Pearl Two

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nar

nar

Member
Joined 2002
Question

On the .pdf, it states that R26=499/1V/2mA which is mostly a typo (on the schematic, it is R28 that is 499R). Assuming the value read on R28 is 1V, it says 2 mA current for the diff pair Q4 & Q5, which leaves each half to 1 mA or so ...

On the opposite side, the Q6 to Q9 run with a 10R source load, which seems a pretty high current compared to the diff. pair of the next stage.
Which leads me to that question : before getting the 370s or 170s, which grade to choose? GR seems fine for the diff pair, matching VGS mostly, but for the input JFETS I would pick some BL grade before matching them by IDSS range ... am I correct ? How to calculate the amount of current in each JFET Q6 to Q9 ?

Best regards,

nAr
 
wayne

wayne

Member
Joined 2002
Paid Member
When I layed out the Pearl Two allowance was made for a lag capacitor around the ZVP3310. After building more of them I find it is not needed. I suggest you just leave it out. Your mileage may vary if you roll your own boards or change parts. Saves finding a good 10 PF cap.
 
nar

nar

Member
Joined 2002
wayne said:
When I layed out the Pearl Two allowance was made for a lag capacitor around the ZVP3310. After building more of them I find it is not needed. I suggest you just leave it out. Your mileage may vary if you roll your own boards or change parts. Saves finding a good 10 PF cap.
Click to expand...

Question: if I use same layout and ground planes but ZVP3306A instead of ZVP3310, will the 10 pF capacitor needed or can I remove it as well :cool:

I have no oscilloscope here to check the square wave :D

Brds,


nAr
 
wayne

wayne

Member
Joined 2002
Paid Member
If you don't have a scope the best thing to do is check the gain at 1K.
51-55 dB is the range. if it oscillates this will usually show wrong.
An inverse Riaa and sweeping works well also. You want that nice HF roll off.
Save $ for a scope they have gotten inexpensive and are invaluable.
 
nar

nar

Member
Joined 2002
Russellc said:
Is this still in the pipeline? I know its a simple power supply and all, just wondering.

Russellc
Click to expand...

The power supply schematic is included in the .pdf ;)

It is simple enough to allow fast, reliable and neat P2P wiring into the dedicated PSU box, in my opinion.

For that project I will use Vishay 1% resistors, Vishay MKP 1% caps for the RIAA correction and bypass output capacitor, Muse for the output ones (22uF/25v); Elna 3300uF/35V and for the 10000uF/40V, the new Mundorf M-Lytics AG séries :)
Input and output RCA connectors will be Silver Bullet ones :p

Best,

nAr
 
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