SUPPORT

When powering on your HG-2, place the unit into the standby (middle) position on the front power switch for at least one minute.  This will allow the tubes to warm up before they receive high voltage, prolonging their life.

Although the tubes will be ready to pass signal and use within one minute or so, they will continue to settle slightly over the next 20-30 minutes.

Although earlier versions of the HG-2 required the use of a selector switch on the back of the unit, switching the voltage between 110 and 220v is no longer necessary.  The HG-2 power supply takes care of it automatically.

If you have an older unit, a recessed selector switch can be found on the back of the unit, next to the power input module.  Just slide the switch into the appropriate position and you’re ready to go.  Take care to double check that the selector is in the correct position for your power.

Although we painstakingly match all tubes and pots by hand , there can still be slight variations at certain positions.  These are generally only a couple tenths of a db and will not be an issue for the majority of users but for critical applications like mastering, we have added a fine left/right trim adjustment.

Unlike a pan adjustment, this fine trim is not in line with the audio signal and works slightly differently.  As you turn the trim fully clockwise, you will get an increase of .2db on the right with a drop of .2b on the left.  In the fully counter-clockwise position, you get an increase of .2db on the left and a drop of .2b on the right.

It’s also important to note that because of the way the trim works, you will get a finer adjustment as you turn the output control clockwise with almost no effect in the fully clockwise position.

Standby mode is designed to lengthen the life of the tubes by cutting off high voltage while leaving power to the heaters. When the high voltage is cut off, a small amount of voltage remains and in some tubes this is enough to still pass a small amount of signal. The amount of signal that passes varies from tube to tube with some not passing any which is why you will often hear signal on one side and not the other in standby. This has ZERO effect on the performance of the tubes or HG-2 itself in use.

While it’s technically possible to swap tubes in the HG-2, there isn’t a lot to be gained from it and here’s why…

6U8As – These tubes were never common in audio so there were never any “boutique” versions made.  There are a number of variations and brands but we’ve gone through all of them and only use NOS JAN Philips tubes both for their sound and reliability.  Any 6U8A will work but we recommend a direct replacement.

12AT7s – The two parallel saturation tubes are the well known 12AT7. There are of course a TON of versions ranging in price from inexpensive to boutique which makes them one of the most common tubes for swapping and upgrading but doing so in the HG-2 will not yield the same results.

The first reason is that the parallel saturation circuit is specifically designed to clip asymmetrically in a pleasing way.  This means that you won’t reap the benefits of a more euphonic or hi-fi tube the way you would in other circuits.  This circuit also requires a tube that clips at a very specific point and delivers a very specific amount of gain.  We’ve gone through every 12AT7 we could get our hands on and chose Electroharmonix because they have the exact balance needs for the circuit to operate as designed.  Other tubes will either not clip soon enough, clip too quickly or not deliver the appropriate amount of gain.  If you do decide to try a different set of 12AT7s, note that because of the unique topology, a higher gain tube will actually give you LESS gain in the circuit so we suggest using a lower gain 12AT7.

We know that some people like things subtle and some people like things big and in your face so we’ve made the air circuit adjustable.

Trimming the air amount is as simple as adjusting two trimmers inside the unit.  You can find the location of the trimmers here.

NOTE:  The HG-2 contains deadly voltage and any internal adjustments should only be made by a qualified technician.

We know that tubes age and eventually need to be replaced so we’ve placed calibration points at every critical stage of the HG-2 to ensure that it can always be calibrated at any point as needed or to accommodate different setups.

All calibration is done with internal trimmers and documentation can be found here.

What can be adjusted….

– Left and Right input trimmers directly after the input transformer
– Left and Right high frequency (sets the top end of the entire unit)
– Left and Right “Air” amount
– Left and Right parallel saturation tube
– Left and Right parallel ALT saturation tube
– Left and Right meter adjust

NOTE:  The HG-2 contains deadly voltage and any internal adjustments should only be made by a qualified technician.

Because of the unique output topology, the HG-2 has a higher output impedance than most gear.  This means that when connecting it to some gear with a low input impedance, you will experience a drop in signal.  In most cases this is not noticeable since the HG-2 has plenty of output gain but on a mastering console where the order of gear can be switched instantly its something to be aware of.  This is not an indication of a faulty unit.  This is simply a small compromise to achieve the sound of the HG-2.  Lowering the impedance means losing the vibe or adding a solid state output stage that the audio has to travel through.