6an8a phase inverter tube

[usersunn]

Can the 6an8 phase inverter tube in my old Sunn be a source of hum??? Is it worth replacing to try to lessen hum , or should I not even bother??? Thanks   usersunn

[mckinnon audio]

   Hi there,any tube can go bad,but typically the hum will be from a bad filter as opposed to a tube.If the 6AN8A is the only tube you haven't changed you could try it,but I'd be looking at filter caps,or maybe a bad ground in the audio path.Hope this helps,Mel.

[Soundmasterg]

As far as tubes go, the 6AN8A is a hummy tube and always has been. That said, the amp shouldn't hum any more than a vintage Fender....so I'd guess you've got something else going on...probably caps or grounds as Mel said.

greg

[Isaac]

Still, it's an easy and relatively cheap thing to try.

I have had a 6AN8A go bad on me, but it didn't hum. I just lost most of the gain.

[usersunn]

***THANKS guys for all the info....very cool!  My 1200s has been behaving, and boy does it sound good with my 63 jazz and 59 p.. I ordered an RCA 6an8 nos off ebay..Ill let you know how it goes! ***

[EdBass]

***THANKS guys for all the info....very cool!  My 1200s has been behaving, and boy does it sound good with my 63 jazz and 59 p.. I ordered an RCA 6an8 nos off ebay..Ill let you know how it goes! ***

Post some pics of your basses; we can always use a little "bass porn"! 

[usersunn]

Sure, would love to post a pic.. but Im not sure how!!

[Isaac]

First, take the pic...

[usersunn]

Ok, and then what??

[Isaac]

If it's a digital pic, post it to a photoserver such as photobucket.com. Then click on the "Insert Image" icon (right under the italics I) and paste the URL for the photo into the message.

[knw]

Hey I just ended up re tubing my 69 1200S and now that I'm reading your post I can remember when I had my amp at about 6 volume and I wasn't playing there was a hum and it only got louder from show to a show.

It didn't bother me that much sine I play in a really loud band and I could never hear the hum over 2 full stacks.  The hub would only be there if I wasn't playing.

I'm also using this amp for bass.

Well anyways while on tour at one of our shows the 1200S started to squeeel like if you are gutting a pug when it was off stand by.

I tried the amp again when I can back from tour and it still had the same issue.

I took it to my tech and when he got around to fix it he cleaned the amp and told me he couldn't find an issue with the amp.

My tech told me my power tubes are fine then I brought up the squeeeel issue when I was talking to him again and he said it might be the pre amp section.  But like I said he couldn't personalty find an issue with the amp.

But I have recording next month and I decided to get it retubed just to see what it would sound like.

The amp sound super clean now and even turned up at 10 there is not even a slight HUM.

I love this amp a lot it's probably my favorite super CLEAN amp that I own I just wish it had more power.

[usersunn]

Although I havent received that NOS RCA 6an8a off ebay yet, Im pretty sure that has nothing to do with the hum..I removed each of the 3 "preamp" tubes, one at a time, turning on the am... after each was removed... the hum was unchanged each time, signaling the hum is not in the preamp/reverb/phase inverter tubes, but rather in the output/power supply section...Just as you guys have said..Further details will be posted after I have the amp serviced....stay tuned