Due to continued interest in building the CCS's and my lack of time to sell boards I've decided to release these versions of the battery bias board layouts to the public domain. If you have batches of boards made up for whatever use drop me an email. I'd like to hear about what you use them for. You will find zipped board files with parts lists in the down loads section.

To use the board file you need to install the latest version of ExpressPCB then open the file. Ordering 1 mini board set using this file gets you 12 CCS boards. You will need to use a large pair of shears to cut the boards apart.

You are responsible for determining the suitability of the CCS circuits for your intended purpose. The author is not responsible for personal injury or property damage caused by use of the information on these pages.

The battery biased CCS just got it's first major update. The board has been redone to use 27A 12 volt alkaline batteries instead of the solder tab lithium coin cells.

There are some tradeoffs. The minus's are the alkaline batteries don't have as flat of a discharge curve and the shelf life is shorter than the lithium batteries . The less stable discharge voltage is offset by making the CCS adjustable. This makes it possible to compensate for the batteries as the voltage drops with age. The pluses are the batteries are much more readily available and easy to change. Radio Shack has them in 2 packs for ~$2.50. It is also very nice to be able to remove the batteries when working on the CCS or modding the amplifier.

The new battery biased CCS.

The performance of the new board layout is measurably better at low frequencies than the old layout. At 100Hz the new circuit measures ~20G ohms where the old layout measures ~6G ohms. Both boards converge at 10Khz and have the same performance above 10K.

Updated September 30, 2002

Protection zener diodes VR1 and VR2 were added. I felt they weren't necessary when the batteries were connected directly to the gate stopper resistors. The batteries themselves protected the MOSFET.

Practical experience proved otherwise as usual. The gate stopper resistors in conjunction with probing the circuit while energized could blow the gates of the MOSFETs.

The board layout was changed to include VR1, VR2, for protection.

Here is the battery biased CCS. It is the same MOSFET circuit used in Rev 4 with out the Pentode and with the bias circuit made as simple as possible. The performance is just slightly behind Rev 4. I suspect the difference is the IRF820 handles the full AC voltage where the upper MOSFET in the Rev 4 circuit only deals with about 1% of the AC voltage.  

Performance numbers for this circuit is 2G ohms and .3pf shunt capacitance. The listening tests I did on this circuit consisted of installing this circuit in my 26 line stage along with putting the support parts (screen dropping resistor, screen stopper, and the 100uf capacitor) for the 6AU6 Pentode on the Pentode socket. With this setup I could listen to it with the Pentode, power down and remove the Pentode, place a jumper plate to cathode in the socket, power the system up and listen to it with only MOSFETs. After a couple of weeks of switching back and forth I came to the conclusion that I could not tell the difference.

This circuit works good for low to moderate currents at high voltage and high currents at lower voltages. For higher currents at high voltage or high power I still think the Pentode on top is the better way to go. It is just easier to dissipate heat in a vacuum tube than a solid-state device with a heat sink. The tubes can radiate a large percentage of the heat where heat sinks rely on convection currents in the air to cool them. Besides, I don't want heat sinks showing on my amps! Been there, done that, don't wana do it again! ;-

Here is a table that should help with selecting R1. These measurements were made on a pair of IRF820 MOSFETs. IRF510 MOSFETs have a slightly lower turn-on voltage so the current will be slightly higher than the table shows. The voltage for each cell is assumed to be 3.3 volts.