Once Bit, Twice Shy . . .

[MicMaven]

Well, obviously you get what you paid for... do you want a "Neumann" class quality with a 27 dollars investment? Do you live on Mars?

Gee Whiz, Mr. Biula, I believe you fail to sense the drama, adventure, and, especially, humor in all of this!

But seriously, folks ... Of course, I had low expectations when I ordered them.

In my defense, however, I previously purchased very nice all-metal U87 copycat microphones as donor bodies for as little as $32 and I am extremely pleased with them. I had "hoped" (but not expected) these to be similar. The point is to inform other DIY mic builders about them as many DIY mic builders are looking for good, low cost donor bodies. So, I took one for the team as it were to see if these were any good. Trust me, I went in with my eyes wide open!

Rest assured, I am neither disappointed nor surprised. They will be useful and productive when I finish the project They represent a DIY challenge, not a poor purchase decision.

And, no, I am not from Mars ... and I am glad glad you did not ask if I am from Venus !!!

Happy trails, old man. All in good fun. James

 

[k brown]

Gee Whiz, Mr. Biula, I believe you fail to sense the drama, adventure, and, especially, humor in all of this!

But seriously, folks ... Of course, I had low expectations when I ordered them.

In my defense, however, I previously purchased very nice all-metal U87 copycat microphones as donor bodies for as little as $32 and I am extremely pleased with them. I had "hoped" (but not expected) these to be similar. The point is to inform other DIY mic builders about them as many DIY mic builders are looking for good, low cost donor bodies. So, I took one for the team as it were to see if these were any good. Trust me, I went in with my eyes wide open!

Rest assured, I am neither disappointed nor surprised. They will be useful and productive when I finish the project They represent a DIY challenge, not a poor purchase decision.

And, no, I am not from Mars ... and I am glad glad you did not ask if I am from Venus !!!

Happy trails, old man. All in good fun. James

. . . you gave that post more of an answer than it deserved!

 

[RoadrunnerOZ]

Maybe your could do a hammer finish paint job - with a real hammer……

 

[MicMaven]

Maybe your could do a hammer finish paint job - with a real hammer……

Ouch ... you guys are killing me !

But seriously folks - I installed an MXL-700 board and capsule which cost me a whole whopping $15 and of course it buzzes out of control, which "suggests" there is a show stopping problem. I covered the board with foil. Then I covered the whole thing end-to-end with foil. And it still buzzes.

So now I wonder what I am missing. I suspect I need ground continuity end-to-end. Do ground the shell? To what? To the Board? To Pin 1? To both? Something Else? Use a different board and/or capsule? (I am showing my ignorance, but I learn by asking some of the time ...)

Maybe I should just finish it with a hammer?

What do I do next? What am I missing? James

(he typed while reaching for his Teflon(R) suit ...)

 

[RoadrunnerOZ]

Ouch ... you guys are killing me !

But seriously folks - I installed an MXL-700 board and capsule which cost me a whole whopping $15 and of course it buzzes out of control, which "suggests" there is a show stopping problem. I covered the board with foil. Then I covered the whole thing end-to-end with foil. And it still buzzes.

So now I wonder what I am missing. I suspect I need ground continuity end-to-end. Do ground the shell? To what? To the Board? To Pin 1? To both? Something Else? Use a different board and/or capsule? (I am showing my ignorance, but I learn by asking some of the time ...)

Maybe I should just finish it with a hammer?

What do I do next? What am I missing? James

(he typed while reaching for his Teflon(R) suit ...)

Maybe try lining the internal shell walls of the body with conductive copper foil tape and try a ground wire of this to the cable shield - not sure how the board you’ve installed is grounded to the cable but obviously it’s needed for power - some combination of grounding or isolating the shield foil using a capacitor may help. You can also get ferrite sheets that have a self adhesive backing for HF shielding - I put a link to one from Mouser in an earlier post #37 - also available from Element 14:
https://au.element14.com/laird-tech...id||ptaid||&CMP=KNC-GAU-CLM-SHOPPING-PMAX-NCA
I have used the copper foil tape and also twin layer aluminium foil shielding in Clavinet preamp shielding boxes with great succes - these buzz like crazy under stage lights. I also do a lot of guitar and bass shielding using the copper foil - I always use the one with conductive adhesive so it makes a 360 degree coverage without having to solder link wiring. The ground wire is then soldered to a point closest to pin 1 in the XLR socket and in your case maybe a ground wire to the mesh basket as well
Bass guitar example - this was an extremely noisy beast until I did a complete screen with copper foil tape - I also lined the jack socket hole and screen wrapped the connecting wires and the whole of the scratch plate:

 

[RoadrunnerOZ]

Alternatively the Spear and Jackson might help:

 

[MicMaven]

Maybe try lining the internal shell walls of the body with conductive copper foil tape and try a ground wire of this to the cable shield -

Right. I believe the problem is the lack of continuity between grill, body-covering foil, and electrical ground on Pin 1. And yet, I confess opening a return case based on misrepresentation (plastic not metal body as stated in the sale listing) appeals more and more as I go along.

Perhaps another solution is to install a dynamic cartridge, or an FET-based capsule and suitable circuit, which would not require all that shielding or grounding, but that seems like quitting, so I will save that for a last resort.

By the way, your guitar grounding project looks good. I paid just $16 for my first electric guitar in 1968, a really cheap Norma brand model that sorely needed similar treatment! The conductive adhesive is a good move.

James

 

[JohnRoberts]

Maybe try lining the internal shell walls of the body with conductive copper foil tape and try a ground wire of this to the cable shield - not sure how the board you’ve installed is grounded to the cable but obviously it’s needed for power - some combination of grounding or isolating the shield foil using a capacitor may help. You can also get ferrite sheets that have a self adhesive backing for HF shielding - I put a link to one from Mouser in an earlier post #37 - also available from Element 14:
https://au.element14.com/laird-tech...id||ptaid||&CMP=KNC-GAU-CLM-SHOPPING-PMAX-NCA
I have used the copper foil tape and also twin layer aluminium foil shielding in Clavinet preamp shielding boxes with great succes - these buzz like crazy under stage lights. I also do a lot of guitar and bass shielding using the copper foil - I always use the one with conductive adhesive so it makes a 360 degree coverage without having to solder link wiring. The ground wire is then soldered to a point closest to pin 1 in the XLR socket and in your case maybe a ground wire to the mesh basket as well
Bass guitar example - this was an extremely noisy beast until I did a complete screen with copper foil tape - I also lined the jack socket hole and screen wrapped the connecting wires and the whole of the scratch plate:
View attachment 116624
View attachment 116625

that looks like a shock hazard waiting to happen... You can ground bond that copper foil through something like a 100k resistor to still provide shielding from noise while limiting current to below lethal current levels to humans.

JR

 

[RoadrunnerOZ]

that looks like a shock hazard waiting to happen... You can ground bond that copper foil through something like a 100k resistor to still provide shielding from noise while limiting current to below lethal current levels to humans.

JR

If the foil is inside the case there’s no contact with the body (human) - the mesh basket could be isolated with a resistor to safeguard against shock - good idea. Most metal body mics are case grounded.

 

[RoadrunnerOZ]

Right. I believe the problem is the lack of continuity between grill, body-covering foil, and electrical ground on Pin 1. And yet, I confess opening a return case based on misrepresentation (plastic not metal body as stated in the sale listing) appeals more and more as I go along.

Perhaps another solution is to install a dynamic cartridge, or an FET-based capsule and suitable circuit, which would not require all that shielding or grounding, but that seems like quitting, so I will save that for a last resort.

By the way, your guitar grounding project looks good. I paid just $16 for my first electric guitar in 1968, a really cheap Norma brand model that sorely needed similar treatment! The conductive adhesive is a good move.

James

If you can open a PayPal dispute the return should be easy.
Barium vinyl sheet is heavy and would add mass to the mic body and shielding in addition to the copper foil as well as reducing handling noise if you decide to keep it - that’s if there’s enough room inside. The good thing with the tape is while the backing is on it’s quite stiff and if you peel back a corner or end and use a round ended piece of dowel you can run the tape up inside the body peeling the backing as you go (long nosed pliers or haemostat clamps - pic below - are handy here) and smoothing the foil to the inside surface.

 

[cyrano]

Barium? I don't think you'd want that in your environment. It' rather toxic. Mind you Cu is also toxic, but in a far less dangerous way.

Or is the barium in that vinyl tape completely covered? You'd still have to cut it though...

 

[RoadrunnerOZ]

Barium? I don't think you'd want that in your environment. It' rather toxic. Mind you Cu is also toxic, but in a far less dangerous way.

Or is the barium in that vinyl tape completely covered? You'd still have to cut it though...

It’s not barium metal, it’s naturally occurring barium sulphate impregnated into a vinyl polymer. Commonly used in cars, boats, engine rooms etc for sound absorption and vibration damping. In a lot of cases MLV (Mass Loaded Vinyl) is comprised of vinyl and other dense mineral salts, not just barium sulphate - these salts are inert and pose no health risks - likely the vinyl is more toxic if it catches fire from too high a sound pressure level . This stuff has been around for decades - they also make MLV curtains for auditoriums. I use products like this for mass loading walls in studio building in addition to high density plasterboard and high density particle board layers - it’s a very good damping product.

 

[cyrano]

Never came across that. Seems safe enough. The MLV I use doesn't contain barium...

 

[k brown]

This stuff is more readily available, and works great:
https://www.amazon.com/3M-Safety-2228-1X10FT-054007507277-Mastic/dp/B001B1AP3O?th=1

 

[RoadrunnerOZ]

Never came across that. Seems safe enough. The MLV I use doesn't contain barium...

Probably calcium silicate

 

[RoadrunnerOZ]

This stuff is more readily available, and works great:
https://www.amazon.com/3M-Safety-2228-1X10FT-054007507277-Mastic/dp/B001B1AP3O?th=1

Yeah I use stuff like that and also mastic putty for blocking air gaps in cable entry points and the like. It doesn’t have the mass of the MLV though. I also use the gun dispensed mastic for floor, wall and ceiling join points in studio construction. It sets to a rubber like consistency - firm yet permanently flexible. The tape works well as a vibration damper but MLV has a much higher damping factor for the same thickness.

 

[k brown]

Yeah I use stuff like that and also mastic putty for blocking air gaps in cable entry points and the like. It doesn’t have the mass of the MLV though. I also use the gun dispensed mastic for floor, wall and ceiling join points in studio construction. It sets to a rubber like consistency - firm yet permanently flexible. The tape works well as a vibration damper but MLV has a much higher damping factor for the same thickness.

Where do you buy it?

 

[RoadrunnerOZ]

Where do you buy it?

MLV is available at most car hi-fi suppliers or electronic stores also Amazon:
https://www.amazon.com.au/s/?ie=UTF...hvtargid=kwd-394639067467&hydadcr=7884_352927
The butyl mastic is available as liquid, tape, gun-tube or as putty. The putty is super dense:
https://www.valvewarehouseaustralia...Pw1IMo49nRsOnwYbDpiB46gl5RlKh4wRoCzeUQAvD_BwE

 

[RoadrunnerOZ]

The thicker the vinyl the higher the density - some places are really expensive but you can get it cheap from places like acoustic curtain companies. The 2mm stuff is 4Kg/sqM, 3mm is 6Kg/sqM
https://www.amazon.com.au/TroyStudi...vinyl+amazon&qid=1699117760&sr=8-1-fkmr3&th=1

 

[RoadrunnerOZ]

One thing I’ve noticed with some of these eBay sales is when you go to a PayPal dispute they’ll give you a refund and not bother about the return of the item - I’ve also had a couple where I did send the items back and then a couple months later I received the items back again with “not at this address”, another where they told me to just keep the item - after initially offering $5 off if I bought another one and kept the one that didn’t work without a refund - I said no, kept the item as they didn’t want it back and supplied my own power adapter off my failed Dashcam which worked fine with the new - total cost $0, total gain 1 x Dashcam.
If the postage back to china is more than the unit cost don’t bother.