The jamLink does not add any delay intentionally. The purpose of the jamLink is to reduce the amount of delay added at each end-point in the jam session so that each musician can synchronize his/her playing with the other just like they would if they were in the same room.
There is always delay between any two sound sources. For every foot of distance between two sound sources in a room there is 1ms of propagation delay (the time it takes the sound to travel through the air to get to the receiver). So, if you are jamming in a room with your friend and you are 10 feet away from his amp, it will take 10ms for his guitar notes to hit your ears. If you are 25 feet away, it will take 25ms for the guitar notes to hit your ears. Research shows that musicians can synchronize their playing effectively without noticing the affects of delay with up to 25ms of one-way audio delay between them. Beyond 25ms, the affects of delay start to become apparent, and the musicians will have to begin to compensate for it.
JamLinks add less than 4ms of delay at each endpoint in a session so that there is a significant amount of Internet distance the audio can travel and still make it to the ears of the other musicians within the 25ms threshold for in-the-room playing. Think of it like this: you have a 25ms one-way delay budget. If each jamlink adds about 4ms to the total one-way delay (4ms from the sender plus 4ms at the receiver), that gives you 17ms of Internet travel time to play with and still play tightly with the other musicians. From San Francisco, CA, average Internet travel times to Los Angeles run in the 12 17ms range. So a musician using a jamlink in San Francisco can play with a musician using a jamLink in Los Angeles (about 450 miles away), like they are in the same room together. At closer distances, this delay tends to be even lower.
If you are streaming locally captured audio from your pc to another person, your computer, sound card, operating system, and other factors can add 20ms or more of delay just capturing and packaging up your audio to be sent to someone else. You can readily see this when using skype, ejamming, or other real-time jamming or communication tools. So if each computer at each endpoint adds 20ms of delay, the 25ms one-way delay budget is exceeded even before the Internet travel time is added in. When you add that in, the total one-way delays get to be 50ms or more which is not conducive to actual jamming.
