Balanced inputs vs rca

[Coytee]

Noticed a McIntosh amp other day that was "fully balanced" and had balanced inputs. (MC-352)

If someone acquires something that requires balanced inputs, can you get an adapter to switch it over to rca?

What are the benefits of a balanced input?

If you DO convert to a balanced input from RCA, do you lose any of the benefits that a "fully" balanced system might have?

[consistent]

Hi Coytee.
As I understand balanced inputs either from pre to power or indeed source to pre to power have a better signal to noise ratio as the earthing and signal transference is better. You can buy XLR (balanced) and RCA adaptors see www.cardas.com

For what it's worth I find an XLR connection is superior to most RCA'S

cheers

[colterphoto1]

The good DrWho should be here any minute....

[Coytee]

Well, if he shows up and I'm not around it only means I'm having breakfast with my family before hitting road back to Knoxville (currently in Atlanta).

Follow up question

If something is balanced from preamp to power amp VERSES using RCA from pre to power...

if the RCA connectors aren't as good (in an absolute sense) as the balanced, dont we have a "weak link" thing here?

ie, if I have a Peach with RCA outputs & convert to balanced input on the amp side, does the balanced "improve" anything over the RCA (I'd doubt it)?

So, aren't I going to have the same net end result as just using the RCA's?

(it's good to know you can convert over though)

[Marvel]

If you run balanced lines, they can be hundreds of feet long with no

degradaton of the signal quality. A balanced line has two signal lines

that are 180 degrees out of phase with each other so that noise picked

up in the cable (emi, rfi, etc) cancels out. So there is great noise

immunity with balanced cables. Also usually low impedance, which is

also a plus.

Unbalanced cables (rca/phono, 1/4 inch phone) don't have the same

luxury. The impedance is also usually higher, and with the capacitance

of the cable involved, will cause high freq. rolloff on long cables.

They also cannot reject/cancel the noise picked up from emi, rfi, etc.

You can balance the output on a preamp with active electronics or with

a transformer. A high quality transformer would work better (Jensen or

Lundhal), but the cost would be greater. For short cable runs, you

probably aren't going to be able to tell the difference. Once inside

the amp, it's all unbalanced. It wouldn't have to be that way, but the

cost would go up dramatically. High end audio consoles are balanced all

the way through.

Bruce

[Coytee]

Thanks Bruce...

so it's fair to say that if the two are side by side then I can just get some kind of adapter and forget about the rest of the stuff?

As a followup, if I for some reason decide to seperate them by 30' (which wouldn't be impossible in my basement though unlikely) then I might want to look at creating a balanced signal at the Peach end of things (output of peach into transformer & output of transformer which is now balanced... to the balanced input of amps 30' away) and then perhaps enjoy the benefit of a balanced line?

[pauln]

RCA (unbalanced) are single-ended?

[klipschfanatic]

MC-352 will accept RCA or XLR input. You can still use your current preamp with RCA's. There are a bunch of preamps with balanced out-most are not fully balanced. McIntosh C-200, & MDA-1000 are all fully balanced. I believe that all of the BAT preamps are fully balanced.

I have been using the MC-352 with a passive preamp & Khorns until last week. Just picked up a McCormack ALD-1 preamp using RCA's. Will try running balanced as soon as I pick up a set of cables.

Have read that some Mc users prefer the RCA over XLR input. As mentioned the noise difference is supposed to improve running balanced. I think the amount of gain is different between the RCA & XLR which could explain why some like RCA better.

Check out www.audiokarma.org there is a McIntosh forum that will fully answer any Mc questions. I sent you a reply to the MC-352 question you asked me from Audiogon.

[DrWho]

Coytee...which device has the balanced jacks and which one has the

unbalanced jacks? I'm quite confused over that point [] Let me know

and I'll give you some links to transformers to do the conversion for

you. If you don't have any noise problems there are also times where

you can completely skip over a transformer and use a special wiring

configuration (ie, going from unbalanced to balanced).

[j-malotky]

XLR was really developed for pro setups, where the Mixer is 100 feet or

so from the mics and power amps on the stage. The only time I use

them for home is when I exceed a 2 meter RCA plug. I find running

longer than 2 meters the signal becomes too degraded where you can

easily hear the loss. Does XLR add quality over a good quality short RCA, NO. I prefer

the sound of a good short RCA cable over a XLR cable.

A few years back, I tried a setup where I had my amps in the basement

under each Khorn whith an XLR connection to my preamp preamp (20feet)

and short 3 foot speaker cables to each speaker. I quickly

abandened the setup going back to having 1 meter RCA interconnects and

20 feet of speakers wire.

I would always suggest using short RCA interconnects and long speakers wires

JM

[Coytee]

Hey Doc...

It's the Mc-352 that has the balanced inputs. I'm not familar with them nor their benefits other than what I've read here.

I own a Peach which has RCA outputs.

[]

[Marvel]

Some audio gear with xlr connectors aren't really balanced. Some, depending on the vintage of the gear, will have pin 2 or 3 tied to pin 1, which is the ground.

Others use cheap opamps to balance the circuit electronically, so that you are really better off going unbalanced.

Good transformers cost a lot, because they have to maintain the freq. response and power handling for line levels. It's all about trade offs.

If you want to go the electronic route, you can have a look at these boxes from Henry Engineering:

http://www.henryengineering.com/matchbox.html

This one is a two way, designed for sound cards on PCs, but could still be used.

Bruce

[DrWho]

Well you might try this, but I bet you will have noise problems:

One other problem you'll run into is whether pin 1 or pin 2 is "hot" on

your amps input (in which case you would have to switch pins 1 and 2 on

your custom cable).

At your local pro audio store you should be able to find a 6 foot cable

with an RCA tip on one end and an XLR on the other end for about $10

and this is by far the easiest way to do it if you don't wanna build it

yourself.

Your other option is to use a transformer:

Which you can get for $15 at Radio Shack:

http://www.radioshack.com/product/index.jsp?productId=2062444&cp=&pg=1&kw=xlr&numProdsPerPage=20&parentPage=search

Combined with this piece I usually use one of these:

http://www.radioshack.com/product/index.jsp?productId=2062455&cp=&pg=7&kw=rca&parentPage=search

Though if you don't like the idea of an extra adapter (which I find

very versatile) then you might consider a pre-made cable like this:

http://www.radioshack.com/product/index.jsp?productId=2103850&cp=&pg=3&kw=rca&parentPage=search

So when do you need to use a transformer? When the noise floor using

the first method isn't low enough. Since I do a lot of PA work I have

all these adapters readily available and can switch between them all to

compare and the noise floor using the transformer is a good 40dB lower.

[Spkrdctr]

At your local pro audio store you should be able to find a 6 foot cable with an RCA tip on one end and an XLR on the other end for about $10 and this is by far the easiest way to do it if you don't wanna build it yourself.

Words of wisdom! I vote for the easy way out........

[Rivendell61]

Coytee,

The ideal way to do this is really quite simple and cheap. You use the differential/balanced input to create a balanced connection. Don't use an adapter (that wastes the balanced input: no noise rejection).

Check with McIntosh re the pin configuration. Then have Blue Jeans Cable wire a shielded twisted pair (they use Belden 1800F) at the pre-amp end (RCA) with cold lead and shield tied together. Terminate the amp (xlr) end as normal per McIntosh. And you have an essentially balanced connection.

The only concern here is the output impedance of the Peach. Ideally you want it good and low..... The Peach has options right? Use the lowest and you should be fine driving a long cable.

Mark

[DrWho]

Coytee,

The ideal way to do this is really

quite simple and cheap. You use the differential/balanced

input to create a balanced connection. Don't use an adapter (that

wastes the balanced input: no noise rejection).

Check with McIntosh

re the pin configuration. Then have Blue Jeans Cable wire a

shielded twisted pair (they use Belden 1800F) at the pre-amp end

(RCA) with cold lead and shield tied together. Terminate the amp

(xlr) end as normal per McIntosh. And you have an essentially

balanced connection.

The only concern here is the output

impedance of the Peach. Ideally you want it good and

low..... The Peach has options right? Use the lowest

and you should be fine driving a long cable.

But really it's not a balanced connection. The second you wire pin 1 to

ground you immediately remove all noise rejection from the polarity

reversal. It's simply not the same...if it were, then it would be way

cheaper to use a 2 conductor wire like an RCA cable for all balanced

interconnects.

Btw, your fancy cable is also simply an adapter with the same

fundamental wiring scheme as all the other nontransformer options

presented. []

One other area of concern is negative feedback used by an unbalanced

output - they don't like driving balanced inputs and you might run into

some noise problems there as well (which wouldn't occur when using a

transformer). So go ahead and try a straight cable adaptor and if you

have "hiss" then go with a transformer. If you get a "buzz" then you

need to connect pin 2 to the ground instead of pin 1. And then you'll

have to check for hiss again (or as suggested you could just contact

the amp manufacturer and find out which pin is the "hot" one).

[Rivendell61]

FirstI should emphasize that Coytee should check with both McIntosh and Mark re wiring. The cable set-up I mentioned is the default normal solution for making a balanced connection with an un-balanced source.but there are pieces of equipment out there which need a different wiring configuration(my gear and references are mainly for SSbut it should work fine for a tube amp with low output impedance).

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Now Doc,

Im not sure why we are so far apart.

Coytee is trying to achieve a good unbalanced/balanced connection.

Balanced, re noise rejection, means equal impedance with respect to ground on both conductors.

He has a balanced ampwhy waste it? He may not need any extra noise rejection in his house. But if he is running a 30ft cable it makes sense to use the simple available option. The connection I mentioned IS effectively balancedalthough certainly not perfectly. It will provide added noise rejection (depending on the ratio of input to output impedance).

There should be no issue (again I speak generallycheck with manufacturers) driving balanced with unbalanced.

Hmm, polarity reversal? Balanced noise rejection comes from the equal impedance on both conductors. An adaptor will NOT do thisno noise rejection-- and wastes the nice Mc balanced circuit. No good with a two conductor. You need the fancy wire :-)

And yes, a transformer will also workand may provide added noise rejection. But unless Coytee knows he has a substantial noise rejection problem (or the preamp/amp impedance relationship is poor), the cable solution (cheaper, less gear in signal path)solves the problem more cleanly.

Mark

[DrWho]

FirstI should emphasize that Coytee should check with both McIntosh and Mark re wiring. The

cable set-up I mentioned is the default normal solution for making a

balanced connection with an un-balanced source.but there are pieces of

equipment out there which need a different

wiring configuration(my gear and references are mainly for SSbut it

should work fine for a tube amp with low output impedance).

Now Doc,

Im not sure why we are so far apart.

Coytee is trying to achieve a good unbalanced/balanced connection.

Balanced, re noise rejection, means equal impedance with respect to ground on both conductors.

He has a balanced ampwhy waste it? He may not need any extra noise rejection in his house. But

if he is running a 30ft cable it makes sense to use the simple

available option. The connection I mentioned IS effectively

balancedalthough certainly not perfectly. It will provide added noise rejection (depending on the ratio of input to output impedance).

There should be no issue (again I speak generallycheck with manufacturers) driving balanced with unbalanced.

Hmm, polarity reversal? Balanced noise rejection comes from the equal impedance on both conductors. An adaptor will NOT do thisno noise rejection-- and wastes the nice Mc balanced circuit. No good with a two conductor. You need the fancy wire :-)

And yes, a transformer will also workand may provide added noise rejection. But

unless Coytee knows he has a substantial noise rejection problem (or

the preamp/amp impedance relationship is poor), the cable solution

(cheaper, less gear in signal path)solves the problem more cleanly.

Mark

well we're essentially recommending the same thing, just have differences on the background stuff []

I'm not sure what you mean about balanced having the equal impedance to

both conductors...the reason for the noise rejection in a real balanced

connection is that pin 1 has its phase reversed at the output of the

first device. The two conductors are now carrying an out of phase

signal, but picking up the same noise along the path. At the input of

the next device the phase on pin 1 is reversed yet again and now the

noise on pin 1 is out of phase with the noise on pin 2. Both pins are

summed together and you get the original signal without any of the

noise picked up along the way (in theory at least).

When you run an unbalanced output directly into a balanced input you

are running the hot signal to pin 2 and then you are running the ground

to both the ground (pin 3) and pin 1. At the input of the balanced

device the ground signal on pin 1 has its phase reversed and is then

summed with pin 2. Since the ground is going to pin 1 you end up with

no change compared to pin 2 (so the summation between pin 1 and pin 2 = pin 2) - though the overall signal is now 6dB quieter as

compared to a balanced connection...which in the end also means a 6dB

reduction in the noise floor. Keep in mind that you don't get the same

noise rejection with this method because the summed total between pin 1 and pin 2 is

still refereneced to the ground (pin 3) which also picks up the same

noise along the path.

Btw, there are only two ways to connect between an unbalanced and

balanced source. The first is the fancy cable trick which we both

suggested to try first because its cheaper and easier. And second (the

"correct way") is to use a transformer (which we both mentioned too).

In both methods the ground signal is the same, but with the transformer

the phase is being reversed on pin 1.

[Rivendell61]

Hi Doc,

Actually the balanced noise rejection stuff is without reference to signal. Don't need a signal on both wires. Signal symmetry will give added benefits re headroom and crosstalk--but not noise rejection.
The 'Balanced' connection and noise rejection is a function of the two signal conductors having equal impedance.
Regarding which is 'correct' (transformer vs twisted pair as above) ...it depends on the situation.
But I will quote Bill Whitlock (Jensen Transformer) who says: "For all intents and purposes, using [the wiring scheme suggested] is THE correct way to connect an unbalanced component to a balanced one".

I'll dig up some pdfs or links to his AES papers, etc about this, and post links (or send them to you?) when I get some time late tonight. Let me know what you think.

Mark

[NOSValves]

Mark,

The Blue Jean cable has great prices on standard RCA's what a find. I can't believe I have never heard of it before.

Craig