Problem with Ultra 550

floresjc · « **on:** 27 Feb 2011, 03:27 pm »

I've been using my Ultra 550 with HT2-TL's without problem for about a year now. This morning I turned on the system and the left channel emits a loud humming noise. It will do this when only the amp is on, so I believe I've isolated the problem. I never had ground loop issues, and this is only one channel, so I eliminated that pretty quickly. I brought down a Double 240 and swapped it in, and alas, the hum goes away and system normal. I've sent in an email to Frank, but I wanted to know if anyone had any inkling what kind of problem this could be. Fuse, tube, left channel circuitry?

Anything user safe to try or check? I'm a complete noob to trouble shooting amps, but any insight/comments would be appreciated.

AVnerdguy · « **Reply #1 on:** 27 Feb 2011, 03:31 pm »

A fuse would leave no audio/hum so you can eliminate that as an issue.

Most likely the 12AT7 tube took a flyer. I'm sure Frank will get back to you on that. In the meantime - you could swap the tube from the good side and see if that solves the issue. If so, cheap (depends on the tube choice!) fix.

Big Red Machine · « **Reply #2 on:** 27 Feb 2011, 04:15 pm »

probably a tube croaked. you can always switch them and check this.

floresjc · « **Reply #3 on:** 27 Feb 2011, 04:18 pm »

This is my first piece of gear that has a tube in it. Any special things not to do? Or just yank it out and put another one in?

The previous owner included a few sets of other tubes she had bought, so I have extras to throw in there.

AVnerdguy · « **Reply #4 on:** 27 Feb 2011, 04:27 pm »

Quote from: floresjc on 27 Feb 2011, 04:18 pm

This is my first piece of gear that has a tube in it. Any special things not to do? Or just yank it out and put another one in?

The previous owner included a few sets of other tubes she had bought, so I have extras to throw in there.

Well, you could do that but you don't know that those are OK. The one in the other channel is working now so swap that and verify that is the problem. If it is, now go into the extras and plug one in (use the same brand if you have them).

Very easy to do. 1st - make sure it's cooled down - them things get HOT. Then pull up/out on the tube and try not to twist it. If a pin gets bent over just carefully push it back into position. The tube socket will help straighten out the pins and the tubes themselves only go in one way. They are keyed by a gap in the pins - looking at them from the bottom of the tube. You'll figure it out.

floresjc · « **Reply #5 on:** 27 Feb 2011, 04:30 pm »

Roger, I'll swap them first.

The tubes that are in the unit are not the stock ones that it ships with. She changed them out. I have the stock tubes in the "extras" box, as well as a couple other pairs of differing brands.

If it ends up being the tubes, I'll probably just throw the stock ones back in.

AVnerdguy · « **Reply #6 on:** 27 Feb 2011, 04:38 pm »

OOPS! You're new to this - I was assuming some things but I used to teach electronics and I learned never to assume anything.

Unplug the unit before attempting anything. There can be some pretty hefty voltages in there (tubes need a high plate voltage). Another good tip is to make sure you're insulated - put on a pair of rubber soled sneakers!. Another good tip is to keep one hand in your pocket to avoid touching anything else and completing a ckt. It's not scary - just take your time and be patient.

floresjc · « **Reply #7 on:** 27 Feb 2011, 04:42 pm »

The unit has been unplugged and setting on the floor for a couple hours (early morning, new puppy). I don't think I will kill myself, I'm more worried about the amp.

When switching out tubes, especially since I have differing brands, I want to make sure they are matched pairs correct? Like don't use the good one in the unit and one of the stock ones?

AVnerdguy · « **Reply #8 on:** 27 Feb 2011, 04:49 pm »

OK, I feel better now. Yes, it's best to use the same brands together.

As far as matched - you wouldn't be able to tell without a bit of test gear. But, for now if you have 2 of the same it will do.

floresjc · « **Reply #9 on:** 27 Feb 2011, 04:59 pm »

Well by matched I just meant same brand, same model. I'm not sure what the tolerances are.

I don't know whats in the amp, I think she said Mallard or Mullard or something like that.

I just went through the "extras" box, I have a pair of Telefunken 12AT7's and a pair marked GE 6201.

I don't know which is better, or if it matters. My wife's busy watching Tivo so I won't be able to try the switch for a bit.

Oh and what a birthday surprise eh? Yep, 29 today.

AVnerdguy · « **Reply #10 on:** 27 Feb 2011, 05:12 pm »

You have Mullards. Very nice. Try the Telefunkens - you'll like those I think. BTW, Happy Birthday!

OldCoder · « **Reply #11 on:** 27 Feb 2011, 06:08 pm »

I had that same problem with my Ultra 550.

It seems that some of the torodial transformers do not like HALOGEN lights and the noise they dump on the power circuit.
I took my amp in to Frank, and everything checked out perfectly. Fortunately he had just returned from a weekend trip where he had encountered the same issue.

Sure enough, I had a halogen light upstairs that was on, and when I turned it off the noise totally went away. I can replicate this at any time to this day.

floresjc · « **Reply #12 on:** 27 Feb 2011, 06:51 pm »

My 550 is on its own dedicated 20 amp circuit, had the electrician put in this line in August. Also, I haven't changed any lights in my home, and none of them are Halogen.

I just did the tube swap from Right channel to left channel, and no effect. The left channel still hums. Upon visual inspection, the tubes look pretty identical, there's fairly even heat "residue" on the glass, and they both light up when the amp goes on.

I figure at this point, its not a fuse, its not the tubes, so maybe something went bad in the left channel circuitry?

AVnerdguy · « **Reply #13 on:** 27 Feb 2011, 07:59 pm »

Too bad. Time for a consultation with Frank.

rcag_ils · « **Reply #14 on:** 27 Feb 2011, 09:48 pm »

any one of the three big caps show any bulging? If so, press on it lightly, sometimes it's the plastic top cover coming loose, other time it's bulging may need to be replaced.

OldCoder · « **Reply #15 on:** 27 Feb 2011, 11:37 pm »

My 550 was on a different circuit than the halogen light, and if a light bulb can do this, I would think there might be other devices capable of contamination too.

How much work would it be to turn off all the circuits at your mains box except for your stereo, and see if the hum disappears?

If it does, it will save you the cost of shipping to Frank and the loss of the amp for a while.

avahifi · « **Reply #16 on:** 28 Feb 2011, 03:37 pm »

1. Turn off amplifier and wait for it to play down completely.

2. Disconnect input cables at the amplifier, leaving it connected to the speakers.

3. Turn on amplifier.

4. If noise is now gone, then the issue is from somewhere ahead of the amplifier (cables, preamp, etc.)

5. If the noise issue remains, even after swapping tubes channel to channel, then we will need to see the amplifier for service.

CAUTION! NEVER DISCONNECT OR CONNECT CABLES WITH THE AMPLIFIER TURNED ON.

Please call me at 651-330-9871 for more help.

Regards,

Frank Van Alstine

floresjc · « **Reply #17 on:** 1 Mar 2011, 12:10 am »

For those interested parties:

I tried your test and here are the results:

First try, nothing upstream connecting to the amp, amp powered on:

Same problem. Left channel humming, perhaps the slightest of right channel buzz.

Second try, nothing upstream, tubes switched on channels, amp powered on:

Both channels buzz. The right channel seems to emit a lower harmonic, the left emits the higher harmonic although its the exact same hum I was hearing before.
When powering the amp down, the left channel emits a very short digital chirp and cuts out immediately. The right channel continues to hum at a low level until the amp drains.

Third try, nothing upstream, replace both tubes in the amp with the stock pair the previous owner sent me:

Same results as the 2nd try, both channels buzzing at a lower and higher harmonic. Same chirp on power off.

I've since removed the amp from the rack and my Double 240 is filling in with no problems. I would imagine you have to see it, any ideas what it might be just on what we've seen so far?

Thanks so much for your help.

Listens2tubes · « **Reply #18 on:** 1 Mar 2011, 05:59 pm »

For clarifcation, when you say 'nothing upstream' did you disconnect the rca interconnects from the amp or just not turn the preamp on?

avahifi · « **Reply #19 on:** 1 Mar 2011, 06:35 pm »

I am already in the process of resolving this issue with the customer. We will need to see the amplifier to investigate.

Inasmuch as the hum first was a one channel issue, but then changed to a two channel issue when the tubes were swapped, and the tubes involved were not the original OEM JJ 12AT7 tubes we supplied, I am very suspect of a defective tube causing collateral damage when swapped to a previously working channel.

We will have to look at this very carefully here.

Regards,

Frank Van Alstine