[GlowWorm]

I wonder if someone would be so kind as to list (or provide link to) all variations of the 12AX7, and 6BQ5 vacuum tubes (compatible w/ MG-Head)? Thanks.

 

[daycart1]

You need the amazing tube variation utility available for free from www.duncanamps.com

Keep in mind that Joe Lau has verified that 12AT7 and 12AU7 are safe for the MGH as well and they have been ear-tested by many head-fiers!

 

[MichaelFranks]

www.vacuumtubes.com gives a list of alternates, as mentioned any 12a?7 tube (and those comparable) should work fine.

 

[GlowWorm]

Thanks guys for the links, they were very helpful. I think I'm gonna try a 12AU7. Any recommendations?

 

[MichaelFranks]

12au7's are (relatively) cheap! You should be able to sample quite a few on a limited budget. Check this thread for a comparison of the various gains.

You might want to try out several of the various types. I can put together a sampler for you if interested, send me a message or pm.

 

[Orpheus]

Quote:

Keep in mind that Joe Lau has verified that 12AT7 and 12AU7 are safe for the MGH as well and they have been ear-tested by many head-fiers!

yes, but Joe Lau's very inconsistent--about this issue and many others. he did say both kinds are safe, but previous to that comment he also said the mg head needed to be modified by adding some resistors for the 12au7. maybe you can do a search and see how to do it for yourself.

anyway, i would stick with the 12ax7's and 5751's as they are directly compatible and work fine.

 

[ServinginEcuador]

Not all replacement tubes are as plug and play as one would suspect. I have been finding some info that points to the fact that the plate dissipation and such of the 12ax7 is higher than most other 12a?7 variants. This will cause some problems. Let me try and dig up the link with the skinny on this.

 

[GlowWorm]

Thanks Doug, I would appreciate it very much if you could get back to me with any further information.

 

[ServinginEcuador]

Here's one site with some info:

http://www.aikenamps.com/TI_Aiken_Q&A.html

Do a search within this window on 12ax7 and see what this guy says. bAsically, the plate and cathode resistors need to be changed sometimes when swapping tubes, or you won't get the optimum sound. It wasn't plate dissipation as much, but the 12AU7 has more than two times the dissipation of a 12AX7.

 

[MichaelFranks]

Quote:

Originally Posted by Orpheus anyway, i would stick with the 12ax7's and 5751's as they are directly compatible and work fine.

Was the MG Head designed to be used with other variants? No, in Joe's own words "the sound is unforeseen" (in reference to the otl 32) but you don't have to worry about your MG Head exploding.

Let your own ears be the judge. Again, exotic 12ax7 and 5751 tubes can empty your pockets quick!

 

[Orpheus]

?

just letting you know it was designed to be used with a 12ax7, and Joe Lau specifically said it has to be modified to accept a 12au7. no, it won't explode, but it will also not perform as well. if you like the sound fine, but you're intentionally underperforming the unit for your sound, which is fine too.

i have mic preamps that intentionally "starve" the tube of voltage on purpose to produce a nicer sound. it clearly results in distortion, but people like it (manual states it adds harmonics.) anyway... do as you will. just know the amp is not performing maximally.

 

[MichaelFranks]

Quote:

Originally Posted by Orpheus ? just letting you know it was designed to be used with a 12ax7, and Joe Lau specifically said it has to be modified to accept a 12au7. no, it won't explode, but it will also not perform as well. if you like the sound fine, but you're intentionally underperforming the unit for your sound, which is fine too. i have mic preamps that intentionally "starve" the tube of voltage on purpose to produce a nicer sound. it clearly results in distortion, but people like it (manual states it adds harmonics.) anyway... do as you will. just know the amp is not performing maximally.

Thanks! It says that in the manual!

 

[Orpheus]

oh, okay. heh he.

i think i just misinterpretted your previous comment. sorry.

 

[tbdoah]

I personally would recommend any triple mica 5751 for an MG Head. I had my best results with my amp when I paired a GB-5751 and some early russian EL-84s.

 

[daycart1]

Quote:

Originally Posted by Orpheus ? just letting you know it was designed to be used with a 12ax7, and Joe Lau specifically said it has to be modified to accept a 12au7. no, it won't explode, but it will also not perform as well. if you like the sound fine, but you're intentionally underperforming the unit for your sound, which is fine too. i have mic preamps that intentionally "starve" the tube of voltage on purpose to produce a nicer sound. it clearly results in distortion, but people like it (manual states it adds harmonics.) anyway... do as you will. just know the amp is not performing maximally.

OK, I see your point. If one is not going to do a bunch of experimenting, it would be smart to start with the spec tube.

But even the 5751 has notably different gain from the 12AX7..... I actually didn't much care for the one 12AU7 I tried with the MG Head, but one or two others who rolled a bunch declared a 12au7 to be their favorite IIRC (and with no mods to the amp). And the tube I found best sounding (over

a few 5751) was a Telefunken 12AT7w.