FET Audio | Hi-End Audio & Electronics DIY Electronics & Repair

Completed to re-design my old D1V3.3 or D1 clone pcb as below:  Name it D1V2 + Zen I/V.  Please write to me if you are interested in the PCB.  No kit offer!  Full assembly Boards with limited supply only.

Totally I have made 3 versions of boards for testing – V17, V28 and V30.  The photos of each version is as below in sequence.

The board can use DAC – PCM63, PCM1702 and PCM1704.  Note PCM170x need to use a converter board as in second picture.  For digital filter, it can use SM5842, SM5843, SM5813, DF1700, PMD100, DF1704, DF1706 etc…  Digital receiver is WM8804 with excellent jitter performance.  More details in the reference manual below.

Compare to D1V33, it is much better in sound stage, imaging, resolution and details.  It still remain the analogy sound of smoothness and best vocal DAC when PCM63 is used.  When DF1704 and PCM1704 is used, the input is set to 16-24 bit digital input mode and output of DF is set to 24 bit mode.  The resolution is found better than PCM63 a bit but remain the smoothness of R-2R DAC sound.

Two versions if Zen IV are tested – J/K and K/K.  Here is the summary of measured results : IV resistors & capacitors and Rail comparison table_v30

Conclusion is to use the KK IV + KK Buffer – 2SK369 or 2SK363 is the optimum design choice using 20V rails.  Nelson Pass original Zen IV using JK IV is having too weak output level at 30V rails.  Also J74 is not available easily with reasonable cost.

Reference Manuals:

D1V2_ZenIV Manual v30.1_ALL

D1V2_ZenIV Manual v28.3_all

D1V2_ZenIV_Manual_V17

Digital filter setting table (apply to all Version boards): DIGITAL FILTER PIN CROSS REFERENCE SM5842_V30.4

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The Zen I/V was posted by Mr. Nelson Pass back in 2010.  I have not enough time to try that due to my work location change and far away from my equipment.  I am back home since 2021 and now it is time to try out the Zen I/V.  Below is the photos of the Zen IV that I put on the D1V33 board and so far the result is very positive. The distortion for SE measurement can be down to 0.002% to 0.004%, in fact that is the distortion spec of the DAC chip.  Here is the information sharing for anyone interested to comment.

1. Rail voltage is only +/-20V as it is the limit of the current D1V33 board default supply. 
2. Use Drain resistor of 1.5k ohm due to limit of the rail voltage and thus give a Vd about 7V for jfet Idss of about 8mA.  This is compromise due to Rail voltage max at 20V.
3. Use daughter boards to put on top of original jfet IV locations.  Since the pins for supply, input and output are not the same, thus I have to design 4 similar boards with different locations of the pins.  The boards are names #1 ~ #4 for identification.  Daughter Board is connected to main board via pins, some holes are not really on top and thus the pin has to be soldered a bit tilted (best locations of pins).
4. Emitter follower is added to the Zen I/V with a pair of transistors to buffer the output to have lower output impedance.  The distortion so far do not see any degrade in readings.  In fact jfets pairs can be used but it will increase the cost!
5. SMD resistors 1206 or MELF 1/4 W and capacitors 0805 are used on top and bottom of boards to make the board as small as possible.
6. Tough job is to remove the original Jfet IV parts on the main board and it is helped by a de-solder station make by YiHua 948 (about US$60).  SMD part is soldered with hot air gun also YiHua 8786D 2-in-1 station (about US%65).  Really handy tools and cheap!
7. I still left some pcbs and thus those interested, I can send to them with cost of SGD$20 for each set (include paypal and shipping cost).  Sorry I do not have any more K170/J74 match pairs for sell!

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3D view of the Zen I/V board: D1_V2_2_ZenIV_3D

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