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Tubes Asylum: Cayin (Spark) TA-30 Integrated Amplifier (Tube) by raindances

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Cayin (Spark) TA-30 Integrated Amplifier (Tube)

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Due to requests, this post contains biasing instructions and general info on adding a passive output to the unit.

DISCLAIMER: THERE ARE LETHAL VOLTAGES INSIDE THE UNIT. I WILL NOT BE HELD RESPONSIBLE FOR ASYLUM MEMBERS OR THEIR EQUIPMENT BEING TOASTED!!! THE HIGH DC VOLTAGES USED CAN KILL YOU!!! IF YOU ARE NOT FAMILIAR WITH WORKING ON TUBE EQUIPMENT, DO NOT TRY! YOU WILL ALSO VOID THE WARRANTY ON YOUR UNIT. THIS POST IS FOR INFORMATIVE PURPOSES ONLY.

An image link is included. Painted on the image in blue is the biasing resistors and corresponding trimpots. In case my painting is incorrect, one end of each biasing resistor connects to pin 8 of each EL34. Counterclockwise on the trimpots reduces bias. To check bias, set multimeter to low range DC volts and CAREFULLY measure the voltage across each resistor. Clip on leads for the multimeter would be helpful. You do not want to short anything out with the multimeter probe. this will destroy the amp and may hurt you. The amp should be WARMED UP first. The correct setting is 0.35V DC. Polarity is unimportant for the meter leads. If it is incorrect, reset by turning the corresponding trimpot slightly, clockwise to increase and counterclockwise to decrease.

If you are installing new tubes, always back off the bias by turning the trimpots counterclockwise a fair bit BEFORE turning the amp on.

I believe 0.35V is the correct setting for EL34's and KT-88's in ultralinear mode in this amp.

To add a passive output (for a subwoofer) connect two high quality shielded cables between wiper and ground on each channel of the volume control. Unsolder the input wires from an input you do not use. Insulate these wires and tuck them away neatly. Solder the new cables from the volume control pot to the (now) unused input terminals and use a self-adhesive label to note this on the rear of the unit. Your subwoofer is responsible for summing left and right. DO NOT short left and right as you will no longer have stereo. Keep the subwoofer cable as short as possible, seeing as this is a passive feed. Volume pot and an input channel are shown painted with pink on the photo.

ONCE AGAIN, LET ME REITERATE THAT YOU SHOULD NOT DO THE ABOVE WORK IF YOU ARE NOT COMFORTABLE WORKING INSIDE SENSITIVE EQUIPMENT CONTAINING LETHAL VOLTAGES. If in doubt, e-mail me.


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Topic - REVIEW: Cayin (Spark) TA-30 Integrated Amplifier (Tube) - raindances 12:44:33 10/9/03 ( 1)