Hello everyone!
I'm in the process of racking a v672/a1, and while I've extensively used the search function there are still a few things that are not quite clear to me - most importantly the relationship between input impedance, gain and frequency curve of this preamp.
From what I understand and have researched here in the forum, the input impedance is set from resistors on the input. Many people have been experimenting with this, but for a gain range from 34 -65db, this manual http://audio.kubarth.com/rundfunk/g...YK96Y?5C8W,E]496-H;FEC86PM36%N=6%L $+G!D9@``
clearly states that this resistance should be 40 ohm, and that Rg for the negative feeback between 2,5k and 330k.
Now I know that a larger input impedance is typically desired, but isnt this the ONLY configuration that preserves maximum recommended gain while still being as close to linear in terms of frequency specs as possible?
So is the trade off for the higher gain settings the smaller input impdedance? It sure seems (if I understand the manual correctly) like this amp is really designed to work best at 34db gain with 2,5k input impedance and everything else is a trade off, is that correct?
The second headscratcher is the 15khz low pass. Many people have been investigating this issue, for example here:
https://groupdiy.com/threads/telefunken-v672-high-frequency-rolloff.43015/or here
https://groupdiy.com/threads/v672-filter.10564/#post-125012
But is A.) the high freq rolloff at higher gains really an issue if one sticks to the original instructions as to how to use this amp as a mic pre (i.e. sticking with 40ohm input impedance)?
And B.) some manuals for the later models (like my v672/a1 or the ANT v672D) state that you can just bypass the low pass by bridging pins 11&12.
Final question: Is there a solution that keeps both input impedance high(ish) (around 1k or greater), gain in the 60db range and a linear frequency response?
Thanks in advance as always,
David
I'm in the process of racking a v672/a1, and while I've extensively used the search function there are still a few things that are not quite clear to me - most importantly the relationship between input impedance, gain and frequency curve of this preamp.
From what I understand and have researched here in the forum, the input impedance is set from resistors on the input. Many people have been experimenting with this, but for a gain range from 34 -65db, this manual http://audio.kubarth.com/rundfunk/g...YK96Y?5C8W,E]496-H;FEC86PM36%N=6%L $+G!D9@``
clearly states that this resistance should be 40 ohm, and that Rg for the negative feeback between 2,5k and 330k.
Now I know that a larger input impedance is typically desired, but isnt this the ONLY configuration that preserves maximum recommended gain while still being as close to linear in terms of frequency specs as possible?
So is the trade off for the higher gain settings the smaller input impdedance? It sure seems (if I understand the manual correctly) like this amp is really designed to work best at 34db gain with 2,5k input impedance and everything else is a trade off, is that correct?
The second headscratcher is the 15khz low pass. Many people have been investigating this issue, for example here:
https://groupdiy.com/threads/telefunken-v672-high-frequency-rolloff.43015/or here
https://groupdiy.com/threads/v672-filter.10564/#post-125012
But is A.) the high freq rolloff at higher gains really an issue if one sticks to the original instructions as to how to use this amp as a mic pre (i.e. sticking with 40ohm input impedance)?
And B.) some manuals for the later models (like my v672/a1 or the ANT v672D) state that you can just bypass the low pass by bridging pins 11&12.
Final question: Is there a solution that keeps both input impedance high(ish) (around 1k or greater), gain in the 60db range and a linear frequency response?
Thanks in advance as always,
David