Tube Break-In sound character change

50-100 Hours will do the trick...you'll give up a little slam but more than make up with transparency, better tonal coloring and texture...
Larry

You replaced 2A3's with 300B's??? I dont' think break-in is at issue here, but compatibility.

For tubes to fully break-in takes at least 75- 100 hrs.
Four hrs. is not nearly enough time!! I guarantee you that you'll hear a big difference after 50 hrs.

>>You replaced 2A3's with 300B's??? I dont' think break-in is at issue here, but compatibility<<

They are 2.5v 300B's made to replace 2A3's.

www.sophiaelectric.com/pages/se/princess_300b_25v.htm

Thanks Larry & Eee. I can already hear it is a bit better. As I mentioned, I just thought that out of the box they would be better than what it was replacing... I suppose not.

The 300B will definitely sound different than the 2A3, but whether they "beat" the 2A3 is a matter of taste. Even after the 300B has broken in you may find you pefer the sound of the 2A3.

Hi,I changed the driver tubes on my cat amps to 40 year old nos amperex and telefunken,they sound a tad forward and aggressive after 20 hours.Will they break-in and how long will it take.

Thanks

Note: EH 2A3 and other popular Russian 2A3 plus the current bigger sized Shuguang 2A3 are all 300B/2.5V by design. Cary amplifier and many other current 2A3 amplifier makers are deisgning the amplifier at much higher plate voltage than a typical RCA standard 2A3 is calling for.

The majority of today's 2A3(actually 300b/2.5V)have already changed the landscape of 2A3 for good. RCA 2A3 is of smaller power thus becoming less less due to the supply of real RCA format 2A3. Sophia Electric is making a real RCA formate 2A3 mesh plate, however, the demand for it, is less than its more power 300b/2.5 cousin for most 2A3 users. The lack of affordable good sounding speakers and speaker drivers are the reasons.

Though this article regards the actual 300B; you'll probably find the info on burn-in helpful: (http://www.stereophile.com/features/229/index2.html)