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In Reply to: RE: Ralph...coupling caps in M-60 Mk. 3.3--what's the impedance... posted by jeffreybehr on March 16, 2016 at 12:51:22
If so, the value for a 50Hz cutoff is about 0.0033uf.
Follow Ups:
....altho I have no HQ caps around that value on hand; my calculator indicates that that load impedance is about 1 Meg-Ohm. Or I could install a new cap at the input feeding the 100K load resistor, and if I'm using only the RCA input, would I also have to add a same-value cap somewhere on the negative half of the balanced-input lead?
Seem to me that having the signal pass thru one pair of caps is only half as bad as having it pass thru 2; yes?
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Tin-eared audiofool, large-scale-Classical music lover, and damned-amateur fotografer.
William Bruce Cameron: "...not everything that can be counted counts, and not everything that counts can be counted."
If we are talking coupling caps, essentially the load is about 1M.
Its unlikely that the caps will have a huge effect. I'd be more concerned about the phase shift that occurs by such a high cutoff.
If you are using the RCA input you will only need one cap to do the job.
...will create a HP-filter of 33Hz. That cap would be a pair of 0.01s in series. The drivers are beginning to roll off acoustically around 200Hz, so 33Hz is about 2-1/2 octaves below their audible-output range.
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Tin-eared audiofool, large-scale-Classical music lover, and damned-amateur fotografer.
William Bruce Cameron: "...not everything that can be counted counts, and not everything that counts can be counted."
You might try a Russian SSG. I think you can buy them in that value. That is the most transparent capacitor I have heard, with the possible exception of the 100X more expensive Vcap CuTf.
...a 0.01uF SoniCap Platinum. FP will be about 16Hz, which is plenty low enough to avoid phase errors in the audible band--of these MR drivers, that is--and high enough to block or greatly reduce DC or large noise pulses which might destroy those irreplaceable drivers.* I tend to do this a lot, but my system has never sounded better, so some good must come of it. ... :-)
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Tin-eared audiofool, large-scale-Classical music lover, and damned-amateur fotografer.
William Bruce Cameron: "...not everything that can be counted counts, and not everything that counts can be counted."
Edits: 03/25/16
I would consider several points:
The amps can make a lot more power than the drivers can handle! Its only prudent to install a tweeter protection fuse of some kind! One mistake could cost you a fuse or a driver: your choice.
You might also consider putting a coupling cap at the output of the amp. It does not have to be very big and could save you some headaches- after all- the output section of the amp is direct-coupled.
Well, they're not fragile; being B-G mag-planar drivers, they simply can't be replaced, new at least, as B-G's new foreign owners decided to stop making them.Of course the tweeter has its high-pass filter in the x-over, but the MR doesn't. I remember asking GR Research's Danny Ritchey, the designer of the speakers, what filter point I should use on a high-pass filter with the 8- and 50-Watt amps I had at the time. We went back and forth, with him answering every number I offered to him (as in 200Hz? 100Hz? 50Hz? 25Hz? None at all?) with an 'OK'. He then said something like my low-power amps were not able to overdrive the panels, so it didn't much matter.
So with each 10" MR driver rated at least 75 Watts power handling by the most-conservative method...
http://gr-research.com/pdf/Neo10.pdf
...the four of them will handle at least 300 Watts, so I'll NOT be adding a new series cap between the amp and the x-over.TYVM for your help.
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Tin-eared audiofool, large-scale-Classical music lover, and damned-amateur fotografer.
William Bruce Cameron: "...not everything that can be counted counts, and not everything that counts can be counted."
Edits: 03/21/16 03/21/16 03/22/16
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...a few years ago to change the 1M-Ohm load resistors to 390Ks and use a 0.01uF SoniCap Platinum, for a high-pass-filter point of 41Hz.
Finished!
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Tin-eared audiofool, large-scale-Classical music lover, and damned-amateur fotografer.
William Bruce Cameron: "...not everything that can be counted counts, and not everything that counts can be counted."
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