[Nick Dangerous]

What a shocker. I arrive at work this evening and my girlfriend says she didn't like the ITT 7025 and put in "the Raytheon".

I FLIPPED OUT because the Raytheon she used had yellow lettering on it. The only Raytheon's I have that fit that description are 12AU7's for my Bottlehead Foreplay preamp. AAAAHHHHH!! UNPLUG!!! UNPLUG!!!

Luckily, nothing melted down. I don't know how the 12au7 differs from the 5751, but inadvertently swapping tubes of the wrong kind can blow up your equipment.

Here's the interesting part:

Donna actually has very good ears. Although she didn't enter the world as a bona-fide audiophile, my habit is rubbing off on her big time.

She told me that the yellow Raytheon 12au7 sounded WONDERFUL in the MG Head OTL, except that it was a little quieter. She reported that the sound quality was practically identical to the Raytheon 5751.

Hmmmmm. Interesting. The Raytheon 12au7 is a cheapie. If 12au7's work in the Head, this would open up a whole new world of tube rolling. I'm assuming a few mods would be necessary to "make it safe"... but I dunno.

Anyone know? Could be a cheap source of great tubes!

 

[Joe Lau]

Yes ! 12AU7 can plug in MG-Head /MG-Head OTL with no any damage but only change in Sound charateristic. It will lower the noise (Lower gain) , Lower the nfb ....... Just try it !

 

[Nick Dangerous]

HA HA HA!!!!

MUAH HAH HAH HAH!!!

This is gonna be one kickin' tube rolling review! I'm almost done with it... so hang in there.

 

[carlo]

mr lau,

seriously? how about 12at7s? ecc82s/e82ccs?

thanks,

carlo.

 

[Joe Lau]

Sure No problem ! 12AT7 is just between 12AX7 and 12AU7.

 

[kelly]

So ... you can use anything that starts with a 12 and ends with a 7?

I'm going to have to learn this whole thing somehow.

 

[chych]

Woha, this just opens the tube thing even more...!

Are you absolutely certain we can do this Joe Lau? These tubes vary from one another... I know that things like the 12AX7 and 5751 are very similar but I'm pretty sure the 12AU7 and 12AT7 are much different...

 

[Nick Dangerous]

Donna is correct. The Raytheon 12au7 sounds very close to the Raytheon 5751... more so than any other 12au7 I have.

The 5751 is still the best in my collection, though.

So far.

 

[timoteus]

Quote:

Originally posted by chych Woha, this just opens the tube thing even more...! Are you absolutely certain we can do this Joe Lau? These tubes vary from one another... I know that things like the 12AX7 and 5751 are very similar but I'm pretty sure the 12AU7 and 12AT7 are much different...

The 12AX7 has the most gain
The 12AT7 has medium gain
The 12AU7 has the least gain

Using the 12AX7/5751 I have never had the volume even close to 12 O'Clock so there is a lot of playing room left if you were to use the 12AT7 or 12AU7. I suppose you could prematurely burn out your lower gain tubes or power tubes if you were driving them real hard. Joe says go for it! Maybe there is a sleeper out there that hasn't been tried.

I'm going to look up the variants of these tubes and post them. More options for everybody.

 

[chych]

Hmm, what about the 12AV7?

 

[timoteus]

In no particular order here are some variants of the three tubes:

12AX7, ECC803S, ECC83, 7025, CV4004, 5751, 6681, 12AX7A, 12AX7WA, E83CC

12AT7, ECC801S, ECC81, CV455, CV4024, CV455, AT900, B739, E81CC, 6201, 12AT7WA, 12AT7WC

12AU7, 5963, B749, ECC802S, ECC82, 7316, CV4003, 12AU7WA, 12AU7A, 6680, 6189, 6189W, CV491, 5814A, E82CC

Please verify these numbers before you try any of these in case I made a typo or my information is bad. I don't want to be responsible for a blown amp or a total world conflaguration.

I'm not sure about the 12AV7 but some variants are E180CC, 5965, 6N1P, 7062, 6829, 6414. I'll leave this one for Joe.

 

[Dusty Chalk]

The only problem (in general) might be if one of the higher gain tubes overdrives a later stage. It sounds, though, that the MG Head can take it, and that this is not the case specifically in this case.

 

[kelly]

Timoteus, how may I pay homage to you and ask the favor of knowledge as it is relevent to the PCL805 tube?

 

[Audio-Me]

I read on Audio Asylum that Telefunken 12AX7 are smooth and warm sounding. Do they work well for the MG Head?

 

[carlo]

i heard one (diamond bottom, definitely authentic, early production) on my unit for (a really sweet) week, but they tend to be relatively pricey. haven't had a lot of experience with rolling the tubes on mine though.

nick, what tubes can we look forward to reading about in your comparison?