Geiri
Well-known member
Is there any particular reason that there is a 12at7 preamp tube in V4 on my mk4 ?? The rest in there is 12ax7. Will it be ok if I change that to 12ax7 ?
Thanks
Geiri
Thanks
Geiri
12at7 Please help.
- Thread starter Geiri
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V4 on your amp is section 1= Second Lead high gain stage
section 2= Reverb Send
It is common to see people use 12at7s in V4 and V5 in your amp as well as other amps, although they might be in different slots on other amps, the P.I is usually after all the preamp tubes, the last 12*7 in the group, as some believe they make a better reverb driver and a better Power tube driver A.K.A. phase inverter or P.I..
With that said if the amp calls for all 12ax7s you may of course do so. It will NOT hurt your amp. There is a slightly lower gain (60)and higher current in an aT7 versus the higher gain(100) and less current in the aX7. If you bought this amp used someone replaced the Ax7 withthe aT7 with the above belief. I am not denying there is a difference, some claim to hear angels, I have not heard using this theory. I have put some of the best aT7s in the same places and if I put some of the best aX7s in the same place I believe I get the same results. Better said " There may be a difference, yet when I put back the aX7, there may also be a difference.
I have not heard any real differences to my "dog ear" that would justify using an aT7. Yet some of the most knowledgable people in the forum can hear the "huge" differences. I like to experiment, yet I can get both tubes that test almost perfect and swap out each one, and think I hear a difference. Yet if I record that sound, swap the tube, record the next tube sound with no settings changed, I still go back to the aX7. This is my experience. I hope this helps you.
/cheers
section 2= Reverb Send
It is common to see people use 12at7s in V4 and V5 in your amp as well as other amps, although they might be in different slots on other amps, the P.I is usually after all the preamp tubes, the last 12*7 in the group, as some believe they make a better reverb driver and a better Power tube driver A.K.A. phase inverter or P.I..
With that said if the amp calls for all 12ax7s you may of course do so. It will NOT hurt your amp. There is a slightly lower gain (60)and higher current in an aT7 versus the higher gain(100) and less current in the aX7. If you bought this amp used someone replaced the Ax7 withthe aT7 with the above belief. I am not denying there is a difference, some claim to hear angels, I have not heard using this theory. I have put some of the best aT7s in the same places and if I put some of the best aX7s in the same place I believe I get the same results. Better said " There may be a difference, yet when I put back the aX7, there may also be a difference.
I have not heard any real differences to my "dog ear" that would justify using an aT7. Yet some of the most knowledgable people in the forum can hear the "huge" differences. I like to experiment, yet I can get both tubes that test almost perfect and swap out each one, and think I hear a difference. Yet if I record that sound, swap the tube, record the next tube sound with no settings changed, I still go back to the aX7. This is my experience. I hope this helps you.
/cheers
Geiri
Well-known member
Thank you lerxstlee
The reason I'm asking is that I tend to use a lot of gain on the lead channel and was trying to get the tone with a little less noise. So due to some recommendations I put a tung sol in V1. It sucks big time, The only thing that changed was the amount of gain got less and the noise too but to get my tone back to where I like it I had to boost the gain and drive settings and in doing so the noise level returned to it's usual state. So this in it self was rather futile
. Then I went reading here on the forum about tubes and pulled out the chassis to find out what was in there and thats when I discovered the 12at7. There is also written above all the preamp sockets 12ax7 exept for V4 where it says 12at7. I also got my self a brand new quad of JJ's 6l6 and now the tweed mode will not work. It's very weak sounding like there is only the preamp playing and the poweramp is somewhere else watching porn. There was a quad of sovteks in the poweramp and everything worked fine with those.
I guess it's tech time for the amp.
And the lesson is, if it ain't broken then just play the friggin thing.
The reason I'm asking is that I tend to use a lot of gain on the lead channel and was trying to get the tone with a little less noise. So due to some recommendations I put a tung sol in V1. It sucks big time, The only thing that changed was the amount of gain got less and the noise too but to get my tone back to where I like it I had to boost the gain and drive settings and in doing so the noise level returned to it's usual state. So this in it self was rather futile
. Then I went reading here on the forum about tubes and pulled out the chassis to find out what was in there and thats when I discovered the 12at7. There is also written above all the preamp sockets 12ax7 exept for V4 where it says 12at7. I also got my self a brand new quad of JJ's 6l6 and now the tweed mode will not work. It's very weak sounding like there is only the preamp playing and the poweramp is somewhere else watching porn. There was a quad of sovteks in the poweramp and everything worked fine with those.I guess it's tech time for the amp.
And the lesson is, if it ain't broken then just play the friggin thing.
Early Mark IVs specified a 12AT7 as the reverb tube. Later versions went to the 12AX7.
Putting a higher gain 12AX7 in its place will probably increase the noise level. The 12AX7 has 40% more gain than a 12AT7.
Here's a chart for pre-amp tube gain factors:
http://www.diyguitarist.com/GuitarAmps/SD-Convertible/patgf1.htm
Hit your "back" button to return to the Forum.
Does your amp still sound weak in Tweed Mode if you re-install the Sovteks?
Putting a higher gain 12AX7 in its place will probably increase the noise level. The 12AX7 has 40% more gain than a 12AT7.
Here's a chart for pre-amp tube gain factors:
http://www.diyguitarist.com/GuitarAmps/SD-Convertible/patgf1.htm
Hit your "back" button to return to the Forum.
Does your amp still sound weak in Tweed Mode if you re-install the Sovteks?
I did notice on your manual there was listing of power amp tubes. There were no listings for the preamp tubes.
If it does suggest an AT7, then there might be a reason. Alot of Fenders use the aT7s for a P.I.. I will not comment on any tubes as for every tube I likethere are ten that will post something down the line of OMG those tubes XXXXX. I let the players love the tubesthey want to love. I know which ones are reliable and I also have my favorites. If someone wants a certian tubethat is fine. I will put the correct value tube(s) in, yet I also know which tubes make me the most money. How,well the ones that need to be replaced over and over. The ones that have a 58% quality variance, and yes there
are those tubes out there. Just grab a copy of Apen pitmans "the tube amp book". You can see what tubes he would
get and basically would have to throw out half or more of them after screening them. There are some tubes with
very low percentages that would surprise most people.
My suggestion is to stay with the tubes that the manufacturer recomends for each socket. A good tube at that.
/best to you
I did notice that V1 suggest a "shield" do you have the shield on V1?
If it does suggest an AT7, then there might be a reason. Alot of Fenders use the aT7s for a P.I.. I will not comment on any tubes as for every tube I likethere are ten that will post something down the line of OMG those tubes XXXXX. I let the players love the tubesthey want to love. I know which ones are reliable and I also have my favorites. If someone wants a certian tubethat is fine. I will put the correct value tube(s) in, yet I also know which tubes make me the most money. How,well the ones that need to be replaced over and over. The ones that have a 58% quality variance, and yes there
are those tubes out there. Just grab a copy of Apen pitmans "the tube amp book". You can see what tubes he would
get and basically would have to throw out half or more of them after screening them. There are some tubes with
very low percentages that would surprise most people.
My suggestion is to stay with the tubes that the manufacturer recomends for each socket. A good tube at that.
/best to you
I did notice that V1 suggest a "shield" do you have the shield on V1?
Geiri
Well-known member
Yes there is a shield on V1
And no I cannot try the sovteks since I clumsily broke one when I pulled them out. The tweed mode has been acting up every once in a while and that was the reason for the tube change in the first place, to see if the sovteks were the problem.
I guess it's time for an overhaul.
And no I cannot try the sovteks since I clumsily broke one when I pulled them out. The tweed mode has been acting up every once in a while and that was the reason for the tube change in the first place, to see if the sovteks were the problem.
I guess it's time for an overhaul.
Geiri
Well-known member
The ones that were in there were, V1 jj, V2 and V3 are electro harmonix the rest is mesa labelled. So I guess I'll leave the V4 be for now and install some jj's in V1,2,3 and 5
How is that going to sound ?
How is that going to sound ?
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