Topic: putting 12ax7 in a 12at7 slot?

[paradayms]

Question to all tube gurus here:

I have a hybrid tube preamp with 2 12at7 and 2 12ax7 slot. Was thinking of replacing the 12at7 with a 12ax7(if its possible). I just feel that it might become more to my likings medyo naninipisan ako sa tunog ng 12at7 based sa experience ko.

So if possible naman any downside/negative that might happen?

TIA mga kapdvd!:)

[paradayms]

PS: natatakot akong itry at baka may kung ano mangyari sa tubes or preamp hehehe

[Superman]

It is not a direct replacement. Also unless you're familiar with the circuit design, I do not recommend swapping them as this might damage either the tubes or the amp itself...

[dodie]

hindi ako guro bossing pero pataas ang gain nyan pag ax7 from at7. pwede siguro na 5751 instead of 12ax7 para mababa ng konti ang gain. bka kse makaapekto sa circuit pag hindi kinaya ang power. magkaiba power handling ng ax at at eh.

[Superman]

hindi ako guro bossing pero pataas ang gain nyan pag ax7 from at7. pwede siguro na 5751 instead of 12ax7 para mababa ng konti ang gain. bka kse makaapekto sa circuit pag hindi kinaya ang power. magkaiba power handling ng ax at at eh.

Agree...5751 is a replacement of 12AX7 with a lower mu...

[geevee]

Try e180cc and 5965. These can be substituted for 12at7.

[JojoD818]

PS: natatakot akong itry at baka may kung ano mangyari sa tubes or preamp hehehe

If you're bent on trying it, go ahead. You shouldn't have any problems electrically, but sonically is another story.

Question to all tube gurus here:

I have a hybrid tube preamp with 2 12at7 and 2 12ax7 slot. Was thinking of replacing the 12at7 with a 12ax7(if its possible). I just feel that it might become more to my likings medyo naninipisan ako sa tunog ng 12at7 based sa experience ko.

So if possible naman any downside/negative that might happen?

TIA mga kapdvd!:)

I suggest you roll your tubes for a couple of times only to get a road map on how it behaves with other tubes. It's meant to be fun but sometimes can be depressing too especially if your preamp does not play well with the tubes.

Heed the advices above, the 5751 is a darling.

Cheers

[paradayms]

Thanks for all the inputs mga sir.


So does it mean na pwede ko naman gamitin ang 12ax7 sa 12at7 slot? Since i dont have a 5751tubes. May excess lang ako na 12ax7 na i want to try. Kaya consult ko muna sa pdvd bago ko itry

[xtian_lugz]

In lay mans term 12at7 are the highest of gain then 12ax7 then 12au7.. You can only use lower but not higher for tube roll

[paradayms]

In lay mans term 12at7 are the highest of gain then 12ax7 then 12au7.. You can only use lower but not higher for tube roll

In short possible yung question ko sir?

[camoteque]

In short possible yung question ko sir?

Try mo na. Mura lang magpagawa pag nasira. Ha ha!

Kidding aside, if you're not sure about the circuit then don't. Kung malakas naman ang loob mo, subukan mo sandali lang kung magustuhan mo tunog. Magkaiba kasi current requirement and operating points ng mga tubes na yan.

Another solution is to replace the pre-amp or replace the circuit to accommodate 12ax7.

[JojoD818]

In lay mans term 12at7 are the highest of gain then 12ax7 then 12au7.. You can only use lower but not higher for tube roll

Wrong, it should be...

12AU7 - Low mu
12AT7 - Medium mu
12AX7 - High mu

mu = amplification factor

[JojoD818]

In short possible yung question ko sir?

naman...

[xtian_lugz]

Wrong, it should be...

12AU7 - Low mu
12AT7 - Medium mu
12AX7 - High mu

mu = amplification factor

Sorry master its been a while already... I just trying to access my stored memory of tubes.. but anyways you can only use lower mu..

[paradayms]

Hmm im a bit confused lang.
As per master jojod's post, he claims that its ok to use 12ax7 with a 12at7 slot.

While with sir xtian said that i can only use lower mu. Meaning cant be kasi 12ax7 has a higher mu than 12at7.?


Hehehe. Can someone pls confirm )

[JojoD818]

Sorry master its been a while already... I just trying to access my stored memory of tubes.. but anyways you can only use lower mu..

No worries, just setting it straight for the TS.

[JojoD818]

Hmm im a bit confused lang.
As per master jojod's post, he claims that its ok to use 12ax7 with a 12at7 slot.

While with sir xtian said that i can only use lower mu. Meaning cant be kasi 12ax7 has a higher mu than 12at7.?

Some designs owe their overall gain in preset parts of the circuit, and one is often based on the mu of the tube. Switching to a different mu tube will change this, worst case will be extreme microphonics, worse nfb and possibly, oscillation.

Hehehe. Can someone pls confirm )

Maybe you are waiting for someone else's confirmation, but afaik, all has been laid out for you now.

Good luck and happy tube rolling anyway.


Cheers

[xtian_lugz]

Based on my own experience i only use lower mu.. I dont want to gamble woth higher ones.. In my amp it uses 12ax7's and rolled with au's and at's.. And my other it uses at's so i just used au's never the ax's due to higher mu.. The only thing when you put a lower mu tubes it will lower down the gain of the amp lets say you listen at 10:00 on your current tubes and put a lower mu tube you'll now be listening to 12:00 more or less to compensate the loss gain.. These are all based on experience and the list that master jojo posted.

[tony]

because the actual gain of a circuit depends heavily on the B+
and the resistors used, interchanging 12ax7 to 12at7 and vice versa
is not usually a problem really, just watch out for the
resulting gains change and flavor if any and see if you like it...YMMV.....

Q: why higher B+?
A: because at higher B+ cathode current increases,
    a higher cathode current increases transconductance, therefore voltage gain...

[tony]

Try e180cc and 5965. These can be substituted for 12at7.

the 12AV7 is even yummier...

[tony]

12AU7 - Low mu
12AT7 - Medium mu
12AX7 - High mu

mu = amplification factor

this is half of the story, jojo has said a lot already...
one has to look at the circuit topology and circuit values,
operating points of the circuit to know the voltage gain....
since no two tubes are exactly alike, even within the same
envelope, dual triodes are not perfectly matched....
test a hundred tubes and you will be lucky to find one or two
that are perfectly matched....

so what the tube rollers find as changing sound flavors,
is nothing more than a shift in operating points...
different tubes will have different current draw in any given circuit,
and so the perceived change in sound character when you tube roll...

the tube data you find in datasheets are nothing more than
the statistical averages for tubes tested, your actual tube
can fall at either extremes of statistics, or it may fall inside
the average or bogey values....

just like any other amplifying devices, tubes follow the laws of
physics and thermodynamics...the amount of gas still left inside the
bottle also has an effect, i had a vintage EF86 die on me just recently,
in a matter of 3 days the gettering flash faded slowly and then it died..

[tony]

Based on my own experience i only use lower mu.. I dont want to gamble woth higher ones.. In my amp it uses 12ax7's and rolled with au's and at's.. And my other it uses at's so i just used au's never the ax's due to higher mu.. The only thing when you put a lower mu tubes it will lower down the gain of the amp lets say you listen at 10:00 on your current tubes and put a lower mu tube you'll now be listening to 12:00 more or less to compensate the loss gain.. These are all based on experience and the list that master jojo posted.

yes, with today's highish level program sources,
higher gains and so higher noise levels are not desirable,
use of the 12ax7 is confined to phono stages
and guitar preamps where high gains are necessary....

[tony]

triode circuits can be designed for maximum gain or maximum output swing...
these two criteria are possible and sometimes given in tube books...
you can not have both and so if i were to choose, i will go for maximum output swing...

[JojoD818]

logically, if one needs gain then one chooses the tube made to operate within the same parameters that would give the highest gain, on a linear point of view.

thanks to today's source levels and impedance, this put all the worries to bed.

[tony]

yes, jojo, that is why i use the 12ax7 for phono and guitar tube amps exclusively...

[meat_eater]

Try mo muna 12at na ibang tube, nos tubes, or current production pero ibang brand. Different tubes react to different amps. Try mo din galawin ung ibang tubes sa amp/preamp mo.... Baka ma compliment yung current 12at

[JojoD818]

yes, jojo, that is why i use the 12ax7 for phono and guitar tube amps exclusively...

and mic preamps, gaganda kaya boses ko pag tube mic preamp gamitin ko sa videoke?

meron ako dito reverb tank iniisip ko gawin reverb para sa mic preamp/mixer for videoke kaya lang baka hindi mapaganda ang boses ko eh...

[juneaki]

Mga masters, based from my back reading of this topic, 12ax7 can be substituted for 12at7, right? My Yaqin MC10T uses four 12AT7 and four EL34 (if I'm not mistaken). Should I substitute the china 12at7 with 12ax7, wala bang negative effect sa other tubes (EL34)?

Somebody is selling me two pairs (4 pcs) of Yamaha 12ax7A-7025 for php 2.5K, cheap ba o mahal?

[tony]

Mga masters, based from my back reading of this topic, 12ax7 can be substituted for 12at7, right? My Yaqin MC10T uses four 12AT7 and four EL34 (if I'm not mistaken). Should I substitute the china 12at7 with 12ax7, wala bang negative effect sa other tubes (EL34)?

Somebody is selling me two pairs (4 pcs) of Yamaha 12ax7A-7025 for php 2.5K, cheap ba o mahal?

i never knew that yamaha made tubes, toshiba and NEC did...
as to price, that depends on you, if you can afford it...
used na ba or NOS?...looks reasonable naman...

[juneaki]

i never knew that yamaha made tubes, toshiba and NEC did...
as to price, that depends on you, if you can afford it...
used na ba or NOS?...looks reasonable naman...

According to the seller it came from a Yamaha t100 soldano guitar amp. Slightly used, accordingly, just used the tubes when the amp was first tested, then pulled it out and used another brand of tubes.