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| Re: U47 voltage questions [message #338326 is a reply to message #338317 ] |
Thu, 01 May 2008 17:03   |
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 J.J. Blair
Messages: 10047
Registered: May 2004
Location: by the sea & sand |
Diamond Member |
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Dan, to make things worse I think I'm getting confused. When I had the mismatched bass response in my C37a capsules, I can't remember if the solution I found was to add another cap in series or in parallel. As Larry may have just clarified for me while explaining the single pole high pass, I guess I must have put it on parallel.
Now, as Larry explained the boominess disappearing at a higher capacitance had to do with a resonant frequency in the transformer, and the higher cap value moved that frequency subsonic, most likely, citing the boominess.
So, in summary, you are absolutely making the correct point: Lower C gives a lower single pole hi pass point. What I was hearing and thinking of was that resonance, not the hi pass. The question I guess Klaus or Oliver can answer is at what cap value the hi pass less or an issue than that resonance. I suppose the results of what I hear after changing that value will also answer that question for me.
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They say the heart of Rock & Roll is still beating, which is amazing if you consider all the blow it's done over the years.
"The Internet enables pompous blowhards to interact with other pompous blowhards in a big circle jerk of pomposity." - Bill Maher
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| Re: U47 voltage questions [message #338384 is a reply to message #337218 ] |
Thu, 01 May 2008 21:23 |
rodabod
Messages: 179
Registered: December 2005
Location: London |
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JJ, Did you try swapping the capsules at any point? That's probably where I'd look first as these can be so variable.
Roddy Bell
BBC / Siemens
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| Re: U47 voltage questions [message #338394 is a reply to message #338384 ] |
Thu, 01 May 2008 22:29 |
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J.J. Blair
Messages: 10047
Registered: May 2004
Location: by the sea & sand |
Diamond Member |
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Of course I did. That's how I determined the problem to be the capsules. The capacitor was my last course of action, after finding out that new capsules were $1,000 each from Sony. If you do a search for C37A, there's a thread discussing the whole thing.
I made a nice, discretely switchable cap, without even having to drill extra holes, so if you want the two mics to have the same bass response for a stereo app, they match pretty well. I haven't noticed any phase weirdness, as Larry suggested might happen, but I'll keep more of an ear out for it next time. But I mainly use them on toms anyway. Best tom mic ever!
temporary webpage
They say the heart of Rock & Roll is still beating, which is amazing if you consider all the blow it's done over the years.
"The Internet enables pompous blowhards to interact with other pompous blowhards in a big circle jerk of pomposity." - Bill Maher
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| Re: U47 voltage questions [message #338414 is a reply to message #338404 ] |
Fri, 02 May 2008 00:02 |
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Klaus Heyne
Messages: 2027
Registered: April 2004 |
Platinum Member |
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Considering the overall impedance of the U47 circuit, the transformer used, the capsule used, etc. 0,5 to 1.0 mfd as coupling cap is totally sufficient, and, even from a view point of measured cut-off frequency, way below any 'booming' possibility. (I generally use a 1.0 mfd in U47, never less, and never more, in 20 years of trying to optimize the mic.)
Your doubling of a coupling capacitance in such a circuit and hearing less bass is erroneous, theoretically nonsensical, and unheard of in the field as well.
My advice: use a good 1.0 mfd coupling cap in the U47' C 2 position (as well as in position C3), and you will be a happy camper. Yo need to look else where for your mysterious lack of bass in your mic.
Klaus Heyne
German Masterworks
www.GermanMasterworks.com
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| Re: U47 voltage questions [message #338455 is a reply to message #338394 ] |
Fri, 02 May 2008 06:55 |
rodabod
Messages: 179
Registered: December 2005
Location: London |
Active Member |
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| J.J. Blair wrote on Fri, 02 May 2008 04:29 |
Of course I did. That's how I determined the problem to be the capsules. The capacitor was my last course of action, after finding out that new capsules were $1,000 each from Sony. If you do a search for C37A, there's a thread discussing the whole thing.
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Hi JJ, I was referring to the Telefunken USA and original Neumann U47 having different bass reponse. It was here that I would expect a difference in capsules.
Roddy Bell
BBC / Siemens
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| Re: U47 voltage questions [message #338530 is a reply to message #338414 ] |
Fri, 02 May 2008 12:14 |
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J.J. Blair
Messages: 10047
Registered: May 2004
Location: by the sea & sand |
Diamond Member |
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| Klaus Heyne wrote on Thu, 01 May 2008 22:02 |
Your doubling of a coupling capacitance in such a circuit and hearing less bass is erroneous...
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Klaus, just to clarify, it was not "my" doubling, or quadrupling. And that's why I believe I posed it as a question, after I had just noticed that cap value, and wondered if that was a factor in what I was hearing.
Here's what I said: "Would quadrupling the capacitance of the coupling cap be the most obvious explanation for this, aside from Oli's concern of the extra heat sucking out the low frequencies from the nickel core of the transformer, and whatever effect the other erroneous values might cause? "
temporary webpage
They say the heart of Rock & Roll is still beating, which is amazing if you consider all the blow it's done over the years.
"The Internet enables pompous blowhards to interact with other pompous blowhards in a big circle jerk of pomposity." - Bill Maher
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| Re: U47 voltage questions [message #338601 is a reply to message #338530 ] |
Fri, 02 May 2008 15:23 |
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Klaus Heyne
Messages: 2027
Registered: April 2004 |
Platinum Member |
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Again, the answer is : NO. Not only not the most obvious explanation, but not a possibility under any circumstances at all.
Klaus Heyne
German Masterworks
www.GermanMasterworks.com
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| Re: U47 voltage questions [message #339224 is a reply to message #338976 ] |
Mon, 05 May 2008 22:20 |
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Klaus Heyne
Messages: 2027
Registered: April 2004 |
Platinum Member |
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| Oliver Archut wrote on Sun, 04 May 2008 21:28 |
With an 1uF capacitor there is a 3dB peak at about 40Hz and increasing that capacitor the distortion gets higher too.
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Distortion going up, because the transformer eventually gets saturated with LF?
If so, have you ever made measurements with a 1.0 vs. 0.5 MFD coupling capacitor, hooked to a stock BV8 transformer?
Klaus Heyne
German Masterworks
www.GermanMasterworks.com
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