Simplistic NJFET RIAA

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Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
I guess you measure voltage across some resistor so to extract IDSS current information. Use simpler and see. Yes, 7.6-7.8 not great matching is OK. It is not audio, its regulator.
 

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nicoch58

nicoch58

Member
Joined 2004
match done not so lucky
How can be the idss difference from channel ?

A----
k6.70-k6.70

k6.84-k6.91

b----
j7.72-k7.77

j7.90-k7.90

c----- but can be better for audio
j7.91-k7.90

j8.02-k8.02

d--- but losting the up combo for audio
k8.00-k8.02

k8.08-k8.09

e----- if idss is not too higth this are the better
k8.26-k8.27

j8.38-k8.37

with one ?
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
Prefer the lowest Idss for Q5. If you have a couple of GR 4-5mA, even better. There is a reason. The lower the idss, the lower the pinch off, and more the breathing space under Vbe. But we don't want too low, so to keep the Zener working strong enough.
 
RCruz

RCruz

Member
Joined 2006
Paid Member
More voicing....

Hi Salas

After replacing the signal cord between 101pre and 103amp with a specially built with silvered 5 pin din and mogami wire, I noticed a good increase in detail.

This detail is welcome in the CDP and the Tuner but the Riaa now sounded a little forward and piercing in the highs.

I reinstaled the stock cable and althou I had no edgy sound, I really missed the added detail.

So I decided to reinforce the bypass on riaa C3 and my first impressions are favorable but I am afraid to be altering the riaa curve.

I have the following values:

C2 = 47.36nF (as measured with the DMM)
C3 = 16.23nF (15720 + 330 + 120)pF

C2/C3 = 2.918 (Looks good)

Am I creating some kind of distortion or time skidding? (The resistors are 47k and 6k8 kiwames 1%)

Acording to http://www.beigebag.com/case_riaa_5.htm I should reduce the resistor values to 46150 and 6720 ohm to reach optimum values but that is not practical.

Ricardo
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
Our Riaa values include the first stage output impedance and second stage loading. Also they are judiciously voiced a bit, so don't go with calculators. In general, I don't think that is a good idea to tweak basic Riaa tonality just to allow for interconnects that you will change again maybe in the future or they will settle softer in a while etc.

Why don't you readjust your VTA first? It is possible that the silver new connector part is a bit over the top for detail, so it could be counteracted that way.
 
RCruz

RCruz

Member
Joined 2006
Paid Member
The riaa is so detailed I can easily set up VTA. Why did I not remenber this in the first place ?

I lowered the arm .3mm and all the harshness went away.

Once again I should have known better :whazzat:

The sound is now better than ever.

I am quite sorry to have reported my previous mod that should never have happened. (Feeling like a :whacko: )

Ricardo
 
RCruz

RCruz

Member
Joined 2006
Paid Member
Nichicon

Today I received from China two 15000uF 63V Nichicon (M) labelled as Marantz.

I bought them believing these were Gold Tune KG caps but the label only states "Marantz"

The size does not appear on nichicon site but they are heavy and look great.

Only 30 minutes after replacing the 10.000uF BHC by these, I noticed lower noise floor and much better bass......;)

Outstanding sound :violin:

Ricardo
 
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