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 on: December 03, 2022, 08:49:06 PM 
Started by brucekaphan - Last post by soapfoot
I'd just like to add in case it's not 1000% clear--even if there's a convenient place to measure filament voltage at the mic PSU, you only want to measure at the tube itself, because everything in-between has resistance which will cause voltage drop.

Also, be very careful to protect not only yourself, but the rare tube inside. If you end up damaging the rare, pricey, needs-to-be-selected tube, it will be a very, very annoying and expensive fix.

That's why it's important to ensure the heater voltage is correct as soon as is practical.  :)

 on: December 03, 2022, 07:31:46 PM 
Started by brucekaphan - Last post by brucekaphan

Thanks again for your help! I especially like all the reminders to not electrocute myself! I have all-day client-attended sessions the next two days, so it will be at least a few days before I'm able to follow your instructions, but in the meantime, I just wanted to thank you for taking the time to educate me and anyone else who might be looking at the same situation.


 on: December 03, 2022, 05:49:50 PM 
Started by brucekaphan - Last post by Kai
Maybe Klaus has a better method, here’s how I do it:

• Arrange everything on a table with non-conductive surface: plastic, glass, dry clean wood - NO METAL!
• Unplug mains power at the wall outlet.
• Plug the mic to the PSU - this way the PSU is fully discharged and safe to open.
• Remove and open the female cable connector, the one that goes into the mic.
• Locate the heater voltage control of your PSU.
Usually you have to open the PSU for that, but some have a screwdriver hole opening.
NOT the stepped, course mains voltage adjust for 110-127-220 V, NOT, really!
• Have a fitting, fully ISOLATED small blade screwdriver handy. The ones electricians use for terminal strips, or the fully plastic ones for electronics adjustments.
• Plug the connector back to the mic.
• Connect a DC voltmeter between pin 4 and 7. Use small clips. Double check the meter clips don’t short with neighboring pins. Then double check again.
• Set meter range to read 5 V DC and switch on the meter.
• Get everybody out of the room, even pets.
• Plug in mains.
• Put one hand in your back pocket and leave it there through the whole process.
 This is a good safety measure to prevent being electrocuted when something goes wrong.
• After a minute the meter should read a value close to 4 V. Else you’re measuring the wrong pins.
• Adjust to 3.9 - 4.0 V. Turn slowly and watch for changes.
No changes -> wrong control.
• Unplug mains at the wall outlet.

If something doesn’t work as expected, start again with “Unplug mains at the wall outlet”, before locating the error.

 on: December 03, 2022, 03:57:37 PM 
Started by brucekaphan - Last post by brucekaphan

Thanks so much for this thorough reply to my questions. I'm now intrigued by your comment on adjusting the heater voltage. I was unaware that changing cable length would require such an adjustment, and I've never done anything of this nature before. Is making this adjustment something you'd be willing to explain in enough detail so that a relative novice at repairing mics wouldn't stand to do damage?

 on: December 03, 2022, 03:25:53 PM 
Started by John M Fleming - Last post by John M Fleming
For sale: digital audio cables and impedance-matching transformer.
The 3 items are being sold as a package.  Price (for all): $74.00.
For pick up only, in Garden Grove, CA, U.S.A. 
Please pm me using the forum tools if interested in buying.

Items for sale are as follows:
Neutrik AES/EBU Digital Impedance Transformer Adapter (110 Ohm to 75 Ohm)
* For Long Cable Runs Via Coaxial Lines
*       For Digital Audio Signals
*       Matches 110 Ohm Cable to 75 Ohm Line
*       Input: 3-Pole XLR Female Connector
*       Output: Female BNC Chassis Connector
*       Durable Aluminum Construction
The Neutrik AES/EBU Digital Impedance Transformer Adapter (110 Ohm to 75 Ohm) allows for long cable runs for digital audio signals via low-attenuation coaxial lines. It passively matches the characteristic impedance of a balanced 110 Ohm twisted-pair cable to that of a 75 Ohm unbalanced coaxial line. The adapter is equipped with a 3-pole XLR female input connector and a female BNC chassis output connector.
Key Features

*       Allows long cable runs for AES/EBU digital audio signals via low-attenuation coaxial lines

Belden 1800F-XMF-15BE

AES/EBU Female XLR to Male XLR High-Flex Blue - 15 Foot cable

1800F-XMF-15-BE - Overview
Designed to provide the latest in precision impedance and flexibility, these new digital audio interconnects will provide reliable performance with AES/EBU interfaces.
Featuring Belden 1800F "Super Flexible" digital patch cable, these tough assemblies include the best features for crush resistance, French Braid shielding and high density insulation which further reduces capacitance and propagation delay, allowing error-free transmissions over extended distances. Supports all devices that require AES/EBU 110 Ohm XLR to XLR interfaces.

75 Ω Apogee Wyde Eye S/PDIF (RCA) to Word Clock (BNC) Cable, 2.5 m. (8.5 ft.) length

This is a speciality cable terminated with a S/PDIF (RCA) connector on one end and a Word Clock (BNC) connector on the other. 

 on: December 03, 2022, 12:34:14 PM 
Started by brucekaphan - Last post by afterlifestudios
Glad to hear it! 

 on: December 02, 2022, 11:50:17 PM 
Started by Eddie Eagle - Last post by Eddie Eagle
A recent TripHop piece I created. Welcome to the hash den

 on: December 02, 2022, 07:45:26 PM 
Started by Safari - Last post by Safari
Не знаєте де можна пограти в онлайн казино без ризиків втрати грошей?  Привіт. Пограти в онлайн казино можна де завгодно, але якщо без ризиків то можу порадити тобі цей сайт. Це казино https://mrcasinos.net/igrovi-avtomati/ не є онлайн-казино без юридичного дозволу. Вони є повністю ліцензованим онлайн-казино. Сподіваюся вам сподобатися і ви не розчаруєтеся.

 on: December 02, 2022, 07:05:10 PM 
Started by brucekaphan - Last post by Kai
Cable microphonics of the type you describe usually origin from the screen litz wires have become brittle and broke over the decades.

I can‘t comment on the sound, but functionally I don’t see a problem using the Gotham cable.
The only thing to watch for is, when changing the length of a tube mic cable, the heater voltage needs to be re-adjusted.
Measurement is done on the mic side BTW.

A bit of under-voltage (longer cable) is less critical than any over-voltage.
Therefore, running a tube mic with varying cables is a bit uncomfortable.

The only source for the 7-pin Large Tuchel plugs are specialists shops and the used market.

The plug is simply called Large Tuchel 7-pin, the one with the thin round pins.
The number is Tuchel (HF) T-3468 (male) and (HF) T-3469 (female) or (HF) NT-3469 (female with swivel stand mount).
A version without HF shield is T-3460 and T-3461 / NT-3461 (swivel).
The HF shield is of minor importance, an active cellphone close to the mic will spill into it any way.

I’ve never seen the version with the larger squared pins (like used in the U-47) in a 7-pin variant, only 3- and 6-pin, so Large Tuchel 7-pin should be the key information.

 on: December 02, 2022, 05:13:53 PM 
Started by brucekaphan - Last post by brucekaphan
This post is essentially a continuation of a tangent thread that evolved within Klaus' M49V evaluation; I didn't want to further distract from the focus of that post, so I'm starting a new one here.

I own a Neumann M249 that Klaus dated at "1964-1965." I recently noticed (by random chance) that the last eight feet of the mic to power supply cable (on the microphone end) was microphonic when handled—when not being handled the cable worked beautifully, but since cables can sometimes be jostled during recording, I didn't want to continue to risk ruining a recording so I decided to cut the offending cable off and re-terminate. My studio is small so I'll never miss that 8' of cable in my room. Following Klaus' detailed instruction on termination, the cable is now working beautifully—microphonics are gone.  However, if I find myself working in other studios, I'm likely to want a longer cable. A few years ago, for a different mic, I purchased a good supply of Gotham 20102 (751) cable—I have plenty left over to build a longer cable. It's double-reussen, and with slight differences in hues, the internal wires follow the same color code and at least appear to be the same gauge as the original Doerffler cable. I'm thinking that on a rainy day, I'd like to build the spare (longer cable).  Does anyone have any thoughts/feelings comparing the original Doerffler to this Gotham cable? Is this Gotham cable as close as I'll be able to come with contemporary cable, to matching quality with the original Doerffler?

Equally pertinent: if I build a spare cable, I'm going to need the appropriate Tuchel 7 pin connectors. Can anyone tell me if these are still being built and if so, where can I find a contemporary source for these? Of course in pursuit of either new contemporary or old stock, it would also be useful to know the actual name or model number for these connectors...

Any help would be appreciated!


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