Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: kiwipie on September 06, 2014, 09:52:59 PM

Title: Left Channel Buzz
Post by: kiwipie on September 06, 2014, 09:52:59 PM: Greetings.

I have just completed constructing a Crack OTL (no speedball yet) for my HD600s and my music has never souded better.

However I've noticed a quiet buzz comming from the left channel. At first I thought it was a bad joint but i've also noticed that I get microphoncs in the left channel only when I tap the chassis, this leads me to belive it may be a bad tube.

Do you think it's worth trying a new power tube before looking for the problem elsewere?

Also if I was to replace the tube what is a good value for money replacement (I intend to install the speedball when I get the money)?
Title: Re: Left Channel Buzz
Post by: i luvmusic 2 on September 07, 2014, 03:55:51 AM: I used RCA,SYLVANIA and CHATHAM/TUNG-SOL 6AS7G's $10-20 per tubes,6080 $6 to $10 per tube and RCA,SYLVANIA,GE 5963 $6 to $15 per tubes.
Title: Re: Left Channel Buzz
Post by: Paul Birkeland on September 07, 2014, 05:43:54 AM: It sure does cost a lot less to touch up all your solder joints before replacing tubes.

-PB
Title: Re: Left Channel Buzz
Post by: kiwipie on September 07, 2014, 09:13:13 AM: Since it's only the left channel effected what joints would you suggest touching up?
Title: Re: Left Channel Buzz
Post by: Paul Birkeland on September 07, 2014, 05:00:34 PM: I would take your needle nose pliers and just start gently tugging on things. If anything moves within its solder joint, it needs to be reheated and reflowed.

-PB
Title: Re: Left Channel Buzz
Post by: kiwipie on September 07, 2014, 07:44:20 PM: I've just tried that and nothing moved a millimeter.

Also I noticed something lose in the big tube. I can't see it but I can here it if I tip the tube back and forth.
Title: Re: Left Channel Buzz
Post by: Paul Birkeland on September 08, 2014, 04:35:05 AM: There's often debris inside the tube from manufacturing, which shouldn't present a problem.

If you can see metal bits rolling around in the tube, that can be a problem. Often times, however, it's just a little bit of leftover glass stuck in the base.
Title: Re: Left Channel Buzz
Post by: kiwipie on September 08, 2014, 08:47:52 AM: So what do you suggest I try now?
Title: Re: Left Channel Buzz
Post by: fullheadofnothing on September 08, 2014, 08:52:38 AM: Have you resoldered your joints yet?
Title: Re: Left Channel Buzz
Post by: Doc B. on September 08, 2014, 09:07:59 AM: Reheating joints is a good idea. Is the hum constant, or does it go up and down with the volume control? If it is constant and reaheating the joints doesn't solve it, you might let the tube run for a few days and see if the hum reduces. If not, send the tube back and well send a new one out to you.
Title: Re: Left Channel Buzz
Post by: kiwipie on September 08, 2014, 07:42:08 PM: The buzz is unaffected by the volume control, and re heating the joints has done nothing to solve the issue. I will try leaving the amp running while I am home over the next few days and see if it helps.

EDIT: I've also just noticed that the microphonics are occuring in the small tube so maybe thats the tube the buzz is comming from.
Title: Re: Left Channel Buzz
Post by: Doc B. on September 09, 2014, 06:08:31 AM: Yes it could be either tube. It's not very often that a 12AU7 is microphonic, but it does happen. And that could correlate with buzzing sounds. We are happy to exchange the tube for you.
Title: Re: Left Channel Buzz
Post by: kiwipie on September 12, 2014, 07:18:29 PM: Just an update.

I went ahead and replaced the 6080 and now the buzzing is gone. The 12AU7 is still microphonic but it isnt affecting my music.

Thanks everone for your help and suggestions.