Decware ZTPRE v2 Owner's Manual page 9

O W N E R S M A N U A L
TUBE HEATER CURRENT
The three tubes of each channel have the heaters wired in series which means that ideally you want all three tubes
to match. It definitely means that where the factory tube compliment of 6N1P-EB tubs are concerned, you either
have to run all 6N1P-EB's or NONE at all. In other words, you can run 6922's, good strong 6DJ8's, or 7DJ8's. Some
Russian 6N23P's may also work well so long as they are relatively matched.
To be clear, you can NOT mix 6N1P's with 6DJ8 or 6922 or 7DJ8 or any other compatible tube at the same time
without side effects. The reason for this is that the 6N1P has a higher current draw on its heaters than all of the other
tubes mentioned. Running tubes with miss-matched current draws like this can have effects like having your 6N1P
prematurely fail, or having one or both of the other tubes run with starved heaters causing higher harmonic distortion
which some people would actually like.
Also, when it comes time to change tubes if you notice one tube that has grown darker in appearance then the
others it is an indication that it was a weaker tube or had a heater that drew more current causing it to run hotter or
both. This is not a real sonic issue, but deserves explanation in so much that if you want all your tubes to balance
out perfectly and last the same amount of time aka wear evenly, then make sure they all match. Match the sections
of each tube and then match the tubes themselves. This will have little sonic benefit except over time, in that you'll
get longer periods of time between tube changes.
The factory tube compliment of 6N1P-EB tubes have a rated life of 6000 hours.
Decware High Fidelity Engineering Co., East Peoria IL, USA www.decware.com