diytube.com

Hi Guys,

It has been a while. I got a pair of MKII amps that I am tinkering with. I was looking at Shannon's board, and curious about swapping the 334Z CCS to an LED string. Is there anything wrong with this? I don't necessarily expect to better the performance, but I like the looks of the dimly lit LEDs during operation, and I thought it would look cool to put three on each side of my LTP.

Will this work?

Thanks!

Blair

No it won't work.
The "Long Tail" refers to the large AC impedance which forces the two sides of the pair into AC balance.
LEDS have very low AC impedance, that is, they are more a constant voltage source not a constant current source.
The LM334 could be replaced by a LED referenced transistor current source but might be difficult to mod the board.

If you want to go this way then cascoded transistors with 2 LEDS are the way to go.
Went looking fo a quick reference - here is one which will give you the idea:
http://www.pastisch.se/faktiskt/diyAudio-CCS-beta3.pdf
This board is way over engineered for what you want, since you only want low current but the schematic is handy. The impedance ("goodness" of teh current source is largely set by the gain (Beta) of the lower transistor.
Cheers,
Ian

Thank you for that link!

Was written by Planet-10 with input from myself and others. He lost his copy and he asked if I still had mine (which I didn't )

Cheers!

Nice board! Thanks!

I do not see pricing for it? Is it on DIYAUDIO?

No need to reinvent the wheel here if there is a marginal improvement, so I am curious if there will be a noticeable improvement over the single 334Z? I am not using a board for this. I was just going to PTP wire it on this driver section I made. It is 1/4" acrylic, which is why I thought having a few LEDs under it would be nice. I can always pull a few volts off the rectifier winding since I will not be using it to light up some LEDs also.

What happened to the attachment function? I would post an image, but I don't see it.

Thanks!

Blair

It's not available on DIYAudio (don't ask, long political story )

Shannon did a comparison of CCS sources/sinks. Don't remember the thread, ATM

With the impedances involved, a MK-II, the improvement with a more advanced CCS would be marginal at best.

Thanks! That's the best part of this forum vs. others. I get straight answers.

I'm actually going to keep these a while, so I'm trying to do it all "right".