01W Audio Outputs

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rev: 02Nov17
Line Outputs 
Connecting to Audio Equipment 
Troubleshooting: No sound from 01
Output circuit description 
Maintenance Information 
Digital-to-Analog (DAC) circuit description 
  DAC fix / free update

Audio Output Jacks
PHONES 1/L 2/R 3 4
The industry standard is to call the stationary connector a "jack" and the portable connector a "plug", regardless of the sex of the connector. A jack is usually a female connector, and a plug is usually male. This is true for the 01.

The Audio Output section has 4 jacks that accept quarter-inch plugs. Only the PHONES jack is stereo. The other four are mono only.

The individual jacks will be described from left to right as you sit at the front of the 01, feeling the back with your hand:

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Headphones Output

Left-most jack is for headphones. This output is a stereo copy of what's going out 1/L and 2/R. In fact, wires go directly from 1/L and 2/R to amplifiers which boost the signal to headphone levels. Since the Master Slider controls output levels 1/L and 2/R, the headphones levels are also affected.

The simplest way to hear your 01 is to use headphones. Plug stereo headphones in the PHONES jack on the back panel.

This jack takes a "quarter-inch male stereo phone plug". You can use headphones with a different plug on them, but you will have to get an "adapter" at an electronic parts or audio store. For example, headphones that come with portable stereos usually have a "mini-plug", so you would need a "mini-to-quarter-inch stereo adapter". Take your headphones to the store with you to make sure the plug mates with the jack in the quarter-inch adapter.

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Line Outputs

The audio outputs are four jacks located between two screws. All four are mono outputs. They are labeled from left to right (as you sit at the keyboard) as "1/L", "2/R", "3", and "4".

Jack 1 is labeled "1/L", or "one-slash-left". This is a mono output that connects to the left channel of your stereo amplifier.

Jack 2 is labeled "2/R", or "two-slash-right". This is a mono output that connects to the right channel of your stereo amplifier.

Jack 3 is labeled "3". This is a mono output. It is an optional output. You use outputs 3 and/or 4 when you want sounds to be processed differently from sounds coming out 1 and 2. A typical application is to send sounds with chorus and reverb out 1 and 2 while sending drums out 3 and 4 without any effects. These four outputs would go into an external mixer where they would be mixed down to stereo.

Jack 4 is labeled "4". This is a mono output. It is used in the same way as Output 3.

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Connecting to Audio Equipment
You can play the 01 through your home stereo system. In most cases, you only need to use 1/L (L = left channel) and 2/R (R = right channel). Connect these outputs to a spare pair of inputs on your stereo. Pretty much any input will work except those designated "phono" (which have special filters for turntables or record players). Inputs labeled "AUX", "TAPE IN", or "DISC IN" should work fine.

The 01 output jacks take "quarter-inch mono" plugs. Most stereos have "phono" jacks, often called "RCA" jacks. You probably have a cable with two phono plugs on each end - one red, the other white or black. Get a couple "phono-to-quarter-inch male" adapters, and attach them to one end of the cable.

As a rule, always plug red connectors into the right channel. This is only to help you remember which color goes where at the other end. The "r" in "red" reminds you of the "r" in "right". (If the other cable is bLack, the "L" can remind you of "left".) You will not hurt anything if you don't follow this rule. It just helps avoid mistakes when you're looking at a clump of spaghetti wiring hanging on the back of an audio panel.

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Panning to Outputs 1/L, 2/R, 3, 4
Now that everything is wired up, you'll want to learn how to pan Progs and Sequences to the four outputs. That's covered on the 01 Panning page.
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Troubleshooting: No audio output

If you have no audio, the first thing to check are the simple things:

1. Unplug all MIDI cables from the 01 (to make sure some MIDI command isn't sneaking in).
2. Turn the power off, wait a few seconds, then turn the power on (so you're starting "clean").
3. Go to Global Mode, Page 0, and make sure Local is ON.
4. Plug headphones in the 01 PHONES jack and listen through the headphones (to bypass any possible problems with other audio gear).
5. You can try re-initializing the 01 to the original factory settings. Beware - this will destroy any custom editing and sequences you have stored in the 01. Click here for instructions.

Circuit Description

Each of the outputs (1/L, 2/R, 3, 4) has a completely separate, though identical, output circuit. That means it is unlikely for two channels to fail at exactly the same time. Listen carefully to each output. If one output sounds defective but the other sounds fine, chances are one of the components in the defective-sounding channel has gone bad.

The only difference between outputs 1/L, 2/R and outputs 3, 4 is that 1/L and 2/R pass through the "Master Volume" slider on the front panel on their way out the back. If 1/L and 2/R both develop problems at the same time, a dirty or defective Master Volume slider would be my guess. (A bit of contact cleaner sprayed in the slider might fix the problem.)

Try sending a defective-sounding Program out outputs 3 and 4 instead of 1 and 2. (You may have to play with pan settings to do this.) Do you hear the same distortion? If you do, that means the problem is further back in the innards of the 01. If you don't hear the distortion, then listen closely to 1/L and 2/R as described above to determine if a component is bad or the slider has worn out.

Click for more details on using outputs 1 - 4.

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Maintenance Info: Jacks that have been used a lot can develop noisy or dead outputs. One possible reason is the solder that holds the jacks to the PC board gets stressed and cracks. A crack can be almost invisible.

Users report it is relatively simple to open your 01 and resolder these connections using a soldering iron and more solder. The jacks are close together, so you must be careful not to let the solder flow too far and short something out. That is, this is not a good project to learn how to solder. Find someone with a little experience.

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D2A Circuit Description
All Sounds are stored as digital (ones and zeros) in on-board ROM or plug in PCM cards. These are sampled (and sometimes modified) waveforms, similar to .WAV files found on home computers.

A microprocessor (IC17, an MB87405) reads these samples out of DRAM. The DRAM bank consists of five 64K x 4 chips (ICs 18-22) organized as 1M x 8 but read out as 512K x 16.

The 16 bits of Sound sample are fed to a 16-bit Digital-to-Analog converter (called a "DAC" or "D2A"). The D2A (IC34, a "PCM55HP") converts the 16 digital 1s and 0s into a current that uniquely corresponds to the digital value present at the D2A inputs.

This current must be converted to a voltage before it can be used. The current comes out of IC34 pin 21 (IC34-21), goes to an operational amplifier ("op amp"), IC37-2 (an M5238FP). The output of this op amp (IC37-1) goes to a  circuit consisting of a resistor ladder (R55-58, 510-ohm 1%) and IC35 (74HC4053).

The output voltage from the op amp (IC37-1) is also sent to one outside pin of a 3-pin connector, CN100A (no pin numbers on the schematic). The middle pin is open, the other outside pin is ground. This appears to be a test-point connector for troubleshooting. It may also be a convenient place to capture (sample) the cleanest waveforms.

It's the single output of IC35 (pins 4, 14, and 15 connected together) that is sent to all four back-panel outputs (and headphone output). If you have an audio problem that is identical on all four outputs, suspect the D2A/current-to-voltage circuit (IC34, IC35, IC37 and nearby resistors, capacitors, reference voltages, and/or traces).

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D2A "Fix"
One 01 user reports that early 01s had a problem with the D2A converter that required a free update to correct. The symptom was excessive noise when effects were used heavily. The sound was also said to clip at medium volume. No further information is known.
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Copyright ©1998-2002 by Ken Westover at Cliff Canyon Publishing Co. All rights reserved.
This material may not be distributed without the written permission of the author.
E-mail questions or comments to cliffcan@indra.com.
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