Ph 14 phone amp

Which tube or tubes  affects the sound the most in the in PH 14

there are 3 tubes in a PH14, the tube closest to the input is always the most important and should be tested for low-noise,
most tube dealers offer this option.
Also in some cases the PH14 has more than usual gain, so replacing either the first or all three tubes with 5751 works very well

Thanks you for that.