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Author Topic: "Franken" U47 opinions welcomed!  (Read 5496 times)

klaus

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Re: "Franken" U47 opinions welcomed!
« Reply #15 on: October 28, 2011, 03:10:36 pm »

Just check the heat developing on these dropping resistors. Try to even out the heat (and power dissipation) over all resistors involved, and determine the resistive value that way. If one resistor does overtime with dissipating heat (and, in the U47 application, soaking up current) over another, it will fail sooner and voltages will drift more.
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

kats

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Re: "Franken" U47 opinions welcomed!
« Reply #16 on: October 28, 2011, 03:25:34 pm »

Thanks Klaus, your aces!
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Tony K.
http://empirerecording.ca

Entertainment is a bore, communication is where it's at! - Brian Jones 1967

klaus

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Re: "Franken" U47 opinions welcomed!
« Reply #17 on: October 28, 2011, 04:03:40 pm »

If the existing resistors don;t seem to be getting too hot, you can slightly lower the output  voltage of the unit by increasing resistor value of one of them. Go to the one which is least hot first. If they are both very hot, add another 10W resistor at the very beginning of the circuit, right after the rectifier.

This all assumes that you are versed in working on high voltage electricity. Work with one hand behind your back when testing or manipulating the power supply when on, or pass the job to someone who has experience with voltages in excess of 300VDC!
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Klaus Heyne
German Masterworks®
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kats

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Re: "Franken" U47 opinions welcomed!
« Reply #18 on: October 28, 2011, 06:40:39 pm »

Well, I am going to have to put the mics down for now because I am booked until the middle of November before I have a break. So here's my last entry until then.

PSU: I decided to remove both resistors and check their values. The 1k tested perfect, the 2k gave me an OL reading. I am thinking that the 10V drift can be due to this. So I'm just going to replace the resistors with stock values and re-test.

K47: I did the "breath test" on the back side, and instant fuzz! I'm sure your right about the contamination. But one thing I have been doing is some extensive testing on the front side because it seems a little brighter than one would expect judging by anecdote. Compared to an old M7 with it's original skin, this k47 is more pronounced in the 10k region. There's an impression that it has ever so slightly less weight in the low end - although it's possible that the extra top end may be influencing the perception. I also compared it to a Theirsch made PVC m7 with the same impression. I have read many times the perception of the k47 to be a darker capsule than a M7, but in my case it seems to be different.

VF14: I decided to kill two birds with one stone and replace a T-USA VF14K (glass tube in steel) with the spare Vf14 that came with this mic. I wanted to make sure the VF14 works, and as an aside compare the difference in sound between the two tubes all else being equal. The good news is that the VF14 (not NOS) works great and is very quiet!

Now I'm sure some may find this interesting regarding the difference between the two tubes. Tonally I found them quite similar. The main difference in tone was a subtle extra presence in the Vf14 (I allowed an hour for each tube to warm up). The impression I got though was that the VF14 seemed to be a little "punchier" (for lack of a better term) or some may say a little more dynamic. The overall impression was that the voice felt bigger or livelier. These differences were subtle and I wouldn't lose much sleep if I had to replace a VF14 with the T-USA VF14k. That said, although the differences were subtle, I had two other producers listen to the files "blind", and they described the differences in similar terms. In other words, subtle BUT noticeable.

Again, thanks for reading my latest adventure and an extra thanks to Klaus for his guidance.
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Tony K.
http://empirerecording.ca

Entertainment is a bore, communication is where it's at! - Brian Jones 1967
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