Spectral DMA-500AR board pictures

ack

VIP/Donor & WBF Founding Member
May 6, 2010
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Here are a couple of board pictures; on the driver board, we are looking at those custom transistors; on the output, MOSFETs. Anyone recognize these devices and processes (SNJ132L 307 1743???) ?

IMG_4331.JPG IMG_4331-1.png

IMG_4335.JPG

IMG_4338.JPG
 
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geppo

Well-Known Member
Oct 27, 2010
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Hi,

It seems to me the big metal can dual FET comes from Interfet process N0132L, see:

https://www.interfet.com/jfet-datasheets/jfet-n0132l-geometry-interfet.r00.pdf

The four digit number is probably the date code, i.e. manufactured in the 43rd week of 2017.

307 might be a customer code as the part seems to be a custom one. Special testing, special package, or anything else, you know. The same die is available in a number of standard parts. Worth to note is all the standard parts listed on the data sheets are singles, with the exception of IF1322 which is available in SMD plastic package and TO-71 metal can. The part in your picture seems to be a TO-78-6. Mystery solved? Just guessing.

Reasons to go with a larger package than normally available? They range from trivial (re-use of PCBs made for another part) to very well taken. Metal packages exert lower stresses on dies and are therefore a) less noisy and b) more reliable (hermetic package).

The IRFP MOSFETs are industry's workhorses from International Rectifier, now Infineon. Good stuff but nothing to call home about. It is the way you use them that makes the difference (ask Mr. Nelson Pass and, well, Prof. Johnson?).

Hope this helps

Best regards

G.
 
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ack

VIP/Donor & WBF Founding Member
May 6, 2010
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Thanks. The world of electronics always fascinated me; every part has pages and pages of manufacturer specs. I was just reading up on the Vishay IRFP 240 MOSFETs, out of curiosity. And then pages and pages of Infineon MOSFETs at https://www.infineon.com/cms/en/product/power/mosfet/ For folks over at diyaudio.com, this is child's play; I gotta hang out there more...
 

Jon Q

VIP/Donor
Jun 16, 2019
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Hi

This transistor (dual JFet) was used in a development program for SSC liquid-argon calorimeters, in 1990, see pdf. pag 6, 7 and 8. The reason was that it was low noise and very stable with temperature (two important factors in the input stage in power amplifier). Spectral made this choice well. Being from "1990" it is normal to have no data sheet in PDF. Possibly only on paper data book.
But the strange is its date of manufacture, indicated !!!
I agree with "geppo", ... "The four digit number is probably the date code, i.e. manufactured in the 43rd week of 2017" ...

About the Vishay IRFP 240 MOSFET mosfet, I have projected devices (power supplies) that I use them. The reason .... I have excellent results with them.

Best regards
Jon
 

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ack

VIP/Donor & WBF Founding Member
May 6, 2010
6,774
1,198
580
Boston, MA
But the strange is its date of manufacture, indicated !!!
I agree with "geppo", ... "The four digit number is probably the date code, i.e. manufactured in the 43rd week of 2017" ...

If it's indeed a date, it shouldn't be strange, as Spectral have said these are custom semiconductors, similar to those we discussed years ago in the 30SV preamp. It sounds like they took some exceptional devices and customized them for even better specs... Based on the sonics I hear in here, they and the designs around them deliver in droves.
 
Last edited:

Jon Q

VIP/Donor
Jun 16, 2019
90
43
150
Lisbon
If it's indeed a date, it shouldn't be strange, as Spectral have said these are custom semiconductors, similar to those we discussed years ago in the 30SV preamp. It sounds like they took some exceptional devices and customized them for even better specs...
yes I agree with that
 

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