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V67G mic mod
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Travst



Joined: 15 Jul 2008
Posts: 9535
Location: Birmingham, AL

PostPosted: Sun Jan 13, 2013 8:38 am    Post subject: V67G mic mod Reply with quote

The MXL V67G has a good reputation as a stock mic and as a candidate for modding over at Gearslutz, so I picked one up a while back. While the pro modders replace headbaskets, capsules, and other parts, there are a couple of caps that can be replaced to open up the mic a bit and I made some time yesterday to do the mods. While I have read about the mods, I have never seen anyone post pics, so I took some along the way in the event they will help someone here.

The steps:

1. Unscrew the knurled baseplate at the bottom of the mic.
2. Unscrew the 2nd baseplate that lies just above the first.
3. Slip the case from the upper portion that contains the headbasket.
4. You will see a circuit board on each side of the structure inside. Locate the one that is not wired to the capsule (wires coming from the headbasket) and remove the opposite board by pulling the two screws that secure it.
5. Pull the loose board to one side. You will see a small cap (C2) soldered to the top of the board that is still secured. Remove it and substitute a 1000pf polystyrene cap or similar. I used a polypropylene cap that I had on hand, but most people recommend polystyrene.



6. Now locate capacitor C3 on the loose board, pull it, and replace it with a .47nf cap. I've also seen reference to .22 caps being used here. Once again, I used an STK polypropylene cap instead of polystyrene.



I found that this mod opens up the mic a bit and adds some low end, giving more warmth to the tone. I did before and after recordings and compared them, but lack the balls to post my acapella singing on the internet. Embarassed I intend to finish the mods listed below today and will add to this thread, but for right now replacing the first two caps is an improvement that took all of 20 minutes to perform.


Here are other mods suggested by Jim Jacobsen at JJ Audio from Gearslutz (http://www.gearslutz.com/board/geekslutz-forum/87802-mxl-v67-mic-mods.html):

You may want to find out what these mods sound like by experimenting with each value capacitor.

C1= .01uf to 047uf I use Wima film caps.
C2= 100, 220,470, 820pf Polystyrene/ Styroflex

Neumann used many different values throughout the years. Record each combination and change you make so you can find the best sound for you.

C3= 470-1500pf Polystyrene/ Styroflex/ Polypropylene

C8 Neumann used in the U87 a 1UF Tantalum electrolytic capacitor in this position. Tantalums do work here however Polypropylene capacitors have a clearer, less colored sound. Again experiment to find the capacitor that you like in that spot.

Film caps: 1uf to 3.3UF(depending on size) and 1UF to 4.7uf on the Tantalum.



If you are interested in these mods and don't want to do them yourself, talk to Jim:

http://jjaudiomic.com/
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I need more practice, not more gear.


Last edited by Travst on Tue Jan 15, 2013 9:28 am; edited 1 time in total
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tangelolemon



Joined: 26 Jan 2009
Posts: 2691
Location: Brooklyn, NY

PostPosted: Sun Jan 13, 2013 9:09 am    Post subject: Reply with quote

polypropylene and styroflex (polystyrene) will give quite different results! Both can be good. Polystyrene will seem to 'disappear' more and be most transparent, most of the time.

I also don't recommend those WIMA caps for applications like this, unless they're the only option due to fit.

They're a metallized film variety, and can be very inconsistent. The inconsistency comes from the way they're constructed-- the leads are attached to the metallized surface of the film with something called a spray-on "schoop" connection. This connection isn't always consistently the same and can cause measurable distortion under tests (can show you documentation if you want), even though the capacitance value will measure fine, and the cap will not technically be 'defective.'

Old WIMA caps from 40 years ago were very very good for audio, and I think many people use the new WIMA caps based on that reputation, because frankly digging into the minutiae of how caps are made and which are good for things like microphones are beyond most peoples' interest level. Very Happy

I do use the pink WIMA 'box' caps though in certain circumstances-- even the bad ones are almost universally better even than a 'good' electrolytic in measured tests, and they do tend to be impressively compact in large values. I've used them to replace tantalums and electrolytics in things like old Ampex 440 tape machines.

Still, however, most of what will limit you in this MXL microphone will be the capsule and transformer. However, working on it WILL teach you a bit about microphones, and 'get your feet wet' with working on them.

Enjoy!!
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Travst



Joined: 15 Jul 2008
Posts: 9535
Location: Birmingham, AL

PostPosted: Sun Jan 13, 2013 9:22 am    Post subject: Reply with quote

Thanks for the comments and tips. Your mic building thread from a ways back started my interest in mic modding. I aspire to achieve your level of skill.

http://reranch.com/reranch/viewtopic.php?t=43423&highlight=u67

I don't have any Wima caps and will not be using them. The subject of the V67G transformer and capsule have been hotly debated in a number of threads. Many feel the stock transformer is adequate, even Michael Joly falls into that group. Although, he does upgrade them as part of his mod package. As for the capsule, people are all over the board. I am thinking about replacing mine after doing all the other mods listed.

Here's what I found for a replacement transformer, I'm sure there are others:

http://www.samaraudiodesign.com/BobbinTransformers.html

I've seen a lot of capsules that are recommended, most notably Peluso. I guess I need to decide how much money I want to invest in mods. What I want to do is mod a pair of them if these mods work well.
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twangster



Joined: 05 Aug 2005
Posts: 9512
Location: Nashville Tennessee.

PostPosted: Sun Jan 13, 2013 10:16 am    Post subject: Reply with quote

Great project.

I worked with Rode on developing the original NT1 , the mic that started the Neumann look-a-like trend. They had a test bed set up and rejected over 30% of the Chinese capsules before assembly (this was in Sydney) .

Since most of these brands now come out of the same factory I wonder if there's any testing at all on the capsules ?
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Wombat



Joined: 01 Sep 2012
Posts: 891

PostPosted: Sun Jan 13, 2013 11:00 am    Post subject: Reply with quote

Quote:
but lack the balls to post my acapella singing on the internet


Use a higher valued cap to roll of the highs ... Laughing
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Travst



Joined: 15 Jul 2008
Posts: 9535
Location: Birmingham, AL

PostPosted: Sun Jan 13, 2013 11:05 am    Post subject: Reply with quote

Wombat wrote:
Quote:
but lack the balls to post my acapella singing on the internet


Use a higher valued cap to roll of the highs ... Laughing


rofl.... I have a cold. I'm going to use that as my excuse.
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Travst



Joined: 15 Jul 2008
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PostPosted: Sun Jan 13, 2013 3:28 pm    Post subject: Reply with quote

I started recording again using my wife as the singer. I'll post the recordings as reference materials after I go further. Replacing C1 with a .01uf metallized film cap added highs and gave the mic a rather fragile top end. I want to try a .022 and then a .047, but will have to order some parts before moving ahead.

I wish I could get her to sing in the same key each time.
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tangelolemon



Joined: 26 Jan 2009
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Location: Brooklyn, NY

PostPosted: Mon Jan 14, 2013 3:56 pm    Post subject: Reply with quote

I'd absolutely do the mods with the stock capsule and xformer first, for two reasons--

One, it will give you a clear picture of exactly which mod is doing what! Good learning experience, etc.

Two, you might either be extremely satisfied as-is, or decide that you may not want to spring for a capsule and transformer that each cost more than the mic itself! Cool Although there would certainly be no harm in doing so, and with a good capsule, tube, and transformer you'd essentially have a good mic.

If you're into mic transformers, absolutely the last word in my opinion and experience is Oliver Archut with AMI/TAB-Funkenwerk. Give him a google... there's good reading on the site, as well, if you dig a little!
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WildIowa



Joined: 06 Mar 2004
Posts: 490
Location: Henderson IA

PostPosted: Tue Jan 15, 2013 7:43 am    Post subject: Reply with quote

You guys are way way way beyond my abilities but sure is fun to read these discussions on mics and especially now with photos. Surprising the level of skill and experiences on this board always good info then the topic fills out with background history and comments from others...great reading.
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Travst



Joined: 15 Jul 2008
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PostPosted: Tue Jan 15, 2013 8:17 am    Post subject: Reply with quote

Thanks for the support, Tangelo. I'm going to record every step of the way to compare components. Also, I found a schematic of the mic and want to understand the circuit and will do some reading. Right now, I am just painting by numbers because I don't have any experience with mics. I have a pretty good understanding of the basics of amps, but this is very different.
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tangelolemon



Joined: 26 Jan 2009
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PostPosted: Tue Jan 15, 2013 9:22 am    Post subject: Reply with quote

post the schematic!
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Travst



Joined: 15 Jul 2008
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Location: Birmingham, AL

PostPosted: Tue Jan 15, 2013 9:26 am    Post subject: Reply with quote

tangelolemon wrote:
post the schematic!


Here's the link, it's a huge .gif file.

http://www.sdiy.org/oid/mics/MXL-V67.gif
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tangelolemon



Joined: 26 Jan 2009
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PostPosted: Tue Jan 15, 2013 10:28 am    Post subject: Reply with quote

C2, C3, C6, and C8 are where I'd focus my improvements.

Replacing C4 with a nonpolar film cap is also a good move if you can find one in the right physical size with the needed value... shouldn't be too hard (try WIMA, actually)
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Travst



Joined: 15 Jul 2008
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Location: Birmingham, AL

PostPosted: Tue Jan 15, 2013 10:40 am    Post subject: Reply with quote

tangelolemon wrote:
C2, C3, C6, and C8 are where I'd focus my improvements.

Replacing C4 with a nonpolar film cap is also a good move if you can find one in the right physical size with the needed value... shouldn't be too hard (try WIMA, actually)


Will do. I waited to order parts until I got some more ideas from the group.
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Mike Aimer



Joined: 03 Jun 2008
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PostPosted: Tue Jan 15, 2013 10:55 am    Post subject: Reply with quote

I don't suppose there happened to be a schematic of the V67Q stereo mic wherever you got the schem for your mic?
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