Piano Tuning Using DOB on the Sanderson Accu-Tuner III and IV

The DOB (Double Octave Beat) feature is available on the Sanderson Accu-Tuner III and IV models. According to the 2011 SAT IV Instruction Manual (see: Page 30), DOB provides piano technicians with the ability to expand or contract the stretch applied during memory tuning. This adjustment is especially useful in situations where more or less stretch is required across the piano’s scale.

How DOB Works

DOB specifically modifies the stretch throughout the piano’s range, but it does not affect the pitch of A4. Instead, every other note is influenced by the DOB setting. When a positive DOB value is selected, the stretch of the memory tuning is increased by evenly raising the notes above A4 and lowering those below A4. Conversely, a negative DOB value reduces the stretch, raising notes below A4 and lowering those above A4.

Technical Details of DOB Adjustment

The DOB setting alters the beat rate of double octaves, measured in tenths of a beat. For example, a .1 DOB setting widens the double octaves by .1 beat per second, while a .5 DOB setting increases the beat rate by approximately .5 bps  or  ½ beat per second. The maximum adjustment is ±2.0, which changes the double octave’s width by up to 2 beats per second, either increasing or decreasing the stretch.

Utilizing DOB During Tuning

When using any memory tuning template with the Sanderson Accu-Tuner III or IV, the DOB feature allows for real-time modifications to the stretch. These changes can be made anywhere within the scale and during the tuning process, providing flexibility and precision.

Impact of DOB on Specific Notes

The following guidelines illustrate the effect of DOB settings on the placement of certain notes, measured in cents:

• A DOB adjustment of .1 at A5 or A3 moves A5 or A3 by .2 cents.
• A DOB adjustment of .1 at A2 or A6 moves A2 or A6 by .4 cents.
• A DOB adjustment of .1 at A7 moves A7 by .6 cents.
• A DOB adjustment of .1 at A0 moves A0 by .8 cents.

Best Practices When Adjusting DOB

It is recommended to add or remove DOB gradually to maintain a smooth and consistent tuning across the instrument. Additionally, the cents buttons on the Accu-Tuner can be used to further refine and smooth out any inconsistencies or ‘hiccups’ that may occur on notes above and below the roll off point.