How to use the almost Group buy Diyaudio CCS circuit

[Original Burnedfingers]

This thread is dedicated to those of us that have our names on the list awaiting the receipt of our Darwin awards.

Some like me haven't used CCS boards and are scratching our heads in wonderment trying to figure out just what the hell is happening on this magic board or possibly perf board for some.

The idea of actually trying to use the board came about for me when I purchased a Dynaco Stereo 70 amplifier with a GSI board which had a circuit that used several LM334-Z of which I haven't been able to get running or keep running correctly because of blowing out components in the circuit. Having said to hell with purchasing some components that cost less than $1 ea and then spending about $8 to ship them I figured I would see what merit this design would bring. Isn't that what DIY is all about?

I will mention that this work is a result of planet10 contacting Morgan Jones about using a 317 for a CCS and as a result pinkmouse came up with a circuit for the constant current sources with input and assistance from SY, EC81010, & Gregg-the Geek.

Now I will start out the list of stupid questions.

1.) How does one figure which board/circuit design to use?
2.) Does one have to use a B+ supply which is high voltage of say
400 volts DC?
3.) Is there a way to use a smaller less lethal supply and use less
costly parts one might have on hand?
4.) Just how hard does the reference string have to run? The info
suggests 5mA. Is it possible to run it less without any dimmenishing results?

These are just a few of the stupid questions that I can come up with before having my second cup of coffee.

Documentation on the CCS boards

http://homepage.mac.com/tlinespeaker...-CCS-beta3.pdf

[Original Burnedfingers]

So second cup of coffee in hand and more stupid questions.

Looking at the amplifiers driver board and at the power supply in General.

Here is what I have in the way of supplies.

1.) I have the original supply that fed the on board CCS circuit which looks to be a negative supply of around aprox 9-10 volts roughly which is a result of the 6.3volt AC winding being rectified and filtered.

2.) I have on hand a bias supply which is negative filtered supply of 80 volts off the first cap and a resistive drop to -70 volts off the second cap.

3.) I have B+ of roughly 400VDC

Which supply can be used and why?

So the result is yet another stupid question...

Is a bigger supply better?

Do I use the 400 VDC supply?

Do I use the bias tap off the transformer and make a smaller positive supply?

[SY]

I assume you're using the CCS as a long tail for the input stage.

If you've got the 9V supply, it's a better bet than the bias rail. Reason is that the bias supply is only half-wave filtered, lots of ripple, and drawing extra current from it will only make things worse (and might take the power transformer closer to saturation because of the offset between the two halves of the secondary). The 400V B+ is an excellent source for the bias string since it will require a large dropping resistor, minimizing the effects of PS ripple on the CCS's reference voltage.

[Original Burnedfingers]

The 9 volt supply is half wave rectified also. The supply circuit on the board I have is not as shown in the schematic.

9 volt supply ... not a good bet then

[SY]

From the somewhat unclear schematic, it looks like it could be a full-wave. Either way, at least there's some Zener regulation so ripple won't be a problem, and since you're not asymmetrically loading the power transformer, you won't have any saturation issues, either..

Here's a quick drawing of my suggestion; R2 could be 200k or so.

[Svein_B]

Half-wave rectifier for the -9V will be OK if you use largish caps of 1000uF or more in a CRC supply.
What is more important than the ripple of the B- supply, is a clean supply for the CCS reference as indiocated by SY's diagram.

See also my thread here with a study of CCS performance vs. B+ and B- supply ripple.
LTP with CCS - IM Distortion

I used only a couple of mA for the reference string.


SveinB

[Original Burnedfingers]

So, in the interest of no negative supply ripple why not just eliminate the -9 and go to ground?

[Svein_B]

The CCS will require some volts to operate. If you connect to gnd, you will need to elevate the grids, and add an input cap. Not desirable.

Ripple on the negative voltage is not a major concern. Remember the CCS appears to be a very large resitor of several MegOhms, thus providing good PSRR.

SveinB.

[SY]

What Svein said- the CCS needs some voltage headroom to operate.

[Original Burnedfingers]

Ok, so I will hook the "In" to the -9volts, the return to the B+, and the out to the cathodes.