I did use apple lightning cable connect with pioneer xpa700 USB port. It can connect with my iPhone 6 Plus but only up sampling to 48kHz and can't up sampling to 96, 192 or5.6M. I am questioning if we insist up sampling to 96' 192 or 5.6M we have to use camera kit to micro usb ?

Do you need apple camera adaptor to contact pioneer xpa 700 micro usb in order to get up sampling or just use lightning cable to usb to pioneer?

Thank you your suggestion of the driver tube, would you pls. Recommend the low noise power tube. I am using sovtek 6as7g, could you pls. Commend!

I am using sovteck 6as7g very musical and power better then 6080. The problem is the quality is not sure fortunately I have more then 24pcs. Of sovteck tubes in stock but only few tubes are low noise.

The noise come from the poor tube , Change the good tube with low noise can be improved. Don't use damper if the tube is getting weak. It doesn't help.

If the signal tube getting weak the noise can be happen. It is easy to know which signal tube is the problem, try to use a pencil light rubbing the tube you can hear the noise in the headphone.

I have the same problem as you, the problem may come from the tube or the resistor. I did I try to change the tube the problem has been improved so I think OTL amp the tube quality is very important, all the tube sound will direct to the headphone.[/B]. I just bought this amp last month so I...