Simplistic NJFET RIAA

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#2,963
RCruz said:
Hi Salas

What type of tilt can one expect here ?

I am going to use 43k on R3... 🙂
Click to expand...

Felipe is going to put in action his special http://www.diyaudio.com/forums/analogue-source/129126-simplistic-njfet-riaa-280.html#post2018041 10.5mA Idss LowMC that has 47k initially. He can expect more presence in the high-mids & highs with 46k. In your case if you put 2.2Meg across 43k its going to 42.17k and you can taste some tonal lift also, but not as much as in Felipe's.
 
#2,964
Thank you Salas

For now I am finetuning the 48dB because I felt it was slightly forward in the mids.

I believe I found a good compromise now (It is sounding better than ever) but it is good to know the effect of fidling with the 47k.

Regards
 
#2,967
Hi Salas & Ricardo,

Measured both silver mica: one 46,3nF & the other 46,4nF, so as all supposed I need to add more capacitance: 0,7nF & 0,6nF

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


So I need to buy:
1 cap 270pF + 330pF = 600pF
2 cap 100pF + 270pF + 330pf = 700 pF

I have several silver mica at home to fine adjustment due to the fact tolerance of these silver mica caps is 1%
 
#2,970
merlin el mago said:
Hi Salas & Ricardo,

Measured both silver mica: one 46,3nF & the other 46,4nF, so as all supposed I need to add more capacitance: 0,7nF & 0,6nF


So I need to buy:
1 cap 270pF + 330pF = 600pF
2 cap 100pF + 270pF + 330pf = 700 pF

I have several silver mica at home to fine adjustment due to the fact tolerance of these silver mica caps is 1%
Click to expand...

If your measurements are good and there is no tendency for less in your LCR bridge (have you got any cross checked cap on another instrument to compare?), then Ricardo's a little more mids is explained with nominal caps. He added a bit of value by ear. I have also found the Riaa caps of other types (MKP, MKT radials) a bit less in the past. Never more.
 
#2,972
Salas said:
If your measurements are good and there is no tendency for less in your LCR bridge (have you got any cross checked cap on another instrument to compare?), then Ricardo's a little more mids is explained with nominal caps. He added a bit of value by ear. I have also found the Riaa caps of other types (MKP, MKT radials) a bit less in the past. Never more.
Click to expand...

No I don't have another instrument to compare the cross checked cap. Mine LCR is very sensitive: measuring pF with or without cables don't measure the same is better without cables: normally cable add some few pF, so I trust in mine LCR, also everytime that I do a measurement with cables 1st I measure without cap & after with cap so the difference is the real value, when I measure without cables the display read always 0.

No I don't trust in mine ears I prefer measured caps for RIAA.

What's your opinion about polysterene caps MKS for RIAA?

--------

Rcruz

Ricardo if you want I can measure your RIAA caps to fine adjustment.
 
#2,974
Sometimes DMM readings are inferior to real value.... I did not need 1700p but only 120p // 47n for C2 (My DMM reads 45,3 on these caps)

On the other cap 15.720n I settled on // 270p.

The resistor values also affect the curve so I know this is a compromise but it sounds really good now.

As usual, I experimented with numerous other values and found the following trick:

For C3 (16n) one must choose the lowest possible bypass value (450p, 330p, 270p, 220p) that does not produce a metallic shin on the sound (270p in my case)

After that you increase C2 (47n) bypass until you loose the excesive high freq forwardness while not loosing "snap".

Ricardo
 
#2,976
RCruz said:
Sometimes DMM readings are inferior to real value.... I did not need 1700p but only 120p // 47n for C2 (My DMM reads 45,3 on these caps)

On the other cap 15.720n I settled on // 270p.

The resistor values also affect the curve so I know this is a compromise but it sounds really good now.

As usual, I experimented with numerous other values and found the following trick:

For C3 (16n) one must choose the lowest possible bypass value (450p, 330p, 270p, 220p) that does not produce a metallic shin on the sound (270p in my case)

After that you increase C2 (47n) bypass until you loose the excesive high freq forwardness while not loosing "snap".

Ricardo
Click to expand...

Thks for sharing Ricardo,

Interesting opinion, I try the same like you as point to start RIAA tuning🙂
 
#2,979
I used to tune my guitar by ear.... (never got a diapasão).

This comes a long way....my mother had a piano at home and I used to "detune" it when very young.... maybe now I will have another go 🙂

Nevertheless, regarding riaa cap tuning I guess I got to the maximum.... I can not lower 16n bypass any more because the sound gets edgy and metalic.... On the other cap I can not go higher because I start loosing "snap" and spatiality.

Ricardo
 
#2,980
RCruz said:
I used to tune my guitar by ear.... (never got a diapasão).

This comes a long way....my mother had a piano at home and I used to "detune" it when very young.... maybe now I will have another go 🙂

Nevertheless, regarding riaa cap tuning I guess I got to the maximum.... I can not lower 16n bypass any more because the sound gets edgy and metalic.... On the other cap I can not go higher because I start loosing "snap" and spatiality.

Ricardo
Click to expand...

Take note, thks again🙂
 
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