Dubbing Buss

OK, I'll try.

Think of the "Dubbing Bus" as a common connection point. It's a place where:

(1) A tape deck can send its output, so that other devices can use or monitor what this deck is playing, and (2) A tape deck can use as its input, so that it can record what another tape deck is playing. If you're trying to dub (copy) from one deck to another, then you would set the switches so that:

- The "input connection" of the deck that you are RECORDING TO, would be in the "down" position, so that it is being fed from the dubbing bus.

- The "output connection" of the deck that you are PLAYING BACK FROM, would be set to the "up" position, so that it is feeding its output to the dubbing bus.

- If you have a third tape deck, you can dub from one deck to both of the others simultaneously... just set both "recording to" decks to take their inputs from the dubbing bus (input switch "down"). There are a large number of other possible combinations of switch settings. In general:

- You should have only one deck's output set to the dubbing bus at any given time. If you have two or more set this way, they will "fight" with one another, with somewhat unpredictable results.

- Similarly, you should have only one deck's output set to the "output to the receiver" setting at any given time. Same problem... they'll fight.

- You should not have any deck's input and output both set to the dubbing bus at the same time. This can cause feedback or weird echo problems.

- To record something from radio or turntable to either or both decks, set the decks' inputs to the "up" position so that they're being fed from the receiver.

Thanks! That's wonderful and easy to follow. I'll copy this and refer to it when I hook up the Tape Control Center. Yes, I understand it now.

The switches on that thing are hillarious.

They do seem a bit over-the-top, but I've seen similar "long brushed aluminum" switches used on a lot of 1970's and 1980's audio gear, I believe.

The arrangment actually makes sense... they marked the "dubbing bus" as a sort of virtual wire running across the middle of the panel, and all of the deck I/Os whose switches are moved to point to the "bus" are actually bussed together inside the box.

I've wondered what that finish was called in those goofy switches. It seems everything in that era had them.

I've heard it referred to as "brushed aluminum" and "matte aluminum". One can probably reproduce it fairly easily, with a rod or plate of aluminum and a wire brush chucked into a drill press or lathe.

I imagine that the switch rods probably used aluminum rod which was run through a long "continuous brushing" jig (push the rod one way, through a set of spinning wire brushes rotating in the opposite direction) and then cut to length.

Any idea how they made those pretty aluminum knobs of the same era with the perfect grooved texture on the face? It's dozens of perfect concentric grooves, some even reflect light in rainbow colors of they're not dirty frmo hands.

the modern versions look like and are cheap crap to the old stuff

Well, I don't know how they made them. However, I do know how I would try to reproduce the effect today (which may be how they made 'em in the first place).

- Cut or stamp or machine the knob to the desired size and shape

- Do any milling of the outer side (traction ridges, etc).

- Polish the front side to a good flatness.

- Spin the knob on its axis (keeping it exactly on a stable axis - this probably means sticking it on a driveshaft and tightening the grub screws to hold it firmly in place) and press it against a flat plate embedded with a fine abrasive. Industrial diamond particles, silicon carbide, something like that. Since this is aluminum and relatively soft, even ordinary aluminum-oxide sandpaper would do... you can get this with an adhesive backing, and just stick a piece on a plate. The finer the abrasive grit, the finer the concentric grooves would be. The more evenly-spaced the grit particles, the more uniform the groove spacing, and the more pronounced the rainbow diffraction colors would probably be.

I imagine that the knobs were anodized after the grooves were cut.

You could probably try this at home with a sample of aluminum, a drill press, and a home-made abrasive plate clamped to the drill press table.

Or take the discussion to news:rec.crafts.metalworking which is a good place to learn metalworking.

On Mon, 08 Oct 2012 16:00:45 -0700, Mack A. Damia put finger to keyboard and composed:

Here is a (partial?) circuit diagram:

- Franc Zabkar