2sk170BL or 2sk369 for MC Stage - diyAudio
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Old 10th December 2003, 01:58 AM   #1
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Default 2sk170BL or 2sk369 for MC Stage

I have breadboarded a simple moving coil preamplifier using 2SK170BL transistors. Next is a cascode of this like the Pass DIY Pearl.
Searching I found that the 2SK369 is quieter. The input capacitance is higher though. Is the 369 better for a quiet MC circuit?
The2SK170 seems to be much more popular, is it supply or sound?

George
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Old 10th December 2003, 08:22 AM   #2
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Smile Which is which?

The K170 has about 10% the K389 and about 20% less capacitance accoarding to the data sheets. Cost will dictate the choice. The K170s (x2) are much cheaper
than the K389, unless you need the close matching of the K389 for a differential circuit go with the K170s.
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Old 10th December 2003, 09:01 AM   #3
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Hi George, hi Fred,
2sk389 is a double 2SK170, 2SK369 has twice the gm of the 170 and half the noise. 'Hifidaddy' made sonic/listening comparisons between many fet's, search the archives. He claimed that 170 has 'more' bass than 2sk369. I found that to be true with SE-designs, e.g. 1-fet-MC-Head amps.
Anyway, it is claimed that there were better sounding fet's not available any more

I found for myself, that it is better to serve a 2sk369 well (active current sources and the like) than to use a single 170. Gives you more gain as well.
regs,
Rüdiger
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Old 10th December 2003, 09:49 AM   #4
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Red face A fet to world peace

Got to stop posting in the middle of the night......

I'm sorry I was thinking of the K389 dual jfet used by many on the forum and as a paralleled pair in the Pass DIY Peal phono preamp. I believe the K369 is similar to the K147 which has been discontinued by Toshiba for quite awhile now. It was a very popular transistor for MC stages with very high Gm (40mS!) and very low noise.

PS
The K389 (1/2) has slightly different characteristics than the K170.
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Old 10th December 2003, 10:12 AM   #5
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Hi,

With a source resistance of 50-100 ohms the 1/f corner is somewhere around 10 kHz with K369’s. I think there are fets that perform much better for MC front end use regarding noise, but if they will sound better ...

Cheers
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Old 10th December 2003, 06:49 PM   #6
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Putting '170s in parallel works about as well as '147s. I've done it lots of times, and it works well in MM preamps.

Jocko, who still has '147Vs stashed away for emergencies.
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Old 10th December 2003, 07:46 PM   #7
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It's been pretty well discussed, but the 369 is the 'replacement' for the 2SK147. This part should be 3 dB quieter than a 170, but two 2SK170's in parallel essentially equal a 147, in both noise and input capacitance. Please, let's not quibble over small differences. The biggest concern should be if the devices have very low 1/f noise, as some Toshiba processes can be more noisy than others. This will be very important in a MC phono stage.
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Old 10th December 2003, 07:50 PM   #8
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Default Speaking of Toshiba.........

John:

Have you ever used 'C2702s? I had a bunch once that had noise burst problems.

Jocko
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Old 10th December 2003, 09:09 PM   #9
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Quote:
Originally posted by john curl
It's been pretty well discussed, but the 369 is the 'replacement' for the 2SK147. This part should be 3 dB quieter than a 170, but two 2SK170's in parallel essentially equal a 147, in both noise and input capacitance.
Would I gain anything with two 2SK369's in parallel? My power supply is very quiet, hum from the phono leads should be the largest noise source.
I am now using two semi-matched 2SK170BL's. It is much noiser than before, the phono without the MC stage was completely quiet. Now there is a little noise, but the system gain is much higher.


George


Please, let's not quibble over small differences. The biggest concern should be if the devices have very low 1/f noise, as some Toshiba processes can be more noisy than others. This will be very important in a MC phono stage.
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Old 10th December 2003, 09:31 PM   #10
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Go for it.
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