If you suspect your console is JTAG, do not connect it to Xbox Live. Microsoft specifically detects the JTAG hash mismatch and will ban your console within hours. RGH consoles have a slightly better (but still risky) chance of staying undetected if using a stealth server.
Some RGH installs are "silent" (using X360Run or Ace V3 chips), so absence of noise does not guarantee JTAG. Presence of noise guarantees RGH.