kcline
Tube Audio Collector
From Dowd AWA Holding from TCA from Ludwell Sibley. In 1962 H. W. McCord Tube Engineer wrote an eight page " Coded Engineering Letter 653-#806" titled "Flicker Noise Test". Flicker noise is a very low frequency type noise. RCA was getting complaints about this. RCA compared RCA 12AX7 to the Telefunken 12AX7. and stated in the report as "usual Telefunken is our model", their 12AX7 was better then any RCA 12AX7 tested only nuvistors 6CW4 & 7895 came close. Testing procedure is very complicated and I do not have all of the report. Now RCA is not saying that the telefunken sounds better only that it tests better in the ficker noise testing. This paper was only read by tube engineering staff