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michel
2010-06-28, 09:41
Several weeks ago I connected my Transporter directly to the amp using XLR cables. I could not be happier with sound quality.
Only problem is headphone listening. As volume obviously has to be zero on Transporter neither cinch nor digital outs carry any signal.
Any ideas how connect a headphone amp?

garym
2010-06-28, 11:07
Several weeks ago I connected my Transporter directly to the amp using XLR cables. I could not be happier with sound quality.
Only problem is headphone listening. As volume obviously has to be zero on Transporter neither cinch nor digital outs carry any signal.
Any ideas how connect a headphone amp?

I would think volume on the transporter would be 100 not zero. In any case, my understanding is that the transporter is sending data out via the XRL cables AND the digital out at the same time. So you could run S/PDIF coax from S/PDIF out (or use optical out) to a headphone amp with S/PDIF input, and you'd be good to go.

michel
2010-06-28, 11:41
I cannot turn volume high cause Transporter is directly connected to amp! Volume has to be zero (-50db)for headphone listeníng.

Soulkeeper
2010-06-28, 15:58
Are you saying that the Transporter is connected directly to your Power amplifier (with no volume control on the amp), and your headphones are also connected to your Power amp?

michel
2010-06-29, 10:24
Transporter is connected directly to poweramp. Volume control is done by Transporter.
When listening to headphone you have to connect a headphone amp. Then you do not want sound from speakers - this is where the problem begins: if you turn volume to zero on Transporter you have zero output on all output digital included hence no sound from cans!

Phil Leigh
2010-06-29, 10:35
Transporter is connected directly to poweramp. Volume control is done by Transporter.
When listening to headphone you have to connect a headphone amp. Then you do not want sound from speakers - this is where the problem begins: if you turn volume to zero on Transporter you have zero output on all output digital included hence no sound from cans!

If you connect a TP directly to a power amp, you MUST have some form of analogue attenuation between TP and amp, to prevent a software bug in the TP from destroying your speakers. Also, you should NEVER have the TP volume control set lower than about 75-80 or you are losing sound quality.

Soulkeeper
2010-06-29, 11:20
Transporter is connected directly to poweramp. Volume control is done by Transporter.
When listening to headphone you have to connect a headphone amp. Then you do not want sound from speakers - this is where the problem begins: if you turn volume to zero on Transporter you have zero output on all output digital included hence no sound from cans!

Can you not disconnect the power amp when you connect the headphone amp? If so, problem solved.

If you want a setup that is easier to switch between speakers and headphones, you are going to need a pre amplifier or at least some sort of input and/or output switcher.

michel
2010-06-29, 11:47
If you connect a TP directly to a power amp, you MUST have some form of analogue attenuation between TP and amp, to prevent a software bug in the TP from destroying your speakers. Also, you should NEVER have the TP volume control set lower than about 75-80 or you are losing sound quality.

I have very revealing speakers but cannot hear any resolution loss when turning volume down. I was always thinking TP handled vol ctrl. in hirez.
I was not aware of a software bug threatening my speakers. Shouldn't be this bug be care taken of?

michel
2010-06-29, 11:53
Can you not disconnect the power amp when you connect the headphone amp? If so, problem solved.

If you want a setup that is easier to switch between speakers and headphones, you are going to need a pre amplifier or at least some sort of input and/or output switcher.

I am aware I could switch off the power amp during headphone sessions but that is a little inconvenient. On the other side turning on power amp and forgetting to turn volume down could at least disturb my neighbors.

andynormancx
2010-06-29, 12:08
I was not aware of a software bug threatening my speakers. Shouldn't be this bug be care taken of?

It isn't a particular existing bug. It is the threat of a currently unidentified or a future bug. No software is perfect and it is possible that a bug that we don't currently know about could cause the output on your Transporter to go to full volume.

You don't want to be plugging your Transporter into your power amp directly without some form of attenuation.

michel
2010-06-29, 12:41
It isn't a particular existing bug. It is the threat of a currently unidentified or a future bug. No software is perfect and it is possible that a bug that we don't currently know about could cause the output on your Transporter to go to full volume.

You don't want to be plugging your Transporter into your power amp directly without some form of attenuation.

'some form of attenuation' would mean a preamp anyway and this means sacrificing sound quality. Do yourself a favor and try a setup without preamp and you will know why I do NOT want to go back.

garym
2010-06-29, 13:20
'some form of attenuation' would mean a preamp anyway and this means sacrificing sound quality. Do yourself a favor and try a setup without preamp and you will know why I do NOT want to go back.

but evidently, you're already sacrificing sound quality by having "low" digital volume. Several technical folks on this forum have posted extensively on the effect of digital volume controls, especially at low volumes. Search for digital volume on the forum and you should find some of these threads. In particular look for John Swenson, Phil Leigh, IPHONE posts....

Soulkeeper
2010-06-29, 13:23
'some form of attenuation' would mean a preamp anyway

Not necessarily. You could always use a linear passive attenuator.


and this means sacrificing sound quality

Everything short of going to an acoustic live concert means a sacrifice of sound quality. When you use the Transporter's analog outputs it acts as a preamp anyway.

But if you're sure that you want as little circuitry as possible between your Transporter and your power amplifier, there's in reality only one option for you, and here it is:

When you want to use the headphones, power off and disconnect the power amp, and connect the headphone amp. Vice versa when you want to use the speakers.

So in light of this quote:


I am aware I could switch off the power amp during headphone sessions but that is a little inconvenient.

You need to choose between sound quality and concvenience. You can't have your cake and eat it too.

andynormancx
2010-06-29, 15:45
'some form of attenuation' would mean a preamp anyway and this means sacrificing sound quality. Do yourself a favor and try a setup without preamp and you will know why I do NOT want to go back.
If I had meant you have to use a pre amp I would have said that. As some one else pointed out you can use a completely passive attenuator which will have zero audible effect on the wave form arriving at your amp, apart from attenuating it obviously.

pski
2010-06-29, 17:42
It isn't a particular existing bug. It is the threat of a currently unidentified or a future bug. No software is perfect and it is possible that a bug that we don't currently know about could cause the output on your Transporter to go to full volume.

You don't want to be plugging your Transporter into your power amp directly without some form of attenuation.

S'Boxen are by their nature preamps. I routinely use two SBR's playing line-level directly to power amplifiers. This is exactly the use that is required to replace my older line-level home network (controlled by "tape-mon" settings and/or Sony Tapecorder selectors and populated with ferrite rings.)

As for "full-volume:" A high percentage of my CD's can be played flat-out without any issue with my amp and Reference 9 Kappa's. This is not classical/jazz boys and girls.. Vandersteens would be running into the horizon.

Based-on what I've read around here, unattenuated would be more accurate output.

Perhaps the TP runs it's own code and is therefore more susceptable to "Full Volume Syndrome" (from here to ever labeled FVS.)

P

Mnyb
2010-06-29, 18:30
Some wiki articles never goes out of style...

http://wiki.slimdevices.com/index.php/Connecting_directly_to_a_power_amplifier

http://wiki.slimdevices.com/index.php/DIY_passive_attenuation

http://wiki.slimdevices.com/index.php/Digital_Volume_Control_and_SNR

The gist of is passive attenuators ( 2(4) resistor per ch does not impact sound-quality, quite the opposite by providing correct gain scaling for the system) This improves SNR and protects amp from overloading by .

1. You playing music full tillt by mistake .

2. A very rare bug (or future bug) that do exist, that makes ip3k players output horrible noise at full volume, I had it in my SB3 once in 4 years, several people have reported it in in the TP, this extremely rare and has eluded all attempts to reproduce (xilink rest is probably proper or factory rest) .

Better gain scaling and SNR, the passive attenuation should be so that 100% volume on the squeezebox plays your quite records just as loud as you ever want to hear them .

pski
2010-06-29, 18:49
Some wiki articles never goes out of style...

http://wiki.slimdevices.com/index.php/Connecting_directly_to_a_power_amplifier

http://wiki.slimdevices.com/index.php/DIY_passive_attenuation

http://wiki.slimdevices.com/index.php/Digital_Volume_Control_and_SNR

The gist of is passive attenuators ( 2(4) resistor per ch does not impact sound-quality, quite the opposite by providing correct gain scaling for the system) This improves SNR and protects amp from overloading by .

1. You playing music full tillt by mistake .

2. A very rare bug (or future bug) that do exist, that makes ip3k players output horrible noise at full volume, I had it in my SB3 once in 4 years, several people have reported it in in the TP, this extremely rare and has eluded all attempts to reproduce (xilink rest is probably proper or factory rest) .

Better gain scaling and SNR, the passive attenuation should be so that 100% volume on the squeezebox plays your quite records just as loud as you ever want to hear them .

If #2 is true, it seems the risk is very low percentage given the few who can afford and then buy transporters.

By the way, a good deal of the time S'boxen don't play the music loud enough to listen. (This with the player settings for such set as disabled.)

P

Phil Leigh
2010-06-29, 22:56
'some form of attenuation' would mean a preamp anyway and this means sacrificing sound quality. Do yourself a favor and try a setup without preamp and you will know why I do NOT want to go back.

No - you don't need a "pre-amp", just some in-line attenuation. You could have used the built-in attentuators in the TP but they are on the coax (rca) outs. You are using the XLR's, you need something like these:
http://www.audioaffair.co.uk/index.php?act=viewProd&productId=3593&md=5e43f74d3cea73499bfcf888755cfa36

These will have much less effect on sound quality than running your TP volume control below 50!

Phil Leigh
2010-06-29, 23:05
If #2 is true, it seems the risk is very low percentage given the few who can afford and then buy transporters.

By the way, a good deal of the time S'boxen don't play the music loud enough to listen. (This with the player settings for such set as disabled.)

P

This issue can affect all software players, not just the TP!

If your music isn't loud enough when the SB and amp are on full, you need a bigger amp (much bigger - say 10x bigger in terms of RMS watts) or more efficient speakers (a much more economical solution) or more sensitive ears (probably not an option...)

cliveb
2010-06-29, 23:06
Also, you should NEVER have the TP volume control set lower than about 75-80 or you are losing sound quality.
I think Phil is being a little over-cautious here. For sure, excessive digital attenuation in the TP does sacrifice a bit of S/N ratio. But let's keep things in perspective. If you have appropriate passive attenuation installed such that the TP's volume control is up around 90% or so for critical listening, then using lots of digital attenuation for casual listening isn't going to be a problem - the noise floor remains below the threshold of hearing. Running lots of digital attenuation is only a problem if you follow it with lots of analogue gain.


'some form of attenuation' would mean a preamp anyway and this means sacrificing sound quality. Do yourself a favor and try a setup without preamp and you will know why I do NOT want to go back.
I'm with you, Michel - I run my TP directly to power amps with XLR. I would never contemplate inserting an active preamp in the signal chain. But as others have pointed out, you can use passive attenuation without loss of quality. (My setup has 13dB passive attenuation).

But let's get back to Michel's original problem: conveniently running headphones from the TP. A couple of possibilities occur to me:

1. Wasn't there an older firmware release where it was possible to specify variable analogue output while keeping the digital output fixed at 100%? I believe this facility was sacrificed to make room for some later feature (digital FX loop, perhaps?) Maybe Michel could track down this older firmware and use a headphone amp with SPDIF input. This isn't practical if he wants to use Squeezebox Network (or whatever it's called this week), of course.

2. It would be fairly easy to build a passive switchbox that takes whatever TP outputs are used, feeds them to the appropriate devices (ie. power amps, headphone amp) and has switches to connect/disconnect as required.

michel
2010-06-29, 23:16
@cliveb
Having digital outs constantly at full volume would be great but as I apply room correction over digital loop I do not think it would work for me.
I am considering buying a Touch for headphone listening.

Phil Leigh
2010-06-29, 23:17
@cliveb
Having digital outs constantly at full volume would be great but as I apply room correction over digital loop I do not think it would work for me.
I am considering buying a Touch for headphone listening.

What are you using for DRC?

Mnyb
2010-06-30, 00:18
Touch + a good headphone amp, would probably be excellent.

Retain the 24/96 capacity and lets you use the touch interface for real .

michel
2010-06-30, 00:48
What are you using for DRC?

Behringer DEQ2496. Excellent value for money (~120USD)!

Phil Leigh
2010-06-30, 01:39
The TP digital volume control (and ReplayGain if you are using that) is before the S/PDIF FX loop, so you are sending a variable level to the DRC when you raise/lower the TP volume.

DRC normally lowers the level even further (to buy some headroom to avoid clipping on boosted freq dips).

I know Cliveb will say I am being ultra-cautious, but I believe that keeping the digital level high out of the FX send into the DRC will give better quality results.

Doesn't the DEQ have a level control? Worth experimenting to see if there is a noticeable difference.

I run my digital at 100% (except for replaygain - -12dB max) into my TACT. The TACT further cuts level by about 6dB to gain the headroom in needs in my setup/room.

michel
2010-06-30, 03:28
[QUOTE=Phil Leigh;558922]The TP digital volume control (and ReplayGain if you are using that) is before the S/PDIF FX loop, so you are sending a variable level to the DRC when you raise/lower the TP volume.
QUOTE]

This is in fact annoying. As far as I remember volume control was on the digital output (back end of loop) in first firmwares. Why was that changed?

Phil Leigh
2010-06-30, 05:40
[QUOTE=Phil Leigh;558922]The TP digital volume control (and ReplayGain if you are using that) is before the S/PDIF FX loop, so you are sending a variable level to the DRC when you raise/lower the TP volume.
QUOTE]

This is in fact annoying. As far as I remember volume control was on the digital output (back end of loop) in first firmwares. Why was that changed?

I could be wrong! - but the digital level control in firmware operates on the data within the Xilinx chip which (I thought) is before it goes to the s/pdif send transmitter...

As I said, I could be wrong... probably am.

Phil Leigh
2010-06-30, 06:44
http://forums.slimdevices.com/showpost.php?p=264853&postcount=19