Could be something to do with my preference for setting bias, which is to ignore the second and minimize as far as possible the remaining harmonics. The bypass seemed to alter the gain a miniscule amount consistent with eliminating the 10-20 ohms cathode impedance of two LEDs. You may recall seeing the one of the attached graphs, the second is the same tube/jig/session with a 1000uF bypass as described above. It's entirely possible the effect is due to a cancellation against the LEDs' non-linear impedance instead of feedback though.
FWIW, when I looked at THD of the signal across the unbypassed LED in my 6SN7 jig, it was higher than the THD at the plate; this is with a small resistor load, not a CCS. That suggests cancellation to me. I'd like to repeat that with two series LEDs- hopefully this weekend. I have a new soundcard that needs a workout...
I think we've strayed a bit OT. Jojo, I'd look for a different recipient for a CCS transplant.
I think we've strayed a bit OT. Jojo, I'd look for a different recipient for a CCS transplant.
ok then... maybe I should really really really go build that HF87 clone we once talked about in another thread.
one last question though. you said that plate CCS don't like cathode resistors, I remember that in a preamp I opened the voltage amplifier (which looks a lot like my input tube) has a plate ccs and an unbypassed 1.8K resistor in the cathode, then it is direct coupled to a cathode follower with a ccs on it's cathode.
could this be a poor approach in the use of ccs circuits?
EDIT:
If I'm not mistaken, it looks a lot like this...
An externally hosted image should be here but it was not working when we last tested it.
The point is that the power supply rejection ratio (PSRR) is pretty much RL/ra, so making RL very large by using a CCS as anode load not only makes the stage very linear because of the horizontal loadline, it also rejects power supply noise. But if you leave the cathode resistor unbypassed, its value is multiplied by mu so that ra becomes ra + mu x Rk, thus destroying your PSRR.
I think SY has already done a part of my homework...
He posted this circuit abotut a year ago - which is exactly what I was about to do an experiment on.
I'm confused as to how to get the 8mA current flowing. SY also mentioned the use of a 20K dummy load to get the 8mA before inserting the tube. The dummy load is for the ccs right?
He posted this circuit abotut a year ago - which is exactly what I was about to do an experiment on.
An externally hosted image should be here but it was not working when we last tested it.
I'm confused as to how to get the 8mA current flowing. SY also mentioned the use of a 20K dummy load to get the 8mA before inserting the tube. The dummy load is for the ccs right?
thanks SY! this is getting very exciting for me
I can always direct-couple this stage to a cathode follower with a bottom ccs right? I'll try to draw it right away.
You see, i was inspired by your heretical linestage so I tried it on a 5692 - sans jensen input transformer (i don't have one) and I was blown away. I heard the difference and I liked it, and that's all that matters to me. It's a surprise how a handful of leds and sand can improve what is already a beautiful linestage.
I can always direct-couple this stage to a cathode follower with a bottom ccs right? I'll try to draw it right away.
You see, i was inspired by your heretical linestage so I tried it on a 5692 - sans jensen input transformer (i don't have one) and I was blown away. I heard the difference and I liked it, and that's all that matters to me.
It's a surprise how a handful of leds and sand can improve what is already a beautiful linestage.
How come some are sying there´s no benefit i n using a CCS in a kathodfoller,why doe´s SY use it in a line stage?
http://www.diyaudio.com/forums/showthread.php?s=&threadid=59244&highlight=:rolleyes:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=59244&highlight=:rolleyes:
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