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In Reply to: RE: I'm open to suggestions and a CCS would be something i'd like to try posted by Tre' on January 08, 2017 at 08:08:07
The plate resistor is now 50K. I am thinking of adding another LED. That should bring the voltage up to a good point. Thank you for the link i will definitely check that out. cheers, Dak
Edits: 01/08/17Follow Ups:
"The plate resistor is now 50K"
Ok, now things make more sense.
"I am thinking of adding another LED"
That will drive the current even lower.
The plate voltage will be higher, like you said, but I don't think the tube will be very linear at such a low current.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Hi Tre, with 3 LEDs the voltages are now; Av 168. Kv 5.57vdc. and the plate resistor is actually 56k. The B+ to the plate resistor is 360 under the conditions set by the 3 Leds.
Ok, those numbers all line up like they should.
With a 56k ohm plate load the load line will be pretty horizontal but with only 3.4ma of plate current that tube will not be as linear as it would be if there was more current.
More current with a 56k ohm plate resistor would take a lot of B+ (supply) voltage.
A CCS will give you your cake (a horizontal load line) and you can eat it to (get about 10 or more ma. of current going).
Then that tube would be very linear (low distortion).
Just something to think about.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
In this situation, with my new amp, i would like to keep the variables as few as possible, so i would rather get one that has seen a lot of people using them and so would be vetted and less worrisome? In other words if i build one i still would not be sure if i had an poor interaction between the CCS and my amp. So, i would rather buy one with a good "track history" as it were.
K&K Audio (here on the AA) sells kits.
Look for "Two Terminal Constant Current Source" on the page linked below.
You want the Cascode ones (2 MosFets per CCS).
I just make my own using a pair of the dn2540 MosFets.
All it takes is 2 of the MosFets, 2 gate stop resistors and a current set resistor. That's it!
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Right, Kevin sells them. i will check that out. But later, do you mind if i contact you about building my own? thanx for the link. regards
Just send email through the AA.
I'll help.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
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