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Hi Kevin,
While reading the specs for your CCS's, the large CCS intended for an external heatsink has a 20W limit, but the general specs mention a limit of 100mA. I also was looking at your blog regarding the KT150 mono power amp project and it looks as though you have a CCS on a heatsink at the rear of the amp and I assume it is for the output stage which would be above 100mA for PP KT-150's.
So finally my question: Do you have a version that can handle 200mA+ up to the 20W limit? Or will I require parallel CCS's? I would like to use it in an output stage where I will have a cathode voltage around 70V and 200mA of cathode current.
Thanks,
John
De gustibus non est disputandum
Follow Ups:
You have good eyes! I used a new CCS for that amp that I haven't yet released as a kit. As a cathode CCS, I have used it up to 350mA, and have no reason to believe it won't do more when coupled to the appropriate heat sink. It's a very different design than the other kits and has far more parts. It is, however, the only current source I've ever used in PP or SE cathodes for bias that has never oscillated under any conditions I've thrown at it. Besides the parts count, there are other disadvantages. The voltage is limited to 400VDC across the terminals and it requires selecting resistors to set the current. A trimpot is used for fine adjustment, though.
Kevin Carter
K&K Audio
www.kandkaudio.com
Do you expect that this CCS will be available to us folks in the future? I could use a couple of them fairly soon. I'm working to build a PP GU-50 amp so I'll need cathode current somewhere around 160-200mA.
John
De gustibus non est disputandum
Edits: 05/28/16 05/28/16
If you can use them then I will do up the kit info in the next couple of weeks. Prod me, if it seems I've forgotten; it might well be true!
Kevin Carter
K&K Audio
www.kandkaudio.com
Hi Kevin,
Since you suggested a prod, I'll bump the thread. Any news or new info regarding the availability of the higher current CCS?
Thank you,
John
De gustibus non est disputandum
Well, I have set the price at $20 each, but I haven't written instructions yet. Those could come this week.
It's probably worth writing a bit more about this current source. It was developed for the purpose of acting as a cathode CCS in medium to high current applications. I have used it over the range of 100mA to 400mA, but don't take these as application limits, as it's certainly usable at lower currents and probably at higher currents, subject to the use of an appropriate heat sink. It is set up so that it's a two terminal CCS, but has a 400VDC limitation between the + and - terminals. I've not examined its behavior below 50VDC between the terminals in a detailed way yet, but it will work well at voltages below that, until there isn't enough voltage to bias the reference current supply. The current is adjustable by means of a 2w resistor in parallel with a 50R trim pot. The 2w resistor choice defines a relatively narrow range within which the trim pot can be used to fine tune the current. There are test points at both ends of a 1ohm resistor to allow for current measurement.
Kevin Carter
K&K Audio
www.kandkaudio.com
Thanks. I appreciate it. Any idea about the price ballpark?
De gustibus non est disputandum
No concrete number until I do the analysis. But it will be in the region of $25+.
Kevin Carter
K&K Audio
www.kandkaudio.com
Sounds good. I'll take two.
Thank you,
John
De gustibus non est disputandum
My experience has been that paralleling current sources in this application is a bad idea. In my amps it has always led to problems with oscillation. I have found a solution that has worked well for me and it's the one Kevin has implemented in his KT150 PP amp.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
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