Since there's been a lot of interest lately in constant-current sources/sinks for use in tube amps and preamps, a few of us have been working behind the scenes to design a set of boards suitable for a wide variety of uses. The format will be a break-apart set of six circuits, both NPN and PNP. The design is a cascode bipolar, similar to the circuits shown in Morgan Jones's "Valve Amplifiers" and discussed at length in several recent threads.
The hard work has been done by our own Pinkmouse. Mr. Jones was kind enough to make some suggestions. And I'm the poor shmoo who has actually laid out the money to get them made.
We'll be announcing the prices and availability shortly. The boards are scheduled to arrive here in mid-February.
disclaimer: I am strictly doing this non-profit. Any portion of the price coming to me will be donated in full to the forum.
The hard work has been done by our own Pinkmouse. Mr. Jones was kind enough to make some suggestions. And I'm the poor shmoo who has actually laid out the money to get them made.
We'll be announcing the prices and availability shortly. The boards are scheduled to arrive here in mid-February.
disclaimer: I am strictly doing this non-profit. Any portion of the price coming to me will be donated in full to the forum.
burnedfingers said:
Yes, the humorously named SYclotron. It's the first stage of my big amp. The big amp has quirky needs, so the entire input stage is useful to about 3 people on Earth. As a stand-alone for more common output stage topologies, I think I can do better these days. And having learned how to make better current sources is one big reason.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=69042&perpage=10&pagenumber=22
what about the ckt posted on post 219 above.
what about the ckt posted on post 219 above.
This is exactly the same, other than the substitution of an LED for the dropping resistor in the other circuit. The current in the reference string is roughly constant, so the drop across that resistor is relatively constant- that's how the cascode is biased up. Given that, the substitution of a voltage reference is easy. At least around here, both red LEDs and resistors are pretty cheap, so there's no real cost advantage one way or the other.
If you like, you can stick a 1k resistor in that slot. Makes no/very little difference, other than 33% less light.
If you like, you can stick a 1k resistor in that slot. Makes no/very little difference, other than 33% less light.
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