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Re: [regsaudioforum] Re: A question for everyone

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  • Ted Rook
    Yes tube amp output transformers make excellent high pass filters! Thinking about DC and offsets I recalled your remarks about the progress Dali made with
    Message 1 of 28 , Oct 31, 2007
      Yes tube amp output transformers make excellent high pass filters! Thinking about DC and
      offsets I recalled your remarks about the progress Dali made with decreasing the "stiction" of
      conventional cones. Most solid state amplifiers have small DC offsets, something steady
      that persists over a long period of time in the order of tens of millivolts. My physics theory
      tells me that the current flow in the drivers due to this will operate in the opposite direction, ie
      resist motion. Quite possibly Dali refer to this in their technical recommendations, along the
      lines of "check your amp once in a while."

      Ted

      On 1 Nov 2007 at 4:03, regtas43 wrote:

      > DC coupled power amps exist for sure.
      > Random(old) sample: Kenwood L07M
      > New example: Parasound Halo JC1
      > I think the Sunfire is DC coupled on the "lab input".
      >
      > But there are many. I just picked a few at random here.
      >
      > REG
      >
      > PS Tube amps are never like this!
      >
      >
      > --- In regsaudioforum@yahoogroups.com, "Ted Rook" <rooknrol@...>
      > wrote:
      > >
      > > Yes that extreme LF passes right through my CD playback via the
      > preamp and power amp
      > > to the speakers at large amplitude. My intuition tells me it is
      > probably air currents causing the
      > > mic capsule diaphragms to move slightly. There's no audible
      > degradation, it came to my
      > > notice visually while the black trim piece was off the speakers. I
      > think it means I have pretty
      > > good LF linearity ;-)
      > >
      > > Ted
      > >
      > > On 31 Oct 2007 at 10:57, Hans-Martin wrote:
      > >
      > > > Hi Ted
      > > > All TacT and Lyngdorf digital amps that are connected via digital
      > > > cables show an extreme low frequency response.
      > > > I have not tested a DC signal because I dont have such test
      > signal-
      > > > and TacT Millennium has a DC protection that shuts down as soon
      > as the
      > > > bridged output optocouplers detect a DC difference.
      > > >
      > > > Playing the Waterlily Mahler5 I get some extremely slow cone
      > movement
      > > > on one channel 2.7Hz and on the other 3.6 Hz.
      > > > It is in the signal of the CD version and the CD-track of the
      > SACD and
      > > > replay via a digital amp. Spectrum analysis and oscilloscope
      > traces
      > > > show them being no L/R correlation, so it was not room noise when
      > > > recording. This signal is close to DC.
      > > >
      > > > At the other end there is some ringing if a tone burst is
      > passing the
      > > > digital amp.
      > > > I think, the perfect pulse response does not exist in a hifi
      > chain but
      > > > the speakers are much more limited with their crossover and
      > chassis
      > > > behaviour and room....
      > > > Regards Hans-Martin
      > > >
      > > >
      > > > > Thinking about the impulse response once more I agree with a
      > point
      > > > Hans Martin made
      > > > > about the path of the pulse first encounters the input
      > capacitor of
      > > > the preamp! After that it is
      > > > > not a pulse any more! So we must remember that the waveform we
      > see
      > > > in the chart that
      > > > > says "such a speaker" is truthfully the performance of "such a
      > > > speaker and a preamp and a
      > > > > power amp" There is a difference. But I understand that timing
      > > > deviations can come from
      > > > > speaker drivers but not from capacitors and transistors at
      > least not
      > > > in the normal way. So
      > > > > any timing deviations are traceable to the drivers.
      > > > >
      > > > > Absence of capacitors is an advantage of passive preamps that
      > I had
      > > > not considered before.
      > > > > Do you know if people make DC coupled power amps to eliminate
      > one
      > > > more hipass stage?
      > > > >
      > > > > Ted
      > > > >
      > > > >
      > > > > On 30 Oct 2007 at 8:33, Uli Brueggemann wrote:
      > > > >
      > > > > >
      > > > > > Ted,
      > > > > >
      > > > > > typically I measure with a good mic and an external mic
      > preamp
      > > > into a PC soundcard line input
      > > > > > (mic inputs are typically not of high quality).
      > > > > >
      > > > > > The story about the tweeter polarity change does not
      > necessarily
      > > > mean that the sound is bas
      > > > > > (see Robert's answer). I have just tried to explain you a
      > possible
      > > > reason for "bipolar" pulse
      > > > > > responses.
      > > > > >
      > > > > > If you like to hear my speakers and my system you can hear
      > it from
      > > > 2.-4.11.07 at the Hifi-Music-
      > > > > > World, http://www.hifi-music-world.de/
      > > > > >
      > > > > > It is an exhibition specialized on DIY products for hifi. We
      > have
      > > > two DIY magazines here in
      > > > > > Germany and you can also get high quality speaker drivers and
      > > > speaker parts ( e.g. Mundorf) for
      > > > > > DIY. The exhibition takes place for 3 days (the first
      > exhibition
      > > > has started 2002 and it has now
      > > > > > well established). Typically the visitors have more
      > knowledge than
      > > > the visitors looking for
      > > > > > expensive stuff at high-end shows.
      > > > > >
      > > > > > This year is the first time I participate and I will show and
      > > > demonstrate of course Acourate®.
      > > > > > Hope it will be successful.
      > > > > >
      > > > > > So if you can come to Gelsenkirchen, Germany, you are very
      > welcome :)
      > > > > >
      > > > > > Uli
      > > > > >
      > > > > >
      > > > > > On 10/30/07, Ted Rook <rooknrol@> wrote:
      > > > > > Thank you all. How are you measuring? With a mic into a
      > PC
      > > > soundcard or does that have
      > > > > > too many limitations?
      > > > > >
      > > > > > I've heard about the tweeter inversion before and I am
      > not
      > > > sufficiently knowledgeable to
      > > > > > comment on the wisdom of the choice. I believe my trust
      > in the
      > > > ears of Alan Shaw is well
      > > > > > placed. I myself have not heard better. But then I have
      > not
      > > > heard your speakers Uli, nor
      > > > > > electrostatics ever.
      > > > > >
      > > > > > Ted
      > > > > >
      > > > > >
      > > > > >
      > > > > >
      > > > > >
      > > > > >
      > > > > >
      > > > > >
      > > > > >
      > > > >
      > > >
      > > >
      > > >
      > > >
      > > >
      > > > Yahoo! Groups Links
      > > >
      > > >
      > > >
      > > >
      > > >
      > >
      >
      >
      >
      >
      >
      > Yahoo! Groups Links
      >
      >
      >
      >
      >
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