Measuring components output (balance)

Ricardo

I would like to measure if all my components (source, preamp, amp) have a "balanced" output. How can I do this? I am pretty sure that the output in one channel is a bit higher than the other; I can correct this moving the balance in the pre, but would really like to check. I have a multimeter so all I need is some guidance on how to do it for each component.

Any help is appreciated.

reeltrouble1

How could they be balanced each has a different output impedance and input impedance??

Why not just use a test tone and an SPL guage and adjust as needed??

RT1

Ricardo

I am talking about balanced between left and right in each component; want to check if any of the components has more output in one channel vs the other.

megasat16

Ricardo wrote: »

I would like to measure if all my components (source, preamp, amp) have a "balanced" output. How can I do this? I am pretty sure that the output in one channel is a bit higher than the other; I can correct this moving the balance in the pre, but would really like to check. I have a multimeter so all I need is some guidance on how to do it for each component.

Any help is appreciated.

Set your DMM to AC voltage (auto setting).

If you preamp has Mono setting, use it at mono mode. Stereo mode has unpredictable result sometimes.

But if you don't have mono setting, don't worry.

Disconnect speakers from the amp and run a test tone on each individual channels (like 1KHz since wave sweep) and check the voltage on the amp output binding post for each channel. You can confirm your theory of that one channel has a tad higher output if the DMM measurements is not the same on both channels.

You can also check at your Preamp output (set your DMM to low setting or auto function should works fine and should be around a volt or less normally).

But please pay extra attention when you are sticking the leads from DMM into any of your amp or preamp output / binding post not to touch anything. It could result in unfavorable outcomes if there is a short. :eek:

I am sure you know but just a caution so don't take any offensive idea about it.

I hope it's what you are looking for? Otherwise, let me know and I'll try again.

Ricardo

That is helpful.

So, for the amp, measure between the + and the - binding posts for each channel, and for the source/preamp measure between the + and the - of each RCA (not sure if this is correctly called + and -, but I get it's between the outer and the inner contacts).

Can I do this without disconnecting the speakers? I have a second set of binding posts.

Thanks!!!

megasat16

Ricardo wrote: »

That is helpful.

So, for the amp, measure between the + and the - binding posts for each channel, and for the source/preamp measure between the + and the - of each RCA (not sure if this is correctly called + and -, but I get it's between the outer and the inner contacts).

Can I do this without disconnecting the speakers? I have a second set of binding posts.

Thanks!!!

That is correct places to measure the outputs but if you have RCA for the preamp outputs. But for the XLR or balanced outputs, I think it's pin 1 and 3, I am not sure about it.

Speakers needs to be disconnected and you want to measure no load output voltage to compare the gains of each channel. You need to do a sine wave sweep from the source such as CD player. I think there is a free test tone CD that can do specific frequency sweep such as 10Hz, 100Hz, 1KHz, etc. You need to get that CD for generating a test tone from the source.

Ricardo

I have a CD with test tones; Thanks!!

I am using the XLR connections, but for this test I will use the RCA to make it easier.

Ricardo

Ok; I measured the amp.

left: 0.137 v
right: 0.133 v

I used a 315 Hz tone because that's the one I have that plays long enough to make the measurements.

Moving the balance a tad to the right balances the output at 0.133 v. I need to measure at the preamp and CD player to see if it comes from down the road or it's at the amp, but I need more time for that.

Is this 0.004 v difference something you could call normal? I definitely can hear something is not quite right, and have moved the balance very close to where it is now.

reeltrouble1

Ricardo,

You are all SS amps right? bad juju to disconnect the speaks from a tube amp or tube integrated.

RT1

Ricardo

Yes, all SS, for now.

SS and paypal rules.

Thanks for the warning though

megasat16

Well, 0.004v is not something I would call a difference due to the amplifiers gains been not always identical due to aging and all that. But your amp outputs are rather low. I have more than 1V at very low volume setting. Are you sure you set your meter to AC Voltage?

Edit : Try 100Hz sine wave sweep. My el cheapo Rat Shack meter is not very accurate and if you have one, we are in the same boat. May be low frequency will provide a little better accuracy for AC. We really need a scope to be doing this.

RT1, you can measure tubes with a resistive dummy load (not speakers) connected.

heiney9

If you are using XLR then you should measure those as well..........since that's what you are using everyday. Do you notice the same problem when using RCA's as well?

Most XLR need to have pins 1 and 3 shorted when using the RCA's. I beleive that's where you would measure the XLR outputs/inputs (at pins 1 & 3), but I am not an EE so furthur investigation is needed.

I do know leaving the XLR "open" as in not using the shorting pins when using RCA's leads to very low input impedance and the output is incorrect whne using the RCA's.

With the Marsh it might be different since there is a switch on the back that probably makes the correct connections internally. The Alpeh comes with shorting PINS for the XLR (pins 1 & 3) if one uses the RCA's.

So in your case with the Marsh (you still have that right?) Just make sure to flip the toggle switch to "unbalanced" if you are measuring at the RCA's and "balanced" if you are measuring at the XLR (which I beleive are pins 1 & 3)

Hope this helps and I haven't made something simple complicated

H9

heiney9

double post

Ricardo

Megasat, I did it at very low volume; I will try again today with higher output.

H9, I am measuring the amp at the binding posts, so no problem there; when I measure the preamp, I will do both RCA and XLR, but I don't think for output the short is required, right?? By the way, which are pins 1 & 3??

Ricardo

Oh, and some tube amps can be turned on without load with no problem; I remember the TAD-60 required initial biasing with no load. But true, I've heard horror stories and it's a good watch out.

heiney9

This should help

Also here midway down--look for XLR3 connections

http://en.wikipedia.org/wiki/XLR_connector

heiney9

I know this isn't from your instruction manual...... but between this and the Wiki article it should help as all XLR for audio signals are standard configuration. The switch on the back of the Marsh essentially does what is stated below, no need for shorting pins.

I have Doug's Marsh here and when I used the balanced connection it didn't sound quite right because I forgot to switch the toggle on the back

The third connection are the balanced inputs, which occur through standard XLR connectors. The balanced input impedance is 52 Kohms. Input pin 1 of the XLR connector is input ground, pin 2 is the positive input, and pin 3 is the negative input. As shipped, there is a shorting jumper between pins 1 and 3, which is the configuration for single-ended input.

This shorting jumper should be used when operating the amplifier with the RCA input, otherwise you will not get the proper gain figure for the amplifier. If you operate the amplifier with balanced inputs, you will remove this jumper, and we advise you to save it carefully for future use.

H9

Ricardo

So if I read correctly, shouldn't the measure be done between pins 2 and 3? (Positive and negative). Also, I've read somewhere that European XLR connectors use pins differently. Not surprised...

My Marsh will not produce any sound in XLR unless the switches are at XLR; I found out when I accidentaly flipped one switch when changing some connectors. Of course I thought I had a dead channel and that was the last thing I looked at.

reeltrouble1

Ricardo wrote: »

Yes, all SS, for now.

SS and paypal rules.

Thanks for the warning though

no problem. good to have mega to handle my light work. Just be careful on procedural advice as many a newb will be reading and not fully understand until its too late.

Lest we forget, Paypal is the illegitimate unclean horror child born from greedy dribble leftovers of Credit Card companies.

RT1

heiney9

Ricardo wrote: »

So if I read correctly, shouldn't the measure be done between pins 2 and 3? (Positive and negative). Also, I've read somewhere that European XLR connectors use pins differently. Not surprised...

My Marsh will not produce any sound in XLR unless the switches are at XLR; I found out when I accidentaly flipped one switch when changing some connectors. Of course I thought I had a dead channel and that was the last thing I looked at.

I'm not sure....try it, you won't hurt anything. I assumed if you are supposed to short 1 and 3 to gain the proper impedance that's where you would measure.

On the Marsh if the switch is set for balanced you will get sound out of the RCA.......it's just very low, I know because this happened on Sunday

Ricardo

I will try both; thanks for all this info Brock.

megasat16

reeltrouble1 wrote: »

no problem. good to have mega to handle my light work. Just be careful on procedural advice as many a newb will be reading and not fully understand until its too late.

RT1

Easy There, Ted.

Ricardo,

What amps and pre-amps are you using? It's no denying I am a little clueless as RT1 put it.

James

Ricardo

Right now using Marsh P2000B balanced pre and Marsh A400s amp

Systems

Ricardo wrote: »

So if I read correctly, shouldn't the measure be done between pins 2 and 3? (Positive and negative). Also, I've read somewhere that European XLR connectors use pins differently. Not surprised...

The standard XLR pin out is pin1=Ground,pin2=Pos(noninverted)pin3= neg(inverted)

When single ended RCA inputs are used usually the inverted input pin 3 is tied to ground pin 1.If you want to compare the levels of each half of the balanced output then first try pin 1 and 2 for the positive half ,and then pin 1 and 3 for the inverted half.

megasat16

Did you make anymore measurements yesterday or just overjoyed with your new thread so you forgot to take new measurements?