Replacement For Toshiba 2SK170/2SJ74

rif

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Joined 2003
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Thanks Darrr

If number 7 is made with two straight lines, then is counterfeit.
Genuine Toshiba jfet's 7 number is curved at his base.
Best regards :)

Is that a definitive method of determination? I ask because I'm looking at photos from the diyaudio store, the 7s have straight lines and there's no way the store is stocking or selling fakes.
 

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Has anybody tried to use the LS FETs instead of the Toshiba's?
The headline of the thread is about finding replacement for the Toshiba's but most posts are about how to get the original Toshiba's. A lot of money could be saved if the LS was a "true" replacement?
 
Ok......it was my assumption that JFETs in production was much cheaper than the rare Toshiba's which are out of production. What was the price level of the 2SK170 when they were in production? …..I know it depends if you buy 10 or 2000......but let us say about 10.
It is interesting that the grade A or GR are the most expensive but there seems no projects for these grades. Most projects use BL-grade.
 
Since the LS are so expensive must be because the demand is small? …..The SK170 and probably also the LS are made for low noise audio purpose. So the demand must have been higher years back. Was it because the JFETs was used in MC / MM preamps and after the CD took over the JFETs was not used anymore by the larger audio companies…...or what happened that caused Toshiba to stop production?
 

6L6

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The world went to surface mount 20yr ago.

Audio has always been a niche.

Designers in the mass market use opamps.

The demand in the real world for a low noise, through-hole, discrete part is very small compared to other solutions that are cheaper, more convenient, and sound as good to 99% of your audience.

Why did they stop production? People stopped buying them in the quantity sufficient to keep production feasible.
 
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When Idss is measured at what Vds should that normally be done to get a "standardized" value for Idss? …..a Vds just before break down to get the max Ids?
Some use 9V.....but that is because they use a 9V battery for the measurement?

It's completely your choice, do it however you please.

Me, I like to get far away from the knee and the linear region. So I prefer to measure well above ~ 4 x |Vpinchoff| which ensures I'm well away from the knee.

For the 2SJ74 in Toshiba's datasheet, that's something well above ~ 3.6 volts. 9 volts is certainly well above 3.6 volts. Naturally, other designers may interpret the data differently, or arrive at a different final preference.

_
 

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Procurement of 2SK170/2SJ74 pairs

I have purchased the 2SK170/2SJ74 from Reichelt and can assure that the once I received DO NOT work as input stage in the BA3!!!
The price of about €4,- was just too attractive but it was impossible to set the biasing of the output MOSFET's at all. Complete failure and hours of frustration wasted!! This was about in April this year and they might have changed their source.

Meanwhile I have purchased matched pairs through NicMac in Milano. These are original Tosh's and of course NicMac has to take more than €4,-. Good message is, that I had biased both channels of my BA3 within about 1hr within the ballpark range you like the bias to be in. Perfect stuff!!
 
After posting in the ACA thread, I thought that I should mention it here too.

I have ready access to genuine Toshiba 2SK170BL's and would be willing to match and supply if needed. No 2SJ74's unfortunately.

I have built a B1 and ACA with pairs that I matched myself. So far I found pairs with Idss between 6.9mA and 10.0mA. If there is a need for quads, I can probably do that too.
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