The Preamp Tubes are Mullard CV-181s Branded GE 5692. These are an Excellent Sounding 6SN7 Variant Which is Why I Wired the Preamp For Them. They Draw Twice the Heater Current as Standard 6SN7s so I Chose a Transformer Spec'd to Handle Them. Note This Preamp is Tube Rectified. I Picked a Navy Branded 6X5 in Honor of our Son Aaron Who is Serving in San Diego, Aye Aye Sir!