Mini Pearl

[jackinnj]

I am experimenting with the Tex Instruments JFE2140, a dual SOIC NJfet available from DK and other sources. Idss is higher than the LinearSystems devices, so you may have to lower the value of R9 (499 Ohms) to allow sufficient current to flow to the JFETs. gfs is lower than the LSK170s or LSK389's, but noise is the same.

 

[Wellerman]

Completed my Mini Pearl SOIC boards. Measurements are with the boards on the bench and power connections made with clip leads.

Soundcard interface loopback
Mini Pearl noise
Mini Pearl 2mV input

The output was 590 mV, so about 49 dB gain

Aren't those thd and thd+n numbers rather high?

 

[kannan_s]

Hi Jack
any PCB left your stash or gerber file available
thanks
kannan

 

[peppennino]

Hi All, did anybody make a Mouser BOM? I need to adapt it both for low output MC that MM with a single switch for both load and gain: suggestions?
Thanks a lot

 

[exojam]

Did I miss when the PCBs became available and also a BOM?

I have to redo my pearl two and I have brand new boards but would really like to try this project instead of the full-size boards for size purposes.

 

[jackinnj]

I guess I should do the boards again! To simplify life, perhaps the Linearsystems 4x LSK170A for the input, and the 2x LSK170B for the output driver.

 

[flaklapp]

I am also interested.

 

[jackinnj]

One of the interesting things which Groner did with his low noise amplifier (LinearAudio Volume 3 IIRC) was to provide test pads on the PCB with which you could match smt JFETs for Idss. With the power on you just place the JFET on the pads and measure Idss.

If you purchase a strip of 10 JFETs you will probably get enough good matches for two boards.

 

[jackinnj]

Could use 4 of the 2SK3557 for the front end (a $0.50 part) and 1 CPH6904 (a dual, $0.63 part) instead of LinearSystems

 

[geoturbo]

Having a surplus set of MiniPearl SOIC boards

 

[beeah]

I am also interested.

+1

 

[geoturbo]

Having a surplus set of MiniPearl SOIC boards

Quoting myself, sorry, these are now spoken for and not available any longer, thanks.