INA103 differential stage

Archived from groups: rec.audio.pro (More info?)

My idea is to use a INA103 but without the second differential stage as
a mic-pre. One possibility would be of course to replace the
differential stage it with another OP or a discrete setup but my
question goes in another direction:

Since I want the output to be symmetrical anyway wouldn't it be possible
to amplify each phase separately with a single OP and use that as a
symmetrical output? Sounds a little to simple, I know. Am I missing
something here?


Thanks,
Rob
35 answers Last reply
More about ina103 differential stage
  1. Archived from groups: rec.audio.pro (More info?)

    >
    > Maybe I am not completely aware of how the input stage of an
    > instrumentation amp works. Is it possible to benefit from the balanced
    > first stage when I use only one of the differential outputs and the
    > other is grounded?
    >
    > >

    Yes you get the full benefit of hum rejection of balanced input
    realtive to the mic cable regardless of how you connect the output of
    the pre-amp.


    If you connect the output of the pre-amp as single ended, then you get
    no benefit of hum rejection at the output cable but that does not
    detract fomr the hum rejection at the balanced input. Think of it as a
    new signal source starting a new trip.


    The INA103 has a single ended output.

    Mark
  2. Archived from groups: rec.audio.pro (More info?)

    "Robert Angst"
    >
    > My idea is to use a INA103 but without the second differential stage as a
    > mic-pre. One possibility would be of course to replace the differential
    > stage it with another OP or a discrete setup but my question goes in
    > another direction:
    >
    > Since I want the output to be symmetrical anyway wouldn't it be possible
    > to amplify each phase separately with a single OP and use that as a
    > symmetrical output? Sounds a little to simple, I know. Am I missing
    > something here?


    ** No - all you need is two op-amps.

    Eg. a NE5532 dual op-amp configured as two inverters with 4.7 kohm input
    and feedback resistors.

    Balanced low noise in - balanced line level out.


    ............ Phil
  3. Archived from groups: rec.audio.pro (More info?)

    >
    > ** No - all you need is two op-amps.

    Ok, another thougt:
    if I connect the symetrical output of the two OPs into a single ended
    input (e.g. RNC) with + hot, - and shield grounded, I will loose the
    entire benefit of the differential construction between mic and output.
    If I'd leave the shield unconnected it should work. Is this correct?

    I sure want to be fully balanced but want to keep compatibility with
    single ended gear as well. Do I in that case have to go the classic
    route: first differential amp and then splitting it up again in two
    differential pairs? In that case I could include an insert jack for my
    RNC fairly easy..

    As an OP I would use an LT1469/8. I plugged them in my SX202 (as
    suggested in this NG) and realy like the results.
  4. Archived from groups: rec.audio.pro (More info?)

    Phil Allison wrote:

    > "Robert Angst"
    > >
    > > My idea is to use a INA103 but without the second differential stage as a
    > > mic-pre. One possibility would be of course to replace the differential
    > > stage it with another OP or a discrete setup but my question goes in
    > > another direction:
    > >
    > > Since I want the output to be symmetrical anyway wouldn't it be possible
    > > to amplify each phase separately with a single OP and use that as a
    > > symmetrical output? Sounds a little to simple, I know. Am I missing
    > > something here?
    >
    > ** No - all you need is two op-amps.
    >
    > Eg. a NE5532 dual op-amp configured as two inverters with 4.7 kohm input
    > and feedback resistors.
    >
    > Balanced low noise in - balanced line level out.

    Phil ! Are you feeling unwell ? He said a mic pre ! That configuration will be
    noisy as hell.

    Using two op-amps like that destroys CMRR too - unless you use say 0.1%
    tolerance resistors.

    The long tailed pair input has far better inherent common mode rejection.

    Graham
  5. Archived from groups: rec.audio.pro (More info?)

    "Robert Angst"
    >>
    >> ** No - all you need is two op-amps.


    ** You trimmed out my name and everything but for one line.

    That is very bad manners.


    ............ Phil
  6. Archived from groups: rec.audio.pro (More info?)

    Phil Allison schrieb:

    > "Robert Angst"
    >
    >>>** No - all you need is two op-amps.
    >
    >
    >
    > ** You trimmed out my name and everything but for one line.
    >
    > That is very bad manners.
    >
    >
    >
    > ........... Phil
    >

    Sorry, won't happen again.
  7. Archived from groups: rec.audio.pro (More info?)

    "Robert Angst"
    > Phil Allison
    >>
    >>>>** No - all you need is two op-amps.
    >>
    >>
    >> ** You trimmed out my name and everything but for one line.
    >>
    >> That is very bad manners.
    >
    >
    > Sorry, won't happen again.


    ** OK.

    As for your additional questions:

    1. Shorting one side of a balanced line to ground is bad practice.

    2. The majority of the CMRR of the INA103 mic-preamp comes from the first
    (differential) stage - a common mode signal gets only unity gain.

    3. The vast majority of external hum field rejection obtained with balanced
    *mic* lines is due to the two wires inside the cable being twisted.


    Sorry if this sounds like heresy.

    It isn't.


    .......... Phil
  8. Archived from groups: rec.audio.pro (More info?)

    Phil Allison schrieb:

    > As for your additional questions:
    >
    > 1. Shorting one side of a balanced line to ground is bad practice.

    Sure, I am just trying to make the box more idiot proof for 'emergency'
    situations when only a TS cable is at hand (or the person who built it
    isn't).

    > 2. The majority of the CMRR of the INA103 mic-preamp comes from the first
    > (differential) stage - a common mode signal gets only unity gain.

    Maybe I am not completely aware of how the input stage of an
    instrumentation amp works. Is it possible to benefit from the balanced
    first stage when I use only one of the differential outputs and the
    other is grounded?

    > 3. The vast majority of external hum field rejection obtained with balanced
    > *mic* lines is due to the two wires inside the cable being twisted.

    That sounds like even if differential input is compromised it's still
    good enough for these 'emergency' cases.

    > Sorry if this sounds like heresy.
    >
    > It isn't.
    >
    >
    > ......... Phil

    I guess I'll build it the way you suggested and use proper cables if I
    want to compress while tracking. That should make a nice two-chip pre.

    Thanks
    Rob
  9. Archived from groups: rec.audio.pro (More info?)

    Robert Angst wrote:
    >
    > Maybe I am not completely aware of how the input stage of an
    > instrumentation amp works. Is it possible to benefit from the balanced
    > first stage when I use only one of the differential outputs and the
    > other is grounded?
    >

    Don't actually connect the other output to ground, but the first stage
    of a classic instrumentation amp has whatever differential gain is
    defined by the gain-defining resistor, and a common mode gain of 1
    always. So for all gains above 1 you'll get some common mode rejection,
    equal to the differential gain.

    I don't know why you wouldn't want to use the second stage of the
    INA103, which is a differencing amp with unity gain and CMR as good as
    resistor tolerances will allow. The main limitation of a whole mic
    preamp constructed that way is that the output stage of the INA103 isn't
    the best thing for driving arbitrary loads on the end of possibly long
    cables. (but then the input stage isn't any better...)

    --
    Anahata
    anahata@treewind.co.uk -+- http://www.treewind.co.uk
    Home: 01638 720444 Mob: 07976 263827
  10. Archived from groups: rec.audio.pro (More info?)

    On Tue, 16 Aug 2005 17:04:38 +0200, Robert Angst
    <robert.angst@tu-berlin.de> wrote:

    >
    >>
    >> ** No - all you need is two op-amps.
    >
    >Ok, another thougt:
    >if I connect the symetrical output of the two OPs into a single ended
    >input (e.g. RNC) with + hot, - and shield grounded, I will loose the
    >entire benefit of the differential construction between mic and output.
    >If I'd leave the shield unconnected it should work. Is this correct?
    >
    >I sure want to be fully balanced but want to keep compatibility with
    >single ended gear as well. Do I in that case have to go the classic
    >route: first differential amp and then splitting it up again in two
    >differential pairs?

    I was thinking there was something 'bad' about your original idea
    of keeping the positive and negative signals separate, and now you've
    mentioned it.
    Another reason(s) to combine them is to cancel out any common-mode
    signal from the input. Passing on such a common-mode signal reduces
    the maximum signal (if the signal path can handle 15V peaks and your
    common-mode noise is 10V peak, your biggest signal is 5V before
    clipping. It also relies on the next device having good CMRR to cancel
    common-mode stuff, which if the next device has an unbalanced input,
    it obviously won't have.

    You absolutely need the differential-conversion stage (with
    highly=precise, matched resistors to get good CMRR) for a mic preamp,
    as the mic signal could be a few millivolts and the common-mode signal
    can be several volts. To turn the situation around so that the mic
    signal is much larger instead, you need to cancel the common signal
    with a very high precision.
    The instrumentation amplifier configuration helps by giving (up to
    about) 1,000 times gain for differential signals, and only a gain of 1
    for common-mode signals, but you still need the differential stage to
    cancel out the common-mode signals.

    >In that case I could include an insert jack for my
    >RNC fairly easy..
    >
    >As an OP I would use an LT1469/8. I plugged them in my SX202 (as
    >suggested in this NG) and realy like the results.

    -----
    http://www.mindspring.com/~benbradley
  11. Archived from groups: rec.audio.pro (More info?)

    In article <ddt5tu$ise$1@mamenchi.zrz.TU-Berlin.DE> robert.angst@tu-berlin.de writes:

    > > 1. Shorting one side of a balanced line to ground is bad practice.
    >
    > Sure, I am just trying to make the box more idiot proof for 'emergency'
    > situations when only a TS cable is at hand (or the person who built it
    > isn't).

    This is why the single-ended so-called "impedance balanced" output
    configuration is so popular. It doesn't matter if you short the
    non-driven side to ground because there's no signal on it. Much
    cheaper than a transformer, simpler than a cross-coupled see-saw
    output stage, and good enough for even some of the finest microphones.


    --
    I'm really Mike Rivers - (mrivers@d-and-d.com)
    However, until the spam goes away or Hell freezes over,
    lots of IP addresses are blocked from this system. If
    you e-mail me and it bounces, use your secret decoder ring
    and reach me here: double-m-eleven-double-zero at yahoo
  12. Archived from groups: rec.audio.pro (More info?)

    "Pooh Bear"
    > Phil Allison wrote:
    >> "Robert Angst"
    >> >
    >> > My idea is to use a INA103 but without the second differential stage as
    >> > a
    >> > mic-pre. One possibility would be of course to replace the differential
    >> > stage it with another OP or a discrete setup but my question goes in
    >> > another direction:
    >> >
    >> > Since I want the output to be symmetrical anyway wouldn't it be
    >> > possible
    >> > to amplify each phase separately with a single OP and use that as a
    >> > symmetrical output? Sounds a little to simple, I know. Am I missing
    >> > something here?
    >>
    >> ** No - all you need is two op-amps.
    >>
    >> Eg. a NE5532 dual op-amp configured as two inverters with 4.7 kohm
    >> input
    >> and feedback resistors.
    >>
    >> Balanced low noise in - balanced line level out.
    >
    > Phil ! Are you feeling unwell ? He said a mic pre ! That configuration
    > will be
    > noisy as hell.


    ** Try reading the context - dickhead.

    The INA103 allows access on pins 5 & 12 to the differential stage's outputs.

    http://focus.ti.com/lit/ds/symlink/ina103.pdf

    The NE5532 would merely buffer those outputs.


    ........... Phil
  13. Archived from groups: rec.audio.pro (More info?)

    Phil Allison wrote:

    > "Pooh Bear"
    > > Phil Allison wrote:
    > >> "Robert Angst"
    > >> >
    > >> > My idea is to use a INA103 but without the second differential stage as
    > >> > a
    > >> > mic-pre. One possibility would be of course to replace the differential
    > >> > stage it with another OP or a discrete setup but my question goes in
    > >> > another direction:
    > >> >
    > >> > Since I want the output to be symmetrical anyway wouldn't it be
    > >> > possible
    > >> > to amplify each phase separately with a single OP and use that as a
    > >> > symmetrical output? Sounds a little to simple, I know. Am I missing
    > >> > something here?
    > >>
    > >> ** No - all you need is two op-amps.
    > >>
    > >> Eg. a NE5532 dual op-amp configured as two inverters with 4.7 kohm
    > >> input
    > >> and feedback resistors.
    > >>
    > >> Balanced low noise in - balanced line level out.
    > >
    > > Phil ! Are you feeling unwell ? He said a mic pre ! That configuration
    > > will be
    > > noisy as hell.
    >
    > ** Try reading the context - dickhead.
    >
    > The INA103 allows access on pins 5 & 12 to the differential stage's outputs.
    >
    > http://focus.ti.com/lit/ds/symlink/ina103.pdf
    >
    > The NE5532 would merely buffer those outputs.

    Ok, I follow you now. From what he said ( about simply amplifying each leg of
    the mic input separately ) I got a different picture of what you meant.

    Why not buffer those points using a voltage follower configuration though ?
    Slightly less noisy without those 4k7s.

    Graham
  14. Archived from groups: rec.audio.pro (More info?)

    "Pooh Bear"
    > Phil Allison wrote:
    >>>
    >> >> ** No - all you need is two op-amps.
    >> >>
    >> >> Eg. a NE5532 dual op-amp configured as two inverters with 4.7 kohm
    >> >> input and feedback resistors.
    >> >>
    >> >> Balanced low noise in - balanced line level out.
    >> >
    >> > Phil ! Are you feeling unwell ? He said a mic pre ! That configuration
    >> > will be
    >> > noisy as hell.
    >>
    >> ** Try reading the context - dickhead.
    >>
    >> The INA103 allows access on pins 5 & 12 to the differential stage's
    >> outputs.
    >>
    >> http://focus.ti.com/lit/ds/symlink/ina103.pdf
    >>
    >> The NE5532 would merely buffer those outputs.
    >
    > Ok, I follow you now. From what he said ( about simply amplifying each leg
    > of
    > the mic input separately ) I got a different picture of what you meant.
    >
    > Why not buffer those points using a voltage follower configuration though
    > ?
    > Slightly less noisy without those 4k7s.


    ** Are you feeling well - Pooh ??

    The reason for preferring unity gain inverting is that it produces less
    HD - since there is no common mode voltage at the inputs.

    The self noise from a unity gain inverter, using an NE 5532 and 4.7 kohms is
    about 3 uV rms ( 1 uV from the resistor, 1 uV from the op-amp & noise
    gain of 2 ).

    Relative to a 1 volt output level, this is a s/n ratio of 110 dB -
    exceeding the spec for the INA103.

    The noise from the preceding op-amp is gonna be more in any case - even at
    unity gain the INA103 is speced at 10 uV output noise ( 70 nV rt Hz) .


    ............ Phil
  15. Archived from groups: rec.audio.pro (More info?)

    Phil Allison wrote:

    > "Pooh Bear"
    > > Phil Allison wrote:
    > >>>
    > >> >> ** No - all you need is two op-amps.
    > >> >>
    > >> >> Eg. a NE5532 dual op-amp configured as two inverters with 4.7 kohm
    > >> >> input and feedback resistors.
    > >> >>
    > >> >> Balanced low noise in - balanced line level out.
    > >> >
    > >> > Phil ! Are you feeling unwell ? He said a mic pre ! That configuration
    > >> > will be
    > >> > noisy as hell.
    > >>
    > >> ** Try reading the context - dickhead.
    > >>
    > >> The INA103 allows access on pins 5 & 12 to the differential stage's
    > >> outputs.
    > >>
    > >> http://focus.ti.com/lit/ds/symlink/ina103.pdf
    > >>
    > >> The NE5532 would merely buffer those outputs.
    > >
    > > Ok, I follow you now. From what he said ( about simply amplifying each leg
    > > of
    > > the mic input separately ) I got a different picture of what you meant.
    > >
    > > Why not buffer those points using a voltage follower configuration though
    > > ?
    > > Slightly less noisy without those 4k7s.
    >
    > ** Are you feeling well - Pooh ??
    >
    > The reason for preferring unity gain inverting is that it produces less
    > HD - since there is no common mode voltage at the inputs.

    That's an interesting assertion. I recall that being said in the 70s. The
    reason being supposed 'common mode failure' of the input pair.

    For a while I followed the 'inverting is best' suggestion but eventually
    abandoned it since it generally leads to increased noise. I see no sign of this
    issue with modern op-amps.


    > The self noise from a unity gain inverter, using an NE 5532 and 4.7 kohms is
    > about 3 uV rms ( 1 uV from the resistor, 1 uV from the op-amp & noise
    > gain of 2 ).
    >
    > Relative to a 1 volt output level, this is a s/n ratio of 110 dB -
    > exceeding the spec for the INA103.
    >
    > The noise from the preceding op-amp is gonna be more in any case - even at
    > unity gain the INA103 is speced at 10 uV output noise ( 70 nV rt Hz) .

    I'm just getting very fussy over *all* noise contributions these days. As you
    correctly point out, even 4k7 makes a significant difference to the overall
    noise of a 5532.

    Graham
  16. Archived from groups: rec.audio.pro (More info?)

    "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
    news:4302B5E7.BE5703E0@hotmail.com...

    > For a while I followed the 'inverting is best' suggestion but eventually
    > abandoned it since it generally leads to increased noise. I see no sign of
    this
    > issue with modern op-amps.

    It's there, although more with FET-input op-amps than bipolars like the
    5532. Try high-frequency IM tests on an OPA-604 or 2604 (same design, dual
    package) in non-inverting mode, first with a low-impedance source, then with
    something like 25k source impedance. More distortion.

    Peace,
    Paul
  17. Archived from groups: rec.audio.pro (More info?)

    Phil Allison wrote:

    > Graham Stevenon - Studiomaster's biggest Enemy
    > >
    > > Phil Allison wrote:

    < snip Phil's insults >


    > >> All you are doing is mindless TROLLING and NETSTALKING me.
    > >
    > > If you think I'm trolling or stalking you - lol - then you clearly have a
    > > serious mental problem.
    > >
    > > I'm contributing to a thread in a *public* newsgroup. Get over it.
    >
    > ** You will STOP posting your mindless garbage under every post I put up.

    I do *not* post every single time you do. Just take a look and see. It does
    happen often though since we both have similar expertise in the audio area -
    and in turn you often reply to one of my posts. Entirely normal behaviour in a
    newsgroup !


    > That is criminal behaviour.
    >

    I suggest you go look up the meaning of criminal. You just make yourself look
    stupid by posting such daft claims.

    > That is netstalking.
    >

    If I wanted to netstalk you, trust me you'd know about it. I don't have that
    mindset nor the interest, inclination, time, money whatever anyway !


    > The one with metal issues is YOU - Graham Stevenon of Studiomaster UK.

    Lol @ metal. Thankfully I'm able to shrug off such nonsence. I only wish you'd
    grow up and get over your persecution complex.

    Come on Phil, I'm sure you're capable of better than this ?


    Graham
  18. Archived from groups: rec.audio.pro (More info?)

    Paul Stamler wrote:

    > "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
    > news:4302B5E7.BE5703E0@hotmail.com...
    >
    > > For a while I followed the 'inverting is best' suggestion but eventually
    > > abandoned it since it generally leads to increased noise. I see no sign of
    > this
    > > issue with modern op-amps.
    >
    > It's there, although more with FET-input op-amps than bipolars like the
    > 5532. Try high-frequency IM tests on an OPA-604 or 2604 (same design, dual
    > package) in non-inverting mode, first with a low-impedance source, then with
    > something like 25k source impedance. More distortion.

    More THD with the high Z source ?

    Ah well, I keep signal impedances low too ! ;-)

    Graham
  19. Archived from groups: rec.audio.pro (More info?)

    "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
    news:43030A15.E99D08CC@hotmail.com...
    >
    > Paul Stamler wrote:
    >
    >> "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
    >> news:4302B5E7.BE5703E0@hotmail.com...
    >>
    >> > For a while I followed the 'inverting is best' suggestion but
    >> > eventually
    >> > abandoned it since it generally leads to increased noise. I see no sign
    >> > of
    >> this
    >> > issue with modern op-amps.
    >>
    >> It's there, although more with FET-input op-amps than bipolars like the
    >> 5532. Try high-frequency IM tests on an OPA-604 or 2604 (same design,
    >> dual
    >> package) in non-inverting mode, first with a low-impedance source, then
    >> with
    >> something like 25k source impedance. More distortion.

    > More THD with the high Z source ?

    IME that's how it usually works.

    > Ah well, I keep signal impedances low too ! ;-)

    ...but not too low. ;-)
  20. Archived from groups: rec.audio.pro (More info?)

    "Ben Bradley"

    > You absolutely need the differential-conversion stage (with
    > highly=precise, matched resistors to get good CMRR) for a mic preamp,


    ** Bullshit - the input stage rejects common mode by the same factor as
    it has gain.


    > as the mic signal could be a few millivolts and the common-mode signal
    > can be several volts.


    ** What planet are you living on ??????????

    Don't just make things up - dickhead.


    > To turn the situation around so that the mic
    > signal is much larger instead, you need to cancel the common signal
    > with a very high precision.

    ** There is virtually ZERO common mode signal with a microphone &cable in
    normal circumstaces.


    >The instrumentation amplifier configuration helps by giving (up to
    > about) 1,000 times gain for differential signals, and only a gain of 1
    > for common-mode signals, but you still need the differential stage to
    > cancel out the common-mode signals.


    ** Like a record stuck in a groove - isn't he ??


    ............... Phil
  21. Archived from groups: rec.audio.pro (More info?)

    Mike Rivers schrieb:

    > This is why the single-ended so-called "impedance balanced" output
    > configuration is so popular. It doesn't matter if you short the
    > non-driven side to ground because there's no signal on it. Much
    > cheaper than a transformer, simpler than a cross-coupled see-saw
    > output stage, and good enough for even some of the finest microphones.

    That would get me going with just one op for the differencial stage and
    two matched series resistors. But the way I understand it, this setup
    will result in half the output amplitude if fed into a symmetrical
    input. Is that correct?

    Rob
  22. Archived from groups: rec.audio.pro (More info?)

    "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
    news:43030A15.E99D08CC@hotmail.com...
    >
    > Paul Stamler wrote:
    >
    > > "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
    > > news:4302B5E7.BE5703E0@hotmail.com...
    > >
    > > > For a while I followed the 'inverting is best' suggestion but
    eventually
    > > > abandoned it since it generally leads to increased noise. I see no
    sign of
    > > this
    > > > issue with modern op-amps.
    > >
    > > It's there, although more with FET-input op-amps than bipolars like the
    > > 5532. Try high-frequency IM tests on an OPA-604 or 2604 (same design,
    dual
    > > package) in non-inverting mode, first with a low-impedance source, then
    with
    > > something like 25k source impedance. More distortion.
    >
    > More THD with the high Z source ?

    More THD, especially at high frequencies and low gain, so the input sees a
    high-level signal, and more high-frequency IMD.

    > Ah well, I keep signal impedances low too ! ;-)

    But sometimes you can't, at which point some interesting juggling becomes
    necessary.

    Peace,
    Paul
  23. Archived from groups: rec.audio.pro (More info?)

    Robert Angst <robert.angst@tu-berlin.de> wrote:
    >
    >My idea is to use a INA103 but without the second differential stage as
    >a mic-pre. One possibility would be of course to replace the
    >differential stage it with another OP or a discrete setup but my
    >question goes in another direction:

    This works very well, and it reduces the total distortion considerably.
    Most of the actual distortion of the INA103 comes from the output stage.

    But if you're going to do this, you might as well just skip the INA103
    altogether and just go with a discrete transistor array for the front
    end.

    >Since I want the output to be symmetrical anyway wouldn't it be possible
    >to amplify each phase separately with a single OP and use that as a
    >symmetrical output? Sounds a little to simple, I know. Am I missing
    >something here?

    Yes, but you don't have an instrumentation amp any more. Do you care
    about CMRR? If you don't really care about CMRR, using a single op-amp
    is just fine.

    If you do care about CMRR, the guys at THAT have just produced a
    chip that is a pin-compatible replacement for the SSM2017. Samples are
    just now coming out. I can't tell you if it performs as well as the
    data sheet yet, but once I get back from Colorado and get another dozen
    higher priority (ie. better-paying) projects out of the way I hope to
    give the things a try.
    --scott

    --
    "C'est un Nagra. C'est suisse, et tres, tres precis."
  24. Archived from groups: rec.audio.pro (More info?)

    Graham Stevenon - Net Stalker


    ** You will STOP posting your mindless garbage under every post I put up.

    That is criminal behaviour.


    > I suggest you go look up the meaning of criminal.

    ** I suggest you go straight into hell.


    > If I wanted to netstalk you, trust me you'd know about it.


    ** You are net stalking me and I do know about it.

    Stop or will contact your employers.

    I promise that will not be the slightest bit funny.


    ............ Phil
  25. Archived from groups: rec.audio.pro (More info?)

    In article <ddvc12$i5$1@mamenchi.zrz.TU-Berlin.DE> robert.angst@tu-berlin.de writes:

    > > This is why the single-ended so-called "impedance balanced" output

    > That would get me going with just one op for the differencial stage and
    > two matched series resistors. But the way I understand it, this setup
    > will result in half the output amplitude if fed into a symmetrical
    > input. Is that correct?

    It's a matter of interpretation. With a symmetrical balanced output
    stage, one side goes to -5V with reference to 0V when the other side
    goes to +5V. To a differential input, that's a voltage difference of
    10V.

    With an impedance balanced, single ended output, one side of the
    differential input always sees 0V since there's no
    "opposite-but-equal" leg of the output. So when the hot side goes to
    +5V, the differential input sees 5V.

    So, yes, you can get twice the output from a symmetrical output stage
    into a differential input because you're essentially connecting the
    two outputs in series. You can't do that if you have only one ouptut,
    of course, but all of that output voltage does indeed get to the
    differential input.


    --
    I'm really Mike Rivers - (mrivers@d-and-d.com)
    However, until the spam goes away or Hell freezes over,
    lots of IP addresses are blocked from this system. If
    you e-mail me and it bounces, use your secret decoder ring
    and reach me here: double-m-eleven-double-zero at yahoo
  26. Archived from groups: rec.audio.pro (More info?)

    On Tue, 16 Aug 2005 14:26:00 +0200, Robert Angst
    <robert.angst@tu-berlin.de> wrote:

    >My idea is to use a INA103 but without the second differential stage as
    >a mic-pre. One possibility would be of course to replace the
    >differential stage it with another OP or a discrete setup but my
    >question goes in another direction:
    >
    >Since I want the output to be symmetrical anyway wouldn't it be possible
    >to amplify each phase separately with a single OP and use that as a
    >symmetrical output? Sounds a little to simple, I know. Am I missing
    >something here?

    You really, really want to get your common-mode rejection
    up-front and believable, preferably before any electronics
    (but that costs money), and trusting to your electronics
    to linearly handle the potentially large common mode
    signal is foolish, not to put too fine a point on it.

    In too many real-world situations *huge* common-mode
    signals can bite one's butt. Don't trust your reputation
    to wishful thinking and Internet wanking. Wanna be
    professional? Think tough; think military; think medical.

    And don't put too much confidence in certain... well....

    Good fortune,

    Chris Hornbeck
  27. Archived from groups: rec.audio.pro (More info?)

    Scott Dorsey schrieb:

    <snip>

    > But if you're going to do this, you might as well just skip the INA103
    > altogether and just go with a discrete transistor array for the front
    > end.

    I read your postings about this approach but I guess I don't have
    experience and time to design something like this from scratch. Now that
    my SX202 is done I get into mic-tinkering again as well (neg. supply for
    fig.8)

    <snip>

    > If you do care about CMRR, the guys at THAT have just produced a
    > chip that is a pin-compatible replacement for the SSM2017. Samples are
    > just now coming out. I can't tell you if it performs as well as the
    > data sheet yet, but once I get back from Colorado and get another dozen
    > higher priority (ie. better-paying) projects out of the way I hope to
    > give the things a try.
    > --scott
    >

    Actually the 103 was intendet to be my workaround for that. I am trying
    to replace an SSM2017 and I was quite pleased with what I read in the
    datasheet of the new THAT1512. Even lower noise than the THAT1510.
    Trouble is I would have to buy 20 pieces or pay 20 EUR shipping if I buy
    just two. I haven't found a single comment on its performance yet, but I
    would realy like to try it. I'll look around a little more..
    Rob
  28. Archived from groups: rec.audio.pro (More info?)

    In article <de1in2$avk$1@mamenchi.zrz.TU-Berlin.DE> robert.angst@tu-berlin.de writes:

    > I was quite pleased with what I read in the
    > datasheet of the new THAT1512. Even lower noise than the THAT1510.
    > Trouble is I would have to buy 20 pieces or pay 20 EUR shipping if I buy
    > just two. I haven't found a single comment on its performance yet, but I
    > would realy like to try it. I'll look around a little more..

    It's brand new, so you probably won't see any in products for a while
    yet. Why not contact THAT and ask for a couple of samples? They're
    still a small company and you can actually reach real people there.


    --
    I'm really Mike Rivers - (mrivers@d-and-d.com)
    However, until the spam goes away or Hell freezes over,
    lots of IP addresses are blocked from this system. If
    you e-mail me and it bounces, use your secret decoder ring
    and reach me here: double-m-eleven-double-zero at yahoo
  29. Archived from groups: rec.audio.pro (More info?)

    Robert Angst wrote:

    > Scott Dorsey schrieb:
    >
    > <snip>
    >
    > > But if you're going to do this, you might as well just skip the INA103
    > > altogether and just go with a discrete transistor array for the front
    > > end.
    >
    > I read your postings about this approach but I guess I don't have
    > experience and time to design something like this from scratch. Now that
    > my SX202 is done I get into mic-tinkering again as well (neg. supply for
    > fig.8)
    >
    > <snip>
    >
    > > If you do care about CMRR, the guys at THAT have just produced a
    > > chip that is a pin-compatible replacement for the SSM2017. Samples are
    > > just now coming out. I can't tell you if it performs as well as the
    > > data sheet yet, but once I get back from Colorado and get another dozen
    > > higher priority (ie. better-paying) projects out of the way I hope to
    > > give the things a try.
    > > --scott
    >
    > Actually the 103 was intendet to be my workaround for that. I am trying
    > to replace an SSM2017 and I was quite pleased with what I read in the
    > datasheet of the new THAT1512. Even lower noise than the THAT1510.
    > Trouble is I would have to buy 20 pieces or pay 20 EUR shipping if I buy
    > just two. I haven't found a single comment on its performance yet, but I
    > would realy like to try it. I'll look around a little more..

    You're really not being very sensible. You're virtually using only the input
    differential pair on the INA103 - kind of a waste ot time.

    A pair of 10 cent 2SA1084s is probably quieter.

    Graham
  30. Archived from groups: rec.audio.pro (More info?)

    Phil Allison wrote:

    > Graham Stevenon - Net Stalker

    < snip >


    > > If I wanted to netstalk you, trust me you'd know about it.
    >
    > ** You are net stalking me and I do know about it.
    >
    > Stop or will contact your employers.

    Oh please do. They're not strictly my employers btw. They're a client.

    > I promise that will not be the slightest bit funny.

    I expect that the Studiomaster guys will find it very funny indeed actually.
    They could do with a laugh. I've already apprised them of your 'bohemian'
    behaviour way back btw.

    Now stop making hollow threats.

    Graham
  31. Archived from groups: rec.audio.pro (More info?)

    Robert Angst <robert.angst@tu-berlin.de> wrote:
    >Scott Dorsey schrieb:
    >
    >> But if you're going to do this, you might as well just skip the INA103
    >> altogether and just go with a discrete transistor array for the front
    >> end.
    >
    >I read your postings about this approach but I guess I don't have
    >experience and time to design something like this from scratch. Now that
    >my SX202 is done I get into mic-tinkering again as well (neg. supply for
    > fig.8)

    If you want a little bit of gain, and you want differential input and
    differential output, you probably want just a simple differential amplifier
    stage with two transistors.

    Get the service manual for the Mackie 1202VLZ Pro and look at the front
    end of the mike section. Steal the design. It's a really good one.

    The RCA Radiotron Handbook has the best description of how the circuit
    works, too. It's old and it uses tubes in the example, but the same
    long-tailed-pair differential amp stage is still one of the most popular
    circuit designs today.

    >datasheet of the new THAT1512. Even lower noise than the THAT1510.
    >Trouble is I would have to buy 20 pieces or pay 20 EUR shipping if I buy
    >just two. I haven't found a single comment on its performance yet, but I
    >would realy like to try it. I'll look around a little more..

    I don't think more than a handful of people have actually tried them
    yet. Don't know about European distribution but shoot them a letter. They
    have talked about getting small quantity distribution through Mouser.
    You might want to ask them if they can sign Buerklin up as well.
    --scott
    --
    "C'est un Nagra. C'est suisse, et tres, tres precis."
  32. Archived from groups: rec.audio.pro (More info?)

    In article <znr1124363024k@trad>, Mike Rivers <mrivers@d-and-d.com> wrote:
    >In article <de1in2$avk$1@mamenchi.zrz.TU-Berlin.DE> robert.angst@tu-berlin.de writes:
    >
    >> I was quite pleased with what I read in the
    >> datasheet of the new THAT1512. Even lower noise than the THAT1510.
    >> Trouble is I would have to buy 20 pieces or pay 20 EUR shipping if I buy
    >> just two. I haven't found a single comment on its performance yet, but I
    >> would realy like to try it. I'll look around a little more..
    >
    >It's brand new, so you probably won't see any in products for a while
    >yet. Why not contact THAT and ask for a couple of samples? They're
    >still a small company and you can actually reach real people there.

    They are right now being completely overwhelemed with sample requests.
    This thing has been in the works for six years now and we keep hearing
    about it, and it's finally out. So everyone and his brother is trying
    to get samples out of THAT right now after years of hearing about it.

    Preliminary tests look pretty damn good.
    --scott

    --
    "C'est un Nagra. C'est suisse, et tres, tres precis."
  33. Archived from groups: rec.audio.pro (More info?)

    Graham Stevenon - Net Stalker


    > Oh please do. They're not strictly my employers btw. They're a client.


    ** As I suspected - you an posturing, unemployed fake.


    >> I promise that will not be the slightest bit funny.
    >
    > I expect that the Studiomaster guys will find it very funny indeed
    > actually.


    ** Then you have no idea what I intend.


    > Now stop making hollow threats.


    ** Fair warning is no threat.

    Go find out the law - you pig ignorant ass.


    .............. Phil
  34. Archived from groups: rec.audio.pro (More info?)

    Phil Allison wrote:

    > Graham Stevenon - Net Stalker
    >
    > > Oh please do. They're not strictly my employers btw. They're a client.
    >
    > ** As I suspected - you an posturing, unemployed fake.
    >
    > >> I promise that will not be the slightest bit funny.
    > >
    > > I expect that the Studiomaster guys will find it very funny indeed
    > > actually.
    >
    > ** Then you have no idea what I intend.
    >
    > > Now stop making hollow threats.
    >
    > ** Fair warning is no threat.
    >
    > Go find out the law - you pig ignorant ass.

    The law would say you're threatening me. It's such a lame threat I don't
    concern myself about it.

    You really are piece of astonishingly mentally defective detritus.

    Graham
  35. Archived from groups: rec.audio.pro (More info?)

    Mike Rivers schrieb:

    > It's brand new, so you probably won't see any in products for a while
    > yet. Why not contact THAT and ask for a couple of samples? They're
    > still a small company and you can actually reach real people there.

    Looks like that was a good hint. One of the distributors in Germany
    promised to send some.. *when* they get some.

    Obviously you guys in the states are asking more samples than THAT can
    produce ;-)

    I'll report my findings when I have them plugged in and compared.

    Rob
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