Interesting timing to this post as I just tried some different tubes on the input of the CAT JL-3 amps. The stock Yugo EI 12AU7 tube was every bit as musical and open as the Telefunken with the EI being more quiet and less prone to microphonics. This was a pleasant surprise.
The Telefunken 12AX7 was no better than the stock tube in this socket either. I do not know what brand the stock 12AX7 tube was but it was not Sovtek. I have had incredible improvements with Telefunken 12AX7's in Aesthetix phono and line stage products. It was just not to be with the CAT amps.
The huge improvement was with the Mullard GoldPin 6922 over the stock Sovtek 6922. The openness and smoothness of the Mullard was phenomenol. I wish I had some Telefunken 6922's to try here.
Jeffcott's final statement is really good advice.
You need to try many brands in your gear; there's just no way to know otherwise.
John
The Telefunken 12AX7 was no better than the stock tube in this socket either. I do not know what brand the stock 12AX7 tube was but it was not Sovtek. I have had incredible improvements with Telefunken 12AX7's in Aesthetix phono and line stage products. It was just not to be with the CAT amps.
The huge improvement was with the Mullard GoldPin 6922 over the stock Sovtek 6922. The openness and smoothness of the Mullard was phenomenol. I wish I had some Telefunken 6922's to try here.
Jeffcott's final statement is really good advice.
You need to try many brands in your gear; there's just no way to know otherwise.
John