Conrad-Johnson Design
Conrad-Johnson Design1 week ago
The question has recently come up of how to connect a conrad-johnson stereo amplifier that has been wired for mono operation. The following instructions are for converting a Classic Sixty from stereo to mono operation - but the procedure is the same for all conrad-johnson tube amplifiers. NOTE that if the amplifier has been factory wired for mono operation, then steps 1 and 3 have already been done at the factory.

The two channels of a Classic Sixty amplifier can be connected in parallel to create a 120 watt
monaural power amplifier. To convert a Classic Sixty to mono operation:
1. Connect the two channel inputs together. This can be done either a) externally with a “Y”
connector, or b) hard wired internally. In the latter case, disconnect the amplifier from A/C
mains. Connect a jumper wire between the center pins of the two input connectors.
2. Connect a short length of speaker wire between the two positive speaker terminals. Again,
this can be done externally, or internally with a wire attached with ring terminals inside the
chassis.
3. The amplifier may need to be configured for a different output load impedance. When the
two channels are connected in parallel, the amplifier’s rated output load impedance is ½ that
of each channel. A factory standard Classic Sixty amplifier is set for a 4 Ohm load, so when
connected for mono operation it will match a 2 Ohm load. To have a mono amp matched to a
4 Ohm impedance (the factory recommended setting) the individual channels must be reconnected
for 8 ohms. See the attached bulletin on setting the output load impedance for a
Classic Sixty.
4. Connections to the mono amplifier can be made to either input connector and to either pair of
output connectors.
Conrad-Johnson Design
Conrad-Johnson Design1 month ago
Phase 2 of headphone development. The prototype pc board fitted to prototype of the chassis. Next step will be fitting dress metal. Then revision of the pc board to (hopefully) final layout.
Conrad-Johnson Design
Conrad-Johnson Design1 month ago
The design team has been working diligently on a totally new product: a headphone amp that just sounds right! We'll show a few steps in the development on this page. First, the proof of concept prototype pc board - completed some months ago - mounted in a convenient chassis that we had on hand:
Conrad-Johnson Design
Conrad-Johnson Design2 months ago
Tea1 gets a face lift. The TEA1 phono stage now sports upgraded casework more in keeping with its flagship status. In a nod to the GAT line-stage, the newest TEA1 units (designated Series 3) will be dressed with a 1/4 inch thick top panel and heavy side panels all in brushed, black anodized aluminum. The increased rigidity will minimize chassis resonances. TEA1s3 units are available now.
Conrad-Johnson Design
Conrad-Johnson Design2 months ago
The ET7 line-stage has now been upgraded to the ET7 Series 2. Upgrades include a much improved power supply reservoir and use of the same extreme quality I/O connectors found in the GAT line-stage. The ET7s2 picture here shows the upgrades, seen in the areas bounded by orange rectangles, and a picture of an original ET7 is shown for comparison.

news from conrad-johnson

news from
conrad-johnson

new ART amplifiers

new ART amplifiers

In celebration of our 40th anniversary, conrad-johnson has introduced two new ART amplifiers: the ART150 stereo amplifier and ART300 mono-block amplifier.

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announcing new classic amplifiers

announcing new classic amplifiers

The conrad-johnson design team is committed to adapting the advances from our state-of-the-art pursuits to more affordable offerings accessible to a wider range of music lovers.

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