Topic: Wunder cm7 gt tube? (Read 12631 times)

matti · « **on:** August 29, 2009, 06:44:56 PM »

Out of curiocity, what tube is used in the cm7 gt, ef86?

Matti

J.J. Blair · « **Reply #1 on:** August 29, 2009, 07:32:05 PM »

He says "The CM7-GT (Glass Tube) uses a NOS Telefunken glass tube, which replaced the VF14/EF14 in 1960-1979."

The EF42 was the glass tube to replace the EF14, so I'm guessing that's what he's using.

matti · « **Reply #2 on:** August 30, 2009, 03:34:09 AM »

Thanks!

Matti

hopsing · « **Reply #3 on:** August 30, 2009, 12:43:12 PM »

I would say, since the ef42 was not produced in 1979 anymore (As far as I know), it should be the ef80, which by the way works pretty good in a microphone circuit, but tends to be microphonic and noisy. But since this tube is dirt cheap and plenty, you can try a few till you find a good one. In my experience with the ef800, which is a telefunken special quality ef80 you need less sorting out and the chance to get a good one is much better. But of course this one is more expensive and I might have been simply lucky.
Tobias

RM · « **Reply #4 on:** November 19, 2009, 02:47:17 PM »

Can anyone confirm the ef800 as this valve?

I have one of these mics that is getting a bit noisy and microphonic. I've tried contacting Mike at Wunder about purchasing a replacement, but haven't heard anything back at this point.

In opening the mic, the print on the tube has either been taken off or is gone due to heat. It looks like photos of the ef80/ef800, but is there another way to tell?

Any thoughts?

Thanks,
RM

Klaus Heyne · « **Reply #5 on:** November 19, 2009, 03:03:36 PM »

Please post a close-up of the tube here.

RM · « **Reply #6 on:** November 19, 2009, 06:15:08 PM »

Here are a couple pics. I apologize ahead of time if they're too big or of poor quality, as this is the first time I've posted pics here.

Thank you in advance for having a look and helping.
index.php/fa/13780/0/

RM · « **Reply #7 on:** November 19, 2009, 06:16:38 PM »

Not sure if needed, but:

index.php/fa/13781/0/

Tim Campbell · « **Reply #8 on:** November 19, 2009, 07:00:44 PM »

It looks like an EF800 to me.

RM · « **Reply #9 on:** November 20, 2009, 11:56:24 AM »

Thanks, Tim.

RM · « **Reply #10 on:** November 24, 2009, 02:02:27 PM »

Hi there,

To update this, I've ordered some NOS Telefunken ef800 valves from Ebay. 4 of them from the same batch.

A question I had (and, please forgive my relative inexperience with this subject), is there a recommended amount of burn-in time for a valve before I can judge it's sound?

Thanks,
Ryan

Klaus Heyne · « **Reply #11 on:** November 25, 2009, 02:58:09 PM »

For miniature tubes like the EF800, EF86 or 6072 I recommend at least a 72 hr. constant operation before judging noise and other performance parameters.

Please make absolutely sure that the voltages each of the tubes under test receive from the power supply are properly adjusted before you start the long-run test.

Please also read all of the tube primers in my "stickies" forum. They address this subject from several angles:

http://recforums.prosoundweb.com/index.php/f/46/318/

RM · « **Reply #12 on:** November 25, 2009, 03:03:56 PM »

Thanks Klaus.

Embarrassingly, I just came here to post that I had just done exactly as you mentioned above and found the info.

Sorry about that.

Thank you for maintaining such an invaluable resource.

scott petito · « **Reply #13 on:** December 07, 2009, 06:17:24 PM »

Hey Ryan and others

have you confirmed the wunder GT tube to be an EF 800 for sure?

I have not gotten an answer from Mike as well and what's with the Secrecy?

thanks

Cheers
Scott

Tim Campbell · « **Reply #14 on:** December 07, 2009, 06:39:43 PM »

The secrecy that you find so frustrating I'm sure has to do with the fact that these tubes are no longer manufactured and so there's a limited supply. Why would any manufacturer who's had success with a model of tube draw attention to it and help insure dwindling the supply further and driving the price up. By voicing publicly the great sound achieved by a particular tube you also end up doing your competitors R&D work for them.

scott petito · « **Reply #15 on:** December 07, 2009, 07:10:15 PM »

I see what you are saying but it seem owners of the mic should have a clue in the event a tube goes down and no one is home at company... besides any competent tube guy could tell what tube it is no doubt..also it seems to me that there's a lot more to the process than just what tube is used but rather how it is implemented everyone knows there is an ef86 in a 67 I ain't heard a clone yet that sound like mine...

but thanks for leading us in the right direction as far as what the tube is!

cheers
Scott

Klaus Heyne · « **Reply #16 on:** December 07, 2009, 09:07:59 PM »

scott petito wrote on Mon, 07 December 2009 16:10

I ain't heard a clone yet that sound like mine...

Great country song lyric!

scott petito · « **Reply #17 on:** December 08, 2009, 11:38:38 AM »

Hey Klaus

If I write the tune I'll give you a co writer credit just for pointing it out!

cheers
SP

RM · « **Reply #18 on:** December 08, 2009, 01:51:46 PM »

Well, I found 4 NOS ef800 valves on Ebay, bought them, let one burn in for 72 hours and the mic is working great. My noise floor problem is gone and sound-wise is back to where I remember it being when I first received it.

Mike's not responding is understandable for the reasons mentioned. I simply thought I'd get much more life out of the valve that came with the microphone (about 9 months).

This, of course, is my experience.

What was the problem with your mic?

Sorry for not updating this sooner.

Ryan McVeigh

compasspnt · « **Reply #19 on:** December 08, 2009, 02:51:32 PM »

Any tube MAY go bad at any time.

Some will last for many years.

Some will test very well, but die a mysterious death sooner than later.

Perhaps with the partial exception of the VF-14-M, which is almost bullet proof.

scott petito · « **Reply #20 on:** December 08, 2009, 08:44:33 PM »

Hi Ryan

mines about 2 years old now .. it's having an increase in overall noise and the typical tube crackle so most likely a new tube and it will be fine

and yes some tubes will last years.. I have ef 86's that have gone for 5-6 years with no problems and others evn good ones like Tele's and Mullards that are bad in less than a year... NOS is a touchy area

at least the 800's are not very expensive relatively speaking
does anyone know ...is the 804 series compatable as well?

cheers
Scott

RM · « **Reply #21 on:** December 10, 2009, 01:50:13 PM »

As Terry mentioned, these things can go anytime.

Now I know to purchase some extras when I buy a mic.

Yes, the current price for these valves is not too bad ($8-$15 a piece), but I sure wouldn't want to see that skyrocket - especially if I was a microphone manufacturer.

I have no idea about the 804.

MI · « **Reply #22 on:** December 10, 2009, 04:32:31 PM »

The EF804 is identical to a EF86 with different pin layout.

MI

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Author Topic: Wunder cm7 gt tube? (Read 12631 times)