GENERAL DESCRIPTION
Bryston’s 2B-LP stereo power amplifier consists of two amplifier modules, each with its own power supply, which can be operated independently or combined (MONO mode) to form a single 200 watt amplifier (8Ω load) in a 1 rack height chassis. Operated indepen- dently (DUAL mode) each channel can deliver 60 watts into 8Ω (or 100 watts into 4Ω). Each of the two amplifier modules use 2 of Bryston’s custom power transistors for a total of 4 output devices per 2B-LP.
POWER CONSIDERATIONS
In general, if your preamp has a three prong grounded line cord you can avoid local ground loops which could cause hum or noise in the system by plugging the preamp’s line cord into the same wall outlet next to the power amp.
CLIPPING INDICATORS
The 2B-LP amplifier uses a pair of 2 colour LEDs with green indicating power on and red indicating actual overload or distortion.
SPEAKER POWER HANDLING & FUSE PROTECTION
Most speakers will safely absorb an undistorted musical signal up to the full power capability of even large amplifiers like the 2B-LP (DUAL mode). However, once the signal starts to be clipped the distortion by-products generated by the overdriven signal can result in very high power levels fed to the smallest and most fragile of the speaker’s components. It should be noted that an amplifier is quite capable of distorted power levels of twice the undistorted rating and that all the excess power goes to the high frequency driver. It is also quite possible to damage the woofer by causing it to exceed its excursion limits and impact against the back of the magnet by doing such things as turning up the bass control on a preamp and playing music quite loud. This is especially true with amplifiers which can develop full undistorted power down to extremely low frequencies as all Bryston amplifiers can. Many speaker manufacturers recommend series fuses to protect the drivers in case overload. If you wish to use fuses follow the manufacturers recommendations since even small increases in current ratings of a fuse will result in large increases in power allowed. Example: A 3A fuse will allow about 70 watts to pass, a 4A fuse 130 watts and a 5A fuse nearly 200 continuous watts.
It should be emphasised that almost any amplifier is capable of inflicting damage on almost any speaker if used in a thoughtless or abusive manner and that Bryston cannot be responsible for speaker damage caused in this way.
BRIDGED OPERATION (MONO mode)
When operated in BRIDGED (MONO) mode the two internal amplifier sections are operated out of phase and the load is connected between the two HOT (RED binding post) terminals with no connection to ground. The two amplifier sections operate together to form a single push-pull amplifier with double the normal output voltage. In this mode the amplifier can generate output voltages of greater than 42v(rms) into loads as low as 8 ohms thus producing output power levels exceeding 200 watts (rms). (N.B. Only the
left channel input is used in MONO mode.)
INPUT CONNECTORS
The 2B-LP is supplied with one pair of input connectors; either unbalanced RCA/phono connectors on the home audio version or 3 pin balanced XLR jacks (pin 1 is ground, pin 2 is positive & pin 3 is negative) with fully discrete active input circuitry on PRO units. PRO models also come equipped with independent, front mounted level controls.
All input connectors are gold plated and should be used only with quality gold plated input cable connectors as a poorly plated con- nector will eventually corrode through the gold flash. Bryston makes cables with appropriately heavily plated, high quality connec-
tors, available through your dealer.
OUTPUT CONNECTORS
The 2B-LP is equipped with four binding post terminals (2 red, 2 black) which can accept either standard banana plugs or bare wire. Refer to the rear panel hook-up diagram and to the descriptions of DUAL (stereo) and MONO operation for details on how to connect speakers to these terminals. Since the binding posts are gold-plated we recommend gold-plated banana plugs be used for the lowest distortion.
N.B. Do not attempt to remove the red or black connector nuts from the binding post connectors. They are not removable and attempting to force them off may break the connector or strip the threads.
OUTPUT CABLES
For some time there have been available on the market special speaker cables constructed for extra high current and low loss and distortion. These cables will cause no difficulty or instability with any Bryston amplifier. In fact, we recommend that low inductance cables be used for the smallest loss of signal between amplifier & speaker.
GROUNDING and the GROUND SWITCH
The left most switch on the rear panel is a GROUND LIFT switch. It is connected between the chassis ground (including the third prong on the power line cord) and the signal ground. This switch is normally left in the connected (closed) position. Occasionally a multi-amplifier rack installation, or an unusual grounding situation with a preamp using a three wire power line cord, will cause a ground loop between the signal ground and the chassis ground. This switch will allow the elimination of the resulting hum in such cases without resorting to a “cheater” plug by switching to the separated (open) position. Note that this switch does not disconnect the chassis from the third prong on the power line cord which must be left intact for safety reasons.
