Manley The WAVE DAC/Preamp 20 Bit Version Serial Code WAVE000-015 1999 - 2002 - Manual (Page 16)

HUM - Once again - several possibilities - several cures. Most likely it is a ground loop. Ideally each piece of gear should
have one ground connection and only one. However, the short list of grounds include the AC mains plug, the chassis bolted
to a rack with other gear, each input and each output. The two most common procedures are: try a 3 pin to 2 pin AC adapter
(about a dollar at the hardware store).This while legal in many countries can be dangerous- We went one better; Method two
- On the back panel loosen the GROUND TERMINALS and slide the wire ground strap to one side. This is way better than
"method one" because it is safer and removes another possible source - the chassis grounding via the rack. Method three -
cutting the shield on oneend of each cable. This is done by some studios at every female XLR to "break" all ground loops.
All the other gear in the rack is "dumping" ground noise onto the ground. Try removing the Wave from the rack so that it is
not touching any metal. You just may have cured a non-loop hum. Some gear radiates a magnetic field and some gear
(especially if it has audio transformers) might receive that hum. A little distance was all it took. The balanced XLR outputs
are very useful for feeding amps at some distance which is often a easy way to set up a nasty hum. You can also experiment
with disconnecting PIN 1 (shield) at EITHER end of the interconnect. Given today's audiophile cables, this may not be
possible but one can disconnect PIN 1 of OUTPUT 3 (or the inputs) inside the Wave as an experiment with probable success.
IT MAKES NOISES WHEN THE FRONT PANEL IS TAPPED - An easy one. Some tubes become microphonic over
time. That means they start acting like a bad microphone. Vibration has caused the supports for the little parts in the tube to
loosen and now the tube is sensitive to vibration. Easy - Replace the tube. Which one? The one that makes the most noise when
you tap it. Usually this will be one of the smaller (gain stage) tubes closest to the front. The Wave will have to be on, connected
and speakers up but not too loud for the sake of your speakers.
IT GOT HISSY - Also easy. This is again a common tube symptom. You could swap tubes to find the culprit but an educated
guess is OK too. Generally the first tube in the path is the one with the most gain and dealing with the softest signals. The
usual suspect is the shorter tubes - the 12AX7 in the preamp. You may find that you need to choose the quietest tube out of
several of that type - like we do at the factory.
DISTORTION - This might be a tube. Swapping is a good way to find out. It may be a wiring thing or mismatch as well.
Wiring problems usually accompany the distortion with a major loss of signal. Mismatches are a bit tougher. The Wave has
a high input impedance and low output impedance that can drive 600 ohm inputs of vintage "style" gear. The first things to
suspect would not be the Wave, but the sources and especially the speakers which do fatigue and seem to be statistically most
prone to those kinds of symptoms. Start out by checking other sources and use the L/R swapping technique to locate the
problem. If the Wave does seem to be distorting, then it is probably related to the load it is driving especially if it being asked
to drive several sets of amplifiers or a 600 ohm input device.
DC OR SOMETHING AT THE OUTPUT THAT IS INAUDIBLE - The RCA unbalanced outputs have a frequency
response that goes way down to below 1 Hz. A little very low frequency noise may be seen as speaker movement when power
amps are sensitive. The XLRs do not exhibit this because the transformers filter below 8 Hz. Also the unbalanced outputs
do not like long cheap high capacitance cable. Occasionally a very high frequency oscillation (200 kHz to 400 kHz) may occur
in these conditions. Once again use the XLR outputs. Problem solved.
THE METERS ARE OUT OF CALIBRATION - This really only applies for our Mastering clients who have chosen the
Wave as their reference DAC that feeds the processing chain. In this situation, "calibration" means high resolution digital
meters and VUs where one can see less than a tenth of a dB calibration error. Usually, a little adjustment on the trimmers are
all that is required. We can also replace the motorized Volume control with a detented 24 position rotary switch which provides
extreme matching of left to right - or- a pair of 10 turn trimmers instead of a big remote controllable pot.
The INSERT outputs are not set up to be a particular level such as -10 dBu or +4 dBm. Instead, they are just the last switch
in a passive relay switching chain. The output will be the same as the selected source, if analog and roughly consumer level
-10 dBu if digital is selected (Digital Full Scale = 8.25 dBu = 2.00 VRms).
THE VOLUME POT IS SCRATCHY. Probably not. Select a different source, scratchiness gone? The source related with
the scratchiness must have DC on its output. The input stage is all direct connected and DC will get passed to the pot which
will make it seem noisy. The fix has to be done at the source that is sending DC which polite well behaved gear is not supposed
to do. If the offending unit can not be repaired, a capacitor or a pair of capacitors can be added at the input jack in line with
the signals. A good value is 10 uF/63V and it should be a film type (like a Wima MKS4, MultiCap, etc) and not an electrolytic.
Smaller values down to 1 uF can be used but may cause loss of CMRR due to tolerance issues, and will also result in a bit
more phase shift in the extreme LF (which is generally inaudible).
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