Needing closest parts for Rebuilding a tube U47

[Khron]

Apart from whatever we might measure in them, my reaction to using them is "wow, that really makes my voice sound great.

Probably not done much double blind testing, though?

(Not trying to be snarky, just realistic - confirmation bias of seeing one of those rare priceless classics in front of your nose can make your mind play fickle tricks on you, kinda "by default"...)

 

[JeffKall]

There really is something special about how mics like U67s, U47s, C12as, and Ela M251s sound that is very hard to quantify. Thats the reason we are drawn to them. Granted there are variations in sound even between like models but these particular mics rarely dissapoint if they are in good working condtion. Apart from whatever we might measure in them, my reaction to using them is "wow, that really makes my voice sound great." It's probably the mic's right combination of compression, THD, TIM, and frequency response that is responsible for most of their "sound". These are measurable, but awfully hard to create with a pile of resistors, capacitors, inductors, etc.

Like Tomas, I'm not too fond of carbon compostion resistors. As for caps, I've been testing them and selecting them for low dielectric absorption. They audibly handle transients better than ones with sloppy dielectrics.

,

There definitely is “something” we hear in those vintage tube mics … probably closely affiliated with the “something” that George Martin heard when he auditioned The Beatles …

I like the term “Wow factor” … and it is one strong reason all of us are off on this DIY quest to try to capture or emulate the sound of these classics in the first place !

As far more brilliant people have frequently noted … the order of priorities to achieving the best possible end result begin with the capsule, tube and transformer … followed by quality of electronic components used in the mic and PSU …

As @Khron wisely noted here … in contemporary times we have far better component choices available to us than were available to the original manufacturers … which likely would have been selected had they been available back then …

But I do recall an attempt several years ago to recreate a Stradivarius … where the builder used wood from the same forest where Stradivari harvested his for his instruments … and even analyzed the finish Stradivari used in an effort to emulate it … The contemporary builder used all the tools of Stradivari’s time and emulated his processes to the best of his ability …

In the end … he created a fine instrument … but it was not a Stradivarius … and it lacked the classic Stradivarius sound …

Subsequently … we can all pursue that extremely subjective Wow factor that we can all agree exists in those classics … with varying result …

But … as George Martin so succinctly noted in the title of one of his books … and loved to remind everyone … “All You Need Is Ears” …

And ultimately it’s OUR ears (and in the case of appearance … eyes) that are all we subjectively truly need to satisfy !!!

 

[Khron]

and it lacked the classic Stradivarius sound

Well, even that's very relative - how do we know a genuine Stradivarius didn't sound like the newly made one, when it was newly made? All we can reference nowadays is a centuries-old acoustic instrument, which may or may not be in identical shap as when it was fresh off the lacquer-drying-rack...

 

[JeffKall]

Well, even that's very relative - how do we know a genuine Stradivarius didn't sound like the newly made one, when it was newly made? All we can reference nowadays is a centuries-old acoustic instrument, which may or may not be in identical shap as when it was fresh off the lacquer-drying-rack...

EXACTLY, sir !

While age and time work wonders on wine and wood … NOTSOMUCH electronics … or humans …

And also absolutely true … that how the originals “sounded” in their freshly minted condition was likely perceived far differently (in that time and space) from how they sound today !

Subjectivity rules !

 

[tomas.borgstrom]

I think we all agree that the vintage classic microphones are great BUT a lot of people can't tell. They listen with their eyes and adore the sound of a broken U47 or a shitty clone with a nice look and a high price tag.

I would never advise anyone to buy an expensive vintage tube microphone (or clone) without the possibility to compare it to a one that is known to perform as expected.

 

[JeffKall]

I think we all agree that the vintage classic microphones are great BUT a lot of people can't tell. They listen with their eyes and adore the sound of a broken U47 or a shitty clone with a nice look and a high price tag.

I would never advise anyone to buy an expensive vintage tube microphone (or clone) without the possibility to compare it to a one that is known to perform as expected.

Agreed, @tomas.borgstrom !
Even the “best preserved” vintage classics are now getting “long in the tooth” and showing the entitled degradation of their age …

All I personally have to compare to is my rapidly aging memory of working with some very well maintained vintage classics in LA in the early 80’s … and I subjectively judge my “modern” vintage classic DIY clone builds against my faded memories !

It’s the best I can do at this stage in time !

 

[DFischer]

Regarding old violins:

Strads

 

[JeffKall]

Regarding old violins:

Strads

Cool blind test !

I lucked out … and guessed right …

The Strad was SLIGHTLY warmer … and a BIT less shrill (screechy) on the top end … at least to my ears !!!

Thank you for this, @DFischer !

 

[Khron]

without the possibility to compare it to a one that is known to perform as expected.

That was my exact point, about what's basically impossible (?) to access anymore nowadays, for completely valid(?) tests / comparisons.

 

[CalavoBob]

I did have the opportunity to do a double blind comparison between (3) U-87s and (3) U67s in a studio in San Francisco where I worked in the early 90s. I had noticed the staff engineers weren't using the U67s because they didn't like the added hassle of connecting through the power supply boxes of the U67s, whereas the U87s only needed the console's phantom power, and they were concerned about possible noise from the tube versions. I hooked up the 6 mics in a mixed order in a row in the studio while the engineers listened in the control room, not knowing which was which mic. They heard vocals, and guitars over each mic. All the engineers picked the U67s as the better sounding mics, and they were surprised at how quiet they were. That studio also had C12As and C414s too. I wish I had conducted the same test on them.

At least when it comes to the question of how these vintage mics have changed over the years, we are lucky to have numerous excellent recordings made on many of these mics when they were in much newer condition. Too bad the studio records likely don't include the serial numbers of the mics that were used. Perhaps for future generations we could give them the gift of logging serial numbers of special mics that we use in our own recordings.

 

[inkster]

Personally I stay away from vintage passives as the caps can be leaky and there are some brands of resistors that could absorb moisture and create noise.
I built a special rig that along with a high voltage supply I can measure cap leakage at operating voltage, I built this after servicing valuable vintage mics that had an output tranny taken out by a leaky cap.

 

[Drea]

10W 1779 ohm resistent. Epoxy adhesive in the middle and a dots arctic silver on the sides.

 

[Drea]

“some speculation “ vf14 tubes that are really heavy are the quietest. I have 10 pieces.

 

[inkster]

10W 1779 ohm resistent.

 

[Khron]

I guess that's what it takes to get that WARM tube sound...

 

[Drea]

LoL Got also the same 5w

 

[ZHOUJUN]

Regarding the 1780 ohm resistor, I once disassembled one of my U47s， It looked like the resistor wire was very thin and wrapped with a layer of silky material， They were not enameled wires. I also purchased a 1780 resistor on the website Reverb. It cost me more than 600 US dollars， The seller claimed that it was the original skeleton, so that I could boldly test it， I compared the two and found that the difference between them was very small and the resistance values were very accurate， I had also done different tests， Compared with modern aluminum-cased resistors of different powers, I found that this old-fashioned resistor has better heat dissipation performance, probably because the heat dissipation area is larger. I have to admire Neumann's designers， Regarding the difference in sound, temperature should affect the components， They are too close to each other, such as the coupling cap, BV08, and the temperature drift of the voltage divider resistor. As for the impact on the sound, I am not sure, but there will definitely be a difference.
I also found that there are replicas for sale on eBay， The frame looks like black plastic? Has anyone used this? But I have doubts about the heat dissipation of the plastic-like material they use, but the price is cheap enough.

 

[JeffKall]

10W 1779 ohm resistent. Epoxy adhesive in the middle and a dots arctic silver on the sides.

I spent some time working for Los Angeles Information Technology Agency (LAITA) installing communications equipment in LAFD vehicles …

They were located in the Erwin Piper Technical Center … whose Hooper Memorial Heliport figured prominently in the movie Blue Thunder …

The LAITA was located in Piper’s old electronics lab that housed all kind of vintage communication gear … and an attic storage area that included all manner of vintage parts including tubes, transformers, capacitors and ceramic style epoxy dipped wire wound resistors of the type shown in your photos …

There were literally hundreds of still unopened cardboard boxes stuffed with every value and rating … which would no doubt be an inventory worth hundreds of thousands of dollars today …

But the LAITA … being a typical government agency … was likely to ignore the actual and intrinsic value of these vintage treasures … and they either still reside in the attic untouched or have since been unceremoniously dumped in the trash and sent off to the electronics recycler … who is happily selling them to us GroupDIYers for $600 apiece …

In Blue Thunder … there were exterior scenes shot in the mid 80’s … showing clearly visible pallets of large spools of various types of discarded hookup wire … that were still occupying the same corner of the security fenced outdoor storage area when I was there in 2015 …

Hundreds of thousands of dollars of discarded vintage parts and copper wire left to decompose …

Tragic !!!

 

[Drea]

There was a time I was surging to old components a few years back like resisters and silver wires. Now Ian completed with that. There are so many 47 miks that I make the N 47 miks from components of the fifty’s. Today I rebuilding the U47.

 

[Biula]

The hand wired resistor is pushed against the bottom of the microphone body and use it as a heat sink. You have to find a similar arrangement for the 10W resistor, otherwise the interior of the microphone will get even hotter than the original U47 and that might affect the performance and lifespan of the electronics.

Keep in mind that in the original design wirewound resistor heath is not "wasted": the mild warming of the body is a great measure agaist moisture condensing... you know, this kind of microphone was used is studio, but also in open air venues...