Any decent 12AU7 recomendations?

I'm tube rolling my Yaqin MC13s which has two 12AX7s in V1 & V4 and two 12AU7s in V2 & V3.

So far I've tried Svetlana Winged C 12AX7s and Mullard 12AU7S. I found the Mullards to be really disappointing with a closed in muffled sound.

However, when I put the Svetlana's into V2 & V3 and used the old chinese 12AX7s in V1 & V2 I got a really nice sound, open, smooth and detailed.

I would stick with this but I'm concerned that using a 12AX7 in place of a 12AU7 may harm the amp?

So can I ask if it is OK to keep using Svetlana's in this way. Any concerns?

If not any recommendations for a decent 12AU7?

Quote:

---

Originally Posted by Intenso

I'm tube rolling my Yaqin MC13s which has two 12AX7s in V1 & V4 and two 12AU7s in V2 & V3.

So far I've tried Svetlana Winged C 12AX7s and Mullard 12AU7S. I found the Mullards to be really disappointing with a closed in muffled sound.

However, when I put the Svetlana's into V2 & V3 and used the old chinese 12AX7s in V1 & V2 I got a really nice sound, open, smooth and detailed.

I would stick with this but I'm concerned that using a 12AX7 in place of a 12AU7 may harm the amp?

So can I ask if it is OK to keep using Svetlana's in this way. Any concerns?

If not any recommendations for a decent 12AU7?

---

I have a pair of these in my power amp. Really ballsy, rhythmic full sound, great for rock and blues. Mullards much more polite IMHO.

https://www.upscaleaudio.com/product...que-12au7-6189

Quote:

---

Originally Posted by Intenso

I'm concerned that using a 12AX7 in place of a 12AU7 may harm the amp?

So can I ask if it is OK to keep using Svetlana's in this way. Any concerns?

---

Without seeing a circuit diagram it's difficult to say exactly what will happen when using 12AX7s instead of 12AU7s but generally valve amps are pretty robust and there's a good chance that no harm will come of it. Worst case scenario is that there will be more power dissipation in a valve or a resistor than they're designed for and they'll either slowly cook or burn out pretty rapidly. Also, a voltage across a capacitor could rise too high and cause failure. However, more likely than not, no harm will be done.
Bear in mind that the operating points for the amplifier will be different and distortion might be worse, maximum power output might be reduced etc. Best to just stick with a 12AU7 where the circuit is designed for a 12AU7 imho.

Always liked NOS Tung Sol "D-Getter" tubes, the new issue ones are also well thought of?
http://www.musiciansfriend.com/acces...sol-12ax7-tube

Quote:

---

Originally Posted by RothwellAudio

Without seeing a circuit diagram it's difficult to say exactly what will happen when using 12AX7s instead of 12AU7s but generally valve amps are pretty robust and there's a good chance that no harm will come of it. Worst case scenario is that there will be more power dissipation in a valve or a resistor than they're designed for and they'll either slowly cook or burn out pretty rapidly. Also, a voltage across a capacitor could rise too high and cause failure. However, more likely than not, no harm will be done.
Bear in mind that the operating points for the amplifier will be different and distortion might be worse, maximum power output might be reduced etc. Best to just stick with a 12AU7 where the circuit is designed for a 12AU7 imho.

---

^ Good advice. +1

I have quite a collection of old 12au7s. You cannot go wrong with RCA cleartops and Sylvania long plates. Both cheap and plentiful on ebay.