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
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
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.
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.
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
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
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.
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.
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 😉
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 😉
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.
Jocko, who still has '147Vs stashed away for emergencies.
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.
Speaking of Toshiba.........
John:
Have you ever used 'C2702s? I had a bunch once that had noise burst problems.
Jocko
John:
Have you ever used 'C2702s? I had a bunch once that had noise burst problems.
Jocko
Hello George, remember me?Panelhead said:
I have built a balanced MC phono headamp with 2SK389's. It was quiet enough for me.
Problem with these large geometry FET's is that you need to cascode them or else sound is too dull for my ears. [Do you read this Jean-Paul?]
Same problems applies to bipolar transistors like MAT02.
If you have a differential amplifier in your circuit a dual monolitic FET is a must or life won't be easy:
http://db.audioasylum.com/cgi/m.pl?forum=tweaks&n=50171&highlight=elso+john&r=&session=
😎
Re: Re: 2sk170BL or 2sk369 for MC Stage
Of course Elso! I see you are a continuing to refine the clock. My latest player is a Marantz sa-8260. The clock looks to be hard to get to, I cannot touch it.
I originally wanted to go to a balanced MC. But the Pearl only has single rail supplies. Guess a floating psuedo split rail could be made to act like a dual supply and cap couple the outputs.
I am going to try the same paralleled 2SK170's and cascode it next. Sounds like a parallel 170 circuit is a lot like the single 369.
The cascode may do the trick! I hope to get the circuit close to the original S/N level. Even with a pair of AN step ups the basic Pearl was dead quiet with the volume all the way up. It just sounded a little flat with the step ups. I think the 4 2SK170BL's in the input of the Pearl posed to much capacitance for the transformers.
The mc circuit added a little grunge, but lead dressing may fix it. It should get as quiet as before with a little work.
George
Elso Kwak said:
Of course Elso! I see you are a continuing to refine the clock. My latest player is a Marantz sa-8260. The clock looks to be hard to get to, I cannot touch it.
I originally wanted to go to a balanced MC. But the Pearl only has single rail supplies. Guess a floating psuedo split rail could be made to act like a dual supply and cap couple the outputs.
I am going to try the same paralleled 2SK170's and cascode it next. Sounds like a parallel 170 circuit is a lot like the single 369.
The cascode may do the trick! I hope to get the circuit close to the original S/N level. Even with a pair of AN step ups the basic Pearl was dead quiet with the volume all the way up. It just sounded a little flat with the step ups. I think the 4 2SK170BL's in the input of the Pearl posed to much capacitance for the transformers.
The mc circuit added a little grunge, but lead dressing may fix it. It should get as quiet as before with a little work.
George
Not if I find 'em first ! 😀
(Sorry, I couldn't resist)
mlloyd1
"do your part to rid the world of the evil V grade JFETs infestation - send them to me"
(Sorry, I couldn't resist)
mlloyd1
"do your part to rid the world of the evil V grade JFETs infestation - send them to me"
Jocko Homo said:
Hello,
a related question. In my current diy-project I'm running into problems and can't track them down.
considering this
My concern is the first stage with those 2sk369.
I build several incarnations of it to find the optimum real world assembly. I do p2p on rastered (I mean dotted, what's the right term?) FR4.
Last incarnation has strange behaviour. The current source sucks 11mA, which should be perfect (5mA for each fet and 1mA dissipation in CS). But the voltage drop on Rload is moving, most times nearly 0V, but then again 10V, somtimes 15V, sometimes even 45V, but never correct (around 23V)
I searched myself to death for cold solder joints an the like...
Between the gates of the input-fets one would await pretty good offset behaior (has been 0,0 mV in previos incarnations), here it moves between 3mV up to 300mV !
The input fet's are closly matched (IDSS is 14,7mA/15,2mA, both having Vp of 169mV) Another pair (12mA/120mV) shows same behaviour)
I've checked fet's over and over with 9V-Block if it delivers correct mA, can it be out of order and rate ok? I guess no...
I changed d'caps (on bases) and tried different values, nothing changed.
I got rid of earlier incarnations, because one was too noisy, the other clipped to soon and had some very nasty routing.
finally, I will build this , but i like to solve the problem before I move on.
I hope this might be interesting for others as well.
I have no clues left, so guess wildly!
Rüdiger
a related question. In my current diy-project I'm running into problems and can't track them down.
considering this
My concern is the first stage with those 2sk369.
I build several incarnations of it to find the optimum real world assembly. I do p2p on rastered (I mean dotted, what's the right term?) FR4.
Last incarnation has strange behaviour. The current source sucks 11mA, which should be perfect (5mA for each fet and 1mA dissipation in CS). But the voltage drop on Rload is moving, most times nearly 0V, but then again 10V, somtimes 15V, sometimes even 45V, but never correct (around 23V)
I searched myself to death for cold solder joints an the like...
Between the gates of the input-fets one would await pretty good offset behaior (has been 0,0 mV in previos incarnations), here it moves between 3mV up to 300mV !
The input fet's are closly matched (IDSS is 14,7mA/15,2mA, both having Vp of 169mV) Another pair (12mA/120mV) shows same behaviour)
I've checked fet's over and over with 9V-Block if it delivers correct mA, can it be out of order and rate ok? I guess no...
I changed d'caps (on bases) and tried different values, nothing changed.
I got rid of earlier incarnations, because one was too noisy, the other clipped to soon and had some very nasty routing.
finally, I will build this , but i like to solve the problem before I move on.
I hope this might be interesting for others as well.
I have no clues left, so guess wildly!
Rüdiger
Maybe something is oscillating at a few hundreds of MHz. Does the bias point change when you move your hand in the neighbourhood of the input JFET's, or when you touch nodes with an isolated screwdriver?
If something is oscillating parasitically, putting lossy ferrite beads around the base and gate leads might help without doing too much harm to the audio frequency noise performance. Alternatively, you can probably use 47 ohm resistors in series with the bases of the bipolar transistors, but not for the gates of the input JFET's, as that would spoil the noise performance.
Thanks for your reply.
I will try that ferrites. Are there design rules to avoid such stray oscillating? Currently, I make signal routing as short as possible. that leads to the fact, that fets and transistors standing very close. Not good?
Shouldn't ´fets get quiet hot if oscillating? They are not.
Any other reasons for this behaviour possible? (So I can try out in a single seesion)
thanks,
Rüdiger
I will try that ferrites. Are there design rules to avoid such stray oscillating? Currently, I make signal routing as short as possible. that leads to the fact, that fets and transistors standing very close. Not good?
Shouldn't ´fets get quiet hot if oscillating? They are not.
Any other reasons for this behaviour possible? (So I can try out in a single seesion)
thanks,
Rüdiger
Keeping the wires short usually helps to prevent oscillations due to wire parasitics, but even with short wires, oscillations sometimes still occur, especially if you use fast devices with a high transconductance.
So in practice it's a matter of keeping signal wires short, placing power supply decoupling capacitors very close to your circuits, keeping your fingers crossed and adding damping devices such as small resistors or lossy ferrite beads if things start to oscillate anyway.
Oscillations do not necessarily cause excessive power dissipation. For example, the dissipation in your input JFET's is limited by the supply voltage and tail current source, whether the JFET's are oscillating or not.
So in practice it's a matter of keeping signal wires short, placing power supply decoupling capacitors very close to your circuits, keeping your fingers crossed and adding damping devices such as small resistors or lossy ferrite beads if things start to oscillate anyway.
Oscillations do not necessarily cause excessive power dissipation. For example, the dissipation in your input JFET's is limited by the supply voltage and tail current source, whether the JFET's are oscillating or not.
Did he really say this???
Not for a JFET???????? You mean all those gate dampers that I have used, the last 30 years or so, are bad????
Silly me.
Somehow I think that trying a gate damper WILL help the oscillation problem, if that is what it is.
As for a BJT, too high of a resistor will definitely eat into noise performance in a low-Z application.
Jocko
Not for a JFET???????? You mean all those gate dampers that I have used, the last 30 years or so, are bad????
Silly me.
Somehow I think that trying a gate damper WILL help the oscillation problem, if that is what it is.
As for a BJT, too high of a resistor will definitely eat into noise performance in a low-Z application.
Jocko
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