I did read your post.
You stated "The frequency response alterations are very dependent on this."
You did not state "The measured input or measured output frequency response alterations are very dependent on this."....your statement is an ambiguous statement and could be taken to be as a statement of theory in light of the fact that we understand this device to be a reactive network of some sort.
I offered sensible suggestion of typical beltpacks usage, which in my experience is usually Shure or Sennheiser wireless IEM systems.
I also gave quote of suggestion of usage of various sources which implies commercial product typical output resistance.
Just what that value is, is open to conjecture.....or schematics.
I am trying to offer useful suggestions/information, and not to be the subject of your carping.
Dan.
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Stuart, I am saying that Shure and Sennheiser IEM systems are THE standard equipment on the big touring shows.
I do not have and cannot find schematics for such beltpack receivers....perhaps somebody has such service info.
Failing that, perhaps you could sweet talk a local production hire company and get them to lend you such a system for your measurements...this would also give you opportunity for system end to end measurements.
An educated estimate for typical opamp headphone amplifier output resistance would be in the range of 50R through 150R...or so.
Nowadays with dedicated headphone amplifier chipamps including Class D output stages, these values can be rather lower.
It might pay to ask the designers which beltpacks they had in mind when developing the REV33.
Dan.
I do not have and cannot find schematics for such beltpack receivers....perhaps somebody has such service info.
Failing that, perhaps you could sweet talk a local production hire company and get them to lend you such a system for your measurements...this would also give you opportunity for system end to end measurements.
An educated estimate for typical opamp headphone amplifier output resistance would be in the range of 50R through 150R...or so.
Nowadays with dedicated headphone amplifier chipamps including Class D output stages, these values can be rather lower.
It might pay to ask the designers which beltpacks they had in mind when developing the REV33.
Dan.
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Ok, thanks, but for modern dedicated HP driver chipamps ?.
IME, opamp HP amplifiers have rather higher series output resistance....eg published Cmoy schematics include 38R and 68R output resistance range.
That said, I would expect the Shure and Sennheiser beltpacks to run dedicated HP chipamps.......Class D is mentioned in the advertising blurb also.
Dan.
Yeah. Hell, iPods have output impedances in that range.
The series output resistor is optional and is typically used to pad down the output for sensitive IEMs. Without it the output impedance is about an ohm or so.
Yeah, but only in relation to ultrasonic noise.
se
I wouldn't bother going any higher than 5 ohms. That's a good range for most all commercial offerings as opposed to DIY projects.
se
Stuart, I presume your preliminary tests indicate a transfer function that varies in a somewhat predictable fashion with changes in source impedance? In lieu of a single number from the company, perhaps a set of measurements across a range of impedance would still be useful - the "official" reference would be likely to fall in there somewhere? Or do your tests indicate something less predictable?
-- Jim
-- Jim
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