Salas, just a hint: look at 2SK117 datasheet and compare to 2SK170.
I like them veeery much & they are dirty cheap
Cheap source?
Edit: never mind, plenty on ebay
The 2SK170s are in the reg for two reasons. Small pinch off so to work well under the Vbe potential in the Vref, plenty of unmatched leftovers from the Riaa project. Since the 2SK117 datasheet shows small pinch off too and adequate noise figures, you can call them a substitute by all means. I have mainly used 8mA Idss in the Vrefs on the various schematics.
Sure.
True. Lower capacitance is good, 50V is good, only watch the 300mW Pd if used as a CCS across enough voltage without any resistor between G,S so to moderate its constant current. When in high enough voltage V1s and V1.1s for the left position between the Leds and ground, for instance. Always check out dissipation when calculating for different voltages anyway. Not that the 2SK170 is any monster in contrast, only 400mW Pd.
7,8,9 will do nicely. All Idss could do, but the Vref resistors or trimmers you see in the later schematics are calculated around 8.5. Because that was our mean average for 170's from Spencer. We had a mini poll for that once in the Riaa thread.
If you are not about measuring and recalculating that is.how to calculate the dissipation?
just see the voltage across 100ohm resistor at the source of jfet?
how much dissipation is safe?
In the particular circuits there is 100R to the left for the Leds one. If you measure the drop across resistors and then divide by its value, you know the current that runs through the adjacent fet as well. That current multiplied with the voltage across the fet represents its dissipation. Stay up to 200mW for 2SK170 and 150mW for 2SK117. If you have a strong enough Idss fet that you want to use across enough voltage, either you find a lower Idss one, or you can moderate it with some 50-100R resistor between its G,S. You connect as in the original circuit from G side now to what is connected to ground.
Talking about schematics....
A lot of effort went into obtaining low output impedance from the regulator. This proven stable build has a capacitor at its output. I wonder -to obtain highest performance- if it would be wise to put this 470uF cap at the load, shunting possible stray fields and wire inductance? If I recall correctly there was an oscillation penalty for using a low ESR ( <0.01 ohm) cap in this position.
A lot of effort went into obtaining low output impedance from the regulator. This proven stable build has a capacitor at its output. I wonder -to obtain highest performance- if it would be wise to put this 470uF cap at the load, shunting possible stray fields and wire inductance? If I recall correctly there was an oscillation penalty for using a low ESR ( <0.01 ohm) cap in this position.
Ah, you tackled that one in your thread. Interesting. You don't screen your regs while actually testing, are you?
Those 'ugly green' Wima MKC make excellent interstage coupling caps. Have a try
Those 'ugly green' Wima MKC make excellent interstage coupling caps. Have a try
Ah, you tackled that one in your thread. Interesting. You don't screen your regs while actually testing, are you?
Those 'ugly green' Wima MKC make excellent interstage coupling caps. Have a try
I will. What do you mean by screen the reg while testing?
Well, my point is that measuring for sub microvolt error signals is only meaningful if you rule out other sources of equal or bigger magnetude like RFI. Did you use a metal case? Sorry for not reading your entire thread if you did so.
I see, no, I don't even try to measure signals smaller than microvolt? Anyone successfully doing it around here? I'm happy with a few microvolts ripple, which I can measure without much of a problem.
So, I can also use the 2SK369-V (I have a full box with this thingies lying under my bed
) in this design as drop in replacement ?
About the magic finger test, and the lower hfe transistors doing better, maybe there is relevance to this, from when K-wood was talking very high Mhz difficult to see oscillations, in his much interesting thread.
''It takes a wideband sampling scope to see the oscillation''
''...Spice seldom sees what your layout residuals are. A good test to see if the circuit is oscillating is to use your finger to probe around the circuit often loading a node just enough to change or stop an oscillation, moreover to show that one is there when performance changes.
K-wood''
http://www.diyaudio.com/forums/solid-state/154070-watt-sucking-fireball-series-6.html#post1979147
''It takes a wideband sampling scope to see the oscillation''
''...Spice seldom sees what your layout residuals are. A good test to see if the circuit is oscillating is to use your finger to probe around the circuit often loading a node just enough to change or stop an oscillation, moreover to show that one is there when performance changes.
K-wood''
http://www.diyaudio.com/forums/solid-state/154070-watt-sucking-fireball-series-6.html#post1979147
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.