update to my earlier post:
the company name is NAIS (sorry for the typo).
There web site is: www.nais-e.com
Click 'mechanical relays' or go directly to the URLhttp://ctlgserv.mew.co.jp/ctlg/acg/eng/relay/mech_eng/@Generic__BookView
I've used the ST type relay in several amps. Their DE type also looks quite fine (from the specs) and is somewhat faster than ST (5mS). (No experience with this type so far).
You will most likely need 3 relays as ST type 1 has one make and one break contact only (allowing for one switch-over contact) and you will need 3 make/brake contacts: input, output and bias switching.
Cost per relay in DL-land is about 8 Euro.
I did not mount the relays onto a PCB. Instead I took a piece of foam and carved out 3 rectangular holes a little more than half-way down the foam so that the 3 relays fit into the holes with their connecting pins facing upwards and outside the foam. Then I glued the relays upside down securely into the foam holes.
The foam itself was securely glued to the amp's chassis.
The wiring is done with appropriate stranded wire 'cause this takes away mechanical stress from the relay solder pins (opposite to solid copper wire).
This mounting method minimises the noise during switching. Now there is only a slight clicking when the amp is switched over instead of a loud 'bump'.
The relays are available in a large variety of coil voltages. So it's quite easy to select the one that best fits the given amp switching voltage environment.
By selecting relays with lower coil voltages you could even implement a speed resistor arrangement which speeds up switching time even more (not tried).
The switching current capability of you transceiver (relay contacts or transistor driver) should be at a minimum of 12 volts at 100mA. Three ST1 type of relays in parallel will consume about 60 mA at 12 volts.
Finally, don't forget to mount a diode across the relay coils and make sure to mount the diode in the right orientation. One diode for the 3 relays is good enough as the relays are driven in parallel.
73, Klaus, DK3QN