Junction

Re: Altec "coke bottle" issue or maybe general tube mi
« Reply #20 on: November 14, 2017, 06:24:25 PM »
Before you go rebuilding the mic, try the "breath test" This is a standard test endorsed by Neumann for their condenser microphones, I dont know this Altec, but I see no reason why the test is not suitable. With your mouth wide open, breathe softly onto the capsule (while it is plugged in and powered up) You are breathing moisture onto the capsule surface. If within a matter of seconds, maybe 5-10 seconds, the audio dies, it might drop 30 or 40dB and then it takes possibly minutes , 3 or 4 minutes before the audio returns to normal level, then you have a dirty capsule. The moisture from your breath and the dirt causes a short across the capsule and hence the dramatic audio level drop. You will then need to clean the capsule surface ... its quite simple, but that's a another story


Junction

Re: Altec "coke bottle" issue or maybe general tube mi
« Reply #21 on: November 14, 2017, 10:43:04 PM »
Note you appear to be responding to the first post, from 2006.
Oops, thanks Doug, must have been still half asleep.

deveng

Re: Altec "coke bottle" issue or maybe general tube mi
« Reply #22 on: November 24, 2017, 01:06:30 PM »
Quote
Well, it does seem that the Altec cable was designed especially for this use.  Unfortunately original cables are selling for crazy $.  I bought Mogami Neglex 3172 but obviously have not tried it yet.  Cable *should* work with just seven conductors.  Whether shielding will be sufficient, capacitance will be an issue, etc. I have no idea.

I just received 25' of Redco TGS-M7 I'll let you know how this cable works out.  It looks really good, soft flexible jacket, one twisted pair and a couple of larger gauge conductors for the filament.  I have purchased the Gotham cable in the past.  Its excellent cable but a bit stiff. 

Regards,
Jeff

deveng

Re: Altec "coke bottle" issue or maybe general tube mi
« Reply #23 on: December 01, 2017, 07:17:15 PM »
Wired up the coke bottle mic (cardioid capsule) with Redco TGS-M7 cable.  It appears to work well although I have no experience with this particular mic.    The Mogami 3172 should be fine too.   The chest plate mic works as well but has lower output (omni capsule).    The re-cap job solved the hum issue.    I only did a quick check for function and noise using a portable Mackie mixer.    Some typical tube mic hiss at high gains but nothing out of the ordinary at first listen.  Neither of the  tubes are microphonic.    I'll buy some replacement 6AU6's for spares and try them out soon.     Now looking at the Rycote Universal shotgun mic mount.  Any recommendations on a suitable shock mount?  Mic body is 28mm at the base.   I have the original mic stand adapter wired with the Redco and I have an extra set of Amphenol 8 pin connectors which I'll wire up for use with the shock mount option.

Regards,
Jeff
« Last Edit: December 01, 2017, 07:20:18 PM by deveng »