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[Barry Hufker]

I performed a search at Neumann's website before asking this question.  Having followed this forum for several years now, I think I am safe in asking my question without it having been covered (within the recent past).

Why is it people seldom speak of the U48?  There's always talk of the 47.  Is the 48 not as well made?  Does it lack the same sonics in cardioid as the 47?  Is it the fact that the 48 offers cardioid and bidirectional?

At the Neumann site I have been greeted with a deafening silence...

Barry

[Klaus Heyne]

I have a couple of observations about the U48:

1. It came much later than the pioneering U47. The reputation of the superiority of the U47 vs. the ribbon and dynamic mics, which were common in the US in recording studios at the time, had been established.

2. The U48 with its almost military-looking matte gray paint was not quite as appealing when it came out, compared to the original U47 with its chrome top, and its long, well proportioned body dimensions.

3. The s/n and dynamic behavior is a tiny bit worse in the U48, because, in order to squeeze out double the center electrode's polarization voltage for the rear in figure eight, the total available 105VDC from the power supply only translates to 50VDC for the mic in cardioid (60V in the U47.)
I.e. the slight loss in polarization voltage, and therefore a slightly worse s/n and altered dynamic behavior of the U48 is audible, but by no means all that objectionable (that deficiency, by the way, can be remedied.)

[Barry Hufker]

Thanks, Klaus.  All very helpful information.

How complex is it to "remedy" the U48 and its polarization/dynamic behavior faults?  Costly?  Time-consuming?

Barry

[J.J. Blair]

Abbey Road has a U47 that was modified by the Neumann factory to have cardioid and figure eight.  I wonder if they did the same modification that differentiates a U47 from a U48.

BTW, a couple of years ago, I saw a U48 on eBay that, rather than being painted grey, had the body bound in brown leather!


"It's looks just like a Telefunken U48 ... with leather."

[Klaus Heyne]

Barry Hufker wrote on Mon, 12 February 2007 18:52

How complex is it to "remedy" the U48 and its polarization/dynamic behavior faults?  Costly?  Time-consuming?

You can do it two ways:

Either sacrifice a true figure eight by jacking up the cardioid polarization voltage with the existing power supply set up, or by increasing the power supply output by roughly 15 volts, and re-calibrating the voltage dividers inside the mic afterwards.

The second course is a bit tricky, as the hand wound heater voltage resistor is precisely calibrated for 105V in, 36V out. But that too, can be overcome...

I often fudge the ideal U48 figure of eight voltages by using a different resistor division to come up with 60, or at least, 58 volts for the cardioid setting, and sacrificing a bit of the true figure of eight, settling instead for a figure of eight that is a bit lobed, with slightly reduced output in the rear.

In either option, you would get genuine U47 performance out of the U48 in cardioid.

As to cost: In the course of performing a complete restoration of a U48, an upcharge of a couple of hundred dollars for the less intrusive option should be about right.

[Barry Hufker]

Klaus,

Again many thanks for the education.

Barry

[delcosmos]

Klaus Heyne wrote on Mon, 12 February 2007 19:32

I have a couple of observations about the U48: 3. The s/n and dynamic behavior is a tiny bit worse in the U48, because, in order to squeeze out double the center electrode's polarization voltage for the rear in figure eight, the total available 105VDC from the power supply only translates to 50VDC for the mic in cardioid (60V in the U47.) I.e. the slight loss in polarization voltage, and therefore a slightly worse s/n and altered dynamic behavior of the U48 is audible, but by no means all that objectionable (that deficiency, by the way, can be remedied.)

Hi Klaus, as I previously stated, I just got a very expensive U48 from VK with an origiginal capsule and VF14 tube.
I thought that U47 and U48 were the same except for the patterns, I even saw on the "Recording the beatles" Book, that Abbey road modified a lot of their U47 in the 60's from 47 to 48 in order to have figure of 8 patterns.

So my question is, do you recomend me to make the modification you mentioned above to my mic in order to improve it's performance? Or is it better to leave it in it's original condition and get a U47 in order to get that "improved" tone?

Thanks.

Armando Avila

[Klaus Heyne]

The answer is clear and simple:

If you have the financial means to supplement the U48 (with its slightly compromised sound quality in cardioid) with a well-working, good sounding U47, by all means, keep the U48 stock.

But if you don't: it would not be hard to restore a mint, vintage, performance upgraded U48 back to stock in case of a sale to a vintage buff. Just make sure that the original parts are given back to you.

[Oliver Archut]

Hello Guys,

it is not a big issue to change the 48 to 47 specs, 60 volt polarization by changing the voltage divider, and just by using one of the none used pins on the tuchel, you can feed 120V to the back capsule. A simple voltage divider can be installed inside the PSU at the 4th filter stage. A procedure like that should be easy to remove if someone wants it all stock. Also in the same way the 47 could be changed to figure of eight.

Best regards,

[delcosmos]

Hi Oliver, thanks for your reply.

So, the mod can be made just in the PSU?

[Klaus Heyne]

No,
Either of the two routes I mentioned earlier requires work inside the microphone as well. If you want the additional variation, as mentiolned by Oliver, of feeding in a separate polarization voltage for the rear dipahrgam via a cable, you may have to replace the original cable and reconfigure the connector terminations in the mic and in the cable too.

The simplest, cheapest way to achieve genuine U47 cardioid performance is to sacrifice a bit of the uniformity of response in figure-eight.

There is another issue you would need to investigate also: late U48s have the infamous BV8 transfromer version which has a 6dB lower output than the previous, most common U47/48 transformer. (Do a search on "BV8", here and at the Neumann Pinboard)

[delcosmos]

Klaus Heyne wrote on Fri, 16 February 2007 12:49

No, Either of the two routes I mentioned earlier requires work inside the microphone as well. If you want the additional variation, as mentiolned by Oliver, of feeding in a separate polarization voltage for the rear dipahrgam via a cable, you may have to replace the original cable and reconfigure the connector terminations in the mic and in the cable too. The simplest, cheapest way to achieve genuine U47 cardioid performance is to sacrifice a bit of the uniformity of response in figure-eight. There is another issue you would need to investigate also: late U48s have the infamous BV8 transfromer version which has a 6dB lower output than the previous, most common U47/48 transformer. (Do a search on "BV8", here and at the Neumann Pinboard)

Well, I don't know anything about electronics but, is that posible to verify what kind of transformer comes with mine by looking this picture?
Also, do you know where I can send my mic to make those mods?

Thanks Klaus.

[Klaus Heyne]

First:
Congratulations!
ou seem to have an all-stock U48 amplifier with the original, 'M' stamped, VF14!

You can identify the BV8 (A of B) by looking on the top of the transformer, closest to the tube (you may have to push the tube out of the way for this): you will find a piece of ID paper glued to the isolation wrapping on the transformer which contains the transformer number you have.

The visible, outermost secondary windings on the transformer is another clue: the "B" version has very thick wire, compared to the older "A" version.

[delcosmos]

Klaus, thank you very much for all this information.
Would you be able to verify the year of my U48 by looking at this picture?

Again, THANK YOU.

Armando Avila.

[Klaus Heyne]

If you give me the serial number, probably.

We do know already that the mic as made AFTER July 1958, because that's when the Bosch capacitor, visible as a silver tube, was made.