woodbutcher65
Well-known member
- Joined
- May 4, 2018
- Messages
- 619
- Reaction score
- 245
Yes, it really is.
The V1 socket is both the input for the whole amp and also the clean (green) stage channel.
It has the highest gain per stage of any stage in the amp, with 220K plate resistors. (Also true of V3A, which feeds the cathode follower that is V3B.)
The value of the plate resistor is the driving factor in how much gain that stage has. 100K is a typical value. 220K is pretty crunchy. 330K is insane gain and you won't find many tubes that are up to the task.
Side note: Most examples of the dual/triple recto schematics you find online don't draw in V1B, the second half of the V1 tube. It's quite a glaring oversight. There are schematics that have it. But you have to look for them.
Sticking a 12AX7 tube in V1, selecting the clean channel in pushed mode, and cranking every control, and controlling the loudness with the output control, is a great way to test your spare tubes for noise, gain, microphonics, and various kinds of instability.
This channel demands so much out of a tube that if the tube doesn't misbehave with all controls maxed out, with you playing at full guitar volume, then you can be pretty well assured that that tube is going to be just fine in any position in most any amp.
Tubes that show problems in the green channel often work just fine in any other socket, or in any other amp.
V3 can also be used for checking tube quality but getting access to the V1 socket is more convenient and works as well. Just pull the outer pair of power tubes and move the speaker plug to the next higher impedance jack if you can. (If you have an 8 ohm cabinet, plug it into the 16 ohm jack if you pull a pair of output tubes. This compensates for the changed load.)
The V1 socket is both the input for the whole amp and also the clean (green) stage channel.
It has the highest gain per stage of any stage in the amp, with 220K plate resistors. (Also true of V3A, which feeds the cathode follower that is V3B.)
The value of the plate resistor is the driving factor in how much gain that stage has. 100K is a typical value. 220K is pretty crunchy. 330K is insane gain and you won't find many tubes that are up to the task.
Side note: Most examples of the dual/triple recto schematics you find online don't draw in V1B, the second half of the V1 tube. It's quite a glaring oversight. There are schematics that have it. But you have to look for them.
Sticking a 12AX7 tube in V1, selecting the clean channel in pushed mode, and cranking every control, and controlling the loudness with the output control, is a great way to test your spare tubes for noise, gain, microphonics, and various kinds of instability.
This channel demands so much out of a tube that if the tube doesn't misbehave with all controls maxed out, with you playing at full guitar volume, then you can be pretty well assured that that tube is going to be just fine in any position in most any amp.
Tubes that show problems in the green channel often work just fine in any other socket, or in any other amp.
V3 can also be used for checking tube quality but getting access to the V1 socket is more convenient and works as well. Just pull the outer pair of power tubes and move the speaker plug to the next higher impedance jack if you can. (If you have an 8 ohm cabinet, plug it into the 16 ohm jack if you pull a pair of output tubes. This compensates for the changed load.)
