The 6C33C's need about a month to burn in..
They start to sing after about 30 mins..
Do you have the option to run on one heater?
(I would give it a while before you switch to one)
Regards
M. Gregg
They start to sing after about 30 mins..
Do you have the option to run on one heater?
(I would give it a while before you switch to one)
Regards
M. Gregg
I have a switch installed.
Will run it for some time before messing with it.
First time since start that i feel like i´m ahead of it.
Will run it for some time before messing with it.
First time since start that i feel like i´m ahead of it.
I have a switch installed.
Will run it for some time before messing with it.
First time since start that i feel like i´m ahead of it.
Thats great! 😀
I'm really looking forward to your progress.. 🙂
Regards
M. Gregg
Just a few tests,
1st stage CCS now has CC 330 Ohm + Ferrite bead.
2nd stage CCS still 270 Ohm + Ferrite bead.
The bead is insulated from the resistor leg (on the gate side) with PTFE sleeve.
No instability and highs are more open..
New 716 orange drop in the PI output to 6C33C's just for a test...burn in taking place...curiosity!
Looking at cathode CVS across existing resistors....
Regards
M. Gregg
1st stage CCS now has CC 330 Ohm + Ferrite bead.
2nd stage CCS still 270 Ohm + Ferrite bead.
The bead is insulated from the resistor leg (on the gate side) with PTFE sleeve.
No instability and highs are more open..
New 716 orange drop in the PI output to 6C33C's just for a test...burn in taking place...curiosity!
Looking at cathode CVS across existing resistors....
Regards
M. Gregg
Measurements tells that bias voltage in the output stage must be stabilized.
The amp delivers about 10watts before it drifts due to lack of stability.
It drifts of into classB land when run hard.
A zener referenced fet will do the job as constant bias voltage i hope.
Another way is to run it hotter someone experienced please shout if i´m on the wrong track.
The amp delivers about 10watts before it drifts due to lack of stability.
It drifts of into classB land when run hard.
A zener referenced fet will do the job as constant bias voltage i hope.
Another way is to run it hotter someone experienced please shout if i´m on the wrong track.
I'm currently experimenting with a MOSFET with a zener in the cathode-circuit replacing the resistor, a pot between the gate and the earthy end sets the bias, 'fine-tune'.
I have retained the de-coupling-cap, but guess it could be omitted....
Initial results are promising....
Hi Alastair,
Another one up and running.. 😀
Keep us in the loop!
Have a good Xmas...... 🙂
Regards
M. Gregg
Another one up and running.. 😀
Keep us in the loop!
Have a good Xmas...... 🙂
Regards
M. Gregg
Sounds good Alistair.
I looked at mosfet/zener and AC resistance is in miliohm region.
The cap shouldn´t do any harm so leave it in.
I looked at mosfet/zener and AC resistance is in miliohm region.
The cap shouldn´t do any harm so leave it in.
Alastair,
Do you find any effect on speed of response of the fet (discharge time of cap) or is it quick enough to stop the charge?
Any effect on bass ?
Regards
M. Gregg
Do you find any effect on speed of response of the fet (discharge time of cap) or is it quick enough to stop the charge?
Any effect on bass ?
Regards
M. Gregg
The fet is definately 'fast' enough to respond to changes in cathode-current on its own.
I left the de-coupling-cap in for fear of possible stability issues, as when I tried something similar a few years ago, I suffered from some hideous oscillations that at that time I could not cure.
I cant remember if I had a de-coupling-cap in circuit at the time though...
The cap certainly wouldn't be detrimental as I see it, The fet referenced zener replacing the resistor completely...
The perceived sound is certainly extremely good, I havent noticed any real change in it so far....
I left the de-coupling-cap in for fear of possible stability issues, as when I tried something similar a few years ago, I suffered from some hideous oscillations that at that time I could not cure.
I cant remember if I had a de-coupling-cap in circuit at the time though...
The cap certainly wouldn't be detrimental as I see it, The fet referenced zener replacing the resistor completely...
The perceived sound is certainly extremely good, I havent noticed any real change in it so far....
Any idea how many watts you are dissipating in the FET?
Just thinking about heat sink size...
I guess the Voltage drop should be constant so the max current...
Regards
M. Gregg
Just thinking about heat sink size...
I guess the Voltage drop should be constant so the max current...
Regards
M. Gregg
Manage to dig out some IRF1010E from the junkbox only 60v but other data looks nice.
One biascontraption coming up
One biascontraption coming up
Now there´s equal pieces of sand and glas in the amp
Interesting....
Have you done any measurements yet? 🙂
I guess no
....I see a difference two of them have more diodes?
So is the bias setting different?
Regards
M. Gregg
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I´m fiddling around with bias.
Lets say one channel is heating the house better then the other right now.
I want to run them a bit hotter but i have no clue where they perform the best and when they start dieing prematurely.
I´ll try some different settings and see how it goes.
Please chip in with some guidelines here
Lets say one channel is heating the house better then the other right now.
I want to run them a bit hotter but i have no clue where they perform the best and when they start dieing prematurely.
I´ll try some different settings and see how it goes.
Please chip in with some guidelines here
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