Shure M67 Mods

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RefD
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Post by RefD » Wed Oct 01, 2008 2:44 pm

RodC wrote:
RefD wrote:a thought regarding the M67 being used for recording the Woodstock soundtrack: maybe they used a buttload of inline pads (those barrel thingies)?
Thats sorta what I assumed....

Images of a "buttload" of metal pads exiting some poor assistant's... run through my head.... Disturbing.... :shock:
geysering?
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Post by Lost on side » Thu Mar 19, 2009 11:05 pm

Old Thread.
I have what may be a foolish question, being a real noob to DIY.

I know that "Germanium" is kinda a current trend/gimmick, but I was wondering if it would be possible, desirable, inconsequential, ill-advised, useless, too complicated, or a neat idea to change the the transistors in one of these to germanium transistors?

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Derrick
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Re: Shure M67 Mods

Post by Derrick » Fri Mar 20, 2009 12:13 pm

RodC wrote:Heck they recorded woodstock with these, not sure how because that leads me to the biggest problem, distortion.
Hi Rod! Have you listened to the Who's set? I realize this is from Youtube, but all my audio and video has this same distorted characteristic. I think it's kinda cool in that it adds some energy and character, but I wouldn't do this for more then one song on a recording. Check it out:
http://www.youtube.com/watch?v=v5gBaCusDeY
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Post by monty marc » Tue Jun 01, 2010 12:58 pm

I work at a community radio station that has been using Shure M67 mic mixers forever on-air. We decided to implement them in our newly renovated production studios because we like the sound and everyone is used to them (it's almost impossible to install different equipment here). By doing some modifications they could now be used as mic preamps for recording. After re-capping the power supply we did the modifications according to Rod?s instructions.

After doing the modifications, I didn?t find it useful to have channel 1 left stock, and it appeared to be confusing for volunteer technicians using the studio that the 1st mic would have a master volume control yet not the other channels. So all channels were modified identically, none were left in the mix buss.

It occurred to me that I could remove the now- unused output transformer and use the resulting free space to accommodate a phantom power circuit. I happened on a designer/supplier of a very well made phantom power PCB (here is the main website: http://sound.westhost.com/. The circuit is Project 96A - P48V Phantom Feed Power Supply). The board cost around $20 including shipping and came with well designed instructions. Most of the parts were available at the local electronics surplus store but I had to order the 3 transistors on ebay. The total cost for everything relating to the phantom power came to around 40 bucks.

I followed the ESP instructions and mounted the parts and wiring on the PCB. I connected a 10mFd/63 volt cap and the two 6.81k 1% tolerance resistors to each xlr input jack (so 1 resistor each to pin 2 and 3 going to +48v, and the cap going from +48v to pin 1). Since the lo-cut filters had been disconnected from each channel, I used those switches for the phantom power to each XLR input. The output from the phantom circuit board was connected in parallel to each lo-cut switch, and each switch was then connected to the resistors/cap and xlr jack. Luckily the M67 I was using was in excellent shape and the switches were clean and fully operational.

ESP explicitly states that the phantom circuit?s power supply has to have its own 30 volt ac transformer. The 30 volt transformer I found was small enough to fit right beside the unit?s original step down transformer and allow room for the mounting screw to still fit. I drilled holes through the bottom chassis and used pop rivets to fasten the transformer. Once all parts and wires were soldered in the phantom PCB, I installed the board on the metal plate where the 2nd output transformer resided. I had to drill one extra hole in this plate and that was a little tricky. I then mounted the phantom power board there using plastic stand-offs and small nut/bolts.

I decided that since the master pot was now un-used, I could remove it and use that space to allow mounting of a switch that could be used to connect each chanel?s output to the VU meter.
-I removed the master fader pot and replaced it with a 50k trimpot
-the green wire originally connected to the master volume control was connected to lug 2 of the trimpot, the yellow wire to lug 3 and I fastened lug 1 under the screw fastening the main pcb to the chassis. The trimpot lays flat and can be adjusted with a screw-driver. I found this helped to adjust the VU meter level measuring the channel 1 set to osc. and referenced on an external VU meter.

I then connected a wire from each individual ?? mic output to a separate pin on the 4 position switch. The common pole of the switch was connected to the channel one blue wire of the mix bus (any of the remaining unused blue wires could be used for this). So now, any of the 4 mic channels can be selected to read on the VU meter. I like these modded mixers so much that i bought 2 for myself to use in a remote recording kit.

outside
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insdie showing phantom power circuit
Image

vu selector switch wiring
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Nick Sevilla
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Post by Nick Sevilla » Wed Jun 02, 2010 8:20 am

Thanks for this RodC!

Now I can use my Shure M67 for cool things!

I will try to do the following to mine though : Keep the Mix buss unaltered, in order to be able to use it as a mixer as well.

How?

I'll tap the output of each channel POST gain knob, to it's own output connector, while leaving the rest of the wiring intact. It should not be too much of a problem.

Since this is an unbalanced circuit, it should be no big wiring deal.

Cheers
Howling at the neighbors. Hoping they have more mic cables.

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Derrick
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Post by Derrick » Wed Jun 02, 2010 10:02 am

Won't that cause some loading?
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RodC
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Post by RodC » Sun Oct 10, 2010 10:44 am

Derrick wrote:Won't that cause some loading?
Yes, however you can use a switched 1/4" jack to disconnect the circuit from the mix bus.

(Sorry for the late late reply, I just ran across this thread when searching for somehting else)
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M267 insert????

Post by changeng » Tue Oct 12, 2010 3:43 pm

Sorry to go somewhat off-topic, but I don't know where else to ask this!

RodC or anyone in the know - how would you go about installing an insert jack into a M267? Using the mix buss, running that into a Shure M63 Audiomaster and bringing it back into another channel in the 267, I can get some neato tone shaping (the M63 has a 100hz pot, a 10Khz pot, plus hi and lo pass filters, with an output transformer - $20 bucks!).

But I'd like to have an actual insert so I can try it with normal EQs - any time I try other models, loading occurs and no one has fun. With the M63, mixing the two inputs of the 267 gives nice variety until the feedback starts.

I tried the 267 against a GAP Pre 73 (with the "TT" mod that Zen Pro Audio offers) using some dynamics and was shocked at how close the Shure came to the GAP. That was before finding a way to sneak the M63 into the mess.

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Post by appreciative » Sun Nov 28, 2010 11:59 pm

With levels at 10 on the m67 is that "gain", or merely "no attenuation"?

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RodC
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Post by RodC » Mon Nov 29, 2010 4:44 am

appreciative wrote:With levels at 10 on the m67 is that "gain", or merely "no attenuation"?
It's gain. If you look at the schematic, a 1k signal is injected at .1 mv, the output before the level control is 8.6 (Wired stock) I have never really checked the gain, but I'm sure its not x86.
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vivalastblues
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Post by vivalastblues » Fri Apr 22, 2011 9:42 pm

Maybe I should make a separate thread...but for anyone who has one of these and has racked them - where did you get the faceplate from? I can't find any images of it right now but I've seen them on eBay with an optional faceplate added.

If anyone can point me in the right direction that would be great. I arleady asked Shure and got no answer.

edit: kinda looks something like this I guess... Image

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shure m67 mod, 48V supply

Post by ricercar.record » Sun Aug 07, 2011 7:54 pm

i've modded two of these units for myself and have been wanting to add the 48V Phantom Feed supply from ESP (Project 96A), similar to what monty marc has done.

However, so far I have been unable to find somewhere to buy a suitable (small in size) 30 VAC transformer that will actually fit in the box.
Does anyone have any possible recommendations for a transformer or for a good place online to buy them?

I know the transformer needed would be a 30 VAC secondary or a 15-0-15V secondaries (without using the center tap) and rated at 30 VA or above.
Each mic will draw about 10ma so needs to be capable of at least 40-50 ma for 4 mics, preferably more. I found this on mouser which would work perfectly,
http://www.mouser.com/Search/ProductDet ... 546-166G30
.....unfortunately it's to large to be able to fit anywhere in the M67.

I have asked a few different people on here for some help/recommendations but no such luck so far,
so any helpful insight from experienced tombers would be greatly appreciated.

otherwise may just decide to use the 48V supply circuit in a different project.

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Post by Matt C. » Fri Sep 23, 2011 7:40 am

I'm trying to transformer-balance the direct outs on my M67, but in my ignorance about transformers, I'm having a hard time finding one that's suitable. all the transformers i've found online are either very expensive (jensen, lundahl, etc) or have what seems to be terrible frequency response (unless i'm reading the specs wrong, i can't imagine 100Hz-12kHz being suitable for music...). they also need to be small since there's not a ton of extra space in the box. edcor seemed to be the closest i've found, but those might be too big. can someone direct me to where i might find something suitable? thanks!

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Post by highvoltage » Mon Feb 06, 2012 1:30 pm

So, what is the difference between the m267 and m67? In term of sound?
Does the older m67 sound more 'vintage'?

Just cause i live in Europe, and the m267 can work at 240v.
Its almost impossible to find an m67-2E here, and im really not good at modding stuff...

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Post by Tavvish » Fri Feb 10, 2012 12:09 am

I have to say you are awesome for doing this, I really like how you had a sub-mission of making it cheap/easy, good man that is how I like my mods AND my women. stupid joke.

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