Hi,
I read through the first 50-100 posts.
After that, lost track
the original circuit given by Mr. Pass,
gives a gain of 24db?
For less distortion, it should be driven at 16V
and not 35V?
Any other simple values changes to try?
I don't have any equipment so faithfully following
what is designed.
thx
I read through the first 50-100 posts.
After that, lost track
the original circuit given by Mr. Pass,
gives a gain of 24db?
For less distortion, it should be driven at 16V
and not 35V?
Any other simple values changes to try?
I don't have any equipment so faithfully following
what is designed.
thx
Just stumbled onto this thread, wow, this is a long one.
Like Bengali, I too have lost count of the different versions
but maybe you could help me with a simple question please.
Can I use a 19V regulated switcher to power the original design? or should I use one of the other version mentioned?
I only listen at low/moderate levels but will be using it to drive 4 D-amp mono's.....
Thank you for any input gents.
Like Bengali, I too have lost count of the different versions
but maybe you could help me with a simple question please.Can I use a 19V regulated switcher to power the original design? or should I use one of the other version mentioned?
I only listen at low/moderate levels but will be using it to drive 4 D-amp mono's.....
Thank you for any input gents.
My thoughts, for what their worth: Though there's hardly any load, your preamp power supply should have almost no ripple, or so I've discovered. Noise in the preamp stage will become amplified in the power stage.
Try your switcher and see. If it's noisy, you could always try playing with an LM317. I've had good luck with this device. The idea is to experiment. Then, you can tell us if it worked.
Another thought, the LM317 needs 3 volts to operate, this would drop the 19 volt switching power supply down to 16 volts.
What do you think?
Try your switcher and see. If it's noisy, you could always try playing with an LM317. I've had good luck with this device. The idea is to experiment. Then, you can tell us if it worked.
Another thought, the LM317 needs 3 volts to operate, this would drop the 19 volt switching power supply down to 16 volts.
What do you think?
what do you think of this proto boards for these pre-amp experiments?
http://cgi.ebay.com/103RAW-wireless...34.c0.m14.l1262&_trkparms=|301:1|293:1|294:30
the traces are 10mils, not good for power or ground but should suffice for signal(?)
http://cgi.ebay.com/103RAW-wireless...34.c0.m14.l1262&_trkparms=|301:1|293:1|294:30
the traces are 10mils, not good for power or ground but should suffice for signal(?)
jboz with 2sk117
I didn't have the 2sk170 but since this circuit was so simple, I tried it with a couple of 2sk117 that I had. I have the original BOZ that drives my Power follower, and I was curious how a Jfet would do the job. There was some interesting details that came out of this jfet preamp. Little more detailed and softer in the top, but not enough gain for my power follower without distorting. I checked the voltage over the drain resistor and it showed 6 v, which leave 14 v between ground and Drain. Tried to lower the source restistor to 5 ohm and increase it to 20 ohms , but that only gave me an voltage altering of +-1v on drain compared to what i started with(14v). Anyone tried this jfet in this preamp? I thinking of increasing the Drain resistor to see if that will help. This Jfet preamp got me in a dilemma of which new power amp to build. As I wrote earlier I have the italien power follower and a prototype of the JLH class A (used the psu from the power follower to test it). I've just ordered 2 pcb boards and trafo to the JLH. I have a amp case that will fit the JLH perfectly. I agree with what I read somewhere in this forum earlier that the JLH favours god recordings and expose bad ones, and the power follower is a little nicer all over The dilemma is that I am now wondering of building the Aleph J instead( Since i have the case , and soon the trafo for it). Anyone have a comment one that? This Diy audio is like a drug. Once you've tried it, you're hooked
I didn't have the 2sk170 but since this circuit was so simple, I tried it with a couple of 2sk117 that I had. I have the original BOZ that drives my Power follower, and I was curious how a Jfet would do the job. There was some interesting details that came out of this jfet preamp. Little more detailed and softer in the top, but not enough gain for my power follower without distorting. I checked the voltage over the drain resistor and it showed 6 v, which leave 14 v between ground and Drain. Tried to lower the source restistor to 5 ohm and increase it to 20 ohms , but that only gave me an voltage altering of +-1v on drain compared to what i started with(14v). Anyone tried this jfet in this preamp? I thinking of increasing the Drain resistor to see if that will help. This Jfet preamp got me in a dilemma of which new power amp to build. As I wrote earlier I have the italien power follower and a prototype of the JLH class A (used the psu from the power follower to test it). I've just ordered 2 pcb boards and trafo to the JLH. I have a amp case that will fit the JLH perfectly. I agree with what I read somewhere in this forum earlier that the JLH favours god recordings and expose bad ones, and the power follower is a little nicer all over
The dilemma is that I am now wondering of building the Aleph J instead( Since i have the case , and soon the trafo for it). Anyone have a comment one that? This Diy audio is like a drug. Once you've tried it, you're hooked 
ChuckT said:Hi guys,
For the 2sk170, if I have only +/-15V on tap and require only 2~3x gain, how much do I need to scale down the drain resistor?
With the -15V supply, do I need to regulate down to -4V to use 680ohm (refer to Juma circuit) or can I use -15V direct with a larger source resistor?
TIA.
If you want to use -15V for negative rail your source resistor needs to have much higher value but then your drain resistor needs to be about 3 times higher than source resistor because their ratio determines the gain of a circuit. Larger value of the drain resistor dictates higher positive rail.
So, there is still no free lunch
you'll have to preregulate negative rail down to about -4V (-3V for +15V pos. rail). In any case +15V (positive rail) is far to low if you want output level higher than 1-2 V RMS.This is how it would look with +15V (gain of 2.2 , undistorted output about 2-2.5V peak max.) :
Attachments
juma said:
If you want to use -15V for negative rail your source resistor needs to have much higher value but then your drain resistor needs to be about 3 times higher than source resistor because their ratio determines the gain of a circuit. Larger value of the drain resistor dictates higher positive rail.
So, there is still no free lunch
This is how it would look with +15V (gain of 2.2 , undistorted output about 2-2.5V peak max.) :
Thank you very much.
I'll definitely try it. I have some matched 2sk170 with Idss around 8.5ma.
So may be I can tweak the values a bit.
I haven't built this circuit yet, but simulation shows that this circuit starts to clip with very little movement of the volume control, if using a cd player with 2Vrms output.
Have people experienced this when using their cd players with this preamp?
Well I have been messing around trying to get more rotation from the pot before clipping.
If you put a 1k resistor across the wiper to ground, then you get about 340 degrees of rotation before clipping.
This experiment applies to linear pots.
1k may not be the optimal value but it does the job.
Have people experienced this when using their cd players with this preamp?
Well I have been messing around trying to get more rotation from the pot before clipping.
If you put a 1k resistor across the wiper to ground, then you get about 340 degrees of rotation before clipping.
This experiment applies to linear pots.
1k may not be the optimal value but it does the job.
