insignificant11
New member
I bought a pair of NOS Mullard 12AT7s in an effort to open up channel 4 on my VH4S. It has too much compression IMO. I placed the tubes in V1 and V2 and it certainly did the trick. I also picked up an RCA 12BZ7 for the V3 position to maintain the nice saturated gain. One of the AT7s went microphonic and I scrapped both (replaced with JJ AX7s). Now I'm wary of their susceptibility.
As I understand it, AT7s are generally more vulnerable to microphonics. According to Wikipedia, "The charged elements in the vacuum tubes can vibrate and the motion would change the distance between the elements, producing charge flows in and out of the tube in a manner identical to a capacitor microphone." It sounds like the solution should be simple. Sturdier construction inside the tube.
I have a JJ AT7 to try, but I'd like to have a few tubes to try when I open up the amp. Can anyone recommend a good quality tube (NOS or otherwise) that would be less susceptible to microphonics? Am I wrong to think my remaining Mullard might crap out on me? I'd hate to be playing a show and have this problem come up.
VH4 tube layout (for the curious)
V1 Used by all channels
V2 Used by channel 4
V3 Used by channel 2/3/4
V4 Used by all channels
V5 Mixer and Send buffer
V6 Return driver (x2 for VH4S)
V7 Phase Inverter (x2 for VH4S)
As I understand it, AT7s are generally more vulnerable to microphonics. According to Wikipedia, "The charged elements in the vacuum tubes can vibrate and the motion would change the distance between the elements, producing charge flows in and out of the tube in a manner identical to a capacitor microphone." It sounds like the solution should be simple. Sturdier construction inside the tube.
I have a JJ AT7 to try, but I'd like to have a few tubes to try when I open up the amp. Can anyone recommend a good quality tube (NOS or otherwise) that would be less susceptible to microphonics? Am I wrong to think my remaining Mullard might crap out on me? I'd hate to be playing a show and have this problem come up.
VH4 tube layout (for the curious)
V1 Used by all channels
V2 Used by channel 4
V3 Used by channel 2/3/4
V4 Used by all channels
V5 Mixer and Send buffer
V6 Return driver (x2 for VH4S)
V7 Phase Inverter (x2 for VH4S)
