help with noise at startup volume turned down

[Doc B.]

Just replace the MJE350s.

[Strikkflypilot]

My apologies.

I received the replacement MJEs from Bottlehead today.
Had to try them of course.
Now there isnt even a startup humm/buzz.
Thanks Doc.

[Adrian]

Boc B:  Thank you - I apologize for my post sounding snarky  .  I just got confused with all the various information and opinions and wanted somthing more definitive.  I have sent the email to "replacementparts" for the MJEs.

[Adrian]

I received the MJE350s today and ready to install but I have a question about the transistor orientation.
These replacement MJE350s do not have the metal side and both sides look the same EXCEPT one side has writing on it.

Do I orient these without the metal side with the writing facing the same way as the original ones?
(I've checked this thread and didn't find this info - maybe I missed it.)

EDIT:  I just compared the old with the new and got about 570 ohms from emmitter (+) to base (-) on both and it looks like the new ones are oriented with the writing to the same side as the old ones.

[Paul Birkeland]

See the sticky on the Crack board regarding MJE350's.

[Adrian]

"PB":  Thank you.  Success - I installed them correctly (just as I had measured them) and it is DEAD QUIET just like before the Speedball install - but the SB makes this little giant sound even better, just like BH promised.
Now off to find out about this "sticky" thingy (I am not well-versed in proper forum terminology).

[Strikkflypilot]

"Stickies" are the first, currently nine, threads, that show up on top of the crack forum with grey background with a little pin. These are threads that don't move when new posts appear. One concerns MJE350 orientation.

[Adrian]

Strikkflypilot:  thank you - this old dog learns something new everyday.

[wookiee]

Sorry to bring this thread up again, but I found it while searching about the problem. I ordered the Crack with Speedball in mid-March, but didn't get around to building it until about a month ago, so I suspect that I may have been supplied with the bad transistors. I just wanted to run my problem by everyone before I request some replacements.

Like most of the posters, I had some humming during tube warm up, but I also experienced the loud buzzing at <5% volume. What's strange is that when I powered on the CD player and played music for about 10-20 minutes, the buzz would go away. But as soon as I even paused the CD player (the power was still on) the buzz would return below 5% volume.

I haven't seen that other posters noticed or mentioned this, so I would appreciate your opinions. Thanks.

[Paul Birkeland]

Is the buzz present without the CD player plugged in?  There are some CD players that will let some noise through when paused.

[wookiee]

I checked last night and the buzz was there without the CD player plugged into the amp.

[Paul Birkeland]

Yeah, it's tough to say.  If the CD player controls whether or not your Crack buzzes, then the Crack is unlikely to be the culprit.  If, however, the Crack will buzz regardless of whether or not the CD player is plugged in, then swapping MJE-350's might be a good idea. 

-PB

[Adamaley]

Hi there. Just purchased a bottlehead crack amp a week ago, and I am experiencing this hum-at-low-volume issue. Is there anyone local to Minneapolis who can lend a hand replacing the transistors for a fee? I am, unfortunately, not handy with anything electrical.

[wookiee]

Yeah, it's tough to say.  If the CD player controls whether or not your Crack buzzes, then the Crack is unlikely to be the culprit.  If, however, the Crack will buzz regardless of whether or not the CD player is plugged in, then swapping MJE-350's might be a good idea. 

-PB

I just changed the transistors and it did the trick.  Thanks for all the help and for making such a great sounding amp!