Simplistic NJFET RIAA

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#541
Re: Shunt up and running

kstlfido said:
..........Shunt notes- seems to pull appx 120 mA. I'm getting 36.7 volts out- so all seems to be working fine. I had to use 1/2W resistors on the 220 ohms and an old 1W carbon comp on the 5.6 ohm. The sink gets VERY hot- it's a 45mm x 45mm finned job and I can barely keep my hand on it for more than 15 seconds! :hot:
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it is a transformer + CCS + Shunt + load.
Try reducing the current passing the CCS. Even a 10% reduction in CCS current could make a big difference to the shunt temperature.
 
#542
Very nice work! I like the construction style. Since I have listened to the Riaa in many systems, and in various constructions, based on your subjective comparisons I think that you must substitute that 82k//82k combination with 43k, and see about an extra buffer stage. Especially with the shunt PSU, the bass is a particularly strong area by experience. Have compared to some ultra $ commercial gear too. The general characteristic of this phono stage is nearer tube than transistor but with resolution and ease. Tune it up, buffer it, listen again. In the mean time, happy Christmas holidays!:santa:
 
#543
Re: Re: Shunt up and running

AndrewT said:
it is a transformer + CCS + Shunt + load.
Try reducing the current passing the CCS. Even a 10% reduction in CCS current could make a big difference to the shunt temperature.
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Sound advice. Use a 6R8 for R1 Kent. That will save you 20mA off. Its a nice construction and the current is plenty, why modify with new big heat sinks? Better reduce Iccs.
 
#545
P.S. See if your MC needs more electrical damping, you may listen to a 500R or lower Rload at the input. That detail thing is usually hinting at not best loading or a need for a better Riaa filter tuning. Or both. We have seen you need a slightly bigger Riaa series resistor earlier, given your final capacitor values.
 
#546
Um, like this one? Sorry pic didnt attach b4.
 

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#548
sorry I meant 6r8... 😀 I have cold and sleepy. Will play with the damping too, thanks.

RIAA accuracy- I've got some Russian green PS caps on the way- hope to stack 3 up then trim with silver mica to get exactly 15 nF. Some say stacking more than 2-3 is not a good idea...I wonder why?

I think this previous pic I found was from Jonners. Will check, thanks!
 
#550
kstlfido said:

Some say stacking more than 2-3 is not a good idea...I wonder why?
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They talk about resonating with each other. Don't know if its just a theory, but sometimes too many start sounding smeared in practice indeed. Some go along well with each other, some not. One is best if its value is right. For space and expenditure too.
 
#551
OK I did the mods you guys mentioned- thanks. Q4 fet in shunt much cooler now- just warm to the touch.

I lowered the Rload to 180 ohms and changed the 2 82k's to one 43k. Base has improved; still not quite like the SUT hook up; but better.

What I am hearing is more articulate base. The SUT 'seems' to have slightly more cohesion- or it could be that the jfet RIAA is separating the instruments out better...! I need to do more listening, probably after xmas passes. I will also try it with a buffer. Sadly many of my old fave records have a lot of sibilance- comes from being played at a college radio station TT with 5 gram carts! :hot:
 
#553
Merry Christmas Andrew! For Kent's RIAA changes see posts #496,497 page #20. He was off a bit from what I have tuned due to practical tolerances with his capacitors. Also he damped differently and more properly his MC cart now. This is hands on stuff Andrew. The analogue rigs can learn you their points of interest only if you mess enough with them, difficult to predict only by proper electronics design. He will still be impressed more when he will substitute his 43K with Shinko or AB resistors. Its bugging for planing but those things do matter in the end. He will also need a buffer. And that simple 150% Idss one proved transparent to Jonners. But I have given a B1 type earlier too. Also sibilance, is tell tale not only of worn out records, but also of something slightly wrong with geometry. Maybe 2 degrees of nose up VTA adjustment and protractor check can yield impressive results. This phono really shows.
 
#555
Not really. Why just AC couple the tonearm ground? Having a low noise floor FFT measurement set up can show the course of such grounding experiments if there is a specific loop to solve. In general it is not needed to mess too much with the metal parts grounding of a TT.
 
#560
nicoch46 said:
I play with Rload , 3k close to much the sound , usally I like 23k , but in my system i think 8-15k range are optimal
(a switch // r for two setting, soft or racing )


Pacific+ dl160+P3 compete with last Pedja dac.....not so bad!!!
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salas said:
The Denon has 160 Ohm Zout, so 1.5k upwards is fully testable for system tonal matching.
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I know I am late and did not build the Salas RIAA "yet" but I am already preparing the "stage". The new RIAA wil be used on my RD80 + Maggeddon + Benz ACE M.

In also want to keep my actual pre so I recently revived a JVC belt drive and installed a DL160... It is a really powerfull cart but I would like to tame it´s high freq response. (In my MM riaa, the load is 47k and the highs are too forward)

How low (in value) can I set the load resistor ?

I would not like to loose any of the thunderous bass the DL160 is providing 😀

Regards

Ricardo
 
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