Simplistic NJFET RIAA

[nicoch58]

Originally posted by wrenchone
Why do you want all that gain? Are you trying to run with a moving coil cartridge?

dl103 at 120€

dl301II at 200€

at33ptg or dv-10x5 at 280 €

a decent stepup cost 100€ I prefer put this money on cartridge

[jackinnj]

Originally posted by wrenchone
I ran into problems with variable gain on the first stage due to the variable load of the RIAA equalization network vs. frequency and finite/relatively high output impedance of the first stage SRPP, and canned the project in favor of another approach. It didn't occur to me to use a higher impedance RIAA network - duh!

For the Sears -- with 255k -- you are going to have a bit (4.6uV) of broadband noise, no?

[Salas]

Originally posted by wrenchone
Why do you want all that gain? Are you trying to run with a moving coil cartridge? One of the reasons I went with the PN4303 was to have a resonalbe stage gain. The gm is olly about 1.5-2k mmoos, about 1/10 the value for a 2SK170.

I want it to be able to cover anything with minor changes, or by using switches, and without step up. A flexible situation. Use commonly measuring 7mA Idss 2SK170BL for instance, take out the second stage 1000uF bypass, and you get 55dB. Perfect for Denon DL160 that I can find for 100 Euro. Drop the first 1000uF cap as well, you get 44dB. Great for a Grado, or any 3.5-5mV.

*Better use 16nF second RIAA cap if dropping bypasses.

At circa 70dB I can compare it at my friend's set up with the low Ortofon and the Steve Bench tube stage we made, without the step up cost.

Plus if a phono stage does not hit around 1V output with a given cartridge and chosen gain combination is generally short for macro dynamics to my subjective experience.

[nicoch58]

I have the same thought, a stepup is another variable, specific to certain cartridge, in the signal path there are two rca, another cable and finally how many meters of wire there will be in the coils.....

[Salas]

Have you listened to Audio-Technica AT33PTG? I would like one.

[nicoch58]

http://www.pinkfishmedia.net/forum/s...ad.php?t=45579

sorry no, but very sexy

[nicoch58]

for AT33PTG I need a new(old) TT

dl103/301 are more in P3 range


denon info
http://www.high-endaudio.com/RC-Denon.html#OTHER

[nicoch58]

lot 160 info in the past denon link and read the fist post here http://www.audioasylum.com/cgi/t.mpl?f=vinyl&m=578062

very decent cartridge

[Salas]

I have one DL-160 that I plan to use. Some tests on load resistor before input stage and it will sing. My circuit is well doing for bass it seems. But in general, if the RIAA is right in the lows, not loaded down by the second stage, and there is a buffer at the output, I think that most cartridges thought as ''thin'' sounding, would fair better.

[wrenchone]

to Jackinnj -

The impedance in the Sears circuit is less than a lot of common tube-based RIAA networks that are used with MM cartridges. Also remember that there are two stages of low-pass filtering after the initial resistor. This may not be an issue anyway, as I can use the same resistive loaded JFET SRPP/source follwer combination for the input section as well as the output. simulated performance for low level signals is quite sweet (0.002% THD). and the follower will drive a lower impedance equalization network with no sweat. I can even jigger up an old prototype I have laying around that has most of the essentials in place. It's two extra parts per stage, but that's still a lot less complex and fiddly than what I'm using now. Everything changes for low level MC cartridges, but I have no desire to use them until I get a much more sophisticated TT than what I'm now using.