I would guess that the tubes that don't "thump" are "thumping" the speakers too, its just at a slower rate, so slow that its inaudible.  You could verify this theory if you could look at the sub speaker during turn on, as the cone excursion should be quite visible.  Its not unusual for systems to need to be turned on in a specific way to avoid "thumps", whether audible or not.  Turning the volume down before turn on (if you can and its easy) is a good practice to get into.


Dan

Thanks Dank and Lord Soth for your recommendations.
I am and always have been (to quote Mr. Spock ) aware of the proper audiophile turn on sequence. I only broached the question because the thumping didn't occur with the three stock 6N1P-EV tubes (although I haven't put them back in since I got my uber expensive Telefunkens to see if things have changed in the CSP+ itself).

My powered sub has no manual on/off switch; it has an auto sensing circuit to turn on/off with the audio signal. I believe the Telefunken/CSP+ combination must be creating an audio pulse at turn on that the 6N1P-EV/CSP+ combination does not and that's the reason for the thumping with the Telefunken's. I imagine Steve or Kevin might have far better technical insight into this. I will ask them both in due course.

The Taboo III also has one of these NOS Telefunkens and even with the volume wide open at turn on   , there is no thump through the main speakers.

Also, took the NOS Telefunken tubes and put them in my Woo WA2 (also an OTL preamp like the CSP+) and there was no thump through any of my earphones with the WA2 volume at off and 9 o'clock on turn on.

Addendum: 6/20/13, 5:20pm

In CSP+ Driver positions, I replaced my matched pair of Telefunken E88CCs with stock 6N1P-EVs and left one Telefunken E88CC in Input tube position. No thumping during turn on whether volume at 0 or above. Looks as if CSP+ and Telefunkens have an issue in Driver positions.

I spoke to Steve yesterday about the turn-on thumping, he confirmed what I suspected from reading up on the SRPP circuit. The CSP+ preamp's SRPP circuit places a heavy demand on tubes in the driver positions. It takes a good strong tube pair to work in the CSP+ driver positions. No doubt this is why Steve prefers the strong Russian 6N1P-EV tubes. That's not to say other tubes don't work as well, my Amperex 7308 work fine, just not my expensive Telefunken E88CCs (6922).

To read more on SRPP:
https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1150678070
http://www.freewebs.com/valvewizard1/srpp.html

And that's the way it is.