ''tuning'' builders. Maybe he will be kind enough to post info and masks after his tests.
 

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Hi Roy,

You did nothing too wrong, the gain remains the same. The resistors you used are OK. Its only that at MM level and gain, the cart self noise and 47k input load will dominate a single 2SK170 anyway. There aren't noise issues even with MC carts and high sensitivity builds, so I wonder if you experienced some noise. What kind of PSU you use? You slightly modified the intended Riaa shape non the less. Use a 1.2k in series with R3 and listen if you like it a bit better. Do you have pictures? What is the rest of the system? What phono stage you had before?
 
Hi salas

thanks for the nice design.
I have build the 41 db version and started to experiment a bit to bring noise down so I paralled Q1 and made R1 2k4 in order to kkep the same gain. I am using it with a stanton 881s cartridge.
It sounds nice but I am not really shure waht I ecxactly did.
Could you give me some advice?
Did I also adjust gain or not?
To optimize the circuit in this way do I have to make some adjustment with Q3?
Is it better to keep R1 the origanl value and put 100 ohm resistors on the drains of Q1 and Q!A?

greetings Roy
 

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Hi Salas,

Thanks for the quick reply. I will try your advice.
I haven't listen to vinyl for 15 years or so. A few months ago I bought an micro ddx1000 and put a rega 350 on it. First I builded
a Indiscreet phonostage from tntaudio. I like it but is has to much gain for the stanton about 60db or so then I saw your design and wanted to try it.
I have build it on a breadboard and with a labpowersupply so it isn't optimal but I will make a pcb soon.
My system at the moment is a Akidopreamp with 2 elektuur LFOA-50 watt monoblocs and a selfbuild and designed threewayhornsystem.
However the hornsystem is demontaged because it is being spraypainted soon. So I listen to the phonopreamp with some computerspeakers. I know that this is not a good way to ascess your design but in this stage when I am experimenting with it it is much saver. I am always a little bit afraid to blow up my loudspeakers.
I will post some pictures of the system soon. I am at work know so no access to them now.
greetings roy