Program EQ PE1A, PE1B and PE1C difference
	The amplifier section in the PE 1A and PE 1B is hardwired. In the PE 1C the transformers and the tubes are placed inside the unit on a printed circuit board. The filter section for the low BOOST/ATTEN and the high ATTEN is the same for all three units. The high boost in the PE 1B and PE 1C has three additional frequencies: 1, 1.5 and 2 KHz

Midrange EQ ME1A and ME1B difference
	The circuit and functions are exactly the same. The amplifier section in the ME 1A is hardwired.   In the ME 1B the transformers and the tubes are placed inside the unit on a printed circuit board.

Opto Compressors CL 1A and CL 1B difference
	The circuit and functions are exactly the same. The amplifier section in the CL 1A is hardwired.   In the CL 1B the transformers and the tubes are placed inside the unit on a printed circuit board . The control circuit is on a PCB in both units.

Difference between CL1B and CL2A
	The TUBE-TECH CL2A design is based on the famous CL1B.   Some differences exist between the two units. The tube circuit is the basically same. The only difference is that the input transformer and the tube amps in the CL2A doesn't deliver the same ( extreme ) amount of gain provided by the CL1B. This has no effect on the sound at all and is not needed for normal operation.   The control circuit has been changed so the CL2A's  max release time is two seconds. (The CL1B has a max  release time of 10 Seconds!)   Since the optical element for the CL1B isn't made anymore, the CL2A features a different optical element, not very different to the element in the CL1B. Especially in manual mode the CL2A and CL1B are pretty similar.   ( Remember that John Petersen bought the stock whole stock of the now discontinued optical element used in the CL1b, and has enough for many years of CL1B's )   Listen to the differences between the TUBE-TECH compressors.

LCA2B Tube Compressor calibration
	Like any other compressor, that uses tubes for the VCA,TUBE-TECH LCA2B occasionally needs calibration.   We recommend that the unit should be calibrated at least once a year.   In real life, depending on the compression tube (ECC81)  the LCA2B will often work perfect for a much longer period of time. A quick test will tell you if calibration needed:   Turn the THRESHOLD for both compressor and limiter fully CCW.  Connect a 1kHz tone at a level of 0 dBU (-4VU) to the input and turn the LIMITER THRESHOLD slowly CW until the LIM led (RED) turns slightly on. If the LIM led (RED) turns on abruptly or even starts oscillating, the balance should be calibrated.   This test can also be done with audio: If the LCA2B needs calibration, the compressor starts pumping with this extreme setting.

SMC2A / SMC2B difference.
	The ONLY difference between multiband compressor SMC2A and SMC2B is the added balance control.

Summing Amp SSA2B unused mono inputs
	IMPORTANT!!   If the SSA2B mono inputs are left open, the L R channel seperation is less than specified. ( Narrow stereo image.)   It is important that the mono inputs are either:   A:Switched to stereo   B:Connected to outputs (even if not used)   C:Terminated by shorting plugs