Clarinet break-in?

analog97 · « **on:** 22 Feb 2006, 01:40 pm »

I have just put about 5 hours on my Clarinet. Mine is completely "stock", except for Auricap upgrades. I notice 3 things that I am concrned about: 1. after turn-on, there are a few "pops" that occur about a couple seconds after the green light comes on and 2. the Clarinet seems to "hiss", not hum thru my speakers. This hiss is not affected by the volume control. 3. there is some intermittent "squeal" at idle. I am guessing this is "tube squeal", but I am new to tubes. Any thoughts out there about cause? Is this related to break-in? Any thoughts warmly appreciated.

Eric H · « **Reply #1 on:** 23 Feb 2006, 07:31 am »

None of that sounds like break-in to me. I'm not sure about 1) and 2) but 3) sounds like it could be tube microphonics. Have you tried swapping tubes, including the rectifier, one-by-one? Might help the other issues, too... what tubes are you using?

analog97 · « **Reply #2 on:** 23 Feb 2006, 02:04 pm »

I am using an RCA 5Y3GT and 2 EI 12AU7's. I have heard off tube "microphonics" and you may be correct. I am less concerned about that than the much more audible "hisss" that comes from the speakers. Last nite I turned on my Clarinet and Cornet2 first, then waited about 10 minutes before turning on my amp. I did not hear the "pops". Maybe this turn-on order makes sense. Thanks for the input.

GRD · « **Reply #3 on:** 23 Feb 2006, 05:28 pm »

It's not unusual to get a voltage spike on the output when first turning on a tube (or even SS) component. So, I turn on the upstream components one by one. Phono stage, wait a minuite or so for the tubes to come on, then the pre-amp, wait a minuite or so again, and then the power amp. Turn-off is the reverse sequence. No pops this way.

Hiss can come from noisy tubes. That would be my first guess. Only way to check is to swap tubes and see if it makes a difference. Not unusual to find a noisy tube every once and awhile. That would be the AU7 tubes, not the rectifier.

Best of luck.

analog97 · « **Reply #4 on:** 23 Feb 2006, 10:17 pm »

Thanks. I will give tube swapping a try. I only have the 2 12 AU7's. I will try to order more. Opinions on good 12 AU7's welcome. Thanks.

GRD · « **Reply #5 on:** 23 Feb 2006, 11:31 pm »

I'll let the other clarinet users name their favorites. And you can check out audioasylum for other opinions. There are also a number of well respected tube vendors who advertise on Asylum.

tanchiro58 · « **Reply #6 on:** 24 Feb 2006, 12:46 am »

I have a Clarinet but there is no problem of hum, hiss and pop. Are you the first owner or just a second one? Reason I am asking that since you swap or roll tubes so many times the pin sockets might cause the hissing problems. Shut off everything then use a small flat screw driver to narrow the pins in the tube sockets. Try this might help to cancel the hiss.

GRD · « **Reply #7 on:** 24 Feb 2006, 01:10 am »

Yes - I do remember seeing some people post about dirty tube pins / bad pin contact causing noise problems. This could be worth exploring. I've never run across it myself. If the tube seats tightly in the socket, probably not the socket. But the pins might need some cleaning.

Eric H · « **Reply #8 on:** 24 Feb 2006, 05:39 am »

I haven't done much tube rolling with 12au7's since I didn't have any before I made my Cornet and Clarinet, and the handful I have now are mostly microphonic. I took me quite a bit of experimenting to find a quiet tube combination for my Clarinet so I stuck with what worked (NEC GZ34, Philips 6189, RFT ECC82). I didn't have problems with microphonics in my Cornet, which has nearly identical constuction... not sure why.

From what I've read about 12au7's opinions seem to be all over the place... maybe circuit dependant? I don't know... (I think people agree a lot more on 12ax7 characteristics) Best bet is to either find somebody to swap tubes with or build up your own collection and see what works for you.

hagtech · « **Reply #9 on:** 1 Mar 2006, 07:33 am »

Hi, I'm back.

Does sound like a tube. Had this very same thing a week ago in a CHIME. And the tube had tested fine. Sounded like it would come around after a few minutes as it started to settle, but I didn't want to take a chance. Chucked it and put in a new one.

Squealing would be the second tube. Caused by the high cathode to heater dc voltage (well within spec). Marginal tubes will squeal in this mode. Needs very good cathode insulation.

jh

analog97 · « **Reply #10 on:** 1 Mar 2006, 01:13 pm »

Quote

Squealing would be the second tube.

What is the second tube? Does each tube serve a specific channel or does each have shared duties? Maybe I should get a matched pair of 12AU7's? Thanks again. BTW, I am 99% sure I built the Clarinet correctly. My skills are my inherent slowness and extreme care.

hagtech · « **Reply #11 on:** 1 Mar 2006, 08:29 pm »

The second tube is the upper half of the SRPP. Channels share tubes. I much prefer to lose a little crosstalk specification than stability. It is far worse to have two gain stages in one tube, as the output is way too close to the input. Instability thanks to positive feedback is the result.

jh

tanchiro58 · « **Reply #12 on:** 1 Mar 2006, 09:22 pm »

Hi Jim,

I have tried to replace the original volume control with a stereo stepped attenuator but I have a big problem since I removed the original one. I just left unfinished work because somehow I could not solder the wire into the small holes on the circuit board. It sounds like too small for the wire but there are six(6) holes too close together. Is anything you can help to complete my work? Thanks.

Regards,
Tan

analog97 · « **Reply #13 on:** 1 Mar 2006, 10:41 pm »

Quote

Channels share tubes.

OK, that means a noisy 12AU7 tube in the Clarinet, either a "squealer" or a "hisser" will be heard in both channels equally. I may have one bad tube, but I have to replace them both? No way to tell for sure without replacing both is what you are saying, Herr Engineer?

hagtech · « **Reply #14 on:** 2 Mar 2006, 03:51 am »

Not necessarily. A dual triode can have just one section faulty. Most likely only one tube is bad. Which one, we don't know. All you have to do is replace one at a time.

jh

Eric H · « **Reply #15 on:** 2 Mar 2006, 06:52 am »

Jim's explanations (thanks!) describe my experience with my Clarinet - the second 12au7 (next to the rectifier) was always the most troublesome. I knew there was a cathode-heater voltage limit but never associated a large heater-cathode voltage with microphonics sensitivity. That's interesting (and I also admit to trying some crappy 12au7's)...

analog97 - you can start by just swapping your Clarinet's 12au7's, or you must have a third one in your Cornet, right? It wouldn't have the same issue as the similar spot in the Clarinet, so try swapping it, too.

analog97 · « **Reply #16 on:** 2 Mar 2006, 11:23 am »

Thanks again. Looks like swapping is in my near future. All I've done so far is re-seat the tubes and also switch the 12AU7's. Hiss was the same, but squealing was greatly reduced.