Buzzin' EL34?

[Soundthought]

Hello all,

I've been spending the last couple of weeks getting aqainted with my Jolida 202A.

I rolled a quad matched set of ElectroHarmonic EL34-EHs in a few days ago.

I've got about 40 hours on 'em.

One of them has a noticeable intermitent(sp?) buzz.

I tried to re-seat it, but no luck.

Any suggestions or other options?

Also,

Is this buzz going to cause me any problems?

Thanks.

[mobile homeless]

You have to be REALLY specific to get trouble shooting from afar.

0. Is the buzz coming from the one tube OR out of the speaker(s)?

1. Does the buzz exist when you put your old tubes back in?

2. Did you notice the buzz ONLY after you changed tubes?

3. IS the buzz out of one or both channels?

4. If out of one channel, when you switch power tube pair to other side, does it follow switch?

5. Does the buzz change with volume attenuation?

6. IMPORTANT: Did you RE-BIAS the amp when you put in the new power tubes?

7. Think of any specifics you can add.

8. Did you get deep and heavy in the the Merlot or bourbon while testing?

kh

[Soundthought]

How do you do Mr Mobile?

Hmmmm.

0. Out of the tube itself.

1. Haven't tried that yet.

2. Yes.

3. One channel.

4. Power Tube?

5. No.

6. Absolutely. All within .2 millivolts of 40.

7. Using the stethascope that I use to check for automotive vaccum leaks, I was able to determine the buzz is coming from an EL34.

In my case, it's coming from the V4 socket.

I currently running a full compliment of EH tubes.

They were cheap and available.

*First I rolled the EH 12AT7s in with the stock Svet EL34s. No buzz.

*Second I rolled the new EH EL34s in, biased them and an audible buzz was heard.

*Third I rolled new EH 12AX7s in. Still buzzing.

*Fourth I read that a buzzing tube may smooth out after it's burned in. So I waited. 40 hrs and Still buzzing.

How long is tube burn in time?

Let me guess...varies from tube to tube, right?

The buzz comes and goes.

It doesn't appear to have any relation to vol pot position.

It does exhibit this behavior whether being fed a source signal or not.

The sound quality or volume level between channels doesn't seem to be affected.

In fact, She sounds really good and i'm almost ready to give my report on my exploration into tubes.

8. Heh, funny guy.

Actually, i've experimented listening whilst sober as well as soused.

Believe it or not.

All in the name of science.

Thanks for your help.

[mobile homeless]

Sounds like it might be a problem with that tube. Isolate which tube it is, and switch to the other socket on taht same side since they MIGHT be matched. See if the buzz moves to that socket.

Now, if feeling up to it, swap pairs so the bad tube (and mate) are on other side. Did the buzz move over there as well? IF so, I would REALLY expect a tube with a problem perhaps.

Put your old tubes BACK in just to see if any buzzing remains. If the tubes are new, send them back and say you are getting some feedback. If they are matched pairs, send the pair back. If matched quads, you can either send all back, or give the reading for the tubes for a identical replacement(actually you could do this for the pair as well).

While it might turn out ok, if the tubes are new, might as well be safe. IF you isolate it to that tube, I'd fire it back.

kh

[Soundthought]

Thanks alot Mobile.

I'm on it.

I'd rather be safe than sorry, anyday.

Although,

I'm a bit leary of swappimg the EL34s between sockets.

I've read and heard alot about keeping them in their appropriated sockets.

There seems to be more than a few reasons why.

Should I be concerned about this?

Also, I forgot to mention in my above post, I had 12AX7s in place of 12AT7s accidentally.

I posted a thread about it not too long ago.

But like I said, I didn't affect the Svetlana EL34s, so I don't expect that to be the cause of my buzz.

"The cause of my buzz"

Ha, that's an intresting line.

It should be the title of a book.

[mobile homeless]

No, switching the EL-34 tubes in the sockets will do nothing at all. In your Jolida, you have two tubes per channel. These need to be matched for the even push-pull use. But switching the tube between these two sockets will do nothing. Indeed, if you got a MATCHED QUAD (which in all actuality, rarely gets done to exacting levels) all should be matched. Still, it is more common to see matched pairs, which is the reason why I said move the tubes in pairs to the other side.

Still, this should be fine for testing purposes. Just move the tube back to where you adjusted the bias for the specific tube. The only pain about the bias with the 202a is that you have to adjust underneath while the 302B has the pots and test points on top.

But dont worry about moving the tubes as I instructed.

kh

[Soundthought]

Cool Man.

I Appreciate all your help Mobile.

I'm a rockin' and a "rollin'" now.

I think i'll have to wait till "Jazz with Bob Parlocha" is over.

NPR is kicking out some smooth jams tonight.