[Ham-Mac] TS-570 Digital Output and iMic Interface Issue

[Philip]

At some time fairly close to Sat, 10 Jul 2004 08:09:55 -0500,
rumor has it that Richard wrote:

> For Tom NU4G and others Mac users
> 
> It is my understanding
> the industry standard is 600 ohms for most rigs as well as the music
> industry.  

Well, it was. If your objective is to maximize _power_ transfer then
impedance matching in audio circuit is important. The telephone system
still requires that the impedance matches. For the rest of us it usually
doesn't matter much. Most equipment will have a low (50-150 ohm) output
impedance and a higher (1k-10k ohm) input impedance.

> Buried in the
> find print on page 62 of the manual is note saying the digital output
> (ACCY2, Pin 3 ANO) is 4.7 kohms.

> >Menu # 34 
> >          Level 1 30 mVpp - 8 mV rms
> >          Level 4 220 mVpp - 70 mV rms
> >          Level 9 400 mVpp - 130 mV rms

That is odd. The levels are more like mic level than line level.
I don't have the manual so I can't check, but are you sure that is the
_output_ and not _input_ impedance?

Anyway, if you found a way to make it work - well done! *smile* In
modern audio circuits impedance is rarely an issue - but getting the
levels in the right range can be mighty important especially for AD
converters!


Google found iMic specs for me at:
http://www.soundprofessionals.com/cgi-bin/gold/category.cgi?item=IMIC-USB-PORT

and on that page it lists these specs:
    * Line input Sensitivity/Impedance -15.0dBu , Greater Than 20kOhms
    * Mic input Sensitivity/Impedance -30.0dBu, 7000 Ohms
    * Maximum Input Signal Level - Line input - 0.0dBu
    * Maximum Input Signal Level - Mic Input -15.0dBu
    * Output Level/Impedance minijack output -2.0dBu , 600 ohms
    * Frequency Response (20Hz - 20kHz)
    * Total Harmonic Distortion (20Hz - 20kHz) 0.03% Line Level Mode 0.07% Mic Level Mode
    * Signal to Noise Ratio 85dB
    * Residual Noise 72dB below nominal input level


**** CAUTION **** 

Griffin's website claims they won't publish specs 'cause it may change
with particular internal parts that might change as they keep to their
choice to keep the price low. 

See:
http://www.griffintechnology.com/support/imic/IMIC-021.html

However, it _does_ have mic and line inputs. Did you try setting the
input to mic level?

If the above specs are kind o' close, then I don't think impedance
mismatch is the cause of your problem - thus you can work on just
levels. *smiles*  That's my opinion, anyway!! :)

 --

                Philip
                73, de KB0SWA