I have a sovtek tube unit that I sometimes bounce through, or run some channels through.. I actually don't mind the sovteks.. I know compared to $100 Telefunkens or Mullards or GEs they probably suck... ANYWAYS, I'm looking to upgrade just for the sake of upgrading and hearing different sounds.. I can get groovetubes for $26 [which they say are copies of mullards], and Electro Harmonix for $16... Which would you guys pick? I don't want to spend more than $30 a tube just because I really don't need anything that costs more.
The GT 12AX7-R is the very same tube as the Tungsol (another EH brand) 12AX7. The prices are pretty similar with these tubes & both are better than the 12AX7EH.
What the 12AX7EH has going for it is low noise. If you already like the sound of your gear, it's the perfect tube to put in just to get a little better performance, but it's not going to transform so-so sounding gear the way a nicer tube can.
Eric is correct that the 12AX7EH (Electro Harmonix) is the same as the GT-12AX7R, however the GT is guaranteed for 6 months as all their tube are.
Your other choices are the GT-12AX7M (mullard copy) which is a long plate tube and while a little noiser than some others it is excellent in certain applications. Another long plate 12AX7 is the JJ-ECC803S which has the same charateristics as the GT mullard, but without the guarantee.
For low noise you cannot beat the JJ-ECC83S, although Groove Tubes sells the exact same tube (GT-ECC83) again with the 6 month guarantee.
Another great tube to try is the Sovtek 12AX7LPS.
For mic pres and high gain guitar amps the ECC83S is the way to go, but for low gain guitar amps or bass amps, the long plate tubes have more character.