Ribbon Clamp Materials

Hi ribbon aficionados

I have been researching ribbon microphone design for some time now with the intention of building a couple of different DIY mics for my own use.

I have a query regarding ribbon clamp materials.

I understand brass plates (sometimes silver plated) are often used to clamp the ribbon in place, and also act as a conductor between the ribbon and the wires to the transformer.

Given that brass has only around 28% conductivity (IACS) as compared to 100% for pure copper, is it worthwhile using high-purity silver-plated copper in this situation to reduce resistance?

Are there any reasons NOT to?

I have read all the topics I could find on GroupDIY and elsewhere on the topic, but the low-conductivity of brass vs copper was not mentioned.

Any thoughts or comments would be appreciated.

Thanks.

Hi!

The ribbon clamps are pretty big compared to the wire coming off them, so I don't think it makes a real difference whether it is brass or copper, except that brass is easier to work with, and copper will deform more easily.

The real 'bottleneck' is the contact between the clamp and the aluminium ribbon, not the clamp itself, which is why silver or gold plating is used by most manufacturers. Some use solid silver.

Silver plating is not a simple process, and I have found that making the clamps out of solid silver is a simpler way to go. It conducts well and is easy to work with.

It may look a bit more expensive, but if you add in the cost of chemicals etc then it probably isn't, unless you are making lots.

Hope that helps!

Stewart

Hi Stewart

Thanks for the reply...

I gather a silver-aluminium contact is probably the best I can do in terms of ribbon/clamp contact. However, I do have an aluminium solder from 'Solder-It' that could help there; Although I assume it would be excruciatingly difficult to implement given the fragility of aluminium ribbons!

I have considered using pure silver for the clamp base but I am hoping to tap some threads in the bottom half of the clamp to accommodate the screws from the top half and assumed, given the softness of silver, it would be hard to tap and perhaps not hold a thread too well..?

You are right about silver plating...most plating businesses charge a minimum to do any plating job...I can buy enough pure silver to make the clamps for about $10 less than it costs to plate brass or copper!

Anyway, thanks for the reply...I intend to post some pics  of the completed mics here when I finally get them done...I have learnt a great deal by trawling through the posts by yourself, Marik, xvlk, PRR and others...

I'm milling up my 'flux-frames' for my MRC and the body tomorrow so perhaps a month to get a pair done I guess...exciting to finally be getting hands-on after so much research and materials gathering!

thanks again

Wayne

Hi Wayne,

If you use  stirling silver or similar grade, it takes a 2mm tap pretty well, nearly as well as brass and much much better than copper does.

Some manufacturers do solder the ribbons, but I haven't had much success. Alusol works at a fairly high temperature, and it tends to vaporise the ribbon. If you oxides the ribbon then contact will get worse, not better.

I have a Japanese mic that has no ribbon clamps at all. The ribbon is just glued and soldered!

Stewart