The TPB.V1 Tube Preamp Buffer (the “Buffer”) internals are composed of the following 3 subassemblies:
There is also a plastic spacer board required by the power supply board to hold the power supply board firmly in place.
The 2 boards slide into and out the enclosure via slotted grooves which hold the boards in place. The tube board is the top most board and goes into the 3rd set of slotted grooves down from the top. The power supply board goes into the bottom most slotted groove.
The entire buffer assembly is accessed and removed from the enclosure by withdrawing/sliding the entire assembly out from the rear of the preamp at the same time. Putting the assembly back into the enclosure is essentially the reverse of removing it.
The removed assembly is shown in the 2 images below. The first shows all 3 subassemblies unfolded yet connected together. The second image shows the tube buffer assembly oriented as it will be as it’s inserted into the enclosure box.
These 3 subassemblies must be connected together prior to insertion into the enclosure box. The front panel will have already been attached to the front of the enclosure box.
We recommend the following procedure:
The entire buffer assembly is inserted through the rear end of the enclosure box according to the insertion sequence described below. Removing the buffer assembly is essentially this same sequence but in reverse.
The tube buffer can operate on either US 120VAC or International 240 VAC mains power. The mains voltage is determined by setting jumpers on J1, a 4 pin header that is inconveniently located between the transformer and the AC input filter on the power supply board as shown in the image below.
The mains voltage level is determined by jumpers (shunts) on the pins of J1 as follows:
The image below shows only 1 jumper placed across pins 2 and 3 indicating that this power supply is configured for 240 VAC mains power.
In order to access the J1 pin header, the buffer assembly will have to be almost fully removed from the enclosure box. The power supply board will have to be withdrawn sufficiently far out of the enclosure box to expose the J1 pin header shown in the image above.
The Buffer has 3 separate fuses. All fuses are standard 5 x 20 mm size.
The mains fuse is located in a drawer that is part of the IEC power input with integral switch located externally on the left side of the rear panel. This mains fuse is rated at 3 amps.
There are 2 internal fuses, F1 and F2.
F1 is the tube heater fuse. It’s located immediately next to the Z1 mains filter as shown in the diagram above. The F1 fuse is rated at 2.5 amps.
F2 is the plate/auxiliary power fuse. It’s located on the opposite side of the power supply board from the J1 mains voltage header. The F2 fuse is rated at 200 milliamps (0.2 amps). In more recent builds this fuse has been jumpered and abandoned due to it being deemed redundant.
The gain setting can be changed by changing the gain setting jumper position on the buffer’s Tube Board as shown in the circuit board layout shown below.
The TPB.V1 usually ships with its gain set at the default 0 dB setting. There are 2 additional optional gain settings; +3 dB and +6 dB.
Please note that there are 4 separate sets of gain jumpers with only 2 sets shown in the image below. For single-ended buffers only one set of gain jumpers will be present adjacent to each tube (2 total jumper sets). For balanced buffers, there will be 2 sets of gain jumpers adjacent to each tube (4 total jumper sets). Jumpers must be set the same on all sets of jumpers.
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