Use the power of DSU to tune A4 accurately to 0 cents.
Because of the high accuracy of the Go A.P.E. System and its ability to be used to do accurate, precise and efficient pitch raises, it is preferred that we tune A4 with an ETD, overpulling A4 by 25%, or underpulling A4 by 33%.
Examples:
Overpulling
A4 at -12 cents? Cut 12 in half twice (to get 25%) 12 - 6 - 3. Tune A4 to 3 cents sharp.
Underpulling
A4 at 9 cents sharp. Cut 9 into 3 (to get 33%) 9/3 = 3. Tune A4 to 3 cents flat.
These are the steps at the piano
1. Mute one string of A4.
2. Tune the DSU clean.
3. Judge/Measure. If A4 is within 1 cent, go to step 6.
4. Move one string in the direction of A4, the amount you are off, measured in step 3.
5. Move the other string and tune the DSU clean again. Go to 3.
6. Remove the mute.
7. Tune the trichord clean.
For this exercise, we only have a DSU, so your steps will be:
1. Tune the DSU clean. (It is not clean at the start)
2. Measure.
3. Move one string the amount you are away from A4 in the direction of A4.
4. Use the other string to retune the DSU clean.
5. Remeasure
Continue with 3,4,5 until A4 is at 0 cents.
Every time you measure A4, it will be added to your tries.
Try to get 3 tries or less. It can be done.
1) Tune the DSU clean.
2) Measure (Try #1)
3) Move one string the approximate amount. Retune the DSU. Measure (Try #2)
4) Move one string the exact amount. Retune the DSU. Measure (Try #3)
Think of it like a Par 3 golf hole.
Try #1. 1st hit off the tee, on the green. (That's when you have to move the DSU a lot, like 4 or 6 cents.)
Try #2. 1st putt. Get close. (That's when you are off by about 1 to 2 cents.)
Try #3. In the hole. (Usually from within 0.3 - 0.5 cents)
Remember, in a real piano, your goal is only to get within 1 cent, not 0 cents.