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View Full Version : 12AX7 or 12AU7 which one is the preamp tube?


teisco
August 22, 2018, 11:02 AM
Got a Chinese integrated tube amp (no schematics) and it uses two 12AX7's and two 12AU7's and I would like to know your thoughts as to which tube set is used for the preamp section.
Shadowfax
August 22, 2018, 11:58 AM
My VAC Pre has the same so I will also be interested in the answers.
joeinid
August 22, 2018, 12:02 PM
12AU7 has been used in my line level preamps (no phono) like my BHK signature preamp and LTA MZ2. I think both are actually used in McIntosh tube preamps.
jdandy
August 22, 2018, 12:52 PM
teisco.......The 12AX7 has the most gain, where the 12AT7 has less gain, and the 12AU7 has the lowest gain of the three vacuum tubes. Often where 12AU7 tubes are used in conjucnction with 12AX7 tubes the 12AX7's are the gain stage tubes and the 12AU7 tubes are employed to control the output impedance. Not having a schematic makes it difficult to determine how the tubes are used in an amplifier's circuit topology.
octadyndude
August 22, 2018, 08:59 PM
It all depends on your speakers IMO. I say that because when I had Dyn C1's with an Octave V110 I found Mullards and Telefunken sounded the best. The Mullard has a quite warm sound and Telefunken less slightly warm but better detail. When I got the Raidho's they sounded horrible. Gec and original Hytrons sounded the best. That said I didn't care for those Mullards and Telefunken with the Raidho's at all. The GEC and Hytrons are the least warm but much more detailed. These were tubes I didn't like with the Dyn's. All tube manufacturers have a 'house' sound just like speakers. Current Gold Lions seem to be somewhere in the middle for a lot less money.
Shadowfax
August 22, 2018, 09:37 PM
Current Gold Lions seem to be somewhere in the middle for a lot less money.

My latest sets were just that and the sound is great. I got matched pairs of each.
blackdog
August 22, 2018, 09:46 PM
If you were more specific as to the make and model, it might be easier to determine what tube does what.
Does the amp have built in phono?
octadyndude
August 22, 2018, 10:34 PM
Brian the Gold lions are a great value for the money. The other tubes I mentioned are going to come with a premium price. Folks need to try them and see what their preferences are in SQ.
teisco
August 23, 2018, 11:27 AM
I just ordered a vintage set of Mullard 12AX7's from an AK member so will see what happens when they arrive. Thanks all for the input.