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Mickeyrouse

Silverado

Posts: 139 Member Since:05/11/2015

#41 [url]

Jun 4 17 8:20 AM

   Oliver Archut designed a mic pre with two ranges of variable impedance, his TAB Funkenwerk V77M. According to the product literature, ribbon mics can be quite variable in their output impedances, and this pre is designed to accurately match impedance on a mic-by-mic basis. I do not have this preamp, though I do have the V78M. It is pretty good.    Since Oliver's passing, product availability from AMI seems uncertain. The AMI website has not been updated in years. They do answer email. Inquiries have been answered with the hope of availability in the future. It does not seem we are there yet.

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gtoledo3

Aqua Marine

Posts: 4,239 Member Since:23/10/2013

#42 [url]

Jun 4 17 9:54 AM

Mickeyrouse wrote:
   Oliver Archut designed a mic pre with two ranges of variable impedance, his TAB Funkenwerk V77M. According to the product literature, ribbon mics can be quite variable in their output impedances, and this pre is designed to accurately match impedance on a mic-by-mic basis. I do not have this preamp, though I do have the V78M. It is pretty good.    Since Oliver's passing, product availability from AMI seems uncertain. The AMI website has not been updated in years. They do answer email. Inquiries have been answered with the hope of availability in the future. It does not seem we are there yet.

He also used to mod v672s to have variable impedance input, because there was something going on with the input transformer that makes it somewhat easy to do.

AMI has still been making products, but I think has focused on the transformer production. I've had no problem getting parts to service other products, here and there.

There was recently a post on the facebook page about some activity with new runs of products and the website : https://www.facebook.com/AMI-305279256175561/

...I believe there's going to be a small run of some mics coming out soon, I think maybe some Cathedral Guitars C12s.

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zakco

Platinum Blonde

Posts: 1,106 Member Since:02/03/2011

#45 [url]

Jun 15 17 12:17 AM

My Buzz Audio QSP-20 mic pres have switchable high/low impedance settings on the front panel. 4k and 1.2k. The different settings definitely affect the tone of some microphones and my preference can go either way depending on the source. I'm curious as to why Tim chose these particular values as compared the typically lower settings I see on other designs...maybe something to do with the transformerless input design?

Last Edited By: zakco Jun 15 17 12:36 AM. Edited 1 time.

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maarvold

Aqua Marine

Posts: 3,209 Member Since:23/01/2011

#47 [url]

Jun 16 17 8:38 AM

hank alrich wrote:
Input impedance for the Gordon preamp is stated as "Impedance, differential-mode 2M ohms".

 
I have talked to Grant Carpenter (designer/builder) about this several times.  His concept is that he doesn't want the mic to 'know' that the preamp is hanging off it's output.  There is also a Lo-Z input mode that is 1 kOhms.  

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