[Ethereal Sound]

  My Pulse Sfi, gets warm, but not HOT to the touch with hours of music playback. I was worried about heat dissipation, compared to my Geek Out 1000. The Pulse Sfi, gets (Warm, NOT HOT.) You still need to keep the home furnace on.

That's a relief.

 

[nudd]

Yeah, same here.

Here I am, today finally realizing that balanced cable gets you twice the power with the same amp and that the balanced out on the Xfi is the same output power as the Sfi and I regret not getting a Xfi, you know, just in case

But if you don't run balanced cables then I think the sfi is definitely the better choice as the outputs get summed
So theres nothing to regret really.

I personally am highly doubtful that at the sort of cable lengths for headphone cables there should be any perceivable difference ....

 

[flipper2gv]

But if you don't run balanced cables then I think the sfi is definitely the better choice as the outputs get summed
So theres nothing to regret really.

I personally am highly doubtful that at the sort of cable lengths for headphone cables there should be any perceivable difference ....

 
No the outputs don't get summed up, well that's what the technical support guy told me by email. That's what he told me:

"I looked through the power specifications for all Geek Pulse units again, and from what I have found, the Sfi has the same power output as the Xfi.
 
The only difference is that the Xfi balanced headphone output has twice the power of the single-ended headphone output of the Sfi (and the Xfi)."
 
and
 
"The only information I have regarding output impedances and voltages for the Sfi are the following:  
Line Out (RCA) Output Impedance: 47 Ohm
Line Out (RCA) Output Voltage: 2 Vrms Max Variable
 
Headphone (1/4”) Output Impedance: 0.47 Ohm
Headphone (1/4”) Output Voltages: 3 Level Gain - 1.8 Vrms, 3 Vrms, 7 Vrms"

 
When you consider these specs for the Xfi:

1. HP Balanced output voltage and impedance: 3.5V / 6V / 13.8V switchable (0.9 Ohm flat in 20~20K Hz range) via dual mono headphone output amplifier

1. HP Single- ended output voltage and impedance: 1.8V / 3V / 6.8V switchable (0.47Ohm flat in 20~20K Hz range)

You're left wondering why there isn't a dual mono output amp in the Sfi too. Maybe because it is single ended, but that's not what I got from the description when I put down my money.

 

[Maelob]

funny received my LPS box yesterday and then received another email indicating that another LPS was shipping. I contributed to one. hopefully the new shipment is my 2g cable. anyway just opened a ticket. though it was kind of ironic given some of the shipping issues. if somebody would like an Lps please pm me.

 

[nudd]

No the outputs don't get summed up, well that's what the technical support guy told me by email. That's what he told me:


"[COLOR=212121]I looked through the power specifications for all Geek Pulse units again, and from what I have found, the Sfi has the same power output as the Xfi.[/COLOR]
[COLOR=212121] [/COLOR]
[COLOR=212121]The only difference is that the Xfi balanced headphone output has twice the power of the single-ended headphone output of the Sfi (and the Xfi)."[/COLOR]
[COLOR=212121] [/COLOR]
[COLOR=212121]and[/COLOR]
[COLOR=212121] [/COLOR]
[COLOR=212121]"The only information I have regarding output impedances and voltages for the Sfi are the following:
[COLOR=212121] [/COLOR]
[COLOR=212121]Line Out (RCA) Output Impedance: 47 Ohm[/COLOR]
[COLOR=212121]Line Out (RCA) Output Voltage: 2 Vrms Max Variable[/COLOR]
[COLOR=212121] [/COLOR]
[COLOR=212121]Headphone (1/4”) Output Impedance: 0.47 Ohm[/COLOR]
[COLOR=212121]Headphone (1/4”) Output Voltages: 3 Level Gain - 1.8 Vrms, 3 Vrms, 7 Vrms"[/COLOR]
[/COLOR]

When you consider these specs for the Xfi:

1. HP Balanced output voltage and impedance: 3.5V / 6V / 13.8V switchable (0.9 Ohm flat in 20~20K Hz range) via dual mono headphone output amplifier
   

1. HP Single- ended output voltage and impedance: 1.8V / 3V / 6.8V switchable (0.47Ohm flat in 20~20K Hz range)
   

You're left wondering why there isn't a dual mono output amp in the Sfi too. Maybe because it is single ended, but that's not what I got from the description when I put down my money.

I initially put my money down for a pulse s as well but i could have sworn they said the output on the pulse s was summed. It was meant to be the X version but for single ended use?

Another unsavoury habit of LHL is the reuse of the same page for multiple campaigns and deletion of existing information...

 

[krikor]

   
No the outputs don't get summed up, well that's what the technical support guy told me by email. That's what he told me:

"I looked through the power specifications for all Geek Pulse units again, and from what I have found, the Sfi has the same power output as the Xfi.
 
The only difference is that the Xfi balanced headphone output has twice the power of the single-ended headphone output of the Sfi (and the Xfi)."
 
and
 
"The only information I have regarding output impedances and voltages for the Sfi are the following:  
Line Out (RCA) Output Impedance: 47 Ohm
Line Out (RCA) Output Voltage: 2 Vrms Max Variable
 
Headphone (1/4”) Output Impedance: 0.47 Ohm
Headphone (1/4”) Output Voltages: 3 Level Gain - 1.8 Vrms, 3 Vrms, 7 Vrms"

 
When you consider these specs for the Xfi:

1. HP Balanced output voltage and impedance: 3.5V / 6V / 13.8V switchable (0.9 Ohm flat in 20~20K Hz range) via dual mono headphone output amplifier

1. HP Single- ended output voltage and impedance: 1.8V / 3V / 6.8V switchable (0.47Ohm flat in 20~20K Hz range)

You're left wondering why there isn't a dual mono output amp in the Sfi too. Maybe because it is single ended, but that's not what I got from the description when I put down my money.

 
I thought that the "summing" referred only to the fact that Pulse S utilizes dual DAC chips, one for each channel, like the Pulse X (whereas the regular Pulse has a single 9018K2M). The balanced output from each DAC chip is then summed prior to the single-ended analogue output stage, which is essentially the same as the Pulse.

 

[wingsounds13]

There seems to be some confusion of terms here between stereo, dual mono, balanced, unbalanced and summing.

The complementary terms are:
Stereo / Dual Mono
Balanced / Unbalanced (or Single Ended)

Dual mono and balanced have no equivalency.

In most audio gear it is common for the two channels to use separate sections of a single part such as an opamp. Dual mono simply means that the two stereo channels are processed as two totally separate signal chains with no electronic components in common. This increases the signal isolation between the stereo channels and can slightly improve the signal quality.

Balanced means that the signal chain is processed with a + signal and a - signal that are the same but with opposite polarities and they are referenced against each other. Unbalanced is just a + signal that is referenced against ground.

Summing is the process of taking the balanced signals and summing them together through a stage that produces a single ended output that is the sum of the two balanced signals. When generating an unbalanced output such as a line out or headphone output from a component that uses balanced signals internally there are two options. One is to simply take the + side of the balanced signals and reference it against ground. The other - and usually better way is to do electrical summing of the balanced signals to generate the single unbalanced signal that is referenced against ground. This summing is done BEFORE the single ended output buffer or single ended headphone amp.

In the case of the Pulse S and X, as I understand it they handle the balanced and unbalanced signals slightly differently.

In the Pulse S, the balanced dual mono signals coming from the DAC chips and through its I/V conversation stage are electrically summed before being sent to the unbalanced line out buffer and headphone amp. This is the technical advantage of the Pulse S. It is dual mono and internally balanced up until the output stages and the balanced signal is properly electronically summed when being converted to unbalanced.

In the Pulse X, the signals are balanced all the way to the outputs. The unbalanced line out and headphone outputs are simply the + balanced signal referenced against ground. To have a properly summed headphone output would require having two headphone amps, one balanced and the other unbalanced. While this would be ideal, it is not practical. On the other hand, I do NOT understand why the line out is not summed. As I understand it, they did go so far as to use separate buffers for the balanced and unbalanced line outputs. If my memory is correct here, it is much better than many equipment manufacturers who simply tap the + side of the balanced line out buffer to make an unbalanced output.

As I answered elsewhere, the unbalanced headphone output of the base Pulse, X and S all have the same output power because they all have the same single ended output voltage. The balanced output of the Pulse X has more power because it has the total voltage of both the + and - balanced lines, twice the output voltage is available across the balanced signals as opposed to the single ended / unbalanced signal.

J.P.

 

[goaliedad39]

Well I must apologize to everyone for providing misleading information.  A few days ago I said that I backed the Pulse xfi on 12/8/13 and that I received info from LH that my unit has shipped so I wanted to let people know so they may judge where they were in the que.  I received my package from LH today, was very excited to open it only to discover that it was the LPS4 that I backed in the forever campaign and paid off at end of March.  I double checked the email from LH and it actually never states what product was shipped.  I just assumed it was the Pulse xfi.  I'm sorry for misleading people and very disappointed it wasn't my Pulse.  Checked LH's tracking page and it still just say's I'm in the que with nothing shipped.  So no idea where I stand or when I can expect it.  Sorry.
 

 

[greenkiwi]

The outputs on the Sfi are summed.  They take the +/- from the DAC and use both to create the + signal for each channel.  In theory this drops the noise floor a bit further.

 

[greenkiwi]

But that doesn't mean that you are getting twice the voltage output.  I think that the rails end up being a function of the input voltage going into the amp.  With a 12V power supply (and no DC step ups), you can only have +-7Vrms output.  With balanced, when you have +7, you also have -7, so you have a 14V swing.

 

[wingsounds13]

@greenwiki, that is not so. (edit.. on rereading your posts I discovered that I had conflated your posts and others, your posts are correct.). When you are using the unbalanced headphone output you only have +-7V referenced against ground. This is a 14V swing, but only ever 7V from the other connection on the headphone transducer. When using the balanced output you have a +-7V line referenced against a complementary -+7V line producing a total of 14V difference across the headphone transducer.

The summing that is being referred to is taking the + and - balanced signals and putting them through a summing amplifier. Putting them through a summing amplifier produces a single unbalanced signal of the same maximum voltage as each balanced signal referenced against ground. This can improve the S/N by 3dB, but does not increase the output voltage or power of the single ended / unbalanced output.

J.P.

 

[nudd]

Thanks for clearing that up guys. I only had a vague recollection of all those discussions but in summary it seems it is correct to say that the op shouldn't have any regrets if the intended use is always single ended mode because those outputs should give theoretically better performance than the xfi which only takes the positive on each output when run in single ended mode. Right?

 

[flipper2gv]

Thanks for clearing that up guys. I only had a vague recollection of all those discussions but in summary it seems it is correct to say that the op shouldn't have any regrets if the intended use is always single ended mode because those outputs should give theoretically better performance than the xfi which only takes the positive on each output when run in single ended mode. Right?

 
Same here.
 
It was a great explanation wings, and it made me again confident I did choose well since I don't have any balanced headphones as of right now.

 

[krikor]

  Does anyone know if the lhlabs.com/tracking portion of their website is still being used? Will my tracking number show up there when/if new products ship?

You should receive an email directly from LH Labs with a tracking number. I just did (yay!) but the tracking number is not listed on my tracking page. Perhaps it takes some time to appear.
 
EDIT (5/15/2015, 8:20 EST): OK, now it is appearing in the LH Labs tracking system... I just needed to be a bit more patient. Still only listed as "pre-shipment" in USPS system though its been there a couple days now. Was hoping it would make it for my birthday this weekend (though I was hoping for the same last year), but it will just have to be a belated gift

 

[miceblue]

Balanced means that the signal chain is processed with a + signal and a - signal that are the same but with opposite polarities and they are referenced against each other. Unbalanced is just a + signal that is referenced against ground.

Technically speaking, balanced connections have to do with equal-impedance wires such that any interference affects both equally. If you have impedance mis-matching, the advantage of balanced signalling becomes less.

Differential signalling is the +/- signals that you refer to.
http://en.wikipedia.org/wiki/Balanced_audio#Differential_signalling

Signals are often transmitted over balanced connections using the differential mode, meaning the wires carry signals of opposite polarity to each other (for instance, in an XLR connector, pin 2 carries the signal with normal polarity, and pin 3 carries an inverted version of the same signal). Despite popular belief, this arrangement is not necessary for noise rejection. As long as the impedances are balanced, noise will couple equally into the two wires (and be rejected by a differential amplifier), regardless of the signal that is present on them.

From the latest Pulse update on Indiegogo:

We were excited to push push push product out, but we had PCB impedance issues from PCB fabrication factory and we change to a better one

And now the problem of "impedance issues" becomes clear in respect to what balanced lines are by definition, equal-impedance lines.