Rack Mounts for Classic Consumer Audio Gear

Introduction

I received my first tape recorder in 1965. It was an RCA 7″ reel, half track mono, which ran at 15/8, 3-3/4, and 7-1/2 IPS. I recorded radio station broadcasts, and copy borrowed 45s to tape in a a “pre-mixtape” era. Some of my tapes were then copied for friends.

I also traded tapes with people I knew. A kid down the street had a father who loved jazz, recorded jazz LPs, and local groups who played at a bar in south Toledo. Anyone in Toledo remember “Rusty’s”? It was fun, and opened up a hobby and career for me.

By 1967 I was a tape-a-holic, trading and recording a lot of content off borrowed records LPs, the radio, and even live performances. I was learning about tape recording, and luckily, I had my brother who worked in radio, and his friends in radio engineering showed me the proper way to maintain and care for tape machines. By my junior year I was repairing and cleaning those old Wollensak T-1500 reel-to-reel tape recorder. Before I could legally drive a car I was following around guys 20 and 30 years my senior, helping them servicing tape and cart machines at Toledo radio stations. I didn’t get paid for it, but the experience was priceless!

Enter Dolby B

AN-80 Rack 04 - Unit before modification
This is the Teac AN-80 before modification. Designed to sit on a shelf or tabletop. It will need to go in a 3-RU rack panel.

In 1968 Dolby-B noise reduction came out for the consumer market, mainly marketed to the cassette crowd. The “Dolby” name comes from Ray Dolby the evil scientist behind the noise reduction method. Actually, I met Ray at one of the engineering shows and he’s a good guy!

The Dolby-B noise reduction system typically made reel to reel tapes about 10 dB quieter, which was a blessing in the days of Scotch 111, 170, and their Ampex, Radio Shack, Shamrock, and Audiotape equivalents. This was before the age of better formulations came out. A friend, Dave Collier, introduced me to Dolby B on a Revox A-77 deck. A good technical description of the Dolby-B process can be found on Sweetwater Sound’s web site.

AN-80 Rack 05 - Back of AN-80 Noise Reduction
The 4 jacks on the left go to the sound system, 4 jacks on the right go to the tape deck. These are the Line-In and Line-Out. Power cord and ground not seen in the picture.

Radio Shack had consumer tape recorders and cassette machines with Dolby-B integrated into the machines.

Radio Shack also sold an outboard consumer Dolby-B unit, the Radio Shack DNR-1 “Noise Reduction System”, model number 14-893, (seen below). It was designed to be an add-on to a home stereo system. Under the top grey cover were the pots for alignment with the tape machine. The unit came with a 5″ reel, and cassette, with the alignment tones on it.

Radio Shack DNR-1 Dolby B

The DNR-1 as very functional and useful in situations where tape noise was a problem. Live school and church performances, spoken word, and even private music sessions benefited from 10 dB less tape hiss. When dubbing from reel to cassette, (using Dolby B) the quality was noticeable over straight no noise reduction copies. Many of the early 70s tapes I recorded were encoded in the Dolby-B format.

Playing back Dolby-B tapes without a decoder sounds odd, since it works by boosting high frequencies on record, and reducing high frequencies, (and recorded noise), upon decoding and playback. So if you listened to the playback of an un-decoded tape, at near “zero VU” levels it sounded a little more treble, but as level dropped it was more noticeable.

Dolby-B received a very bad rap because users who often recorded with different brands and formulations of tape found the playback sounded funny. Recording of tapes on machines not properly biased and aligned to the tape caused tracking errors. Uneducated users reported loss of high frequency content, or tracking errors when trying to record on a machine set up for Ampex 632 when they used Radio Shack Metal-Chrome high output.

Regardless, it worked for me because I knew how to use Dolby properly, and I still have more than 2,000 tapes recorded in either the quarter, or half-track format with Dolby-B. Some of these tapes contain recording sessions and content which is priceless.

In 2020, and getting close to retirement, I decided to copy off many of my tapes. Dolby units were retrieved from storage, re-capped, aligned, and cleaned up. But now I had another problem. Over the years I had converted all my tape machines to rack mounts, with four racks to hold things. The only equipment not racked was the Audio Technica LP-120 turntable, and the custom audio control console on the desk. So, what now? The answer was clear, build rack mounts for classic gear!

Creating Rack Mounts

Three pieces; front panel with a rectangular hole which the device fits through, side panels, and pair of handles.

I designed my rack mounts around three pieces. A front plate, side supports, and handles.

You can design a shelf system and have the equipment sit on a tray, and even make a face panel to cover the tray.

With a tray, unless you secure the unit, when you press a button on the front of the equipment, the gear can get pushed back into the rack.

This is why I went with the three part design for my equipment.

The side supports mount to the unit using an existing screw used to hold on the cover. It then attaches to the front panel. A #8 screw attaches the side support, through the front plate, and is captured by the handles. When everything is tightened up, nothing moves. Its all one piece ready to go into the rack cabinet.

AN-80 Rack 01 - Side Piece, Handle, Front Panel
The side plate is aligned on the back of the front panel. A #8 screw, .375 to .500″ long goes through the back side panel, to the front panel, and is captured by the handle threads.

The side panel is made of steel, with a .5000″ lip bent at 90 degrees. The holes on the bend correspond to the handle alignment, and line up with the front panel. See the pictures to the right.

When assembled, the front plastic panel of the AN-80 is tight against the metal rack panel. The unit is supported by the front bottom opening

The back is captured to the equipment by a screw which goes through the side piece into an existing hole on the AN-80 used to secure the cover. Note, this screw is a metric. If the existing screw from the AN-80 is not long enough, you will need to get another screw which needs to be about .375″ long.

The side panels are easy. Just a 90-degree bend, locate where the holes need to be, and you’re done. The front panel can be a little trickier. There are three ways to make one.

1 – You can make a rough rack panel with opening with a band saw, or scroll saw, with a lot of care and patience. Aluminum plate is available at most home store like Lowes and Menards.

2 – Optionally, have Front Panel Express make them for you with their easy to use software. You design the panel, send the file to them, and they make it and sent it back to you.

Front Panel Express version of AN-80 Rack Panel

3 – Another source is Markertek’s custom metal services, which I’ve used in professional builds. Markertek also has blank panels, sold separately, and in bulk “contractor packs“.

4 – If you have access to a CNC machine you can make panels easily. The stock should be at least 0.0787402″ thick (2mm), 19.00″ wide by 5.25″ tall, for a three RU panel. The Teac AN-80 required a rectangular hole, (4) round holes for mounting the side plates to the front panel, and (4) oblong holes for mounting to the rack mount to the rack cabinet.

The handles were from Lowes, kitchen cabinet department. Specifically, I used “Rusticware” 3.0″ Center to Center Chrome Rectangular Handle Cabinet Door Pull, Item #1442765, Model #993CH, ($7.53 each, need 2). I use the square style handle for my audio gear, and the round chrome handles for my RF and ham radio equipment. (The Sugatsune Cylindrical Handle Cabinet Door Pull, Lowes Item #1270138, Model #H-42-B-8, is perfect for 3.5″ rack panels). With grey paint, and chrome handles, it has that “military look”.

After all the metal panel parts are made, I took them, and the handles, to a powder coating shop and had all the parts coated the same color as the Teac AN-80. They used PPC “Satin Black” powder coat, and the match was perfect to “Teac black”.

While metal and paint were underway, I recapped the AN-80 so I had ready for action when the panels were attached. I also changed the VU meter incandescent light to a light-blue LED.

As soon as all the AN-80 Dolby units are done I have Teac AN-50 and AN-60 to do. Also on the build schedule are mounts for a Teac X7R and A-3440 reel to reel machines. I’ll probably write an article on making them since trying to find Tascam A-34404 mounts is like trying to find Jimmy Hoffa.

Here is AN-80 #1 hot off the bench.

Finished AN-80 mounted in rack panel.

References and Resources

1). Format Characteristics and Preservation Problems Version 1.0 – [PDF]

2). Richard L Hess—Audio Tape Restoration Tips & Notes – [Web Page]

3). Fun article from the Chicago Tribune – [Web Page]

About Frederick R. Vobbe

I work as the Director of Engineering for TV broadcast affiliates. In my nearly 50 plus year broadcast career I have worked at recording studios, radio, and television stations. Hobbies include; collecting “oldies” from the years 1955 to 1990 that charted in the radio industry in the Whitburn/Billboard charts for Rock and C&W. I also restore old tape recordings of radio jingles, airchecks, and broadcast production music from tape and records. I also design circuits and home-brewing equipment such as audio processors, tube compressors, switcher & control systems, audio distribution amplifiers, and audio mixers. My amateur radio call sign, W8HDU, was granted via the F.C.C. vanity call-sign program, and was my grandfather’s call.
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