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Shure M67 Mods
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famous beagle
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Joined: 04 Mar 2014
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Location: Dallas, TX

PostPosted: Tue May 20, 2014 4:02 pm    Post subject: Re: Shure M67 Mods Reply with quote

Darlington Pair wrote:
I recently modded an M267 for a guy and I just clipped the high pass cap and wired where it is from the switch to a direct out on three of the channels. So now when the switch is in normal position everything goes to the bus, when the low cut is on it cuts it from the bus and only does the direct out.


Sorry for the newb question, but when you say "to a direct out," could you tell me where that would be? Thanks!
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Darlington Pair
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PostPosted: Wed May 21, 2014 1:34 pm    Post subject: Re: Shure M67 Mods Reply with quote

famous beagle wrote:
Darlington Pair wrote:
I recently modded an M267 for a guy and I just clipped the high pass cap and wired where it is from the switch to a direct out on three of the channels. So now when the switch is in normal position everything goes to the bus, when the low cut is on it cuts it from the bus and only does the direct out.


Sorry for the newb question, but when you say "to a direct out," could you tell me where that would be? Thanks!


This is a four input mixed to mono mixer, by doing this mod you can cut channels from the mix bus (the mono out) before the limiter and just use each channel as a stand alone mic preamp. In the case of the one I did for my friend, he has the option of four separate mic pres, three unbalanced outputs that just have the input transformer, amp, and volume control; and one that follows the original signal path running through the master section. OR he can mix four preamps to mono.
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famous beagle
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PostPosted: Wed Jun 11, 2014 11:40 pm    Post subject: Re: Shure M67 Mods Reply with quote

Darlington Pair wrote:
famous beagle wrote:
Darlington Pair wrote:
I recently modded an M267 for a guy and I just clipped the high pass cap and wired where it is from the switch to a direct out on three of the channels. So now when the switch is in normal position everything goes to the bus, when the low cut is on it cuts it from the bus and only does the direct out.


Sorry for the newb question, but when you say "to a direct out," could you tell me where that would be? Thanks!


This is a four input mixed to mono mixer, by doing this mod you can cut channels from the mix bus (the mono out) before the limiter and just use each channel as a stand alone mic preamp. In the case of the one I did for my friend, he has the option of four separate mic pres, three unbalanced outputs that just have the input transformer, amp, and volume control; and one that follows the original signal path running through the master section. OR he can mix four preamps to mono.


I swear I posted this before, but now I don't see it.

I understand the concept you're talking about. I was talking more specific with regards to how to wire it as such. For example, when you say:

"I recently modded an M267 for a guy and I just clipped the high pass cap and wired where it is from the switch to a direct out on three of the channels. So now when the switch is in normal position everything goes to the bus, when the low cut is on it cuts it from the bus and only does the direct out."

I understand clipping the high pass cap, but how do wire the switch as a direct out? In other words, which wire goes where?

Thanks!

Also, I just opened this thing up to take a look, and I'll be damned if I can even get the PCB flipped over! (I did unscrew the 4 screws.) Do I have to desolder the connections on the front side (pot side) to be able to turn it over?
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Darlington Pair
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PostPosted: Thu Jun 12, 2014 9:51 am    Post subject: Re: Shure M67 Mods Reply with quote

The Low Cut switch just shorts across the cap to take it out of circuit. So if you clip the cap when you turn on the low cut it will disconnect from the buss, but there is still signal present on the preamp side of the switch. I don't have mine open to tell you which place to put the wire, but it's the preamp side of the cap you just took out. I just took the caps out and shoved a wire in one of it's pads. There will always be signal present on your individual outs.

I'm traveling and on my phone right now and the schematic is blurry on it, but the caps you're looking for are C101, 102, 103, 104, they are the Low Cut caps. You have a 50/50 shot if you just guess which side. I would like to tell you that it's at the junction of R? and C101 but I can't read the resistor numbers, but once you take the cap out just turn the low cut on, send signal in and touch an output wire to each pad.
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famous beagle
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PostPosted: Thu Jun 12, 2014 10:11 am    Post subject: Re: Shure M67 Mods Reply with quote

Darlington Pair wrote:
The Low Cut switch just shorts across the cap to take it out of circuit. So if you clip the cap when you turn on the low cut it will disconnect from the buss, but there is still signal present on the preamp side of the switch. I don't have mine open to tell you which place to put the wire, but it's the preamp side of the cap you just took out. I just took the caps out and shoved a wire in one of it's pads. There will always be signal present on your individual outs.

I'm traveling and on my phone right now and the schematic is blurry on it, but the caps you're looking for are C101, 102, 103, 104, they are the Low Cut caps. You have a 50/50 shot if you just guess which side. I would like to tell you that it's at the junction of R? and C101 but I can't read the resistor numbers, but once you take the cap out just turn the low cut on, send signal in and touch an output wire to each pad.


Ok thanks for the info. I'll give it a shot and see what I can come up with!
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famous beagle
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PostPosted: Fri Jun 13, 2014 9:40 am    Post subject: Re: Shure M67 Mods Reply with quote

Darlington Pair wrote:
The Low Cut switch just shorts across the cap to take it out of circuit. So if you clip the cap when you turn on the low cut it will disconnect from the buss, but there is still signal present on the preamp side of the switch. I don't have mine open to tell you which place to put the wire, but it's the preamp side of the cap you just took out. I just took the caps out and shoved a wire in one of it's pads. There will always be signal present on your individual outs.

I'm traveling and on my phone right now and the schematic is blurry on it, but the caps you're looking for are C101, 102, 103, 104, they are the Low Cut caps. You have a 50/50 shot if you just guess which side. I would like to tell you that it's at the junction of R? and C101 but I can't read the resistor numbers, but once you take the cap out just turn the low cut on, send signal in and touch an output wire to each pad.


Ok, I took a look last night, and I think I'm starting to see my issue. I was confused at first, but now I think I understand.

So .... the mod you did isn't in addition to all the mods that RodC (starter of this thread) did, correct? It only shares some common ideas. That's where I was getting confused.

Is this the extent of your mods (in a nutshell)?

1. Add TS output jacks for Channels 2, 3, and 4.
2. Snip low cut filters for each channel
3. Add wire from CH pots (using the correct terminal on the switch) to corresponding tips of output jacks.
4. Ground all output jacks.

Is that basically it, or am I missing something else?

Sorry to keep bugging you. I'm handy with a soldering iron, but I'm still a little green when it comes to tracing circuits and understanding how it all works.

Thanks!
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Teacher's Pet
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Joined: 09 Apr 2008
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PostPosted: Wed Jul 23, 2014 12:22 pm    Post subject: Re: Shure M67 Mods Reply with quote



As you can see my $10 M267 seems to have had the AC cord removed. It works fine with batteries but I want to be able to plug it in.

Is this as simple as finding two points where I can attach a 2-prong plug? Or do I need an external power supply?



(I may need to re-post larger images, I think maybe imageshack changed their free deal.)
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Darlington Pair
takin' a dinner break


Joined: 03 Jun 2008
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Location: Staunton, VA

PostPosted: Wed Jul 23, 2014 1:36 pm    Post subject: Re: Shure M67 Mods Reply with quote

Looks like the power transformer is there so unless all the AC to DC power supply stuff is screwed you should be able to add a grounded (3 pin) power cord to the unit.

Shure has been kind enough to provide the schematics and circuit board layout so that you can see where the wires go.

http://cdn.shure.com/user_guide/upload/955/us_pro_m267_english_ug.pdf

Be careful with mains power, wire it wrong and you're dead.
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Darlington Pair
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PostPosted: Wed Jul 23, 2014 1:39 pm    Post subject: Re: Shure M67 Mods Reply with quote

famous beagle wrote:
Darlington Pair wrote:
The Low Cut switch just shorts across the cap to take it out of circuit. So if you clip the cap when you turn on the low cut it will disconnect from the buss, but there is still signal present on the preamp side of the switch. I don't have mine open to tell you which place to put the wire, but it's the preamp side of the cap you just took out. I just took the caps out and shoved a wire in one of it's pads. There will always be signal present on your individual outs.

I'm traveling and on my phone right now and the schematic is blurry on it, but the caps you're looking for are C101, 102, 103, 104, they are the Low Cut caps. You have a 50/50 shot if you just guess which side. I would like to tell you that it's at the junction of R? and C101 but I can't read the resistor numbers, but once you take the cap out just turn the low cut on, send signal in and touch an output wire to each pad.


Ok, I took a look last night, and I think I'm starting to see my issue. I was confused at first, but now I think I understand.

So .... the mod you did isn't in addition to all the mods that RodC (starter of this thread) did, correct? It only shares some common ideas. That's where I was getting confused.

Is this the extent of your mods (in a nutshell)?

1. Add TS output jacks for Channels 2, 3, and 4.
2. Snip low cut filters for each channel
3. Add wire from CH pots (using the correct terminal on the switch) to corresponding tips of output jacks.
4. Ground all output jacks.

Is that basically it, or am I missing something else?

Sorry to keep bugging you. I'm handy with a soldering iron, but I'm still a little green when it comes to tracing circuits and understanding how it all works.

Thanks!


Oops, sorry I missed this before.

You are correct, it's similar mods to a similar but different unit.

Yes, to ground the output jacks I just ran a buss wire across their terminals and a wire from that to ground. The chassis should be enough, but the dude wanted me to mount them to the top lid and I wanted to make sure that everything had a good soldered ground.
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floid
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PostPosted: Fri Jul 25, 2014 8:30 pm    Post subject: Re: Shure M67 Mods Reply with quote

just picked up a second m68 at a music shop today - 15 bucks, too good to pass up.

when i opened it up i noticed it has different transformers than my other m68. that one has cans that are roughly 1.5 in. tall by .75 in. wide, they look to be the same type as the inputs in my pair of sr107s. These are about 1.25 x 1.25 with a black plastic cap - noticeably bulkier, tho this may only be the shield and not the contents. It's worth noting all 5 trannys in each unit (4 inputs plus output) appear to be the same type, tho i've not yet confirmed this with any measurements. will post back when i've done so and modded a channel for direct comparison.
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Shattersignal
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Joined: 28 Aug 2012
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PostPosted: Wed Mar 29, 2017 1:22 pm    Post subject: Re: Shure M67 Mods Reply with quote

Hey RodC, have you tried transformer-coupling the channel outs? I followed your modification plan and it sounds like each channel will have only a single-ended output. I realize that purchasing four 1:1 transformers will essentially quadruple the cost of the project, but I'd also have a hard time imagining using a single-ended output regularly in my studio. I'm curious if you or anyone else has given it a try.

Thanks for publishing this mod! I just ordered my M67 this morning.

Cheers!
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Shattersignal
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PostPosted: Wed Mar 29, 2017 1:42 pm    Post subject: Re: Shure M67 Mods Reply with quote

I have a stash of Cinemag Cm0B-4s transformers and I'll try installing them on the channel outs. I'll try to remember to report back about it.
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