# Tube Question **URL:** \ **Category:** Audio Components\ **Created:** [November 13, 2022, 9:25pm UTC](https://forum.psaudio.com/t/tube-question/31065 "2022-11-13T21:25:09Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![clrvlewis](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@clrvlewis](https://forum.psaudio.com/u/clrvlewis)\ **Post date:** [November 13, 2022, 9:25pm UTC](https://forum.psaudio.com/t/tube-question/31065/1 "2022-11-13T21:25:10Z")
I searched in the Tube rolling thread but can’t find what I am looking for. I have switched the tubes in my BHK Pre and BHK 250. I installed 12AX7A/ECC83 in my Pre and 7308/E188CC in the BHK 250. The volume does not seem to work. As I increase the volume it hardly rises until somewhere around 25, and 52. Then a pop and a large volume increase. I obviously didn’t play around with it and shut it off. I didn’t think I needed to change any of the jumpers but maybe I am wrong? Any help would be appreciated. ---
**Author:** ![jeffreybehr](https://sea1.discourse-cdn.com/flex015/user_avatar/forum.psaudio.com/jeffreybehr/32/36_2.png) [@jeffreybehr](https://forum.psaudio.com/u/jeffreybehr)\ **Post date:** [November 13, 2022, 10:01pm UTC](https://forum.psaudio.com/t/tube-question/31065/2 "2022-11-13T22:01:42Z")
Those are two rather-different tube types that are NOT interchangeable… Not only do they use different heater Voltages but they have different pin-outs… I’m suprised either of those work at all. Put the 'X7s back in the preamp and the 6DJ8/ECC88/7308s back in the poweramp and see if they work. FWIW, members of the 12A\*7 tube family are theoretically interchangeable, but each’s electronic performance is NOT the same so results may be audibly poor. And I hope you didn’t fry any of your tubes. ---
**Author:** ![clrvlewis](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@clrvlewis](https://forum.psaudio.com/u/clrvlewis)\ **Post date:** [November 13, 2022, 10:07pm UTC](https://forum.psaudio.com/t/tube-question/31065/3 "2022-11-13T22:07:51Z")
I took the 12AX7A/ECC83 out of the BHK Pre and that fixed the issue. I left the E188CC/7308 in the BHK250. Are you saying that’s not a good idea? I thought the 12AU7 was interchangeable with the 12AX7 ---
**Author:** ![RonP](https://sea1.discourse-cdn.com/flex015/user_avatar/forum.psaudio.com/ronp/32/213555_2.png) [@RonP](https://forum.psaudio.com/u/RonP)\ **Post date:** [November 13, 2022, 10:49pm UTC](https://forum.psaudio.com/t/tube-question/31065/4 "2022-11-13T22:49:24Z")
Research carefully before rolling tubes. 12AX7 generate much different gain than do 12AU7, for example. ---
**Author:** ![joe-appierto](https://sea1.discourse-cdn.com/flex015/user_avatar/forum.psaudio.com/joe-appierto/32/294192_2.png) [@joe-appierto](https://forum.psaudio.com/u/joe-appierto)\ **Post date:** [November 14, 2022, 12:02am UTC](https://forum.psaudio.com/t/tube-question/31065/5 "2022-11-14T00:02:04Z")
The amplification factor (mu) of a 12AX7 is 100 while for a 12AU7 it’s 20. ---
**Author:** ![vkennedy61](https://sea1.discourse-cdn.com/flex015/user_avatar/forum.psaudio.com/vkennedy61/32/41241_2.png) [@vkennedy61](https://forum.psaudio.com/u/vkennedy61)\ **Post date:** [November 14, 2022, 12:20am UTC](https://forum.psaudio.com/t/tube-question/31065/6 "2022-11-14T00:20:34Z")
> [@clrvlewis](#): > > I left the E188CC/7308 in the BHK250 While I had a 250, that was my favorite tube in it. Enjoy! ---
**Author:** ![clrvlewis](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@clrvlewis](https://forum.psaudio.com/u/clrvlewis)\ **Post date:** [November 14, 2022, 1:13pm UTC](https://forum.psaudio.com/t/tube-question/31065/7 "2022-11-14T13:13:14Z")
Thank you ever one for the replies and help.