12AT7WC tube in an AVT150H

studioc62 · Newbie Alert Joined: 08 Jul 2006 Posts: 3

Hi,
I am curious to try different 12AX7(ECC83) pre-amp tubes in my AVT150H to see how they change the amps sound and to see which I like best.
Along with 4 diferent brands of 12AX7's I ordered a JAN-Philips 12AT7WC (ECC81). I also wanted to try a GE 5751 but the TubeStore is currently out.
My main question is: Will installing either the 12AT7WC or a GE 5751 cause any damage to my AVT150H? Anything I would need to be aware of or adjust with these lower gain tubes? Is anyone out there using these tubes in an AVT150 and do you like the sound?
Thanks in advance for any help...
Rob (StudioC62)

pizza8guy888 · Little Hamster Joined: 17 Jun 2005 Posts: 77 Location: NJ

Changing the tubes in the AVT series will not ahrm anything. I have changed the tube in my AVT50 and like the sound i got. As long as you stay with the same type of pre amp tube you will be fine. To decide which tube you should use, first evaluate what style music you play most (clean stuff, overdrive stuff, or full out distortion) and then take a look online at different preamp tube cahracteristics such as tubes that breakup real fast or stay clean, etc etc. you can find some of this info on the groovetubes site.

studioc62 · Newbie Alert Joined: 08 Jul 2006 Posts: 3

Thanks for the response. From everything I read it seemed a safe thing to do. Since most of what I read was not specific to the AVT Amps I thought it would be good to check before risking any damage.

pizza8guy888 · Little Hamster Joined: 17 Jun 2005 Posts: 77 Location: NJ

yourm post also made me interested in playing with my pre amp tube again as well. One word of advice if oyu havent tried changing the tube out already then keep this in mind. The tube socket is only a cheap plastic one which is fine, it is nice secured. I find the best easiest way with the least stress to the socket and circuit board in general was to lightly n gently wiggle the tube out in a gentle circular motion as u soft softly pull up. I know this is probbly a stupid reply or thing to share but i'd hate to see anyone ruin the socket and the solder joints. anyways take care.

- Chris

studioc62 · Newbie Alert Joined: 08 Jul 2006 Posts: 3

Hi Chris,
Not a stupid thing to share at all. Actually, I found it very useful. I swapped out my pre-amp tube yesterday and tried each of 5 different types in its place. Man that socket is tight. The way that the board is attached to the amp cabinet lets the circuit board flex quite a bit too. Rocking the tube gently back and forth (or in a circle as you suggest)seems to be the only way to get them in or out. Even at that I was worried I'd crack the board or damage the socket.

If anyone is interested, I wound up liking the sound of the JJ / Tesla ECC83-S the best with the Tung-Sol 12AX7 a close second, and the Electro-Harmonix 12AX7-EH third. The 2 JAN-Phillips tubes I tried (a 5751 & a 12AT7WC) both had an annoying sound quality even at low gain. I am wondering if it was what is referred to as "Microphonics". It was kind of like a high pitch rattle. The JJ / Tesla seems to have a nice warm fuzzy distortion and a well toned clean sound. Anyway, that is what my ears told me... Smile