Telefunken U47 noise issue

[Biula]

This is an original 1958 Neumann NG47 power supply, unregulated, with original condenser: no issues, dead silent, perfectly working... who said vintage designs cannot withstand modern standards?

 

[tomas.borgstrom]

This is an original 1958 Neumann NG47 power supply, unregulated, with original condenser: no issues, dead silent, perfectly working... who said vintage designs cannot withstand modern standards?

I've serviced many original U47 and never had any issues with the NG PSUs. Even the selenium rectifiers seem to work forever.

 

[Mr. Moscode]

I've serviced many original U47 and never had any issues with the NG PSUs. Even the selenium rectifiers seem to work forever.

They highly over rated, so to speak. The seleniums don't have switching noise and at the low current the resistive voltage drop is negligible. Take the paint off one of the cells and you have a solar cell.

Even though the long R-C filter is slower than the cut off frequency of the amplification you still have performance that varies with power line voltage, but slowly.

And say what you may about quality of parts, today's electrolytic caps are far superior to those in the 40s - 80s. That PS would benefit with a PP cap as the last one in the R-C string. Solen makes some that are appropriate.

However - get it fixed or preferably replaced under warranty to minimize down time, have your favorite attitude adjuster and be patient.

 

[Accelerator]

@lunatic_ash

I disassembled the PSU again and took a picture of the back side of the board.

I think it looks terrible. Even tho I have literally no knowledge about it, I can feel it.. lol Plz look into it.

View attachment 134986

Is it bad??

How could the PSU of 10000 dollars microphone be soldered like this?

I’m sorry that I have to tell you man, but for your hard-earnest $10.000 U.S.D. that you spend to buy this hilarious & ridiculous over-priced microphone I wouldn’t accept anything less than a true P-2-P (point to point) construction “from head to toe”, from capsule to P.S.U. outer plug, with the highest today’s quality Mundorf TubeCap 200uF 550V capacitors at P.S.U., with a real NOS Telefuken GmbH EF-14 tube rather than this B.(arbara) S.(treisand) fake “VF-14” aka a 6028 - 408 A tube with a resistor in a metal can…

I’m sorry that you feeling like you are the “fool for today” but unfortunately as you know all of these marketing B.(arbara) S.(treisand), with all of hired and paid “Influencers” who “praise & raise” B.(arbara) S.(treisand)s like: “this one sounds like the original” doesn’t come cheap and someone has to be the “fool for today” to pay them, especially with his hard-earnest $10.000 U.S.D. for something that he does for his living…

Meanwhile the Wunder Audio CM7 Suprema at $7795 U.S.D. and the Flea Pro Audio Flea 47 Vintage at €4.407,54 both of them use NOS Telefuken GmbH EF-12 tube(s), both of them are at much more reasonable prices, but they both don’t have all of this over-hyped marketing B.(arbara) S.(treisand)…

 

[Khron]

for your hard-earnest $10.000 U.S.D. that you spend to buy this hilarious & ridiculous over-priced microphone I wouldn’t accept anything less than a true P-2-P (point to point) construction “from head to toe”, from capsule to P.S.U.

So except for being expensive for the sake of being expensive, what's better about point-to-point construction in the dead-simple power supply?

(I'm agreeing about the ridiculousness of the price, but not necessarily the... "motivations"(?)...)

 

[Accelerator]

@Khron​

So except for being expensive for the sake of being expensive, what's better about point-to-point construction in the dead-simple power supply?

(I'm agreeing about the ridiculousness of the price, but not necessarily the... "motivations"(?)...)

The main advantage to point-to-point constraction is thermal durability over time, moisture resistant & electrically insulating (especially if we are talking about Garolite G-10/FR4 & Garolite G-11/FR5 Glass fabric laminated with an epoxy resin boards), ease of maintenance and modification.

Components are simply desoldered from their eyelets, turrets or terminal strips and new ones are put in their place.

Tone wise “theoretically”, there's not necessarily any difference.
Practically speaking, however, there's a fairly fundamental difference:

Air has a much lower dielectric constant than epoxy (which is what most PC boards are made out of).
This means even a fairly small gap of air between PTP wires reduces the capacitative coupling to a very low level.

Achieving exactly the same (or even less) capacitance between traces on a PC board is always possible, but often quite impractical.

In our “case” for this dead-simple NG47 power supply circuit, I wouldn’t accept even for a lesser price anything less than the highest today’s quality Mundorf TubeCap 200uF 550V capacitors with the Huntington MRA05 1k Ohm 5W or even the 1,0k 25W wirewound resistors and a collaboration with 8H chokes at the P.S.U., but that means that we have got a real Telefunken GmbH NOS VF-14 Vacuum Tube in our hand, something that doesn’t exist in this certain microphone with the fake “VF-14” tube, otherwise with a real Telefunken GmbH NOS EF-14 Vacuum Tube in our hand we have to design a deferent P.S.U. with separate HT+105 DC Volts & LT+ 5.8 DC Volts…

Hell, even the all Authentic & Original Neumann-Telefunken GmbH U-47 microphone with the all Authentic & Original Neumann-Telefunken GmbH NG47 power supply cost $ 390 U.S.D. back in time, something equal to $ 2.000 U.S.D. in today’s money rate, not this hilarious & ridiculous over-price of the $ 10.000 U.S.D….

 

[Khron]

ease of maintenance and modification.

But if it's an expensive, "properly" executed and exquisite power supply, why would it need maintenance or modification?

So except for being expensive for the sake of being expensive, what's better about point-to-point construction in the dead-simple power supply?

Tone wise “theoretically”, there's not necessarily any difference.
Practically speaking, however, there's a fairly fundamental difference:

Air has a much lower dielectric constant than epoxy (which is what most PC boards are made out of).
This means even a fairly small gap of air between PTP wires reduces the capacitative coupling to a very low level.

Please try to stay on point; perhaps consider re-reading (more carefully) the question i posed (quite clearly, i believe)?

 

[Accelerator]

@Khron​

But if it's an expensive, "properly" executed and exquisite power supply, why would it need maintenance or modification?

Because as the Rolling Stones sang:

“Time waits for no-one & no-one waits for me…”

Even if we had the today’s “case” of:

“an expensive, "properly" executed and exquisite power supply,”

Nothing’s gonna gives you any “1.000% warranty” that this expensive, "properly" executed and exquisite power supply will work flawlessly day in ~ day out, 24-7, in 10, 20, 30, 40, 50, 60 years without any problems or needs for modifications and replacements…

That’s why it would need this P.S.U. the ease of maintenance or even modification(s) that the P2P plentiful offers you more than the PCB board construction…
And that’s why all of these old P2P valve microphones, P2P tube guitar amplifiers, P2P valve equipment(s) etc. etc. etc. “gains” their timeless “saga”…

 

[Khron]

Right...

 

[Cqwet Dbdfte]

Air dielectric is superior to anything for high power RF, but for LF dielectric losses are miniscule.
The supply of NOS VF-14 is problematic, Telefunken had quality concerns back 60 years ago getting low noise tubes and switched to JFETs. I do not think the supply of selected low noise VF14s has improved since.
To the OP concern about noise, his mike's tube may need some burn-in, to wake it up, as the tube is run on the cold side. I would leave in on for a few hours before use.
Use it with cable up, to minimize capsule heating.

 

[Coggins]

1. Do not open the power supply or mic, take them back to your dealer and let them deal with it. You don’t want to void your warranty by trying to do it yourself, as it sounds like you are not qualified.

2. After your warranty expires, it’s time for a do it yourself solution.

 

[amplexus]

Easy - cheap(?) labor, or expensive labor performed by people who couldn't give two f**ks about it. That being said, i've seen worse, but I'm confused about the two-layer board being "required" for such a dead-simple design... But I guess they had to make it look "worth the money"..?

If anyone remembers how the modern “Telefunken” company started and the scam that they were pulling with their $1500 Apex/Nady/etc rebranding…. It shouldn’t be a shock.

The price to value for their mics is an absolute joke.

 

[tomas.borgstrom]

They highly over rated, so to speak. The seleniums don't have switching noise and at the low current the resistive voltage drop is negligible. Take the paint off one of the cells and you have a solar cell.

Even though the long R-C filter is slower than the cut off frequency of the amplification you still have performance that varies with power line voltage, but slowly.

And say what you may about quality of parts, today's electrolytic caps are far superior to those in the 40s - 80s. That PS would benefit with a PP cap as the last one in the R-C string. Solen makes some that are appropriate.

However - get it fixed or preferably replaced under warranty to minimize down time, have your favorite attitude adjuster and be patient.

I replace the electrolytics with F&T screw caps. I know that components today have better specs but my point is that the NG still work 70 years later. I'm not so sure that the same applies to the Telefunken USA PSU that is discussed in this thread. It's even shipped with a hum.

 

[RuudNL]

If anyone remembers how the modern “Telefunken” company started and the scam that they were pulling with their $1500 Apex/Nady/etc rebranding…. It shouldn’t be a shock.

That was a long time ago, but the memory remains...
http://recordinghacks.com/articles/telefunken-m16-and-apex-460-comparison/

 

[tomas.borgstrom]

Air dielectric is superior to anything for high power RF, but for LF dielectric losses are miniscule.
The supply of NOS VF-14 is problematic, Telefunken had quality concerns back 60 years ago getting low noise tubes and switched to JFETs. I do not think the supply of selected low noise VF14s has improved since.
To the OP concern about noise, his mike's tube may need some burn-in, to wake it up, as the tube is run on the cold side. I would leave in on for a few hours before use.
Use it with cable up, to minimize capsule heating.

The Telefunken USA microphone does not have a NOS VF-14. It has a grass tube hidden inside a metal case that says VF14k . It has nothing to do with VF-14. They are far from the only one miseading their customers by naming other tubes and solid state replacements after the original part.

 

[ZHOUJUN]

I replace the electrolytics with F&T screw caps. I know that components today have better specs but my point is that the NG still work 70 years later. I'm not so sure that the same applies to the Telefunken USA PSU that is discussed in this thread. It's even shipped with a hum.

I have repaired several Telefunken USA U47s, and their power supplies were terrible, including their M251 power supplies. Many of them started to buzz in a very short period of time. The culprit was probably poor circuit design and inferior components. This is similar to The original NG is too different.

 

[Cqwet Dbdfte]

Telefunken USA, seems like Tele-fakery.
Time to get the funk out of here.

 

[kingkorg]

Telefunken USA, seems like Tele-fakery.
Time to get the funk out of here.

Don't be like that. Not everything Telefunken makes is bad, and expensive. It is just that everything is based on 120 years old heritage, German, American, Irish, who cares as long as it says 120 years old....

 

[Mihobro]

Back in the 40's and 50's many German/Austrian/Swiss mic manufacturers used rectifiers that consisted of coated metal(steel?) squares stacked up. in their power supplies. These rectifiers worked well and were in some of the finest tube mics ever made, but, it would not take much moisture to make them corrode and fail(short). While it may be worthwhile to preserve totally original mics, in the interest of reliability, it is probably better to replace the whole power supply with an aftermarket supply, or at least have a spare one on hand. When you have session with 85 musicians coming in at union scale in NYC and have no spare M50's they probably need to work. Amazingly, as an emergency move, a high voltage modern diode will do in a pinch. The circuit design of these power supplies are pretty simple and conventional. Easy to understand and repair. Especially compared to modern switching supplies. (just throw it away and get a new one)but, original parts are almost impossible to find, like the V-14 tube. As a practical matter, modern components can successfully replace them. But, not all changes should be considered progress,

 

[Khron]

But, not all changes should be considered progress,

By the same logic, not everything that's old is necessarily to be worshipped...