Adding Pre-Out / Main-in to an integrated amplifier. Second try.

[sansadresse@nullepart.xyz]

Trying to add a Main-in/Pre-out to a Sony amplifier:

(There were useful replies, in an earlier thread, from K. Robinson,
Jerry G. and NSM about this topic)

The amplifier model: Sony TA-F590ES, with motorized volume control.

The amplifier has an "adaptor loop" with bridged IN & OUT cinch(RCA)
connectors before the volume control.

The aim is to insert a 2-way active crossover, and resend the
high-range output to the Sony. The adaptor loop won't do since it come
before the volume control.

One point worth mentioning: the "Pre-out" and "Main-in" under
discussion need not have "universal" characteristics, since they will
*only* be dealing with an active crossover (and perhaps an equalizer.)

It has been suggested by NSM: "post a circuit diagram and several of
us could tell you where to add them"

Here are the block ad circuit diagrams:
http://nom.de.plume.free.fr/temp_files/
The diagrams are for the TA-F590ES and a variant, the TA-F690ES.
The latter has a Pre-out, but no Main-in.
We are discussing here the TA-F590ES

(Please consider that the content of the files may be copyrighted.)

Thank you, in advance, for your contributions.

 

[NSM]

Trying to add a Main-in/Pre-out to a Sony amplifier:

The amplifier has an "adaptor loop" with bridged IN & OUT cinch(RCA)
connectors before the volume control.

The aim is to insert a 2-way active crossover, and resend the
high-range output to the Sony. The adaptor loop won't do since it come
before the volume control.

What will you do with the low out? I would do almost anything to use the
adaptor loop.

N

 

[SansAdresse]

The low-out will go to a powered subwoofer.

(I don't really understand your statement " I would do almost
anything..." Just a problem with subtleties of English.)

 

[NSM]

The low-out will go to a powered subwoofer.

(I don't really understand your statement " I would do almost
anything..." Just a problem with subtleties of English.)

OK.

"I would do almost anything..." == that is so easy and everything else is so
hard.

I use an unpowered subwoofer. For your case, I would tap the low off from
the speaker outputs, combine them and feed that to the powered subwoofer.
That way the remote vol control will still work as expected. I'd use two 100
ohm resistors feeding a 10 ohm resistor and connect the powered subwoofer
input to the connection point.

N

 

[SansAdresse]

The idea is to cleanly separate the frequencies (I am just going by
the textbook!), and to avoid sending to the main speakers the low
frequencies which may drive them into distortion. (Bach's organ music
is played on the system.)

================================================

 

[jakdedert]

The idea is to cleanly separate the frequencies (I am just going by
the textbook!), and to avoid sending to the main speakers the low
frequencies which may drive them into distortion. (Bach's organ music
is played on the system.)

You shouldn't have to worry about distortion in a subwoofer, but I admire
your fortitude. Yes, you are doing it the 'right' way, but certainly you
are doing it the 'hard' way. I'd try NSM's solution first, then if you have
objectionable distortion....

jak

 

[SansAdresse]

You shouldn't have to worry about distortion in a subwoofer

The distortion would be in the woofers of the main speakers.

Yes, you are doing it the 'right' way, but certainly you are doing it the 'hard' way.
I'd try NSM's solution first, then if you have objectionable distortion....

I did buy the powered subwoofer and the crossover (a venerable
Nakamichi model), only to discover that the jumpered connectors on the
back of the Sony integrated amp are an "accessory loop" (pre-volume
control) and not a Pre-out/Main-in pair.

I would expect higher quality reproduction if things are done the
"right way": not just less distortion, but cleaner sounding music. Are
you saying that the difference wouldn't be perceptible?

[PS: Changing the amp means getting also a new tuner since the latter
get its remote control signals from the amp.]

 

[NSM]

I did buy the powered subwoofer and the crossover (a venerable
Nakamichi model), only to discover that the jumpered connectors on the
back of the Sony integrated amp are an "accessory loop" (pre-volume
control) and not a Pre-out/Main-in pair.

I would expect higher quality reproduction if things are done the
"right way": not just less distortion, but cleaner sounding music. Are
you saying that the difference wouldn't be perceptible?

I did browse through the diagrams you posted. Adding the connections you
desire is going to be performed in the 'no fun' zone. Try the easy way for
now, and if you are not happy I'll try to give you a more technically
correct answer.

 

[SansAdresse]

Note that I don't need a full fledged Pe-in/Man-out pair, which must
have "universal" properties (driving a variety of external power amps
for instance.)

I just just need a "loop" after the volume control where I can hook a
high quality active crossover.

 

[jakdedert]

The distortion would be in the woofers of the main speakers.


I did buy the powered subwoofer and the crossover (a venerable
Nakamichi model), only to discover that the jumpered connectors on the
back of the Sony integrated amp are an "accessory loop" (pre-volume
control) and not a Pre-out/Main-in pair.

I would expect higher quality reproduction if things are done the
"right way": not just less distortion, but cleaner sounding music. Are
you saying that the difference wouldn't be perceptible?

Not necessarily. I'm just saying that the results may be perfectly
acceptable for the application, by going the route NSM detailed: ie dropping
the speaker sig to an appropriate level for the input of the sub with a
resistor network. This is considerably less work than adding pre outs to
the amplifier and should work quite well. In fact, you could 'kludge up' a
network with just the resistors and a pair of RCA cables connected to the
'B' speaker outs in half an hour or so.

If you do not like the results--or you have a lot of time on your hands and
like to experiment--suss out the preamp wiring in your amp and go it the
hard way.

If you have limited experience, you may end up destroying your reciever; in
which case you can then get one which has a sub output or at least a preamp
out.

jak

 

[SansAdresse]

If you do not like the results--or you have a lot of time on your hands and
like to experiment--suss out the preamp wiring in your amp and go it the
hard way.

One part of my question got lost in the discussion: We don't need a
full-fledged Pre-out that can drive a power amplifier, with all that
goes with that.

We only need to *insert* a line level active crossover (a "simple"
filter) on the signal path after (right after?) the volume control.

Can't that be done on the cheap? Just cut the signnal path and insert
two pairs on cinch connectors Out==In.

 

[Gary J. Tait]

One part of my question got lost in the discussion: We don't need a
full-fledged Pre-out that can drive a power amplifier, with all that
goes with that.

We only need to *insert* a line level active crossover (a "simple"
filter) on the signal path after (right after?) the volume control.

Can't that be done on the cheap? Just cut the signnal path and insert
two pairs on cinch connectors Out==In.

That's what I would do.

 

[jakdedert]

One part of my question got lost in the discussion: We don't need a
full-fledged Pre-out that can drive a power amplifier, with all that
goes with that.

We only need to *insert* a line level active crossover (a "simple"
filter) on the signal path after (right after?) the volume control.

Can't that be done on the cheap? Just cut the signnal path and insert
two pairs on cinch connectors Out==In.

BTW, nothing should be "cut" in order to simply give you a line level out.
That would interupt the signal path...an example of why I think you should
try the easy way, first...requires very little technical knowledge and *NO*
opening up of the unit...much less any modification.

To do it correctly, you find the appropriate point in the signal
flow...preferably the input to the power amp drivers. At that point, you
can 'try' merely connecting cables to the sub x-over input. My guess is
that this will (maybe) affect the overall signal level to the unit's power
amps...perhaps do other interesting things as well. If it does, then you'll
need to construct a unity-gain isolation stereo amp...and feed the output of
that to your x-over.


If you want to convert to a full biamped system, using the receivers built
in amp for either the highs or lows, then another stereo amp for the other
section, that's an altogether different animal than you first presented.

jak

 

[SansAdresse]

If you want to convert to a full biamped system, using the receivers built

in amp for either the highs or lows, then another stereo amp for the other
section, that's an altogether different animal than you first presented.

This what it is about: the subwoofer is powered, it has its own amplifier and
line level inputs.

I need to insert a crossover, send the low-pass part to the sub, and keep the
high-pass part to feed it back to the integrated amp. That's a very classical
scheme:

INTEGRATED AMP - (Pre-out) ---> [...Active crossover...]
INTEGRATED AMP - (Main-in) <--- [High pass]...[Low pass] ---> POWERED SUB

Thank you for your time.
==========================================================

 

[NSM]

That's what I would do.

This is not your old style basic circuit diagram. It looks more like a
refugee from the space station. It's doable, but not trivial to add the
required outputs.

 

[jakdedert]

If you want to convert to a full biamped system, using the receivers
built in amp for either the highs or lows, then another stereo amp
for the other section, that's an altogether different animal than
you first presented.

This what it is about: the subwoofer is powered, it has its own
amplifier and line level inputs.

I need to insert a crossover, send the low-pass part to the sub, and
keep the high-pass part to feed it back to the integrated amp. That's
a very classical scheme:

INTEGRATED AMP - (Pre-out) ---> [...Active crossover...]
INTEGRATED AMP - (Main-in) <--- [High pass]...[Low pass] ---> POWERED
SUB

Thank you for your time.

Do you already have a suitable stereo active x-over? Have you decided what
the x-over point should be? The sub amp should have an low-pass filter, so
all you really want to do is reduce the amount of low frequency info sent to
the main amplifier and speakers, right?

In that case--although I would still try the resister network first [KISS
theory]--you could try to find a suitable take-off point in the amplifier
which comes after the volume control, but *before* the tone controls (if
such exists...the tone controls could come before the volume, in which case
you're screwed....). That way, you could send unequalized audio to the sub
input, and use the amps tone controls to reduce the l-f signal to the main
speakers.

Sorry, but I still think you're *way* overcomplicating this. Try tapping
the speaker output and see how it works. You might like the sound of the
main speakers complimenting the output from the sub (be sure to try the
phase switch in both positions). You can achieve much the same as the above
by simply turning down the bass control on the amplifier and turning up the
sub.....

jak