Fyi, they should all be 220R, or 100R, whatever is convenient.
Not 910R.
The FET is not "evil" at all. In fact it is quite nicely behaved and far less obnoxious sonically than things like electrolytic caps of any sort or Nicads in the cathode. Try one some time - you'll be pleasantly surprised.
In some applications it is quite superior to any thermionic device.
Everything depends upon how you use it, and where you use it as to how "good" or "bad" it happens to be. In this case the FET current source is a superior solution in many ways.
Feel free to build your stuff as you feel is best for you, these are only my personal opinions and preferences.
_-_-bear
Not 910R.
The FET is not "evil" at all. In fact it is quite nicely behaved and far less obnoxious sonically than things like electrolytic caps of any sort or Nicads in the cathode. Try one some time - you'll be pleasantly surprised.
In some applications it is quite superior to any thermionic device.
Everything depends upon how you use it, and where you use it as to how "good" or "bad" it happens to be. In this case the FET current source is a superior solution in many ways.
Feel free to build your stuff as you feel is best for you, these are only my personal opinions and preferences.
_-_-bear
coupla other points...
Ur input impedance is gonna look like 250kohm. High. Your cables will like to see more like 47k ohm or 25 kohm...
If you put the level control at the transformer secondary your input impedance can be set to whatever is optimum for your source - the DC is removed from the POT and the secondary gets to see a nice resistive load from the pot, and gets to be optimally loaded pretty much correctly from assorted amps that you might try to drive...
Then you get to set the gain of the stage as you might want for maximum linearity, knowing what the max imput signal is likely to ever be, and make the stage as linear as possible with that in mind.
What is the secondary impedance?? Set ur pot value close to that.
_-_-bear
Ur input impedance is gonna look like 250kohm. High. Your cables will like to see more like 47k ohm or 25 kohm...
If you put the level control at the transformer secondary your input impedance can be set to whatever is optimum for your source - the DC is removed from the POT and the secondary gets to see a nice resistive load from the pot, and gets to be optimally loaded pretty much correctly from assorted amps that you might try to drive...
Then you get to set the gain of the stage as you might want for maximum linearity, knowing what the max imput signal is likely to ever be, and make the stage as linear as possible with that in mind.
What is the secondary impedance?? Set ur pot value close to that.
_-_-bear
Hi Bear,
you could set the pot after the secondarys. But the 5842 tube don't like huge voltage swing from a source. So you have to reduce the signal from your sources!
Greetings Barossi
you could set the pot after the secondarys. But the 5842 tube don't like huge voltage swing from a source. So you have to reduce the signal from your sources!
Greetings Barossi
Huge?
1 volt?
Or just put a little fixed attenuator at the input...
Reduce the gain by changing the cathode value a little?
Dork the output tranny impedance?
Use a lower value plate resistor, cap couple the tranny??
Ok, run it as a follower and use the tranny for voltage gain.
I dunno... seems like it will handle the usual line level stuff ok...
Heck, I didn't pick it for a line stage gain tube... 😀
_-_-bear
1 volt?
Or just put a little fixed attenuator at the input...
Reduce the gain by changing the cathode value a little?
Dork the output tranny impedance?
Use a lower value plate resistor, cap couple the tranny??
Ok, run it as a follower and use the tranny for voltage gain.
I dunno... seems like it will handle the usual line level stuff ok...
Heck, I didn't pick it for a line stage gain tube... 😀
_-_-bear
As recomended i have highered the workingpoint of the tube.
This is how it looks now:
schematic
This is the parts and preleminary layout, some parts are missing.
The pcb is just there to show the space taken by the tubes, the extra tube will act as part of Shuntregulator, but thats coming later.
layout
Here is the schematic of the unregulated powersupply:
http://hififorum.knaak.dk/kasra/br/fullwave3.jpg
The powersupply will be separate for each channel as seen.
Capacitors are all Mundorf MCap.
Each main transformer deliveres 150mA in 260-0-260VAC
This is how it looks now:
schematic
This is the parts and preleminary layout, some parts are missing.
The pcb is just there to show the space taken by the tubes, the extra tube will act as part of Shuntregulator, but thats coming later.
layout
Here is the schematic of the unregulated powersupply:
http://hififorum.knaak.dk/kasra/br/fullwave3.jpg
The powersupply will be separate for each channel as seen.
Capacitors are all Mundorf MCap.
Each main transformer deliveres 150mA in 260-0-260VAC
Im also going to put bleeder resistor in the powersupply.
Was thinking 47k 5 watt, how about that?
Was thinking 47k 5 watt, how about that?
- Status
- Not open for further replies.