I don’t know where this nonsense about 6DJ8, E88CC’s not working in the BHK PreAmp came from. The amp is designed for them and they work fine. I have used many of these over the years with excellent results. Some can be noisy and those should be disregarded. Not all tubes are equal. Many supposed NOS are actually “Pulls” from old equipment. They may have many hours on them or none. Invest in a Tube Tester and you’re covered. I paid $150 Canadian for my B&K Dyna 606 and it’s like new and has saved my butt many times. My favorites after 3 years with the BHK Preamp are the Telefunken 6DJ8’s.