GroupDIY

Project Specific Discussions => Microphones => Topic started by: Gus on September 14, 2018, 08:35:19 PM

Title: thread at another forum
Post by: Gus on September 14, 2018, 08:35:19 PM
This thread
https://www.gearslutz.com/board/geekslutz-forum/1229343-how-extend-low-end-rolloff-vintage-87-a.html (https://www.gearslutz.com/board/geekslutz-forum/1229343-how-extend-low-end-rolloff-vintage-87-a.html)

Some IMO questionable information posted and kind of an attack of this forum. Now why would people want to help?

First if it is a clone microphone what capsule was used and does it have any low end ? Has the capsule been tested in another microphone that has low end?

Jakob  even posted and it was good information







Title: Re: thread at another forum
Post by: shabtek on September 14, 2018, 10:44:27 PM
thats a good place to get responses!
Title: Re: thread at another forum
Post by: kingkorg on September 15, 2018, 02:45:26 AM
GS is oasys for people looking for quick fixes.

Is it expensive piece of gear, or one magic capacitor that solves everything, doesn't matter. It's never about craft, ears, experience, time invested, it's always that one thing that keeps being out of reach, one magical secret no one is willing to share.
Title: Re: thread at another forum
Post by: ruffrecords on September 15, 2018, 04:31:44 AM
I think the OP on GS appended his question to an already very long thread. I think he would have got a better response if he had posted a new thread here. GS is a magnet for technical anarchists who delight in spreading false information so  it is not a good place to get answers to technical questions.

Cheers

Ian
Title: Re: thread at another forum
Post by: RuudNL on September 15, 2018, 04:35:02 AM
I agree that the change from 470 pF to 1000 pF doesn't make any sense in such a high impedance circuit!
Also I think this remark is a bit strange:

Don't expect a lot of depth from that design, it's not really there with that capsule and transformer design.

So what is wrong with the design? As far as I can see it is a copy of the original schematic.
Is he saying that Neumann makes pretty crappy microphones?

An increase from 22 to 47 uF of the source decoupling capacitor may increase the level of extreme LF a fraction, although I don't expect a significant change.

Best way to really extend the low end, is to modify the permanent roll-off filter, by increasing the value of C5 (0.033 or 0.047 uF).
I have measured the LF response of U87 microphones and often the electronics are not within spec.
At 40 Hz attenuation should be 3 dB, but usually I measured a higher value. This could be corrected by changing the value of C5.
Title: Re: thread at another forum
Post by: Wordsushi on September 15, 2018, 12:55:47 PM
That was me. I got tired of waiting for responses to the actual question I had asked twice here. I'm glad I did post it at GS, because regardless of the clown show over there, I ended up getting a few suggestions, especially the one from Ian.

The additional discussion about the theoretical circuit stuff is pretty amusing.

And Ian, I actually did post the same inquiry as a separate question here in June.
https://groupdiy.com/index.php?topic=69342.msg883289#msg883289 (https://groupdiy.com/index.php?topic=69342.msg883289#msg883289)

I had also previously posted it in the D87 thread, (maybe even twice) where it got lost in the fray or ignored or whatever. 

And Gus, the answer to the capsule question is that it's a prototype built for me by a guy who has several decades of professional capsule development and manufacturing. I'm not allowed to say any more about it at the moment, but suffice it to say that it was tested in a transformerless circuit where it exhibited the kind of bottom end I was expecting, yet not hearing in the D87. I built 3 D87's with different transformers, all with the same bottom end.

It's actually not the first time it was suggested to me that the circuit was the issue with not getting the low end extension I'd like to have from this mic. After having this mic shot out against a vintage u87i owned by a Grammy-winning engineer/Producer in Philly at his studio and having it reported back that pretty much everything below 600hz was identical (the only difference he heard was the D87 was a bit darker at 12k, but could be EQ'd to match), I've now come to believe that Dany's circuit is an absolute faithful recreation of the standard 87i as it was originally designed by Neumann, but it's my desire to see if I can mod it to get a bit more low end to customize it to my needs that precipitates the search to see if it can easily be done with a cap swap or two. And Ian's suggestion over at GS is the one I'm going to try after I get my next Mouser order in.  So again, Thank You, Ian!
Title: Re: thread at another forum
Post by: EmRR on September 15, 2018, 01:12:13 PM
It is true that the average build thread here is so long and cluttered that almost no one who knows anything bothers to read them very often, mostly full of simple questions from beginners that get answered over and over....because they don't take the 2-3 hours required to make a condensed set of notes from a 124 page thread.   I don't think there's a solution to that. 
Title: Re: thread at another forum
Post by: kingkorg on September 15, 2018, 01:30:23 PM
If you shootout a real Neumann against your clone you will be dissapointed over and over again, untill you get a real Neuman capsule in real Neumann body.

There is no substitute for that combo PERIOD!

And you can not even shootout a vintage mic against new one from a certain company, let alone third party capsule against vintage original that has been used for years.

The fact that guy is a grammy winner doesn't mean his mic is in perfect shape. It could mean quite oposite, that it was used heavily during the years.

Here are two vintage u87s measured side by side at my place. Identical electronics, both used at national TV and same batch, age.

You will get closer by just using an eq instead of wasting you time because of couple db of difference. You will never be able to match them that close.
Title: Re: thread at another forum
Post by: Wordsushi on September 15, 2018, 02:19:12 PM
Yeah Kingkorg, I'm sure the guy who has worked with John Lennon, Bob Dylan, Amy Grant, Cypress Hill, Sting, Anthrax, Aerosmith and lots of other major artists and owns busy studios on both coasts, has no idea what a good 87 sounds like, especially the one that he calls his favorite mic of all time. If his mic is thrashed, then I'm sure he's a fool to be using it. And I'm sure the guy who has designed capsules for decades and built thousands of them has no idea what a good capsule sounds like, either. With all your obvious expertise, I should put you in touch with them to consult them on their sonics.

Your post is the epitome of why I get frustrated at this forum. Instead of telling me what I "can't" do just so you can puff up your chest to show us all what an expert you are in what apparently can't be done, it would be nice if, like Ian, you had an actual answer to the question posted in what possibly could be done. Think of it as a hypothetical... maybe it can't be done, but what if..? and if so, how? Now that's constructive. If you are capable of such a constructive response,  and if you actually know this circuit as well as you claim to, I'm open to any ideas.
Title: Re: thread at another forum
Post by: EmRR on September 15, 2018, 02:59:53 PM
I'm sure the guy who has worked with John Lennon, Bob Dylan, Amy Grant, Cypress Hill, Sting, Anthrax, Aerosmith and lots of other major artists and owns busy studios on both coasts, has no idea what a good 87 sounds like, especially the one that he calls his favorite mic of all time. If his mic is thrashed, then I'm sure he's a fool to be using it.

In all fairness, you get used to what you are hearing, even if it's broken.  If it's your special mic, you make assumptions.  His mic may be brilliant, it may be somewhere less.   Mics are far harder to objectively quantify, and I know for certain you can go through a pile of same type preamps by ear and think they all sound fine merely because they pass non-offensive audio in a certain context, yet measurements will tell you some number of them have significant problems, like no low end at all.  The brain is really great at filling in missing content...just think of the crazy bandpass filtering people do in mixes to make things fit.   I don't mean to offend, but the point needs to be considered.  You have had a direct comparison, so that's a bit more than the average report around here, if you compare against a 3rd and 4th sample you'll know even more. 

kingkorg's points are well taken, and must be considered in the overall context.  I and many others rarely if never find a clone that sounds anything like the real thing, and it's a fallacy that has to be constantly dismissed.  People waste vast amounts of time chasing clone perfection to no satisfactory end, when the $/time ratio still votes in favor of getting the real thing.   If you're happy with you mic on it's own terms, that's a different thing.  There's plenty of info in this and all the other mentioned threads.  Spend the 3 hours making a personal notes document from the threads if you haven't, it's really the only way I've found.  Followed by making changes and recording control samples to compare. 

I believe Jim Williams and Klaus Heyne both change C4 as much for phase effects they claim to hear, as anything.  I think Klaus removes it altogether, which risks destruction of the FET from spurious events, though he says it never seems to happen. 

The capsule and the transformer always make the biggest difference, any mic, period.  Even a Neumann capsule will show the variance kingkorg shows in his graph and be within factory spec.   Changing either of those parts will do more for you than changing amplifier parts IMO.   Good luck. 
Title: Re: thread at another forum
Post by: kingkorg on September 15, 2018, 03:06:00 PM
Well i just did tell you what can be done. You have to find original capsule and headbasket.  I don't have better answer untill i find capsule that performs like original.  And even then you might get situation like mentioned above with original capsules and low end response. And none of these to are busted. Those capsules are in great shape and have 5db of difference in low end.

Untill then you can use eq.

The sound of the microphone is also determined by off axis response. Good luck finding capsule/grille combo that performs like an original.

Your "grammy friend" arguments are pretty much  why people stay away from GS in the first place.

Like i mentioned in my first reply, you are looking for quick fix. There isn't one.
Title: Re: thread at another forum
Post by: analogguru on September 15, 2018, 03:07:09 PM
.... the guy who has worked with John Lennon (rem.: † 1980), Bob Dylan, Amy Grant, Cypress Hill, Sting, Anthrax, Aerosmith .....
I am only wondering if this alleged 70's-grammy-guy is still recording or if he is already retired.... and if he is able to hear 10kHz after 40 years in business.
Title: Re: thread at another forum
Post by: shot on September 15, 2018, 03:22:33 PM
It is true that the average build thread here is so long and cluttered that almost no one who knows anything bothers to read them very often, mostly full of simple questions from beginners that get answered over and over....because they don't take the 2-3 hours required to make a condensed set of notes from a 124 page thread.   I don't think there's a solution to that.

Actually there is a solution!
Check out Volker's build threads on D-AOC or D-LA2.
First post is edited from time to time to provide links to posts containing answers, and there are also compiled infos in pdf from the same thread.
There are a lot of gigantic build threads (GSSL, 1176...) that even when you want to read you cannot. It's impossible to stay focused going through them. But this sort of META stuff inside the build thread is very helpful.

But this doesn't excuse users not going through those build threads and asking same questions over and over!

:)

Luka
Title: Re: thread at another forum
Post by: Gus on September 15, 2018, 03:36:26 PM
Wordsushi

First thing I would do is place the capsule in a real known good u87 get a baseline for the sound change from the capsule. Then you take the real u87 capsule and place it in your build note the changes think about it then redesign your build to work with that capsule.

Another thing why do people want to build the old u87 circuit? adjust the newer circuits you will be better off.

If the Ian adjustment is increasing the coupling cap value to transformer there is a trap in that don't think RC think LRC. I am surprised Ian posted that.  There is at least one thread at this forum about this. Here is a hint I would not do what has been posted. There are only so many parts in u87 gain stage

You need a different circuit or an adjusted circuit. You might need to pay someone for this.

So why should someone post this on the web? to give it away to "botweek microphone "designers""?

Last time I posted an adjust MXL v67 etc. circuit here I felt I was attacked in the thread by some people.

I stopped making detailed microphone posts, however I do post hints to help someone figure it out if they do research.

I also could be the capsule environment Has the capsule been used in a real 87? this would be for the capsule grill interactions that clones don't always get right.

What transformer are you using? This is a big deal.

Title: Re: thread at another forum
Post by: ruffrecords on September 15, 2018, 04:05:42 PM
I am really disappointed in this thread. It sounds more like GS than GS. It is not so much what people say more the way they say it. It puts my back up and I am not even the OP. The guy asked a simple question and he has got some good suggestions but the phrasing of many of the answers leaves a lot to be desired. Sorry Wordsushi, it is not usually like that here.

Cheers

Ian
Title: Re: thread at another forum
Post by: Gus on September 15, 2018, 04:48:57 PM
I am really disappointed in this thread. It sounds more like GS than GS. It is not so much what people say more the way they say it. It puts my back up and I am not even the OP. The guy asked a simple question and he has got some good suggestions but the phrasing of many of the answers leaves a lot to be desired. Sorry Wordsushi, it is not usually like that here.

Cheers

Ian

Why are you disappointed?

If it was what I posted , look at the transformer coupling cap values in all the microphone schematics you can find note were they "hover" around. Then try different values measure and also test by ear.
Title: Re: thread at another forum
Post by: EmRR on September 15, 2018, 05:05:54 PM
Actually there is a solution!
Check out Volker's build threads on D-AOC or D-LA2.
First post is edited from time to time to provide links to posts containing answers, and there are also compiled infos in pdf from the same thread.


Yes!  A few originators do manage to summarize, but not very many. 
Title: Re: thread at another forum
Post by: Wordsushi on September 15, 2018, 05:15:11 PM
Thanks Ian. :) I appreciate that. You are a true gentleman. I will try the suggestion you posted on GS.

Analogguru, yes. Never stopped. Always busy. Since June, he has been working on the new  album for a superstar artist whose probably best known for her first album, which not only debuted at #1 on the Billboard charts but won Album of the Year and Best New Artist Grammys. I have a feeling his ears work quite fine.

The shootout with the D87 was done on a day off from that record and if anything, it completely validated that Dany Bouchard's circuit is right on the money and delivers the goods as promised. I really like the sound of this mic a lot and I know the capsule is capable of more low end. I just wanted to see whether I could coax it out of the D87 circuit somehow. It's that simple. I don't know why asking this question always seems to get so convoluted.

I've said all I feel there is to say for now and will leave you to your tinkerings. Thank you to all for jumping in. It's been enlightening and amusing and quite revealing on many levels. You made this Saturday afternoon pretty entertaining. I'm not mad at anyone, nor do I think any of you are stupid or full of crap. I think there are a lot of people passionate about mics here and if by chance, Ian's solution or some other solution achieves what I personally am looking for in customizing this mic's sound for my own personal use, I will post my findings here... that is unless I decide GS is more deserving of the post. ;) LOL.
Title: Re: thread at another forum
Post by: ruffrecords on September 15, 2018, 06:16:49 PM
Why are you disappointed?

If it was what I posted , look at the transformer coupling cap values in all the microphone schematics you can find note were they "hover" around. Then try different values measure and also test by ear.

Not really you but a little bit. I was more concerned about the attitude shown to the OP. Many of the replies I thought were not constructively helpful. Some of the attitudes shown I found to be patronising.

Cheers

Ian
Title: Re: thread at another forum
Post by: Gus on September 16, 2018, 07:09:56 PM
I have not found the thread that zebra50 posted graphs with different cap values from plate to transformer.
IIRC it was Gefell or RTF microphone the thread might have been in the mid 2000's.

Anyone remember this thread?

EDIT found this https://xaudiaelektrik.blogspot.com/2010/02/neumann-gefell-um57-microphone.html (https://xaudiaelektrik.blogspot.com/2010/02/neumann-gefell-um57-microphone.html)
Title: Re: thread at another forum
Post by: analogguru on September 17, 2018, 03:45:32 AM
As to be expected the bigger the coupling capacitor the less resonant the circuit becomes.
Title: Re: thread at another forum
Post by: RuudNL on September 17, 2018, 07:48:30 AM
With a bigger capacitor the resonance frequency shifts down and because of more losses becomes less obvious.
I have seen many bad combinations of transformer inductance and output capacitor causing LF 'bumps'.
Title: Re: thread at another forum
Post by: dmp on September 20, 2018, 08:27:51 PM
There are two kinds of common posts that don't contribute much and rub people the wrong way... a lot of good examples of them.

1) instead of trying to answer the question explain why the question is wrong in a generally unhelpful way.
Example: how do I build a great bass DI? Answer: great bass is in the fingers, learn to play like jamerson.

2) implying you know the answer but not giving it.

Probably good to just hit cancel if your thinking of posting either of these kinds of things. Much better to do your best to be as helpful as possible.

I agree with what someone else said, it's most likely nobody saw the question vs the 'forum' trying not to be helpful. Lots of people around here go out of their way to help and answer questions.


Title: Re: thread at another forum
Post by: Phrazemaster on September 27, 2018, 09:47:50 PM
I am by no means an expert in anything audio, much less designing circuits or answering complex questions.

However, I'm a teacher by trade, computers and technology. While I know a certain core set of things like nobody's business, in most of my day to day I get asked questions I have absolutely no idea the answer to.

I can generally look at the question, and figure it out. But I don't already know the answer - I have to think about it, try stuff, and then come up with a solution.

I'll be honest I get a little pissed off at the same people asking me how to do things over and over again - that I don't know how to do yet I apply myself and figure out - but that they are not willing to even try. They act like I owe them the answer and I get really annoyed at this. Because it takes something out of me - my life, my time, my energy, that I could spend on other things.

I don't begrudge the greats here for not always spoon feeding. Even though they may know the answers, it doesn't mean they owe it to me or anyone else to take their life time and energy to respond.

Ultimately it's better to learn to fish.

Mike
Title: Re: thread at another forum
Post by: abbey road d enfer on September 28, 2018, 12:55:43 AM
I actually did post the same inquiry as a separate question here in June.
I remember I saw it at the time, but I had no clue what "C5 in Dany's circuit" is, and was not willing to start a goose chase. Had you attached a schemo to your post, you may have got more answers, probably one from me.

BTW I had a look at the GS thread.
One of the posts read "Most of my mics go down to lower than 20 hz by design. I like the depth and tightness of the low end when the phase shift is removed. I like to feel the low end on recordings, it adds energy. A HPF removes any unwanted low end. "
Anybody with decent knowledge of signal processing knows that a HPF produces at least as much phase-shift as reducing the LF response in the head amp.
Some of the answers about phase-shift just make no sense; it has been demonstrated times and again that phase-shift audibility is extremely program-dependant. The rule of 10 applied to amplitude response is a remnant of the past, when systems had few stages interconnected, but in a modern electroacoustic chain where dozens of stages are interconnected, the multiplication of individual 0.05dB losses can become significant. OTOH, the corresponding 6° phase-shift's audibility is highly questionable.
Remember that one of the reasons for this rule of 10 was concerned about capacitors losing their capacitance due to aging.

Now if you think that kind of answer is more useful than those you get from here, you're entitled to your opinion, but I don't share it.
Title: Re: thread at another forum
Post by: Gus on October 04, 2018, 07:47:35 PM
What transformer are you using? This is a big deal.
Title: Re: thread at another forum
Post by: kingkorg on October 04, 2018, 08:43:00 PM
He found the solution, but failed to report here. I am puzzled even more, but whatever... it was something something he was missing

Quote from GS:
Well, I figured this thread deserved an update.

I had my Mouser shopping cart ready to go with Wima 2.2, 3.3 and 4.7 caps, as suggested, along with some other project stuff, and just as I was about to buy it all, I had a kind of epiphany. My experience with U87's goes back to recording on 2" tape and, with the 416 as my main axe for years, I've never used one to record straight to digital.

I started to think what my ears were missing was a good old fashioned "tape bump". So, I inserted the UAD Ampex ATR-102 plugin right before my DAW and... boom...there it was... the little touch of "something-something" extra in the lows I wanted to hear on my voice. Previously, I had tried just goosing the lows with different EQ's, but it wasn't nuanced exactly how I wanted. Given how these mics were originally designed to record to tape, it just kinda makes sense somehow and, again for my purposes, on my voice, it makes this mic sound how I like... all without having to perform surgery on it.
Title: Re: thread at another forum
Post by: gyraf on October 05, 2018, 05:24:32 AM
 ::)
Title: Re: thread at another forum
Post by: abbey road d enfer on October 05, 2018, 04:36:17 PM
Well, I think he doesn't like the kind of answer he got from here because they are too technical. Apparently he prefers adding some dose of magic than actually trying to find a scientific solution.
Title: Re: thread at another forum
Post by: kingkorg on October 05, 2018, 04:43:35 PM
The thing i would do is to measure the plugin for frequency response and THD and try to get that in the circuit.

However my experience with some other tape plugins tell me there might be multiband compression going on. Companies use it to emulate some tape properties.