Simplistic NJFET RIAA

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#13,881
AndrewT said:
I am alleging the opposite.

But if you have dirty DC and bring that dirty DC to the inside of the sensitive amplifier without filtering at the entry to the screening chassis then expect interference to affect your internal circuits.
Sometimes that interference will be audible.

But trying to filter the interference too early leaves the cables still able to pick up interference. And then to inject that interference to sensitive circuits once the cable enters the screening chassis.

You have two different jobs when the circuits are susceptible to interference.
Make the DC good. Adding an RC at the PSU end is good, provided the final C is adequate to maintain a stable non varying DC.
Add an RF filter to EVERY cable that enters/leaves the screening chassis/case.

And for good measure if the susceptible circuits have a changing current then good decoupling at the circuit is required.

None of this has anything to do with
Click to expand...

Nice Andrew.... Hehe I almost believed you had lost your sense of humour....

Anyway I stand with my statements as they only apply to my builds.... I have good clean DC coming out of the psu, I use shielded cable to transport it into the riaa amp, I decouple it locally (but not with large caps) and in reality I can really hear differences when I fiddle with the smoothing caps in the psu.

As a matter of fact, I just reduced the 56nF bypassing the 10000u AG to 12nF and lost some mid freq glare. The difficulties lies on choosing the right value for bypassing.... One must aim at clearer sound but without proéminences.

I believe smaller caps intrude latter in the freq band..... The higher the capacitance, the lower in freq you intrude.
 
#13,882
AndrewT said:
You have two different jobs when the circuits are susceptible to interference.
Make the DC good. Adding an RC at the PSU end is good, provided the final C is adequate to maintain a stable non varying DC.
Add an RF filter to EVERY cable that enters/leaves the screening chassis/case.

And for good measure if the susceptible circuits have a changing current then good decoupling at the circuit is required.
Click to expand...
Just to prove I always take you seriously, I do consider these statements as best practice for ALL
 
#13,884
Salas said:
Start with 54mm sinks. But keep a couple of 15R low ppm 2W in hand. In your situation using a single input JFET with high value source resistor, its bias drift tendency with ambient temp is very much reduced. So use a criterion of no more than 50C average internal air temperature with a ventilated lid put on (drill few holes under and over each sink's vicinity). You maybe have a K thermocouple wire or kitchen probe to monitor that. Allow for summer room temp usual rise in your location. Good you had tangible subjective improvements. It took you enough precise work to make those nicely populated matrix board regs.
Click to expand...

Update on the bigger sinks: I've got the 54mm sinks in. It's cooler but still pretty hot. I can hold my finger on them but not over 5 seconds. I may have to go to the 15ohm resistors. I am assuming this will change V out?
 
#13,886
RCruz said:
Nice Andrew.... Hehe I almost believed you had lost your sense of humour....

Anyway I stand with my statements as they only apply to my builds.... I have good clean DC coming out of the psu, I use shielded cable to transport it into the riaa amp, I decouple it locally (but not with large caps) and in reality I can really hear differences when I fiddle with the smoothing caps in the psu.

As a matter of fact, I just reduced the 56nF bypassing the 10000u AG to 12nF and lost some mid freq glare. The difficulties lies on choosing the right value for bypassing.... One must aim at clearer sound but without proéminences.

I believe smaller caps intrude latter in the freq band..... The higher the capacitance, the lower in freq you intrude.
Click to expand...
the "glare" if it existed may well have been interference !

Adding low esr capacitors across PSUs is a risky business.
That is why we see so many now suggesting using snubbers.
There were many that did the wrong thing. I did it back in the '70s. But I was stupid then. I believed nearly everything that sounded "about right".
 
#13,892
Look what the Magician Kings of Orient have brought😀
 

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#13,897
AndrewT said:
the "glare" if it existed may well have been interference !

Adding low esr capacitors across PSUs is a risky business.
That is why we see so many now suggesting using snubbers.
There were many that did the wrong thing. I did it back in the '70s. But I was stupid then. I believed nearly everything that sounded "about right".
Click to expand...

Hi Andrew

Why is it risky to use low esr caps on psu's ?
 
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