[rodbac]

Quote:

Finally, a post in this thread that makes sense and sounds legit. Thanks!

Sounds legit to who??

It "sounded" legit to you because it seemed to be backing you up and didn't really say anything meaningful, then tossed in a couple of made-up terms ("type one" and "type two") to boot.

To be fair, I'm still trying to plow through the vast pages of bull**** and see exactly what's being claimed with these systems.

If anyone has links to legitimate discussions of what's going on in this 'pseudo-balanced' system, I'd appreciate seeing them.

[edit]

I'm reading Tim D's links...

[edit 2]

First link said nothing at all. It explained an unbalanced connection in detail, then said that with a differential amplifier, the usual ground is powered with an equal signal of opposite polarity (which we already knew) and then detailed precautions for using that setup.

On to read the second, hoping for some sense to be made of this...

 

[Tim D]

This is nothing new and nothing that you can't find a wealth of information on if you look up 'bridged' or 'differential' vs single-ended, etc.

I have a no-nonsense stereo amp that can switch to bridged mode - mono mode with greater current output. Nothing 'magical' or new about it.

http://www.rane.com/par-b.html#BTL
Look up 'BTL'

One more
http://www.dckits.com/app1.htm

 

[dip16amp]

Quote:

Originally Posted by rodbac Sounds legit to who?? It "sounded" legit to you because it seemed to be backing you up and didn't really say anything meaningful, then tossed in a couple of made-up terms ("type one" and "type two") to boot. To be fair, I'm still trying to plow through the vast pages of bull**** and see exactly what's being claimed with these systems. If anyone has links to legitimate discussions of what's going on in this 'pseudo-balanced' system, I'd appreciate seeing them. [edit] I'm reading Tim D's links... [edit 2] First link said nothing at all. It explained an unbalanced connection in detail, then said that with a differential amplifier, the usual ground is powered with an equal signal of opposite polarity (which we already knew) and then detailed precautions for using that setup. On to read the second, hoping for some sense to be made of this...

The "type one" and "type two" voltage level terminology comes from balanced interface device standards which specify whether it has a reference to ground or is floating with no reference to ground.

 

[Dreamslacker]

Quote:

Originally Posted by taylor afaik (everything I saw about electronics is afaik, I'm not an EE) there are two kinds of balanced. First is the balanced signal, where it eliminates RFI and EMI. I really have no idea how this works.

From my computer device knowledge (mainly SCSI because I use it):
A differential device is concerned with the voltage difference between the hot and cold signals. It's not concerned with the voltage difference between hot-ground and cold-ground.
Hence, a twisted pair wire is used to transmit the hot and cold signal. Since any interference is applied to both hot and cold, the voltage difference is the same.
ie. Hot = +2v, Cold = -2v, Difference = 4v.
Interference adds 0.1v to both:
Hot = +2.1v, Cold = -1.9v, Difference is still 4v.

 

[saint.panda]

Sorry for the perhaps confusing thread title but it's just as ayt999 said about the intended direction of this thread. Maybe using the term "differential" instead of "balanced" would have been more appropriate and less misleading.

Tim D, those links were excellent, especially the extremely informative rane.com site.

Quote:

Originally Posted by Dreamslacker From my computer device knowledge (mainly SCSI because I use it): A differential device is concerned with the voltage difference between the hot and cold signals. It's not concerned with the voltage difference between hot-ground and cold-ground. Hence, a twisted pair wire is used to transmit the hot and cold signal. Since any interference is applied to both hot and cold, the voltage difference is the same. ie. Hot = +2v, Cold = -2v, Difference = 4v. Interference adds 0.1v to both: Hot = +2.1v, Cold = -1.9v, Difference is still 4v.

Common mode rejection (CMR).

From rane.com:
A common-mode signal drives both inputs with the same polarity. It is the job of a well designed balanced input stage to amplify differential signals, while simultaneously rejecting common-mode signals. Most common-mode signals result from RFI (radio frequency interference) and EMI (electromagnetic interference, e.g., hum and buzz) signals inducing themselves into the connecting cable. Since most cables consist of a tightly twisted pair, the interfering signals are induced equally into each wire. The other big contributors to common-mode signals are power supply and ground related problems between the source and the balanced input stage.

For those interested, Tyll Hertsens from Headroom raises slew rate, shared ground and power in regards to the Blockhead vs. Max: http://www6.head-fi.org/forums/showt...68591#poststop

From what I gathered so far:
Differential Output->
1a. half impedance seen by each channel -> double current (I)
1b. Same voltage swings in both channels but out of phase (180 degrees), '+' and '-', instead of '+' and 'ground' for single-ended -> double voltage (U)
1a & 1b -> P(ower) = U x I -> 4-times power (which in reality apparently never happens due to restraints from the power supply to provide the required current at a given voltage, thermal reasons or current restraints from the ICs used in the amp)
2. Slew rate (in audio) = 2 Pi x Fmax x V-peak; Fmax is constant because f=1/T and T is constant for single-ended or differential in a given scenario. V is doubled -> Double slew rate
(I hope this is all correct...)

Other virtues about differential drive amps include: Lower distortion, which is quite a confusing issue and I'll need to read up on this. Apparently, there's a difference between single differential and dual differential, which have different distortion behaviours. Not sure which of these two would apply here.
From an old post by Kevin Gilmore, it says that balanced amps (differential output) have "3db less THD due to matching of slew rates." but also "3db more signal to noise ratio if driven balanced." I think it's 3db because of double everything. Another obvious disadvantage is that you basically need 4 entire amplifiers, 2 per channel, which can be quite expensive...

Anyway, it seems that there's much more to it than just "more power = awesome" (which according to Tyll Hertsens's post in the link above does not make the big difference) or "no shared ground = awesome" (again, Tyll Hertsens post in regards to the PPA). So far the slew rate issue seems to be of most interest but reading through various diy threads here, mostly about the PPA, it appears that there's even more to it than just "double slew rate = awesome". For example, in the shared ground issue it seems that the PPA uses a methology, which avoids the noise floor issue common in "normal" single-ended amps. So it would make sense to me that there's far more out there, which can't be reduced to these concise yet simplifying statements (handy for interested audiophiles like me but not necessarily meaningful). For instance, there are threads on diyaudio mentioning that slew rate is more of an end condition to distortion rather than the cause. Of course, this is completely taken out of context and should only point out the complexity of this issue. Perhaps posting a thread about this topic in diyaudio would lead to some interesting input.

What I have learned from this thread and the following research is that the implementation of a design is more significant than a fundamental discussion on differential vs. single-ended (or maybe not). So due to lack of technical understanding, I'll leave it be. Hopefully, I'll be able to compare two highend SS amps, a balanced Dynamight to a non-balanced dual mono Headcode to at a mini-meet in less than two months time. Technical discussions, as attractive as they might be, have only little meaning if a they're thrown of by practical listening tests. But in the end, this is more due to the fact that I don't really understand all this technical verbiage

In any case, don't mind me and keep the ideas coming. This has been a very informative thread so far!

 

[taylor]

Think it's safe to say this - if you have a push/pull amp, give it a try, see which you prefer (and be sure to tell us). If your amp is single-ended, no big deal.

Dreamslacker - good explaination.

edited because I can't spell.

 

[rodbac]

Quote:

I have a no-nonsense stereo amp that can switch to bridged mode - mono mode with greater current output. Nothing 'magical' or new about it.

Sorry- I realized it wasn't "magical" (and didn't mean to imply such). If I hadn't, I wouldn't have bothered taking part in the discussion.

I haven't been around for TOO long, but from all I've read on the subject, this is a fairly new concept to the "audiophile" world (10-15 years or so as a 'fad' (no offense)?), if not electronics, due, as saint.panda's (et al) post illustrates, to it's inherent drawbacks (increased cost, more circuitry in the loop, etc).

Anyway, there's a lot of information to research and mull over on slew rates as they relate to this... off to read.

 

[Mastergill]

Quote:

Originally Posted by saint.panda ... Hopefully, I'll be able to compare two highend SS amps, a balanced Dynamight to a non-balanced dual mono Headcode to at a mini-meet in less than two months time. ...

saint.panda, for a fair comparison i hope the Headcode amp is totally dual mono up to the phone output with two 1/4" mono jack.

One big advantage with all balanced headphone amp is the totally separated ground for the Left and Right channel at the headphone output. But that can be done with almost all single ended amp, especially those with a real dual mono design, you have to put two mono jack instead of one stereo jack.
Of course the headphone need to be rewired with 4 separated leads, you're not sharing common ground for Left and Right and it's easy to understand this will give you a better, more stable soundstage.

Now about driving the phone in real balanced mode, i have to eat my words, yes it's possible, the ground is left floating and the transducer only 'see' the positive and negative of the balanced signal. At first i thought this is a really weird way of feeding an headphone (or speaker) but now i can understand some benefit, the driver is pushed and pulled with authority, so maybe you can have a better control of the driver's membrane movement.

OTOH with single ended operation you keep the signal integrity, it's not splited.

In the speakers world, as far as i know, almost nobody feed his/her speakers in truly balanced mode, at least for passive speaker. It would be interesting to see if some active pro monitor use this method, as they are all dealing with balanced input it should be far more easy to implement than with passive speakers.

IMO, but i'm not EE, true balanced operation can be only usefull if you have very inefficient, hard to drive speakers that need LOT of current and/or voltage.

I don't see the point with headphone, they don't need extraordinary level of 'juice'. By example a 300B can give all the voltage swing necessary and more, while keeping a good signal integrity. IME, simple solution has always been better with music reproduction.

 

[saint.panda]

Quote:

Originally Posted by Mastergill saint.panda, for a fair comparison i hope the Headcode amp is totally dual mono up to the phone output with two 1/4" mono jack.

Mastergill, the amp does have two jacks but both being stereo. However, that's an interesting idea you have brought up and I'll talk to the amp builder about the possibility/advantages/disadvantages of using two mono jacks.

 

[Tim D]

Of course it isn't cost-effective...you basically have to have twice the amp for pretty much twice the power (theoretically 4x, but practically not much more from 2x from what most sources say). And then there are considerations of if you even need twice the power. However the original topic seemed to be about technical benefits and from what I can tell, Tyll's explanation of benefits is not far off from what is cited with textbook regularity in a variety of independent sources. Of all the audiophilia marketing that exists out there, I'd say it would rate pretty low in BS factor. In fact he pretty much states the benefits increase as you ramp the volume up, and the converse of that is pretty obvious as well. And it is pretty obvious what the practical drawbacks are when I convert my stereo amp into mono-bridged...it translates to 2x the cost to basically get 2x more power.

But I find it curious how we try and divert the flow of discussion from 'technical' benefits to focusing on end practicality and drawbacks to save face from the fact that there was a hypothesis made for which there were no technical benefits and any such claims were absolute BS. But hey if you can't win that battle, just change the topic to practicality and cost-effectiveness and stand behind a new flag and be the champion of non-bias and truth again.

But yes I am sure no one notices the shift in platform from claiming no theoretical or technical benefits to no practical ones.

I have no qualms with people that attempt to think more objectively or scientifically, but too often I see bias and presumptions and an attempt to just search for qualifying data to support presupposed claims which is really no different than the world of 'audiophile' subjectiveness with their bias and presumptions and their attempts of qualifying data. I have less aversion to the latter quite simply because they rarely claim to stand behind any objective principles.

Not that there isn't a wealth of good science formed out of false hypothesis or top-down approaches (and plenty of bad science from sticking to presuppositions), but for it to be used mainly as a vehicle to shake up the status quo. Its like watching the Jerry Springer equivalent of a kids science show. But for those that get their jollies off doing so, I'd have to say you'd probably be more successful sticking with the low hanging fruit.

 

[rodbac]

Tim,

Once it was established that this type of setup isn't really a balanced configuration (which was a valid point, in case you missed it), but rather 'pseudo-balanced' (using some of the characteristics of a balanced system), I don't really see anyone calling it BS.

We're all proud of you for having known about this stuff previously, but it's evident that there isn't a wealth of information out there on it.

Judging by your registration date and position as a respected moderator, you should know very well that threads on semi-complicated subjects very often evolve as certain facts become established.

As such, it's not unusual, and not deserving of your criticism, for this discussion to have evolved from "is this a lot of the same 'audiophool' bullsht we always read about" to "how does it work and is it worth me pursuing".

 

[Tim D]

*edit* timoteous cited a reference to psuedo-balanced that has little to do with either the Gilmore Balanced or Headroom Blockhead. If you re-read it, it claims that true balanced operation basically requires practically twice the components, etc. It is pretty obvious to most people that both the Gilmore Balanced and Headroom Blockhead have this and its not just XLR inputs converted back into unbalanced, which is what the 'psuedo-balanced' was refererring to. Those amps are balanced/differential period and require special recabling of headphones (much like the Sharp push-pull miniplug interface). There is nothing 'fake' or 'psuedo' about it in regards to those amps.

Finally this unbiased reference that talks about hype in balanced/differential amps comes from a hi-end pre/amp manufacturer which qualifies the benefits of single-ended design qualified by good ol'fashioned subjective experience.

 

[saint.panda]

Quote:

Originally Posted by Tim D Of course it isn't cost-effective...you basically have to have twice the amp for pretty much twice the power (theoretically 4x, but practically not much more from 2x from what most sources say). And then there are considerations of if you even need twice the power. However the original topic seemed to be about technical benefits and from what I can tell, Tyll's explanation of benefits is not far off from what is cited with textbook regularity in a variety of independent sources. Of all the audiophilia marketing that exists out there, I'd say it would rate pretty low in BS factor. In fact he pretty much states the benefits increase as you ramp the volume up, and the converse of that is pretty obvious as well. And it is pretty obvious what the practical drawbacks are when I convert my stereo amp into mono-bridged...it translates to 2x the cost to basically get 2x more power. But I find it curious how we try and divert the flow of discussion from 'technical' benefits to focusing on end practicality and drawbacks to save face from the fact that there was a hypothesis made for which there were no technical benefits and any such claims were absolute BS. But hey if you can't win that battle, just change the topic to practicality and cost-effectiveness and stand behind a new flag and be the champion of non-bias and truth again. But yes I am sure no one notices the shift in platform from claiming no theoretical or technical benefits to no practical ones. I have no qualms with people that attempt to think more objectively or scientifically, but too often I see bias and presumptions and an attempt to just search for qualifying data to support presupposed claims which is really no different than the world of 'audiophile' subjectiveness with their bias and presumptions and their attempts of qualifying data. I have less aversion to the latter quite simply because they rarely claim to stand behind any objective principles. Not that there isn't a wealth of good science formed out of false hypothesis or top-down approaches (and plenty of bad science from sticking to presuppositions), but for it to be used mainly as a vehicle to shake up the status quo. Its like watching the Jerry Springer equivalent of a kids science show. But for those that get their jollies off doing so, I'd have to say you'd probably be more successful sticking with the low hanging fruit.

I thought the topic still is about the technical benefits. I don't know who you are referring to with this post but anyway: As a scientist (or rather ongoing scientist) myself, the last thing I want to do is to shift the topic from a scientific to a practical discussion. That comparing amp thing was just the end of my post. Also, I was stating the fact that I personally cannot keep up with the amount of information provided, hence raising the point of implementation vs. fundamental discussion, which I still consider important. About the cost of an amp being higher (b/c 4 amps in total), that was just a side-point taken out of the context of the whole post.
Am I trying to defend a cause? Certainly not because I'm just as curious as anybody else reading this thread. And what battle are we fighting again?
What I was trying to say is that the scientific date is there (which I listed in my post) but due to lack of technical understanding I cannot interpret them to an extent (due to lack of information on the exact implementations) that I can say "balanced is better because ... ". In fact, after this discussion, I do wish I could afford the Blockhead because it really seems that driving headphones balanced has its advantages. According to Tyll Hertsens postin the Max vs. Blockhead thread, it does appear that the only difference between these two amps is that the Blockhead is "basically" 2 Max amps glued together driving headphones in differential mode.

Anyway, these subtleties aside, please carry on with the technical discussion.

 

[saint.panda]

Edit. Had to take the chill pill due to a misunderstanding my part

Same for the post above but editing it out now would be cheap.

 

[Tim D]

Hi panda,

No harm intended. Keep the discussion going and keep it technical as you have been doing. You haven't been one to throw any chairs. I was referring to those that for whatever motivations questioned the existance of true differential balanced Gilmores or Blockheads and that they must perform some sort of tom-foolery to work because headphones just can't be operated that way (i.e. but that would mean they would require special cabling...OH WAIT THEY DO!).

Getting back to topic, I'm wondering about the merits of just using a better plug like 4-pin XLR and dual-mono operation myself. I'm not a fan of TRS plugs.