Balancing a vinyl rig

[Smeggy]

If it fall over when you let it go, it's not balanced.

I dispute that.

People have claimed for years that I was unbalanced, and yet I rarely fall over unless drunk or stoned. I believe I'm fully balanced and that both my positive and negative sides are strongly driven. Though I'm frequently ungrounded now, I was grounded a lot when I was younger for humming when I was supposed to be quiet.

I'm unsure if I was ever single-ended except as a fetus. At that time I was well shielded with a common ground and didn't hum.

There, I think that explains it all?

[Dusty Chalk]

Huh? I said I have no problem being corrected when I am wrong. This implies that Nate corrected me and I WAS WRONG. Sheesh.

No. Here, watch, I'll say it:

I have no problem being corrected when I'm wrong.

Does it sound to you like I'm admitting that I'm wrong? 'Cause I'm not.

When used with a balanced amp, the k1000 is balanced. When used with an unbalanced amp, the k1000 isn't balanced. I said that when used with a speaker amp with a common ground (the norm), it's not balanced. That's it. Balanced amps drive + and - actively. Balanced headphones don't share a common ground. Balanced cables have +, -, and shield. Whether something is balanced or not is entirely based on context.

First of all, thanks for dropping the personal attacks, and returning to the actual technical discussion. Secondly, we're going to have to just disagree. I mean, if you have a balanced pre going to a balanced power amp, and you have an XLR cable going between them, it's a balanced connection. If you have two sets of XLR->RCA adapters and you use single-ended interconnects, it's not a balanced connection, despite both sides being balanced. I'm not arguing against doing it that way, you'll still get some of the benefits of having the pre and the power balanced, but the terminology -- it's not a balanced connection you're making -- and its implications -- that there's a difference between the two, and if you lived in a community where everyone did it that way, one might forget that there is a proper way to do it in other contexts.

[grawk]

I mean, if you have a balanced pre going to a balanced power amp, and you have an XLR cable going between them, it's a balanced connection. If you have two sets of XLR->RCA adapters and you use single-ended interconnects, it's not a balanced connection, despite both sides being balanced. I'm not arguing against doing it that way, you'll still get some of the benefits of having the pre and the power balanced, but the terminology -- it's not a balanced connection you're making -- and its implications -- that there's a difference between the two, and if you lived in a community where everyone did it that way, one might forget that there is a proper way to do it in other contexts.

The difference you're describing is what everyone else has said all along. Balanced drive vs balanced transmission. The benefit to balanced transmission is improved noise reduction. The benefit to balanced drive is improved power, speed, etc. They're different things, and that they have the same name is where you're getting hung up. You can connect the balanced amp to the balanced preamp to the speakers any way you like, and as long as there are conductors for positive and negative, they're being driven balanced. You may get noise if you run the cables too far, or through a noisy environment. That's where balanced transmission provides a benefit. But shielding can have positive and negative side effects. Run fully shielded balanced connections to each earpiece in your headphones, and you'll stop wearing headphones due to neck strain.

[kevin gilmore]

see the problem is everyone is trying to fit new technologies into a name and a way of transmitting

audio that is more than 40 years old. Back then, everything was pretty much tubes, which had

a high output impedance, so all the professional stuff was designed to use input and output transformers

to match everything. And so for long runs of cable, everything was balanced and 600 ohms. A lot of

professional audio stuff is still done that way.

Enter lots of present day audio gear that do balanced, except without any kind of isolation. And you

get issues of whether or not the 3rd wire should be connected at both ends or not, and that ends up

causing issues related to common mode voltages, and the ability of electronics to reject that. The fact is

that for safety reasons, the ground wire of both unbalanced inputs and balanced inputs is referenced to

power ground. So on some equipment if you connect both ends of a balanced cable to ground, you may

still end up with an audible ground loop.

As far as what we call balanced output these days, we really should use a different term entirely. And that

term should be bridged output.

Wadia had it right, although way to late and way to expensive. The inputs to our power amps should be seperated

fiber optic digital running at 2.56 or 5.12 mhz with seperated clock and data. No more ground loops ever.

Same thing for hdmi.

[philodox]

No. Here, watch, I'll say it:

I have no problem being corrected when I'm wrong.

Does it sound to you like I'm admitting that I'm wrong? 'Cause I'm not.

No, because the context is completely different.

[swt61]

Very interesting read Kevin, thanks.

Bridged output does seem to be more accurate.

I seem to have a ground loop hum only noticeable in my active monitors. If I turn the volume up just one step the hum goes away, but if I turn off my gear I get the hum. So I have to disconnect the XLR cables from my speakers when I'm not using them. I never thought that the problem might be related to the balanced configuration of my gear.

[n_maher]

I seem to have a ground loop hum only noticeable in my active monitors. If I turn the volume up just one step the hum goes away, but if I turn off my gear I get the hum. So I have to disconnect the XLR cables from my speakers when I'm not using them. I never thought that the problem might be related to the balanced configuration of my gear.

Steve, seems to me that you could try a couple simple experiements. First have a look and see if the ground pin on your XLR cables (should be pin 1) is connected on both ends. If it is you could try disconnecting it at the speaker end and see if that helps. Or you could try using a cheater plug on the power cords for the monitors and see if that makes a difference.

[swt61]

Good ideas Nate. I'm off to work, but I will try that when I get home and let you know if it works. Thanks!

[Dusty Chalk]

They're different things, and that they have the same name is where you're getting hung up.

No, I think where I'm getting hung up is that I was probably taught by someone who was more "old school", and was more familiar with the 40-year-old technology that KG refers to in his post. I'll wander off and do some more research about the difference between balanced transmission vs. balanced drive, though. You are correct in that I could know more about that.

As far as what we call balanced output these days, we really should use a different term entirely. And that term should be bridged output.

That's pretty much what I've been trying to say, from the reverse (or "negative") perspective. I.E. we should be calling "things which are not 'bridged output'" something other than "balanced output". Do you have a term for that? 'Unbridged output'? 'Single-ended output'?

[grawk]

No, I think where I'm getting hung up is that I was probably taught by someone who was more "old school", and was more familiar with the 40-year-old technology that KG refers to in his post. I'll wander off and do some more research about the difference between balanced transmission vs. balanced drive, though. You are correct in that I could know more about that.That's pretty much what I've been trying to say, from the reverse (or "negative") perspective. I.E. we should be calling "things which are not 'bridged output'" something other than "balanced output". Do you have a term for that? 'Unbridged output'? 'Single-ended output'? That's the bible I've been thumping.

Things that aren't bridged (or balanced, or differential drive) are singled ended, unbalanced, or "peter preskin like"

[Smeggy]

Given the apparent level of confusion, I wonder how many 'balanced' systems out there are either not or only partially balanced. That leads me to also wonder how much of the massive differences people say they hear are real and how much is expectancy. I imagine even partial balance would help somewhat, I've never heard a balanced system myself so can't say.

[Dusty Chalk]

Things that aren't bridged (or balanced, or differential drive) are singled ended, unbalanced, or "dusty chalk like"

How about 'NFB'? No, that looks too much like 'negative feedback'...

Given the apparent level of confusion, I wonder how many 'balanced' systems out there are either not or only partially balanced. That leads me to also wonder how much of the massive differences people say they hear are real and how much is expectancy. I imagine even partial balance would help somewhat, I've never heard a balanced system myself so can't say.

I suspect a lot of 'balanced' systems out there are not fully balanced. The benefits are real, as even without the ground reference, improvements are had, as long as something else doesn't get screwed up in the process -- like putting signal on the shield instead of tying the shield to ground.

[Dusty Chalk]

If I turn the volume up just one step the hum goes away, but if I turn off my gear I get the hum.

Actually, this makes me think it's an impedance mismatch, especially the first part. What's your gear, again?

[swt61]

Good ideas Nate. I'm off to work, but I will try that when I get home and let you know if it works. Thanks!

Nothing connected to pin 1 at the speaker end, so I guess I'll buy some 3-2 prong converters for the power cables and see what happens.

[swt61]

Well the 3-2 prong converters on the speaker power cords don't help either. As I stated, if I turn the volume dial to even 1 the hum goeas away, but after I shut down my gear it comes back, and I have to disconnect my speakers. It's kind of a pain. Any other ideas?

[Dusty Chalk]

Well, I asked what your setup was, but I'm thinking that you may want to put a small resister across the load that gets turned off. Value of resister depends on input and output impedance of the two devices that are connected. A switch (the equivalent of disconnecting your cables) would accomplish the same thing. That's assuming you don't mind always listening to whatever louder than whatever your minimum is.

What it seems like to me is going on is, is that when you turn your equipment off, it's effectively the same as turning the volume all the way down, input impedance-wise.

Just guessing.

[swt61]

Yes I think powering off the preamp (PS Audio PCA-2) is effectively the same as dropping the volume to zero.

[kevin gilmore]

Yes I think powering off the preamp (PS Audio PCA-2) is effectively the same as dropping the volume to zero.

maybe, maybe not. If there is no relay in the output circuit then the off impedance is very high. If there

is a relay in the circuit, then that could be where your ground loop is coming from.

[swt61]

I'm not sure how I'd determine this, you're talking to a complete simpleton when it comes to electronics. And would there be an easy fix in either case?

[Dusty Chalk]

I'm confused -- you're shutting off your preamp, which is part of...your speaker rig? And hearing buzz...in your headphone rig? Do me a favor, please, start over -- source, pre, amp, speakers, headphone amp, headphones, where do the two chains split, what are you shutting off. (I also want to look up input and output impedances, where the information is available.)

[swt61]

I'm confused -- you're shutting off your preamp, which is part of...your speaker rig? And hearing buzz...in your headphone rig? Do me a favor, please, start over -- source, pre, amp, speakers, headphone amp, headphones, where do the two chains split, what are you shutting off. (I also want to look up input and output impedances, where the information is available.)

Source:

HifiDIY CD Transport/Zapfiltered Twisted Pear Audio Opus DAC

Preamp:

PS Audio PCA-2

Amp/Speakers:

Paradigm Reference Active 20 (built in amps) and AV123 Rocket UFW-10 powered subwoofers (2)

Headphone Amp:

4 Channel Balanced β22 w/dual sigma22s in separate case

Headphones:

Modded AKG K340, Modded AKG K240 Sextette, Chocolate Donuts (Modded Yamaha YH-100 Orthodynamic drivers in custom wooden housings), Modded Sennheiser HD 580. All phones are cabled balanced

The chain is as follows...

The CD transport digital coax output is connected to the digital coax input of the Opus DAC. The Opus DAC balanced outputs are connected to the β22 balanced inputs. The β22 balanced outputs are connected to the PCA-2 balanced inputs. One pair of the PCA-2's balanced outputs are connected to the Paradigm Active 20's balanced inputs. The other pair of the PCA-2's balanced outputs are connected to the pair of AV123 Rocket UFW-10's balanced inputs.

I hear no buzz or ground loop through any of the headphones. I also hear no buzz or ground loop through the subwoofers. The only place I hear the buzz is through the speakers, and then it's only when the preamp is set on zero volume (where it automatically is set upon startup), or when I turn the preamp off (the speakers are always left on, but only power up upon receiving an input signal, same for the subwoofers).

The PS Audio PCA-2 does have some unique features, for example the active volume control. I'll link PS Audio's PCA-2 info page for reference.

http://www.psaudio.com/products/pca2_overview.asp

[Dusty Chalk]

Okay, so possible impedance mismatch -- only when off or volume set to zero -- between the pre and the active speakers.

(think think think...think think think)

Will wander off to read the stuff about the active volume control, I'm thinking it's that ("active" == "doesn't work when powered off" -- so, yeah, that's my reasoning).

One possibility would be to never turn off your pre. Does it have a mute? Does it buzz when you mute?

[swt61]

One possibility would be to never turn off your pre. Does it have a mute? Does it buzz when you mute?

It does have a mute, and it still buzzes with mute on when the volume is at zero.

[luvdunhill]

It does have a mute, and it still buzzes with mute on when the volume is at zero.

try unplugging one of the PCA-2's balanced outputs

[Dusty Chalk]

He does -- it doesn't buzz when he unplugs them (impedance == infinity).