Twist Turner
Well-known member
I know this was discussed here several years ago but there was never really a real definitive answer given. I have a Altec 518a power supply for a Altec M11 mic system but it is missing the TBB-103 transformer. Can anyone suggest a suitable replacement for this?
Here is the info I found on the net for these -
This is a low level input transformer for operation from a 500, 250 or 30 ohm line into a 70,000 ohm secondary load. The secondary may be used either single ended or in a push-pull arrangement, as both secondary windings have balanced capacities to ground. The frequency response is flat within 1 db from 20 c.p.s. to 20,000 c.p.s. The maximum operating level is -20 db from a reference of 6 mw.
Shielding: the electrostatic shield is brought out to term S and should be connected to the equipment ground. The transformer is potted in a nest of high permeability cans within the case, providing 90 db of magnetic shielding.
Primary connections:
connect to 1-3 for 500 ohms
connect to 1-2 for 250 ohms
connect to 2-3 for 30 ohms
Secondary connections:
70,000 ohms connect to 7-10 strap 8-9
17,500 ohms connect to 7-10 strap 7-9, 8-10
for single ended use ground number 7.
This unit is housed in a steel can with 3 mu-metal round cans nested inside each other within this outer enclosure. In between the nested cans are copper shading cylinders. I wish you could see the pictorial of how these cans all nest (tuck) inside each other... each can is deep drawn and has a bottom lid with two holes (to route the lead wires). Once assembled the whole thing is wax filled.
There are two electrostatic shields which isolate the high impedance secondary windings from the primary windings.
The secondaries are wound with angel's hair (42 gauge wire). Pri dcr is approx 36 ohms. Sec dcr is balanced btwn the halves... with each half having 1620 ohms.
This unit is built on a mu-metal core (80 percent nickel)
Here is the info I found on the net for these -
This is a low level input transformer for operation from a 500, 250 or 30 ohm line into a 70,000 ohm secondary load. The secondary may be used either single ended or in a push-pull arrangement, as both secondary windings have balanced capacities to ground. The frequency response is flat within 1 db from 20 c.p.s. to 20,000 c.p.s. The maximum operating level is -20 db from a reference of 6 mw.
Shielding: the electrostatic shield is brought out to term S and should be connected to the equipment ground. The transformer is potted in a nest of high permeability cans within the case, providing 90 db of magnetic shielding.
Primary connections:
connect to 1-3 for 500 ohms
connect to 1-2 for 250 ohms
connect to 2-3 for 30 ohms
Secondary connections:
70,000 ohms connect to 7-10 strap 8-9
17,500 ohms connect to 7-10 strap 7-9, 8-10
for single ended use ground number 7.
This unit is housed in a steel can with 3 mu-metal round cans nested inside each other within this outer enclosure. In between the nested cans are copper shading cylinders. I wish you could see the pictorial of how these cans all nest (tuck) inside each other... each can is deep drawn and has a bottom lid with two holes (to route the lead wires). Once assembled the whole thing is wax filled.
There are two electrostatic shields which isolate the high impedance secondary windings from the primary windings.
The secondaries are wound with angel's hair (42 gauge wire). Pri dcr is approx 36 ohms. Sec dcr is balanced btwn the halves... with each half having 1620 ohms.
This unit is built on a mu-metal core (80 percent nickel)
