How to test the loadbox of a Torpedo product
The loadbox design in the Torpedo products are the result of years of development with, among other things, reliability in mind. As a result, they are pretty sturdy circuits, and they very rarely fail. Most of the issues encountered when using a Torpedo product can be traced back to something else than the loadbox. Before considering that the loadbox is the source of an issue, you should first check for other causes.
That being said, the loadbox in the Torpedo products are still electronic circuit,and as such, there is always a possibility that they fail. If you suspect the loadbox in your Torpedo product (VB-101, Studio, Live, Reload or Captor) is defective, here is how to test it.
The Torpedo C.A.B. and Torpedo C.A.B. M don't have integrated loadboxes. They are not concerned by this article.
A) Electric test
This test will measure the DC resistance of the loadbox. This value won't tell the whole story because the loadbox is reactive, but can still show potential issues. An ohmmeter is required for this test. If you don't have an ohmmeter, proceed to the next test.
Plug a jack cable in the Speaker Input of the Torpedo product. Unplug any other cable from the unit (except the power cord, if applicable). Power on the unit, if applicable.
Using an ohmmeter, measure the DC resistance between tip and sleeve of the cable. Check the measured value in the following list (small variations up to 10% are normal):
- Torpedo VB-101: 8 ohms
- Torpedo Studio, 4 ohms setting: 14 ohms
- Torpedo Studio, 8 ohms setting: 28 ohms
- Torpedo Studio, 16 ohms setting: 56 ohms
- Torpedo Live: 28 ohms
- Torpedo Reload, 4 ohms setting: 14 ohms
- Torpedo Reload, 8 ohms setting: 28 ohms
- Torpedo Reload, 16 ohms setting: 46 ohms
- Torpedo Captor, 4 ohms version: 14 ohms
- Torpedo Captor, 8 ohms version: 28 ohms
- Torpedo Captor, 16 ohms version: 46 ohms
- Torpedo Captor X, 8 ohms version: 28 ohms
- Torpedo Captor X, 16 ohms version: 46 ohms
B) Direct audio test
This test will let you compare the sound coming out of your amplifier in two cases: when used normally on a real speaker cabinet, and when used on the loadbox of the Torpedo product. This can be used to detect abnormal behavior of the amp when played on the loadbox, which can be a sign of a loadbox malfunction.
This test is not applicable to the Torpedo Reload.
Connect your amplifier to the Speaker Input of the Torpedo product. Connect a speaker cabinet to the Thru output of the Torpedo. This way, the amplifier is directly connected to the speaker cabinet, just as if the Torpedo product wasn't even there. Connect the line output of the Torpedo to your DAW.
Set the amp and DAW to record a track, then record a short guitar (or bass) sample. If possible, record a clean sound, then a distorted sound.
Then, unplug the speaker cabinet from the Thru output of the Torpedo. This will place the amp on the loadbox, instead of the speaker cabinet. Don't modifying any setting on the amp, Torpedo, sound interface or DAW.
Record the same short sample. Try to play it the same way, as much as possible.
From there, you can compare the two samples. Listen for volume rise or drop, frequency difference like loss or gain of treble, mids or bass, or different amount of distortion. Small differences in the sound are OK (because the loadbox don't have the exact same impedance as your particular speaker cabinet), but any significant difference may be an indication of loadbox issue.
Don't hesitate to send us the samples for analysis if needed.
C) Indirect audio test
This test will let you compare the sound coming out of your amplifier and real speaker cabinet, and the sound coming out of your amplifier when used on the loadbox of the Torpedo product. This can be used to detect abnormal behavior of the amp when played on the loadbox, which can be a sign of a loadbox malfunction.
This test requires a microphone.
Connect your amplifier to a speaker cabinet. Place a microphone in front of the cabinet, and connect it to your sound interface and DAW. Set the amp and DAW to record a track, then record a short guitar (or bass) sample. If possible, record a clean sound, then a distorted sound.
Then, connect your amplifier to the Speaker Input of the Torpedo product. Connect the line output of the Torpedo to your DAW. Don't modifying any setting on the amp. Record the same short sample. Try to play it the same way, as much as possible.
From there, you can compare the two samples. They will probably be quite different, because your own speaker cabinet may not be available in the Torpedo. You can however still listen for obvious defects: frequency difference like loss or gain of treble, mids or bass, or different amount of distortion.
Don't hesitate to send us the samples for analysis if needed.