Will be selling a late U47, PS and accessories-What's the best way to test?

[Ivan K.]

In about a month, I'll be picking up a U47, power supply, etc. that has been stored at a friend's for the last 30 years or so. I expect to re-cap the power supply, but would recommend to a potential buyer that they get a new, regulated supply, rather than adding regulation to the current one. Is there a consensus that this is the right approach?

I'd appreciate any advice about powering it up and testing it. I would naturally, test its PS and use a Variac to slowly bring it up to line voltage (120VAC). I would measure any accessible parts first in both the mic and PS. The S/N is 5xxx something and may be a Nuvistor version. I don't have the exact S/N handy.

I also have 3, VF14 tubes with it of unknown quality. They were purchased about the same time as the mic, but from a different source. I think 2 are new. I'd appreciate any test tips, especially if the U47 is a Nuvistor version as I won't be able to plug them into the mic. If I can find the right socket or make one, I could copy the U47 schematic and test the tubes as Hi-Z amplifiers. Is this practical? I have an Audio Precision One that I can use for frequency response, THD, S/N, etc.

All advice appreciated!

Thanks,
Ivan

 

[sodderboy]

Honestly, if you or someone else are selling it, I would not touch it, especially if it has original caps in it. If you can prove that it has not been touched in 30 years, it will be worth more to a serious collector/engineer than if you or I work on it. The "time capsule" vibe is more valuable than a DIY service unknown to a fat cat buyer. Don't power it, and be really careful when opening it to take pics.

A vintage U47 should be treated differently than a worn-down duplex property when the plan is to flip it.

If it is serious I can PM a phone number of such a person, but in the words of The Boss, "this guy don't dance".
Mike

 

[MagnetoSound]

+1

If you were to have it serviced for sale to a serious user rather than a collector, it should be done by a recognised name in the field - Drefahl, KH, etc - and the cost included in the sale price. But that still might command less bucks than an untouched collector example.

Of course much of this depends on the cosmetic condition of the microphone and the originality of the existing parts.

Insofar as powering up for testing, the variac is a good move and should be done very slowly, while monitoring the output for any untoward noises.

 

[Khron]

+1

If you were to have it serviced for sale to a serious user rather than a collector, it should be done by a recognised name in the field - Drefahl, KH, etc - and the cost included in the sale price. But that still might command less bucks than an untouched collector example.

Of course much of this depends on the condition, cosmetic and working, of the microphone and the originality of the existing parts.

Just as "food for thought" sort of, i can't help but wonder what others might consider more valuable - 100000% genuine-original-untouched but not working, or a serviced but completely well-working one?

I guess my cynicism just wants to gauge the rough level of "insanity"(?) in such circles...

 

[MagnetoSound]

Just as "food for thought" sort of, i can't help but wonder what others might consider more valuable - 100000% genuine-original-untouched but not working, or a serviced but completely well-working one?

In my experience, and I fully accept that opinions might vary widely on this, any vintage item worth investment is at peak value when just the minimum of parts replacement needed to get it working properly has been carried out and as many original components as possible are still in place, so the next owner can decide to investigate what further service might be necessary for the future.

And of course any parts replaced should be included in the sale as evidence that they might have failed.

Nobody wants to feel that a piece may have been ‘robbed’ of working vintage parts before they buy it.

 

[GeorgeToledo]

If it is setup for a Nuvistor it *could* still have the VF14 socket. Neumann had two different ways of doing the Nuvistor mod and one (the earlier, iirc) would use the original socket.

I agree with posts above.

 

[PrivatCollector]

In about a month, I'll be picking up a U47, power supply, etc. that has been stored at a friend's for the last 30 years or so. I expect to re-cap the power supply, but would recommend to a potential buyer that they get a new, regulated supply, rather than adding regulation to the current one. Is there a consensus that this is the right approach?

I'd appreciate any advice about powering it up and testing it. I would naturally, test its PS and use a Variac to slowly bring it up to line voltage (120VAC). I would measure any accessible parts first in both the mic and PS. The S/N is 5xxx something and may be a Nuvistor version. I don't have the exact S/N handy.

I also have 3, VF14 tubes with it of unknown quality. They were purchased about the same time as the mic, but from a different source. I think 2 are new. I'd appreciate any test tips, especially if the U47 is a Nuvistor version as I won't be able to plug them into the mic. If I can find the right socket or make one, I could copy the U47 schematic and test the tubes as Hi-Z amplifiers. Is this practical? I have an Audio Precision One that I can use for frequency response, THD, S/N, etc.

All advice appreciated!

Thanks,
Ivan

Hi Ivan,
Curious how this developed

 

[Ivan K.]

Sorry to say, I have not had the time to pick up my U47 or other items at my friend's in Texas. He does not, understandably, want the responsibility of shipping everything to me and it is a 3 day round-trip drive for me to a rural part of the state to get the items. Even flying and renting a car would take 2 days. I will try later this month / beginning of November and can notify you when I have everything at home, inventoried and tested.
Regards,
Ivan

 

[PrivatCollector]

Hi Ivan,
please do

 

[PrivatCollector]

Hi Ivan,
dont hesitate to reach out by PM once ready

 

[PrivatCollector]

Hi Ivan, Did you find some time? Interested

 

[Ivan K.]

Hi Ivan, Did you find some time? Interested

Sorry to say, no time. Thank you for your patience. If you wish to share your direct email with me, I'll be sure to contact you after I collect my microphones--probably not for another month though. Regards, Ivan

 

[Delta Sigma]

If it were me, I'd make sure that bugger was working, even if it fetched less money. The idea of selling a potentially usable mic to a collector for their bragging rights makes me feel ill. Not judging any decision you'd make though; money doesn't grow on trees!

Member @Ericbazaar is likely one of the most knowledgable around when it comes to U47 restorations. Unfortunately, he announced on his IG that he's no longer doing repairs/restorations for those outside of Europe any more. Would be interesting to know if he has anyone he'd recommend in the US.

 

[PrivatCollector]

If it were me, I'd make sure that bugger was working, even if it fetched less money. The idea of selling a potentially usable mic to a collector for their bragging rights makes me feel ill. Not judging any decision you'd make though; money doesn't grow on trees!

Member @Ericbazaar is likely one of the most knowledgable around when it comes to U47 restorations. Unfortunately, he announced on his IG that he's no longer doing repairs/restorations for those outside of Europe any more. Would be interesting to know if he has anyone he'd recommend in the US.

Uh.. Delta Sigma: i'm not completely sure what you are implying, but i sense a bit of a stinch.... If i'm reading wrong i sincerely appologise, but your statement that "selling to a collector" thus means that a mic is kept away from serving many future beautifull recordings couldn't be farther from the truth. On the contrary i would say.

 

[Delta Sigma]

Uh.. Delta Sigma: i'm not completely sure what you are implying, but i sense a bit of a stinch.... If i'm reading wrong i sincerely appologise, but your statement that "selling to a collector" thus means that a mic is kept away from serving many future beautifull recordings couldn't be farther from the truth. On the contrary i would say.

This is regarding keeping the mic in original - possibly not working order - vs restoring the mic to a functional state. If someone wants a restored U47 and puts it to use, this is what a mic is meant for. A lot of assumptions though, the mic may already be in working order, depending how it was stored. Either way, I'm in favour of putting it in the hands of a qualified technician.

Likely less common in microphones than cameras, but a lot of the world's best vintage cameras and lenses are sitting on someone's display shelf, never to be used.

 

[terry setter]

A few years ago, an older man I knew, a doctor who collected microphones, brought me two U47s to check out because they were not putting out signal and he was selling his collection. I was not the first person into the mics (I know this because the wax seal that Neumann puts over one of the body screws before it leaves the factory was already removed). They were both completely original inside and showed no signs of work having been been done on them. They had been sold in the USA, because the had the red dot my their serial numbers. But my tests quickly showed that the capsules had failed (and their sputtering showed degradation). I swapped the heads for one of mine and the mics then worked very well. I counseled the owner to advertise them with the same description that I just wrote out and with a clear statement that the capsules needed replacement. The pair sold in two days for $20,000, sight unseen. I don't think he would have gotten much above $10,000 each had he gone through the hassles of getting them repaired. So yes, I agree that there is a value to buyers when mics are as close to original as possible. Sadly - well kind of sadly - my U47 works very well and garners compliments for its "original, vintage sound", but it has a Thiersch blueline capsule, a BV08 clone transformer from Oliver Archut, and modern resistors. I'll never get top dollar for it, yet I've never found one that does a better job of what that mic was designed to do.

 

[TLRT]

I'm starting now to service one 1951 U47, I can show some important details what is needed to check first:

 

[Ivan K.]

Thanks everyone for your posts! This will be my second U47 that I will be selling. In my ignorance, my assumption was that anyone buying this mic and power supply would want it to be in working condition! Fortunately, the mic worked fine. I did have to replace the crumbled reddish foam supports. I didn't have the original PS and and had built a fully regulated one years ago, using an LM317HV and well filtered. The eventual purchaser, an overseas studio, owned another U47 and had a spare original PS, which the owner claimed had a "purer" sound, so I was fortunate that it worked out.

I'm not a complete stranger to these vintage mics, having also sold a U67, ELA M 251, M49, KM 54, 56, 84, CM51 & 61, SM2, SM69, etc.

I look forward to hearing from TLRT on details to check. This time, before adventuring into repair turf, I'll see who wants to buy it before doing anything more than basic examination.

I also should have 3 VF14 tubes. I think 2 are NOS and 1 is used. Any thoughts on testing them? I thought about making an external circuit board and configuring it per the U47 schematic and checking for noise & frequency response, gain, etc. on my Audio Precision. I'd probably need to use lower value resistors (scaled) to get an accurate frequency response given the 100kOhm input Z of the AP, or an impedance converter.

New Year's greetings to all!
Ivan

 

[Khron]

In my ignorance, my assumption was that anyone buying this mic and power supply would want it to be in working condition!

Yeah, people are (REALLY) weird...

 

[TLRT]

Thanks everyone for your posts! This will be my second U47 that I will be selling. In my ignorance, my assumption was that anyone buying this mic and power supply would want it to be in working condition! Fortunately, the mic worked fine. I did have to replace the crumbled reddish foam supports. I didn't have the original PS and and had built a fully regulated one years ago, using an LM317HV and well filtered. The eventual purchaser, an overseas studio, owned another U47 and had a spare original PS, which the owner claimed had a "purer" sound, so I was fortunate that it worked out.

I'm not a complete stranger to these vintage mics, having also sold a U67, ELA M 251, M49, KM 54, 56, 84, CM51 & 61, SM2, SM69, etc.

I look forward to hearing from TLRT on details to check. This time, before adventuring into repair turf, I'll see who wants to buy it before doing anything more than basic examination.

I also should have 3 VF14 tubes. I think 2 are NOS and 1 is used. Any thoughts on testing them? I thought about making an external circuit board and configuring it per the U47 schematic and checking for noise & frequency response, gain, etc. on my Audio Precision. I'd probably need to use lower value resistors (scaled) to get an accurate frequency response given the 100kOhm input Z of the AP, or an impedance converter.

New Year's greetings to all!
Ivan

To test vf14 for noise you need an external unit which simulate the u47 high impedance part and working voltages then you can monitor the noise thru AP( but it is a bit overkill) I simply use my RME card's Digicheck Totalyzer sw+good headphone. If the tube is noisy, it can be "rejuvenated" with special gear.