living sounds
Well-known member
Why not?
Is there any new mic you can buy or a kit to build that sounds as good as a vintage U87i?
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living sounds
Well-known member
After listening to the recordings again I sent it to Andreas Grosser to check it and do his magic. It sounds good, but I bet he can make it better. Will report back.
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So then I'm guessing in the U87i, C5 shown here, would be the same low end rolloff filter as the u87ai's C104?
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RuudNL
Well-known member
Yes, in the past the value was even 33 nF!
Thank you so much, Ruud. The 33 is what I have in my Bouchard 87s. Looking forward to modding them as the thinner-than-I-prefer low end was the only thing I didn't love about it.
UPDATE: Just added the 100nf to the back of the 33nf and wow, what an amazing difference. Love it.
UPDATE 2: After giving it a critical listen this morning with my full rig and fresh ears, I'm hearing some oddness/muddiness in the low end. I'm going to remove the 100nf cap and see if it's still there.
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RuudNL
Well-known member
Of course a 'value in between' may be the best solution for your situation!
Yup! Replaced 100nf with 47nf. I'm preferring this so far. Thanks Ruud!
living sounds
Well-known member
Got my U87ai back from Andreas Grosser. From a quick glance yesterday and according to the report he changed at least one cap, added another one and changed and rebiased a transistor.
From my measurements the frequency response was altered quite a bit more drastically than I had anticipated. The upper midrange and presence region was noticeably reduced and the low end extended.
Subjectively, the mic has lost the aggressive, peaky midrange that made it borderline unuseable. At very close proximity the low end starts to get overbearing, but at a resonable short distance it is perfect. It sounds quite balanced and very nice, much better detail and dynamic integrity than my DIY mics, but it hasn't become a U67, and the high end is still a little raspy. May it's the capsule or the 60V polarization voltage. Will try it with a tube preamp when I get that.
From my measurements the frequency response was altered quite a bit more drastically than I had anticipated. The upper midrange and presence region was noticeably reduced and the low end extended.
Subjectively, the mic has lost the aggressive, peaky midrange that made it borderline unuseable. At very close proximity the low end starts to get overbearing, but at a resonable short distance it is perfect. It sounds quite balanced and very nice, much better detail and dynamic integrity than my DIY mics, but it hasn't become a U67, and the high end is still a little raspy. May it's the capsule or the 60V polarization voltage. Will try it with a tube preamp when I get that.
RuudNL
Well-known member
Is it obvious what was changed? (That would be interesting to know.)
living sounds
Well-known member
I haven't looked in detail, but I think so, yes. I'm not sure it is ethical to disclose the secret sauce (or rather, what can be gleamed from looking at the results of the mod) of an expert who does this for a living on a public forum though.
living sounds
Well-known member
No, guess I should have asked for it.
I guess you should still insist on that. Depending on which one it is it might be obsolete and sought after, or may become. You might at one point decide to go back stock for whatever reason. This goes really for all the components he removed. I am somehow cetrain he didn't just dump them in a trash can.
RuudNL
Well-known member
If I repair a microphone, I always return the replaced parts to the owner.
And I can't imagine there is 'something secret', to a relative simple design as a U87.
(I even share improvements to U87 microphones here, nothing 'secret' about that! See #30 and #34)
There are even pictures of microphones modified by 'microphone guru' Klaus Heyne on the internet...
And I can't imagine there is 'something secret', to a relative simple design as a U87.
(I even share improvements to U87 microphones here, nothing 'secret' about that! See #30 and #34)
There are even pictures of microphones modified by 'microphone guru' Klaus Heyne on the internet...
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living sounds
Well-known member
All right, I'll have a look soon and report. I've got "before" pictures.
Klaus' mod is interesting... What's wrong with the Neumann trafo? And I don't think I've ever seen a polymer cap in a microphone.
living sounds
Well-known member
And yes, technically those parts taken out are still my property.
That'll most likely be the cathode resistor bypass cap - those organic polymer caps are most of the time low-voltage, and stupid-low ESR. Not sure if or how much difference that might make in a microphone circuit like this, but...
Those blue ones were Sanyo OS-CON first(?) generation, i think.
RuudNL
Well-known member
Of course it is a good thing to check and eventually readjust the bias of the FET.
But as long as the FET is not defective, I don't see a point in replacing it.
living sounds
Well-known member
I think the mod lowers the output a few dB and the new FET is supposed to be much lower noise than the original, so the mic should end up with lower noise as well as a higher headroom.
RuudNL
Well-known member
Unlikely. A single FET circuit will always suffer from a limited max. output, no matter which FET you use.
