[gunnet]

Hi, what is the best way to connect unbalanced output to balanced input of
an amplifier? I've seen that there are some boxes to convert, or I could
just make a modified cable?
thank you

[Walt]

gunnet wrote:

Hi, what is the best way to connect unbalanced output to balanced input of
an amplifier? I've seen that there are some boxes to convert, or I could
just make a modified cable?

The "best" way is highly dependent on the nature of the gear involved
and without knowing more than the information provided I can't tell you
the best way.

But 95% of the time you can just use a modified cable: just wire the +
output to the + input, connect the shields and it will work acceptably
well. If it's a transformer input, you'll need to tie the other leg of
the input to ground, otherwise you can let it float. You may run into
ground loop issues, but probably not.

Note that you will lose some gain doing it this way. Unbalanced gear is
usually -10dbV and balanced gear is usually +4dbu If that loss can't
be made up somewhere else, you may need an interface widgit of some
sort. But it's worth trying the cable first before spending money on
something you may not need.

//Walt

[Todd H.]

"gunnet" writes:

Hi, what is the best way to connect unbalanced output to balanced input of
an amplifier? I've seen that there are some boxes to convert, or I could
just make a modified cable?
thank you

What you seek is a DI box ("direct injection" also known as a "direct
box." With what components cost and host inexpensively you can get
your hands on one, there's not much reason not to grab one off the
shelf.

They come in active and passive flavors. The highest quality passives
use Jensen transformers (which are the $ part of the device) to create
the balanced signal via a centertapped audio transformer.

Here's a $20 passive model:
http://www.musiciansfriend.com/produ...Box?sku=182498

Here's a $24 dual channel active:
http://www.zzounds.com/item--BEHDI20

Or a couple of more in-line form factor transformer based passives,
one male, one female on the XLR end:
http://carvin.com/products/single.ph...=MTM65&CID=ACS
http://carvin.com/products/single.ph...=MTF60&CID=ACS

Hope that helps.
Best Regards,
--
/"\ ASCII Ribbon Campaign | Todd H
\ / | http://www.toddh.net/
X Promoting good netiquette | http://triplethreatband.com/
/ \ http://www.toddh.net/netiquette/ | http://myspace.com/mytriplethreatband

[Richard Crowley]

"gunnet" wrote ...
Hi, what is the best way to connect unbalanced output to balanced
input of
an amplifier? I've seen that there are some boxes to convert, or I
could
just make a modified cable?

You can *probably* just use a modified cable, but since
you did not identify either the source or the destination
equipment, we can offer only generic suggestions.

[Richard Crowley]

"Todd H." wrote ...
"gunnet" writes:
Hi, what is the best way to connect unbalanced output to balanced
input of
an amplifier? I've seen that there are some boxes to convert, or I
could
just make a modified cable?
thank you

What you seek is a DI box ("direct injection" also known as a "direct
box." With what components cost and host inexpensively you can get
your hands on one, there's not much reason not to grab one off the
shelf.

They come in active and passive flavors. The highest quality passives
use Jensen transformers (which are the $ part of the device) to create
the balanced signal via a centertapped audio transformer.

Here's a $20 passive model:

http://www.musiciansfriend.com/produ...Box?sku=182498

No, absolutely not. Sorry, direct boxes are NOT cure-alls.
You do NOT want something with a 110:1 impedance ratio
for this application. If you use a transformer at all (which is
questionable), you want something like 1:1.

[Arny Krueger]

"gunnet" wrote in message

Hi, what is the best way to connect unbalanced output to
balanced input of an amplifier? I've seen that there are
some boxes to convert, or I could just make a modified
cable?

Here is a general reference:

http://www.rane.com/note110.html

[Eeyore]

gunnet wrote:

Hi, what is the best way to connect unbalanced output to balanced input of
an amplifier? I've seen that there are some boxes to convert, or I could
just make a modified cable?

Is the balanced input on an XLR ?

Take the unbalanced signal screen to pin2 ( hot ) and the signal to pin3 (cold
). You can leave pin1 ( earth/screen ) on the balanced input unconnected.

Graham

[Eeyore]

"Todd H." wrote:

"gunnet" writes:

Hi, what is the best way to connect unbalanced output to balanced input of
an amplifier? I've seen that there are some boxes to convert, or I could
just make a modified cable?
thank you

What you seek is a DI box

No he doesn't at all.

That'll mess up the signal horribly with its transformer !

Graham

[Eeyore]

Walt wrote:

gunnet wrote:

Hi, what is the best way to connect unbalanced output to balanced input of
an amplifier? I've seen that there are some boxes to convert, or I could
just make a modified cable?

The "best" way is highly dependent on the nature of the gear involved
and without knowing more than the information provided I can't tell you
the best way.

But 95% of the time you can just use a modified cable: just wire the +
output to the + input, connect the shields and it will work acceptably
well. If it's a transformer input, you'll need to tie the other leg of
the input to ground, otherwise you can let it float. You may run into
ground loop issues, but probably not.

Avoid tying the shields. It's 100% unnecessary.

Take hot(+) to hot and cold to cold. It really is that easy.

Graham

[Randy Yates]

Eeyore writes:

Walt wrote:

gunnet wrote:

Hi, what is the best way to connect unbalanced output to balanced input of
an amplifier? I've seen that there are some boxes to convert, or I could
just make a modified cable?

The "best" way is highly dependent on the nature of the gear involved
and without knowing more than the information provided I can't tell you
the best way.

But 95% of the time you can just use a modified cable: just wire the +
output to the + input, connect the shields and it will work acceptably
well. If it's a transformer input, you'll need to tie the other leg of
the input to ground, otherwise you can let it float. You may run into
ground loop issues, but probably not.

Avoid tying the shields. It's 100% unnecessary.

Take hot(+) to hot and cold to cold. It really is that easy.

You'll lose 6 dB of gain this way, but that's probably perfectly OK.
--
% Randy Yates % "With time with what you've learned,
%% Fuquay-Varina, NC % they'll kiss the ground you walk
%%% 919-577-9882 % upon."
%%%% % '21st Century Man', *Time*, ELO
http://home.earthlink.net/~yatescr

[Eeyore]

Randy Yates wrote:

Eeyore writes:

Walt wrote:

gunnet wrote:

Hi, what is the best way to connect unbalanced output to balanced input of
an amplifier? I've seen that there are some boxes to convert, or I could
just make a modified cable?

The "best" way is highly dependent on the nature of the gear involved
and without knowing more than the information provided I can't tell you
the best way.

But 95% of the time you can just use a modified cable: just wire the +
output to the + input, connect the shields and it will work acceptably
well. If it's a transformer input, you'll need to tie the other leg of
the input to ground, otherwise you can let it float. You may run into
ground loop issues, but probably not.

Avoid tying the shields. It's 100% unnecessary.

Take hot(+) to hot and cold to cold. It really is that easy.

You'll lose 6 dB of gain this way,

No you won't. Do explain why you think so.


but that's probably perfectly OK.

It is.

Graham

[Peter Larsen]

Eeyore wrote:

Take the unbalanced signal screen to pin2 ( hot ) and the
signal to pin3 (cold). You can leave pin1 ( earth/screen )
on the balanced input unconnected.

This is early morning local time, I need you to explain this, because
the standard bal-unbal wiring I am familiar with is pin 2 to hot, pins 1
and 3 to cold.

Graham


Peter Larsen

[Richard Crowley]

"Peter Larsen" wrote ...
Eeyore wrote:

Take the unbalanced signal screen to pin2 ( hot ) and the
signal to pin3 (cold). You can leave pin1 ( earth/screen )
on the balanced input unconnected.

This is early morning local time, I need you to explain this, because
the standard bal-unbal wiring I am familiar with is pin 2 to hot, pins
1
and 3 to cold.

So reverse them, the principle is the same.
Perhaps you never had the pin-2 vs pin-3 hot
confusion in your country. Consider yourself
lucky.

[Arny Krueger]

"Eeyore" wrote in
message
Randy Yates wrote:

Eeyore writes:

Walt wrote:

gunnet wrote:

Hi, what is the best way to connect unbalanced output
to balanced input of an amplifier? I've seen that
there are some boxes to convert, or I could just make
a modified cable?

The "best" way is highly dependent on the nature of
the gear involved and without knowing more than the
information provided I can't tell you the best way.

But 95% of the time you can just use a modified cable:
just wire the + output to the + input, connect the
shields and it will work acceptably well. If it's a
transformer input, you'll need to tie the other leg of
the input to ground, otherwise you can let it float.
You may run into ground loop issues, but probably not.

Avoid tying the shields. It's 100% unnecessary.

Take hot(+) to hot and cold to cold. It really is that
easy.

You'll lose 6 dB of gain this way,

No you won't. Do explain why you think so.

Agreed. One loses 6 dB in a true active balanced - unbalanced connection,
but not the reverse.

[Mr.T]

"Richard Crowley" wrote in message
...
Take the unbalanced signal screen to pin2 ( hot ) and the
signal to pin3 (cold). You can leave pin1 ( earth/screen )
on the balanced input unconnected.

This is early morning local time, I need you to explain this, because
the standard bal-unbal wiring I am familiar with is pin 2 to hot, pins
1 and 3 to cold.

So reverse them, the principle is the same.
Perhaps you never had the pin-2 vs pin-3 hot
confusion in your country. Consider yourself
lucky.

Yes, we are here too. But Peter's suggestion of tying cold and earth
together remains valid.

MrT.

[Eeyore]

Peter Larsen wrote:

Eeyore wrote:

Take the unbalanced signal screen to pin2 ( hot ) and the
signal to pin3 (cold). You can leave pin1 ( earth/screen )
on the balanced input unconnected.

This is early morning local time, I need you to explain this, because
the standard bal-unbal wiring I am familiar with is pin 2 to hot, pins 1
and 3 to cold.

Pin 1 to cold is entirely optional. Leaving pin 1 unconnected will also remove
any possibility of a hum loop. You also can't connect pin 1 to cold if there is
a centre-tapped input transformer involved ( although thankfully this is almost
unheard of now ).

Consider pins 2 and 3 to be a floating ( or quasi floating ) differential input.

Graham

[Eeyore]

Arny Krueger wrote:

"Eeyore" wrote
Randy Yates wrote:
Eeyore writes:
Walt wrote:
gunnet wrote:

Hi, what is the best way to connect unbalanced output
to balanced input of an amplifier? I've seen that
there are some boxes to convert, or I could just make
a modified cable?

The "best" way is highly dependent on the nature of
the gear involved and without knowing more than the
information provided I can't tell you the best way.

But 95% of the time you can just use a modified cable:
just wire the + output to the + input, connect the
shields and it will work acceptably well. If it's a
transformer input, you'll need to tie the other leg of
the input to ground, otherwise you can let it float.
You may run into ground loop issues, but probably not.

Avoid tying the shields. It's 100% unnecessary.

Take hot(+) to hot and cold to cold. It really is that
easy.

You'll lose 6 dB of gain this way,

No you won't. Do explain why you think so.

Agreed. One loses 6 dB in a true active balanced - unbalanced connection,
but not the reverse.

Indeed, although the 'servo-balanced' type of output will correct for this when
the cold side is grounded too.

Graham

[Eeyore]

"Mr.T" wrote:

"Richard Crowley" wrote in message

Take the unbalanced signal screen to pin2 ( hot ) and the
signal to pin3 (cold). You can leave pin1 ( earth/screen )
on the balanced input unconnected.

This is early morning local time, I need you to explain this, because
the standard bal-unbal wiring I am familiar with is pin 2 to hot, pins
1 and 3 to cold.

So reverse them, the principle is the same.
Perhaps you never had the pin-2 vs pin-3 hot
confusion in your country. Consider yourself
lucky.

Yes, we are here too. But Peter's suggestion of tying cold and earth
together remains valid.

Tying cold and earth will have a small beneficial impact of RFI immunity but may
also create a hum-loop with multiple-earthed equipment.

Graham

[gunnet]

You can *probably* just use a modified cable, but since
you did not identify either the source or the destination
equipment, we can offer only generic suggestions.

thank you very much guys. I'm using cd player -----amplifier

I've got some cable and connector: 2 XLR, 2 Jack 6,3mm mono, 2 RCA and 2
meters of cable with one conductor and one shield. I think I have all to
make a good cable. For this work it's better a cable with 2 conductor or
with one conductor and one shield? I've seen that all rca cable have one
conductor and one shield so I took this...


Now I've got also the manual wich has some illustration:

Pin 1: shield
Pin 2: hot
Pin 3: cold

Here's what it says:
XLR unbalanced: Hot to pin2 Shield to pin1 and to pin3. Why pin1 and pin3
are are in short circuit?

JACK 6,3mm unbalanced: hot with hot, shield with shield.

It's better to use tha jack or the XLR, or it's the same?

Here is a general reference:
http://www.rane.com/note110.html
Before I made a cable as illustrated at number 17, but I get some noise
coming from the speaker

Is the balanced input on an XLR ?
The amp has got both XLR and Jack 6,3mm, wich it's 1/4'' in english
mesurement, right?

Consider pins 2 and 3 to be a floating ( or quasi floating ) differential
input.
I didn't understand well this sentence

How do I know if the XLR connector I've got have all pin corrisponding to
right.

[Eeyore]

gunnet wrote:

You can *probably* just use a modified cable, but since
you did not identify either the source or the destination
equipment, we can offer only generic suggestions.

thank you very much guys. I'm using cd player -----amplifier

I've got some cable and connector: 2 XLR, 2 Jack 6,3mm mono, 2 RCA and 2
meters of cable with one conductor and one shield. I think I have all to
make a good cable. For this work it's better a cable with 2 conductor or
with one conductor and one shield? I've seen that all rca cable have one
conductor and one shield so I took this...

Now I've got also the manual wich has some illustration:

Pin 1: shield
Pin 2: hot
Pin 3: cold

Here's what it says:
XLR unbalanced: Hot to pin2 Shield to pin1 and to pin3. Why pin1 and pin3
are are in short circuit?

It's a mystery to me. I can't think of any reason why you can't leave pin 1
unconnected.


JACK 6,3mm unbalanced: hot with hot, shield with shield.

It's better to use tha jack or the XLR, or it's the same?

XLR's are better connectors.


Here is a general reference:
http://www.rane.com/note110.html
Before I made a cable as illustrated at number 17, but I get some noise
coming from the speaker

What sort of noise ? That ought to work OK. But you need 'balanced' cable (
screen plus 2 conductors ) to do that.


Is the balanced input on an XLR ?
The amp has got both XLR and Jack 6,3mm, wich it's 1/4'' in english
mesurement, right?

Yes.


Consider pins 2 and 3 to be a floating ( or quasi floating ) differential
input.
I didn't understand well this sentence

You wouldn't unless you're familiar with technical terms.


How do I know if the XLR connector I've got have all pin corrisponding to
right.

I'm not sure what you mean. Make sure you identify the pins correctly though.

Graham

[Arny Krueger]

"Eeyore" wrote in
message
Arny Krueger wrote:

"Eeyore" wrote
Randy Yates wrote:
Eeyore writes:
Walt wrote:
gunnet wrote:

Hi, what is the best way to connect unbalanced
output to balanced input of an amplifier? I've seen
that there are some boxes to convert, or I could
just make a modified cable?

The "best" way is highly dependent on the nature of
the gear involved and without knowing more than the
information provided I can't tell you the best way.

But 95% of the time you can just use a modified
cable: just wire the + output to the + input,
connect the shields and it will work acceptably
well. If it's a transformer input, you'll need to
tie the other leg of the input to ground, otherwise
you can let it float. You may run into ground loop
issues, but probably not.

Avoid tying the shields. It's 100% unnecessary.

Take hot(+) to hot and cold to cold. It really is that
easy.

You'll lose 6 dB of gain this way,

No you won't. Do explain why you think so.

Agreed. One loses 6 dB in a true active balanced -
unbalanced connection, but not the reverse.

Indeed, although the 'servo-balanced' type of output will
correct for this when the cold side is grounded too.

I admit it, I forgot about those. ;-)

However, that technology can only work within the bounds of the dynamic
range of the output stage, and still can't exactly duplicate what a
transformer can do.

[Walt]

Eeyore wrote:
"Todd H." wrote:

"gunnet" writes:

Hi, what is the best way to connect unbalanced output to balanced input of
an amplifier? I've seen that there are some boxes to convert, or I could
just make a modified cable?
thank you

What you seek is a DI box

No he doesn't at all.

Agreed.

That'll mess up the signal horribly with its transformer !

1) Not all DI boxen contain transformers
2) Not all transformers mess up the signal horribly

Yes, a cheap DI box will cause these problems, a good active DI, or one
with a good transformer will not.

That said, a DI box is not the right tool for this job. A DI box is
designed to take an instrument level hi-Z unbalanced signal and convert
it to a mic-level low-Z balanced signal. Since he's not starting with
an instrument level signal and he doesn't want a mic level signal, it's
the wrong tool.

Yes, it may work in a pinch, and I've used DI boxen this way when I had
to solve a problem quickly, but it's a bit like using a pair of pliers
to loosen a nut - wrong tool, but if it's all you've got you can make it
work. It's not the "right" approach by any means.

//Walt

[gunnet]

So in the end to sum all:

I make the cable: hot to hot, shield to shield, easy......
and I don't loose 6db because power for me is important as I have to play
music laud in party.

So this item is useless in my case
http://www.behringer.com/DI600P/index.cfm?lang=ENG

It would be usufull if I would connect an instrument, yeah?

[Jim Gregory]

Can i try to help?
Joining Unbal to Unbal
Usually you tie screen to Ground (Earth) -only- at an u/bal receiving end
(an input) in -grounded- equipment, just using -core- from a grounded u/bal
line-level
source, especially if it's far away. The source signal voltage still arrives
there.

But if CD player is Ground (Earth)-free, then you -have- to also use screen
at its o/p.
If stereo, repeat for other chnl.

But -in this case as the amp has two floating, differential inputs- you just
connect screen to -ve and core to +ve of the bal'd i/p (same way for each
channel) and use both conductors at sending ends.
Do not swap a + with a - as phase reversal (inversion) will happen!

i/p XLR Pin 1 is probably connected to either chassis or PSU's centre rail
0V (if dual rail) or -ve (if single rail), and could be tied to XLR pin3
-only- if it reduces any hum present on amp (but normally Pin 1 goes to the
screen of a screened twisted-pair input cable, but is wired only
at -receiving end-
to avoid ground loops).
Some pro bal o/ps have an Earth/Ground Lift switch to cater for the Pin 1
option.

Jim

"gunnet" wrote in message
...

You can *probably* just use a modified cable, but since
you did not identify either the source or the destination
equipment, we can offer only generic suggestions.

thank you very much guys. I'm using cd player -----amplifier

I've got some cable and connector: 2 XLR, 2 Jack 6,3mm mono, 2 RCA and 2
meters of cable with one conductor and one shield. I think I have all to
make a good cable. For this work it's better a cable with 2 conductor or
with one conductor and one shield? I've seen that all rca cable have one
conductor and one shield so I took this...


Now I've got also the manual wich has some illustration:

Pin 1: shield
Pin 2: hot
Pin 3: cold

Here's what it says:
XLR unbalanced: Hot to pin2 Shield to pin1 and to pin3. Why pin1 and pin3
are are in short circuit?

JACK 6,3mm unbalanced: hot with hot, shield with shield.

It's better to use tha jack or the XLR, or it's the same?

Here is a general reference:
http://www.rane.com/note110.html
Before I made a cable as illustrated at number 17, but I get some noise
coming from the speaker

Is the balanced input on an XLR ?
The amp has got both XLR and Jack 6,3mm, wich it's 1/4'' in english
mesurement, right?

Consider pins 2 and 3 to be a floating ( or quasi floating ) differential
input.
I didn't understand well this sentence

How do I know if the XLR connector I've got have all pin corrisponding to
right.

[Randy Yates]

Eeyore writes:

Randy Yates wrote:

Eeyore writes:

Walt wrote:

gunnet wrote:

Hi, what is the best way to connect unbalanced output to balanced input of
an amplifier? I've seen that there are some boxes to convert, or I could
just make a modified cable?

The "best" way is highly dependent on the nature of the gear involved
and without knowing more than the information provided I can't tell you
the best way.

But 95% of the time you can just use a modified cable: just wire the +
output to the + input, connect the shields and it will work acceptably
well. If it's a transformer input, you'll need to tie the other leg of
the input to ground, otherwise you can let it float. You may run into
ground loop issues, but probably not.

Avoid tying the shields. It's 100% unnecessary.

Take hot(+) to hot and cold to cold. It really is that easy.

You'll lose 6 dB of gain this way,

No you won't. Do explain why you think so.

I guess it depends on the differential driver/receiver operation. In
the case of the TI parts (actually they're the old Burr-Brown parts)
DRV135 and INA137, my statement is correct.

INA137: http://focus.ti.com/docs/prod/folders/print/ina137.html
DRV134/135: http://focus.ti.com/docs/prod/folders/print/drv135.html

If the single-ended input voltage to the 135 is V, then the 135
outputs +V and -V, for a differential gain of +6 dB. Then the 137
would be configured for a differential gain of -6 dB, so that the
single-ended output is V when the differential inputs are +V and -V.

In other words,the 137 output is (1/2) * (V+ - V-), so if the
6 dB expected from the transmitter isn't there, you get 6 dB
attenuation.

However, if the driver and receiver have 0 dB differential gain,
then there would not be a 6 dB loss.
--
% Randy Yates % "How's life on earth?
%% Fuquay-Varina, NC % ... What is it worth?"
%%% 919-577-9882 % 'Mission (A World Record)',
%%%% % *A New World Record*, ELO
http://home.earthlink.net/~yatescr

[Todd H.]

"gunnet" writes:

So in the end to sum all:

I make the cable: hot to hot, shield to shield, easy......
and I don't loose 6db because power for me is important as I have to play
music laud in party.

So this item is useless in my case
http://www.behringer.com/DI600P/index.cfm?lang=ENG

No not useless, contrary to what others seem to think. But what do I
know, I've only actually used DI boxes in this situation with good
success, have an EE degree and have worked professionally as a circuit
designer.

It would be usufull if I would connect an instrument, yeah?

It's switchable -- instrument, line level, even from an amplifier
output that particular unit can handle on its input.

If you're running stereo, you'll need 2 of them.

Or, you can opt for this active unit that's stereo, and has adjustable
padding as well 0 to -40dB:
http://www.behringer.com/DI20/index.cfm?lang=ENG

The cable will work and is the cheapest and "cleanest" solution
perhaps, but if that 6dB is important to ya, it's not entirely clear
how your unit will respond. For me, given what my time is worth, I'd
be happy to throw $30 at the problem to get a QA tested mass produced
item versus having to scrounge for the proper cable, connectors and
firing up the soldering iron.

You'll get where you wanna go either way though. Let us know how it
turns out.

Best Regards,
--
/"\ ASCII Ribbon Campaign | Todd H
\ / | http://www.toddh.net/
X Promoting good netiquette | http://triplethreatband.com/
/ \ http://www.toddh.net/netiquette/ | http://myspace.com/mytriplethreatband

[Randy Yates]

(Todd H.) writes:

But what do I know, I've only actually used DI boxes in this
situation with good success, have an EE degree and have worked
professionally as a circuit designer.

If arrogance were a substitute for intelligence, many of the folks
around here would be brilliant. (And I'm NOT referring to you, Todd.)
--
% Randy Yates % "She has an IQ of 1001, she has a jumpsuit
%% Fuquay-Varina, NC % on, and she's also a telephone."
%%% 919-577-9882 %
%%%% % 'Yours Truly, 2095', *Time*, ELO
http://home.earthlink.net/~yatescr

[Eeyore]

gunnet wrote:

So in the end to sum all:

I make the cable: hot to hot, shield to shield, easy......

That wouldn't work with a transformer inout which is why I made a different
recommendation.

If you said what the amplifier was it would save a lot of guesswork.

Graham

[Eeyore]

Randy Yates wrote:

Eeyore writes:
Randy Yates wrote:
Eeyore writes:
Walt wrote:
gunnet wrote:

Hi, what is the best way to connect unbalanced output to balanced input of
an amplifier? I've seen that there are some boxes to convert, or I could
just make a modified cable?

The "best" way is highly dependent on the nature of the gear involved
and without knowing more than the information provided I can't tell you
the best way.

But 95% of the time you can just use a modified cable: just wire the +
output to the + input, connect the shields and it will work acceptably
well. If it's a transformer input, you'll need to tie the other leg of
the input to ground, otherwise you can let it float. You may run into
ground loop issues, but probably not.

Avoid tying the shields. It's 100% unnecessary.

Take hot(+) to hot and cold to cold. It really is that easy.

You'll lose 6 dB of gain this way,

No you won't. Do explain why you think so.

I guess it depends on the differential driver/receiver operation. In
the case of the TI parts (actually they're the old Burr-Brown parts)
DRV135 and INA137, my statement is correct.

INA137: http://focus.ti.com/docs/prod/folders/print/ina137.html
DRV134/135: http://focus.ti.com/docs/prod/folders/print/drv135.html

These parts are as rare as hens teeth in the real world.


If the single-ended input voltage to the 135 is V, then the 135
outputs +V and -V, for a differential gain of +6 dB. Then the 137
would be configured for a differential gain of -6 dB, so that the
single-ended output is V when the differential inputs are +V and -V.

In other words,the 137 output is (1/2) * (V+ - V-), so if the
6 dB expected from the transmitter isn't there, you get 6 dB
attenuation.

However, if the driver and receiver have 0 dB differential gain,
then there would not be a 6 dB loss.

You seem to be confused by the specifics of these parts.

Graham

[Eeyore]

"Todd H." wrote:

"gunnet" writes:

So this item is useless in my case
http://www.behringer.com/DI600P/index.cfm?lang=ENG

No not useless, contrary to what others seem to think.

It's completely useless since it introduces a 20dB drop in signal level for one
thing ! ( 50dB if you use the pad ).


But what do I
know, I've only actually used DI boxes in this situation with good
success, have an EE degree and have worked professionally as a circuit
designer.

Heck, me too and I've been working in pro-audio since 1973 !

Graham

[Randy Yates]

Eeyore writes:

Randy Yates wrote:

Eeyore writes:
Randy Yates wrote:
Eeyore writes:
Walt wrote:
gunnet wrote:

Hi, what is the best way to connect unbalanced output to balanced input of
an amplifier? I've seen that there are some boxes to convert, or I could
just make a modified cable?

The "best" way is highly dependent on the nature of the gear involved
and without knowing more than the information provided I can't tell you
the best way.

But 95% of the time you can just use a modified cable: just wire the +
output to the + input, connect the shields and it will work acceptably
well. If it's a transformer input, you'll need to tie the other leg of
the input to ground, otherwise you can let it float. You may run into
ground loop issues, but probably not.

Avoid tying the shields. It's 100% unnecessary.

Take hot(+) to hot and cold to cold. It really is that easy.

You'll lose 6 dB of gain this way,

No you won't. Do explain why you think so.

I guess it depends on the differential driver/receiver operation. In
the case of the TI parts (actually they're the old Burr-Brown parts)
DRV135 and INA137, my statement is correct.

INA137: http://focus.ti.com/docs/prod/folders/print/ina137.html
DRV134/135: http://focus.ti.com/docs/prod/folders/print/drv135.html

These parts are as rare as hens teeth in the real world.

Really? Is that why the Analog Devices parts SSM2141/2142 also operate in an
identical manner for similar usages?

http://www.analog.com/en/prod/0,,765...SM2142,00.html
http://www.analog.com/en/prod/0,,765...SM2141,00.html

And is this why both of these manufacturer's parts are referenced
in at least one on-line article on building XLR interfaces?

http://blackwidowaudio.com/index.htm

???

You seem to be confused by the specifics of these parts.

You mean by parts from two different manufacturers that are intended for

Audio Mix Consoles
Distribution Amplifiers
Graphic and Parametric Equalizers
Dynamic Range Processors
Digital Effects Processors
Telecommunications Systems
Industrial Instrumentation
Hi-Fi Equipment

???

Unless there is a standard (defacto or otherwise) for XLR/differential
interfaces, a potential 6 dB drop (pun intended) remains a reality.
--
% Randy Yates % "The dreamer, the unwoken fool -
%% Fuquay-Varina, NC % in dreams, no pain will kiss the brow..."
%%% 919-577-9882 %
%%%% % 'Eldorado Overture', *Eldorado*, ELO
http://home.earthlink.net/~yatescr

[Eeyore]

Randy Yates wrote:

Eeyore writes:
Randy Yates wrote:
Eeyore writes:
Randy Yates wrote:
Eeyore writes:

Avoid tying the shields. It's 100% unnecessary.

Take hot(+) to hot and cold to cold. It really is that easy.

You'll lose 6 dB of gain this way,

No you won't. Do explain why you think so.

I guess it depends on the differential driver/receiver operation. In
the case of the TI parts (actually they're the old Burr-Brown parts)
DRV135 and INA137, my statement is correct.

INA137: http://focus.ti.com/docs/prod/folders/print/ina137.html
DRV134/135: http://focus.ti.com/docs/prod/folders/print/drv135.html

These parts are as rare as hens teeth in the real world.

Really?

Yes really.


Is that why the Analog Devices parts SSM2141/2142 also operate in an
identical manner for similar usages?

http://www.analog.com/en/prod/0,,765...SM2142,00.html
http://www.analog.com/en/prod/0,,765...SM2141,00.html

And is this why both of these manufacturer's parts are referenced
in at least one on-line article on building XLR interfaces?

http://blackwidowaudio.com/index.htm

Pro-audio designers don't go to websites to learn how to 'build XLR interfaces' !!!

I just took a peek and they can't even design a decent headphone amp !


???

?????


You seem to be confused by the specifics of these parts.

You mean by parts from two different manufacturers that are intended for

Boutique parts for those who don't understand component level design.


Audio Mix Consoles
Distribution Amplifiers
Graphic and Parametric Equalizers
Dynamic Range Processors
Digital Effects Processors
Telecommunications Systems
Industrial Instrumentation
Hi-Fi Equipment

Those would be their target markets wouldn't they ?

Have you even the tiniest idea what price those SSM and TI parts are and how that relates
to the price ppl expect to pay ??


???

Unless there is a standard (defacto or otherwise) for XLR/differential
interfaces, a potential 6 dB drop (pun intended) remains a reality.

No. You've fundamentally misunderstood how a differential input works. I'm sure the INA
and SSM parts won't have the imaginary problem you describe anyway since no-one would buy
them if they did.

Graham

[Randy Yates]

Eeyore writes:
[...]
These parts are as rare as hens teeth in the real world.
Really?
Yes really.

Is that why Jensen's Bill Whitlock references them in his June 1995
JAES article "Balanced Lines in Audio Systems: Fact, Fiction, and
Transformers"?

Even if you "roll your own" using opamps, the differential gain is, as
far as I can tell from several sources, unspecified. It's up to the
designer.

No. You've fundamentally misunderstood how a differential input works.

I'm all ears - why don't you explain it to me?

I think I've given anyone who's even remotely competent in circuit
design enough information to see that my claims are true. I'm
giving up on you.

I'm sure the INA and SSM parts won't have the imaginary problem you
describe anyway since no-one would buy them if they did.

So rather than crack a datasheet you'd rather hurl false accusations? I
see.
--
% Randy Yates % "Though you ride on the wheels of tomorrow,
%% Fuquay-Varina, NC % you still wander the fields of your
%%% 919-577-9882 % sorrow."
%%%% % '21st Century Man', *Time*, ELO
http://home.earthlink.net/~yatescr

[Mr.T]

"Eeyore" wrote in message
...
Tying cold and earth will have a small beneficial impact of RFI immunity
but may
also create a hum-loop with multiple-earthed equipment.

Yep, it is possible. But that's why most commercial boxes have a ground lift
switch, and of course when you are making a dedicated lead, it's possible to
do whatever is necessary for the particular application.

MrT.

[Mr.T]

"gunnet" wrote in message
...
thank you very much guys. I'm using cd player -----amplifier

I've got some cable and connector: 2 XLR, 2 Jack 6,3mm mono, 2 RCA and 2
meters of cable with one conductor and one shield. I think I have all to
make a good cable. For this work it's better a cable with 2 conductor or
with one conductor and one shield? I've seen that all rca cable have one
conductor and one shield so I took this...


Now I've got also the manual wich has some illustration:

Pin 1: shield
Pin 2: hot
Pin 3: cold

Here's what it says:
XLR unbalanced: Hot to pin2 Shield to pin1 and to pin3. Why pin1 and pin3
are are in short circuit?

JACK 6,3mm unbalanced: hot with hot, shield with shield.



So what you are saying is the amp already has an unbalanced input, where all
you would need is a readily available RCA-Phone jack lead, and for some
reason you are trying to complicate the issue as much as possible?

MrT.

[Eeyore]

Randy Yates wrote:

Eeyore writes:

These parts are as rare as hens teeth in the real world.
Really?
Yes really.

Is that why Jensen's Bill Whitlock references them in his June 1995
JAES article "Balanced Lines in Audio Systems: Fact, Fiction, and
Transformers"?

So ?


Even if you "roll your own" using opamps, the differential gain is, as
far as I can tell from several sources, unspecified. It's up to the
designer.

You don't understand how they work in that case. What exactly do you mean by
'unspecified' anyway ?


No. You've fundamentally misunderstood how a differential input works.

I'm all ears - why don't you explain it to me?

Pick up any competent design 'cookbook'. Do you have any to hand ?


I think I've given anyone who's even remotely competent in circuit
design enough information to see that my claims are true. I'm
giving up on you.

I don't need your approval. I've been designing top-notch pro-audio for decades.


I'm sure the INA and SSM parts won't have the imaginary problem you
describe anyway since no-one would buy them if they did.

So rather than crack a datasheet you'd rather hurl false accusations? I
see.

Go learn some basic electronics and don't fall for the sales pitch so easily.

Graham

[Eeyore]

"Mr.T" wrote:

"Eeyore" wrote in message

Tying cold and earth will have a small beneficial impact of RFI immunity
but may also create a hum-loop with multiple-earthed equipment.

Yep, it is possible. But that's why most commercial boxes have a ground lift
switch,

That's because they're 'jacks of all trades'.


and of course when you are making a dedicated lead, it's possible to
do whatever is necessary for the particular application.

Exacty and it's the best idea here.

Graham

[Eeyore]

"Mr.T" wrote:

"gunnet" wrote in message
...
thank you very much guys. I'm using cd player -----amplifier

I've got some cable and connector: 2 XLR, 2 Jack 6,3mm mono, 2 RCA and 2
meters of cable with one conductor and one shield. I think I have all to
make a good cable. For this work it's better a cable with 2 conductor or
with one conductor and one shield? I've seen that all rca cable have one
conductor and one shield so I took this...


Now I've got also the manual wich has some illustration:

Pin 1: shield
Pin 2: hot
Pin 3: cold

Here's what it says:
XLR unbalanced: Hot to pin2 Shield to pin1 and to pin3. Why pin1 and pin3
are are in short circuit?

JACK 6,3mm unbalanced: hot with hot, shield with shield.


So what you are saying is the amp already has an unbalanced input, where all
you would need is a readily available RCA-Phone jack lead, and for some
reason you are trying to complicate the issue as much as possible?

No, he's not connecting the amp's inverting (cold) input which isa big mistake.
The shield ( screen ) connection on a balanced input is a largely unimportant.

Graham

[Mr.T]

"Eeyore" wrote in message
...
Here's what it says:
XLR unbalanced: Hot to pin2 Shield to pin1 and to pin3. Why pin1 and
pin3
are are in short circuit?

JACK 6,3mm unbalanced: hot with hot, shield with shield.


So what you are saying is the amp already has an unbalanced input, where
all
you would need is a readily available RCA-Phone jack lead, and for some
reason you are trying to complicate the issue as much as possible?

No, he's not connecting the amp's inverting (cold) input which isa big
mistake.
The shield ( screen ) connection on a balanced input is a largely
unimportant.

IF he uses the unbalanced 1/4" jack input, there is NO cold input to worry
about!

Please tell us what advantage he has by connecting the CD player to the
balanced input (as an unbalanced signal), with or without the shield
connected to ground, as opposed to simply connecting to the 1/4" unbalanced
jack input in the first place?????????

However *IF* the CD player is a long distance from the power amp, then a DI
box should be used to create a balanced signal at the CD player end, and use
proper balanced XLR cables.

MrT.

[Eeyore]

"Mr.T" wrote:

"Eeyore" wrote in message

No, he's not connecting the amp's inverting (cold) input which isa big
mistake. The shield ( screen ) connection on a balanced input is a largely
unimportant.

IF he uses the unbalanced 1/4" jack input, there is NO cold input to worry
about!

There is. It's the shield / screen / earth / chassis !


Please tell us what advantage he has by connecting the CD player to the
balanced input (as an unbalanced signal), with or without the shield
connected to ground, as opposed to simply connecting to the 1/4" unbalanced
jack input in the first place?????????

Most of the usual advantages of balanced operating wrt noise rejection. Plus
with the shield broken, it'll break any 'hum-loop'.

Also, there's a subtle improvement wrt the input noise of the amplifier by
providing the cold side of the input with a low-Z source.


However *IF* the CD player is a long distance from the power amp, then a DI
box should be used to create a balanced signal at the CD player end, and use
proper balanced XLR cables.

Absolutely no point whatever. The identical performance can be acheived with
Rane's fig 17 arrangement from the link Arny posted using 'twin screened' (
balanced ) cable for the interconnect.

Graham