Tube mic problem?

[gnd]

Hi.
I got tube mic, SE Gemini, and I think something may be wrong with it, but am not sure. Maybe somebody of tube experts can help, please? Or maybe somebody has same SE Gemini mic, and can tell me if his mic is doing the same?

When I turn mic power supply on, and sound comes in, there is a popping sound, repeating approx. once every second. It sounds like somebody would be softly tapping on a mic with a finger, low bass popping sound. After some minutes this sound becomes lower and lower in volume, and after some 10 minutes it dissapears fully. Then mic works as any other mic, no more popping.

Is this behavior normal for tube mics as part of warmup? Or is it broken? What do you suggest?

(I have another tube mic, oktava MKL2500, but that one is not popping)

thnx
gnd

 

[pucho812]

hmmmm. Sounds like it could be a bad tube. Have you replaced that yet? Might be time to do that. Also might be time to replace caps :?

 

[gnd]

Pucho, mic is relatively new. I think this series came out in 2004, so it cannot be more than 2 years old. I bet capacitors are still ok.

It is a bit unique, it has 2 tubes inside. http://www.seelectronics.com/Gemini.html

Is there a way to figure out if tubes are finished, without replacing them?

...

 

[skipwave]

This belongs in The Lab, don't it?

I just did a quick search and found that the Gemini is a transformerless output dual tube mic. ECC83 amplifier stage (and maybe phase splitter), ECC82 cathode followers (I assume) output stage. Wow. I can't help but think the idea was to sub a five dollar tube for a twenty dollar transformer. Sure, lots of innovation has come about in the interest of cost cutting, but yikes.

Like Pucho said, start by replacing both tubes. Hopefully they are socketed and not soldered in.

EDIT: Hah! I was composing this post while gnd posted that last response.

 

[gnd]

This belongs in The Lab, don't it?

Sorry for mistake. I thought Lab is for DIY Group projects....

Like Pucho said, start by replacing both tubes. Hopefully they are socketed and not soldered in.

Yes, socketed. luckily!

...

 

[Gus]

there was even a thead about possable Transformerless tube microphone circuits in the past

change the tubes first.

 

[burdij]

You should also check to make sure the line voltage switch is set correctly for your locale.

 

[gnd]

[quote author="burdij"]You should also check to make sure the line voltage switch is set correctly for your locale.[/quote]

It as on euro 240V standard when I got it, and I got it from Germany, so I guess that should be fine, I'm in Europe too.


Thnx for info, everybody.
Would anybody have some recommendations regarding tube manufacturer? Are some tube manufacturers considered better for tube mics? I've never changed tubes, ever, so I have no idea what to buy.

Are ecc82/83 easy to get? Are there some ecc82 and ecc83 direct replacements? Are there any good tube distributors here in Europe?


thnx.
gnd

 

[synthi]

ECC82 & 83 are very common tubes, they are the same as 12AU7 and 12AX7.

Search for low noise and microphonics, tubedepot and other online tube source can test the tubes for you.

Synthi

 

[gnd]

I got info from some hifi guy, that the sound I'm hearing, is due to tubes heating up, and there is some mechanical stretching inside tubes because of temperature rise, and then you can hear that popping/bumping sounds.

Is this possible? Is this having some effect on sound quality? Is this happenig only with old tubes, or is it possible that I have this with tubes that are still just fine? Because it is strange to me, that tubes need replacement already - this mic cannot be older than some 2 years.

Do tubes need to be replaced so fast, every 2 years???


thnx
...

 

[gnd]

Hi.
Need advice...
I found some tubes in drawer.... JAN 6072A and 12AX7.
Can I temporarily replace ECC82 and ECC83 with JAN 6072A and 12AX7, just to see if ecc's are fulty? Would this work or will I BLOW-UP something?
I know 12AX7 is same as ECC83.
How about 6072A? Would it work in place of ECC82? Can I do some damage if I put in 6072 instead of ecc82?

thnx
....

 

[synthi]

Hi gnd, the 6072 is the same as a 12AY7, different gain factor but you could use it for testing in place of the ECC82.

About life of tubes, "normal" tubes are about 1000 hours but there are military versions with longer life (10.000 hours). I dont know the life for new tubes, but because the poor construction vs old ones, I bet is not for better...

Also about your first question, I think the pop sound would be something with the capsule (contamination) or something with he polarizing voltage, maybe the voltage is too high and the backplate is sucking the membrane (gus???)

Synthi

 

[gnd]

[quote author="synthi"]Hi gnd, the 6072 is the same as a 12AY7, different gain factor but you could use it for testing in place of the ECC82.

Also about your first question, I think the pop sound would be something with the capsule (contamination) or something with he polarizing voltage, maybe the voltage is too high and the backplate is sucking the membrane (gus???)

Synthi[/quote]

Hi.
GREAT NEWS!!!!
I replaced ECC82 with 6072A, and all is fine. Those poppings while warmup are gone.

First I replaced ecc83, but there was no imprivement. So it seems ecc82 was weak.

I will order some TAD tubes from Germany, people seem to have good opinion about them, and they are not too expensive either.

So, I'm good. Damn, this is one seriously good sounding mic...

Thank you all for help. you are the best.

gnd
...

 

[synthi]

good news

Also compare the sound with the ecc82 vs 6070A when you get it, maybe you like it better with the 6072... And you could use the 6072 instead of the 12AX7 also, search the forum and you will see the 12ax7 is not recomended for microphone use by respected members of the group.
Experiment and choose by ear!

Synthi

 

[CJ]

crap.
another 6072 convert.
stock up now!
GE is the secret word.

 

[pucho812]

just because it's a new mic does not mean the tubes will be good after 2 years. Many things can happen such as damage in shipment as mics are shipped with the tubes inside. Could have been a tube going bad from the get go. Big problem with a lot of companies is using cheapo tubes to cut cost but in the long run it just creates problems.

glad it's all better now. As for tubes stretching thats a new one to me. Next he will be telling you to give it a good coat of c-37 :razz:


Ge nah the Jan military tubes are where it's at. Now if I can just find an inexpensive 421A price has prevented me from getting that freebie amp working as I need some new ones for it. :evil: