6SN7 tube question


Hello,

I need to replace the tubes in my Rogue 99 line preamp, which uses the 6SN7 tube. I was looking at an online seller who offers the following options with an affordably priced 6SN7 for a few dollars extra:

1. Balanced Triodes
2. High Gain
3. Low Noise and Microphonics
4. Matching

Options 3 and 4 seem most desirable for a preamp. My question is whether it is worth the extra few dollars (approx. $6 per tube) or is it just a pure marketing ploy to get suckers like me to drop more dough?
actusreus
How do you check the filament voltage?
It would have to be checked by touching or connecting the probes of a voltmeter (or a multimeter set to measure volts) to the filament pins of one or more of the tube sockets, under the chassis, or to some other circuit points that are connected to those pins. (To assure a meaningful result the measurement should be done while the tubes are in their sockets, as opposed to removing the tubes and accessing the socket pins from above the chassis). Lethal voltages will be present on some of the other pins on those sockets, as well as elsewhere under the chassis. And if the probe tips were to momentarily come into contact with two adjacent pins simultaneously damage to the component may occur. So it’s a task that is best left to a qualified technician.

Also, regarding the references to 6.3vac and 7vac, many designs provide dc voltages to the tube filaments rather than ac. In those cases, of course, the meter function should be set for dc volts rather than ac volts, and the probes should be connected with appropriate +/- polarity.

Best regards,
-- Al

The filaments of a 6SN7 are on pins 7 & 8. If the supply is DC it is probably regulated and spot on unless there is a problem. AC supplies generally depend on the incoming line voltage. If it is consistently high then the filament voltage could be too.

There are octal  adapter with all pin out, with your amp/preamp switch off,plug the adapter and plug your tube on top of the adapter.Use alligator clip on your multimeter's volt AC and clip them the pin 7 & 8.switch on your equipment and if the reading is about 6.3 volts?that is correct.but if the reading is not 6.3~ ,switch off and turn your meter to dc volts.Switch off your gear before removing those clips.6.0  to 6.7 is normal  for tubes with 6.3 filament. 
You are looking for a platinum matched tubes which are balance in Gm & Ip, non-microphonic and very  low noise.It's worth the money if your gear is in push pull configuration,but if it's in cascade,you just need  a very low noise and non-microphonic.