Mark IV revA 12AT7 tube

[psycle_1]

If I don't plan on using the reverb, do I have to use a 12AT7 tube in V4 or can I just put a 12AX7 in there and call it a day?

 

[Bullen]

I used a 12ax7 in that slot when I had my "A". No problem.

 

[psychodave]

In my Mark IVa I think the 12AT7 sounds better than the 12AX7.

 

[scottcrud]

In my .50 Cal+ I took it out alltogether, a little known trick for .50 cals, it adds a little more gain.

 

[psychodave]

In my .50 Cal+ I took it out alltogether, a little known trick for .50 cals, it adds a little more gain.

Hmmm.

Is it safe to remove the tube altogether in, lets say, a Mark III or Mark IV?

 

[scottcrud]

Not sure about that, but I know it's safe to do in my .50 Cal.

 

[fatbagg]

Called mesa today, and they said 12ax7 for markIVA should be a 12at7, as the 12ax7 alwasy runs 100% gain, and with lose alot of clarity in your reverb, as well as make it super strong. The 12AT7 runs about 60% gain, keeping reverb beautiful and full. So I put the 12at7 in and wow...........................Theres the great reverb I was lookin' fo.

 

[psychodave]

Called mesa today, and they said 12ax7 for markIVA should be a 12at7, as the 12ax7 alwasy runs 100% gain, and with lose alot of clarity in your reverb, as well as make it super strong. The 12AT7 runs about 60% gain, keeping reverb beautiful and full. So I put the 12at7 in and wow...........................Theres the great reverb I was lookin' fo.

8)

 

[Russ]

Nice when things work as designed, huh?

 

[edward]

Not to mention the difference in gain, as was already stated, but equally importantly is an 12AT7 tube can handle more current than an 12AX7.

Reverb circuits designed for an AT7 *should* use an AT7 because that high-current is probably the reason that tube was chosen in the first place. Conversely, reverb circuits designed for an AX7 *can* safely use an AT7 since the latter both lowers the gain and has a higher current capacity (thus taxes nothing and is taxed itself even less). Whether you prefer the sound, OTOH, is up to you. In my DC5, I DO prefer the reverb with the AT7 over the AX& that it was designed to use.

Edward

 

[cradlefish]

Called mesa today, and they said 12ax7 for markIVA should be a 12at7, as the 12ax7 alwasy runs 100% gain, and with lose alot of clarity in your reverb, as well as make it super strong. The 12AT7 runs about 60% gain, keeping reverb beautiful and full. So I put the 12at7 in and wow...........................Theres the great reverb I was lookin' fo.

Thanks for getting this question answered. This should be a sticky as many well ask this question again.

I did swap out my 12ax7 for a NOS Philip 12at7 that i had lying around for years but never used it. Couldn't have picked a better time. I do noticed the difference!

 

[topcat0399]

Called mesa today, and they said 12ax7 for markIVA should be a 12at7, as the 12ax7 alwasy runs 100% gain, and with lose alot of clarity in your reverb, as well as make it super strong. The 12AT7 runs about 60% gain, keeping reverb beautiful and full. So I put the 12at7 in and wow...........................Theres the great reverb I was lookin' fo.

Thanks for getting this question answered. This should be a sticky as many well ask this question again.

I did swap out my 12ax7 for a NOS Philip 12at7 that i had lying around for years but never used it. Couldn't have picked a better time. I do noticed the difference!

Holy 6 year old thread resurrection Batman!


When my MkIV went to Mesa for rehab they called me and said
"We are changing out your 12AX7 in the reverb to a 12AT7, ok?"

Probably for warranty purposes. A 12AX always worked just fine.

 

[cradlefish]

Called mesa today, and they said 12ax7 for markIVA should be a 12at7, as the 12ax7 alwasy runs 100% gain, and with lose alot of clarity in your reverb, as well as make it super strong. The 12AT7 runs about 60% gain, keeping reverb beautiful and full. So I put the 12at7 in and wow...........................Theres the great reverb I was lookin' fo.

Thanks for getting this question answered. This should be a sticky as many well ask this question again.

I did swap out my 12ax7 for a NOS Philip 12at7 that i had lying around for years but never used it. Couldn't have picked a better time. I do noticed the difference!

Holy 6 year old thread resurrection Batman!


When my MkIV went to Mesa for rehab they called me and said
"We are changing out your 12AX7 in the reverb to a 12AT7, ok?"

Probably for warranty purposes. A 12AX always worked just fine.

I've only owned the Mark IV and first time owning a IV for about a 1 year now.As you know amps get bought and sold to different owners all the time. The 12ax7 does work fine but with the 12at7, the reverb sounds natural and better.