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Powering 600 Ohm DT880s with Focusrite Saffire Pro 40

post #1 of 15
1/30/12 at 2:27pm
Thread Starter 

Hi. Firstly thanks to Zombie for his Beyer thread!

 

After much research I have decided to go with DT880s over DT990s (despite them being equivalent to $109 more where I live) because I am a sound engineer/producer and need the neutrality.

 

At the moment I cannot afford to get a specific headphone amp and will therefore use my Focusrite Saffire Pro 40 interface.

 

My question is whether it will be sufficient to drive the DT880 600 Ohm model (as opposed to the 250 Ohm - my other choice).

 

The only stats I can find are:

 

 

Headphone Outputs
• Frequency Response 20Hz-20KHz +/- 0.1dB
• SNR 109dB "A"
• DNR 109dB "A"
• Maximum Output into 32R +12.4dBu (+10.2dBV)
• Power into 32R 250mW
• Output Impedance < 7Ohms
• Load Impedance > 24Ohms

 

 

As well as some blurb on the FAQ page, the key parts being:

 

"A decision was made that the headphone drivers should never, under any circumstances, clip internally. We felt that accurate monitoring was a mandatory requirement for such a product. In any analogue circuit there is a maximum headroom, and our circuit is optimised to meet this headroom at full scale, but never exceed it.

As a result, whilst Saffire is louder than most soundcards (indeed louder than Mbox, which we designed for Digidesign), it is certainly true that by overdriving the headphone circuitry we could have achieved higher level. We chose not to, to ensure that you never suffer the effects of clipping whilst monitoring, since this is almost inevitably counterproductive to any critical listening. The output drivers on Saffire are optimised so that any headphone impedance will not present an issue, although it is true to say that higher impedance headphones have a tendency to output lower levels. We can confirm that the figures we publish relating to flatness of frequency response, THD+N and output levels are correct.....If high output levels are required, then a headphone amplifier with either a larger headroom, or the capacity to overdrive the output will resolve your issue. As stated above, we chose not to provide this functionality within the box, quite simply so that it was impossible to get a distorted signal"

 

I would really appreciate some advice specific to this unit. I may be able to get a headphone amp in the coming months (more likely years!) yet although this is a relevant consideration it's by no means definite (baby in May!)

 

Thanks and great forum :-)

 

 

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post #2 of 15
1/30/12 at 3:37pm

It is not exactly clear from the specs what the voltage output would be to 600 Ohm, but assuming the worst case (it is 3.23 Vrms unloaded, and has 7 Ohm output impedance), you would get slightly less than 17 mW power. That is enough for about 106 dB sound pressure, which is roughly comparable to driving an HD598 with a portable player that outputs 0.6 Vrms. It might be sufficient for you (especially if the manufacturer's claims of "never clipping" are true, so the maximum power is actually usable), but if you are worried, you could get the slightly worse 250 Ohm version instead, which will increase the power to at least 39 mW, and the maximum SPL to 110 dB.

 

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post #3 of 15
1/30/12 at 4:11pm
Thread Starter 

Thanks for the reply. I am not sure what 106dB or 110dB sounds like through a headphone although I do of course appreciate the logarithmic nature of the scale. I mean is that loud? I consider iPods/smart phones at maximum volume into a 40 Ohm pair of headphones I have not loud enough and the HD598 are 50 Ohm so I guess based on your comparison the answer is 'no'?

 

I have emailed Focusrite asking for more detailed specifications particularly voltage to 600 Ohm and SPL at 600 Ohm. The idea of getting new headphones gets more and more expensive and I guess it might be beneficial to at least price a relatively low-budget suitable headphone amplifier in the UK. I will post Focusrite's reply here if I get one. Ideally if the Saffire is up to it I'd like to use it...

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post #4 of 15
1/31/12 at 10:12am

Quote:

Originally Posted by sidepartings26 View Post

I consider iPods/smart phones at maximum volume into a 40 Ohm pair of headphones I have not loud enough


It depends on what 40 Ohm headphones you have, the sensitivity of headphones can vary greatly.

 

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post #5 of 15
1/31/12 at 11:32am
Thread Starter 

Samsung Galaxy S2 full volume into Sennheiser CX 300 II Precision in-ears I would say is loud enough:

 

 

Frequency response (headphones) 19 - 21000 Hz
Impedance 16 Ω
Sound pressure level (SPL) 113 dB
Jack plug 3.5 mm (angled)
Cable length 1.2 m
Transducer principle Dynamic

 

Sensitivity (dB/V) 113dB (1kHz/1Vrms)

Samsung Galaxy S2 full volume into Technics headphones (awful I know) is not loud enough:

Model No RP-HT350E-N
Driver Unit 40mm
Impedance 40Ω
Sensitivity 100dB/mW
Power handling capacity 1000mW
Frequency response 10Hz - 27kHz

 

I have looked at possible headphone amplifiers but availability is soooooo poor in the UK. Originally I thought £123 ($193) for DT990s was too much for me at this point in time. Then I decided to go all out for DT880s at £199 ($313). Then I realised the 250 Ohm and 600 Ohm are the same price!

I know in an ideal world I would go with say a Schiit Valhalla and the DT880 600s yet even the idea of buying just the headphones and say an Fiio9 is daunting financially. I am pretty handy with a soldering iron and have researched that option a bit but I don't really just want an 'OK' amplifier (Starving Student amp?) and good ones e.g. the Bottlehead Crack kit with shipping and import tax are up at about the same price as Graham Slee amps available and readily built here. 

 

I really don't want to sell myself short for the future and go for the 250 Ohms version if the Saffire won't even really power them properly!

 

It's just a matter of trying to grasp what the figures mean subjectively...

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post #6 of 15
1/31/12 at 1:59pm
Quote:

Originally Posted by sidepartings26 View Post
 

I am pretty handy with a soldering iron and have researched that option a bit but I don't really just want an 'OK' amplifier (Starving Student amp?) and good ones e.g. the Bottlehead Crack kit with shipping and import tax are up at about the same price as Graham Slee amps available and readily built here.


You may want to check the O2 (Objective2) amplifier, that is available pre-built for about $150, but can be made DIY for somewhat cheaper: ~$100 for a complete build with shipping costs, or as low as ~$30 for just a bare PCB with no enclosure, batteries, or AC adapter. The schematics, PCB layout, and part list are available here. Extensive documentation and measurements have also been released. It is similarly powerful to the E9, but the sound quality is better (not that the E9 is bad).

 

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post #7 of 15
1/31/12 at 2:42pm

I found some information about the Samsung Galaxy S2 here, according to the article it can output a maximum of 0.703 Vrms, and has an output impedance of 49 Ω. Although I am not sure if this is correct, because based on the available specs the Technics headphone should be louder. Maybe the Samsung Galaxy S2 has other revisions without the high output impedance, or Panasonic lied about the sensitivity of the RP-HT350E-N. But if I believe all the specs, then the SPL values are as follows:

 

CX 300 II Precision: ~98 dB (99 dB assuming it is really 20 Ohm, 110 dB assuming zero output impedance for the Galaxy S2)

RP-HT350E-N: ~104 dB (111 dB assuming zero output impedance for the Galaxy S2)

 

Edit: 113 dB/Vrms looks somewhat low for a 16Ω IEM. If I calculate with 113 dB/mW instead, the maximum SPL is almost 116 dB.

 


Edited by stv014 - 1/31/12 at 2:51pm
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post #8 of 15
1/31/12 at 3:02pm
Thread Starter 

In which case a predicted sound pressure level achieved with the DT880 600 Ohm of 106 dB will be louder or similar to the Galaxy S2 at full blast through my loudest pair of headphones, the CX 300 II - I think Technics lied ha ha (although I assume I will not be doing the DT880s justice due to the nature/limitations (voltage?) of the headphone amplifier in the Saffire?).

 

I await a response from Focusrite although I severely doubt I will get one. I never dreamed there was so much to headphones and amplifying them until I discovered this site. I've been through this sort of learning process with guitar amplifier selection, tubes for them, speaker selection, effect pedal and pickup selection. This is similar I guess in that it's a whole world of possibilities in searching for tone or neutrality as it is in this case.

 

Argh! - in this case I might just need to make a quick decision which is edging towards the 600 Ohm, deal with the consequences now and get a decent tube amplifier later. Saying that, most of my mixing is done on my nearfield monitors and maybe 110dB through the DT880 250 Ohms is good enough? I have never tried high end headphones through a dedicated amplifier, I don't know how much out I am missing out on? The other factor is I may have to give up my home studio in which case the 600 Ohm model with a good amplifier may become my mixing 'main' at home and worth it for that reason. Are 600 Ohm models a LOT better than 250 Ohm models?

 

Thanks so much for the help stv014!

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post #9 of 15
1/31/12 at 3:28pm
Quote:

Originally Posted by sidepartings26 View Post

 

Are 600 Ohm models a LOT better than 250 Ohm models?

 

I have not compared them myself, since I only have a 250 Ohm version. Here is a thread that compares the different versions, and the OP of it seems to be quite familiar with all of them. Alternatively, for a technical comparison, here and here are some graphs and measurements of both, although the differences may partly be due to random manufacturing variations. If you do choose 250 Ohm, there is also a "pro" version of that, that costs slightly less, but has a higher clamping force (having some effect on the sound, too) and a coiled cord.

 


Edited by stv014 - 1/31/12 at 3:33pm
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post #10 of 15
2/1/12 at 2:33pm
Thread Starter 

Focusrite said that FAQ blurb only applies to legacy models. They also said they don't actually have figures for any other loads than 32 Ohms!!!

 

Maybe, a little more for the AKG K702s (62 Ohms) or Sennheiser HD650s (300 Ohms) will eliminate the need for an amp and be the solution I need!

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post #11 of 15
2/1/12 at 2:52pm
Thread Starter 

stv014 - How do you work out what power into other impedances is on the basis that it's 250mW into 32R. I think that up to 250-300 Ohms may be OK based on other forum posts - other people saying they are running 300 Ohms HPs off Saffire Pros.

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post #12 of 15
2/1/12 at 3:00pm
run them off the line outs. it has professional balanced +4dbu outputs right? if so, it should have good amount of voltage for the dt880 since balanced lineouts send atleast around 4v since they're meant for balanced/professional sources and see how they sound. you can pick up a pair of female 1/4'' TRS to dual male 1/4'' jacks at radisoshack or guitar center if you have any local. if not,then amazon or even ebay will carry them. try it out and see how it sounds. i tried my 600ohm sextetts and 240DF off balanced line-outs of my echo audiofire 2 with +4dbu/professional setting and works very well with them.
Edited by RexAeterna - 2/1/12 at 3:01pm
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post #13 of 15
2/1/12 at 3:15pm
Quote:
Originally Posted by sidepartings26 View Post

stv014 - How do you work out what power into other impedances is on the basis that it's 250mW into 32R.


For that, it is necessary to find out the maximum output voltage and the impedance (for low impedance headphones only, the maximum current may also be an issue). Unfortunately, the specs released by the manufacturer seem to contradict each other to some extent. "• Maximum Output into 32R +12.4dBu (+10.2dBV)" - these mean about 3.23 Vrms, suggesting that voltage can actually be output while using a 32 Ohm load. However, 250 mW into 32 Ohm is only about 2.828 Vrms, with 3.23 it would be more than 320 mW. The two specs do not agree. So maybe the 3.23 Volts is meant for no load, or the 250 mW is some rounded approximate value. The output impedance is specified as "less than 7 Ohm", which is somewhat ambiguous; but with 5 Ohm, and 3.23 V unloaded voltage, the power would be ~244 mW. This is only guessing, so depending on how the confusing specs are interpreted, the correct values may differ by up to 1-2 dB.

For simplicity, let's stick with the 3.23 Vrms and 5 Ohm. This gives the following power values:

  62 Ohm: 144 mW (111 dB @ 89.4 dB / 1 mW, source: doctorhead.ru)

  250 Ohm: 40 mW (110 dB @ 90 dB / 0.38 mW, source: innerfidelity.com)

  600 Ohm: 17 mW (106 dB @ 90 dB / 0.43 mW, source: innerfidelity.com)

 

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post #14 of 15
2/1/12 at 3:31pm
Quote:
Originally Posted by RexAeterna View Post

run them off the line outs.


Yes, those can output slightly more voltage: "• Maximum level (A-weighted): 15.7dBu at 0.883%". Although I am not sure why it is A-weighted, and there is unspecified and possibly high (>= 100 Ohm) output impedance.

 

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post #15 of 15
2/1/12 at 3:57pm
Thread Starter 

Thanks both. It looks like the Saffire won't be an issue for amping then (unless possibly choosing a 600 Ohm model) which leads me to the - by the looks of it - classic Vs: HD650 Vs K702 Vs DT880 (250 0hm).

 

The HPs are for mixing and mastering purposes.

 


From what I have read (quite a lot!) the K702 seems to be bass-light. I think they are beautiful though I mean whaoah: http://www.dv247.com/assets/products/60698_l.jpg (maybe except the alien like outer bands). I still want to 'enjoy' the headphones though and I'm not sure I can do that with thin bass.

 

I don't really like the look of the HD650 although they are OK. Significantly more expensive. In the UK the HD650 is + $102. But hugely popular and ranked #5 on here (K702 #28 and DT880 #70). Joint 'One of the best' (with DT880 250 Ohm) in a Sound On Sound shoot-out (for mixing):http://www.soundonsound.com/sos/jan10/articles/studioheadphones.htm (see bottom)

 

I originally was drawn to the DT880. I like the look and the comfort. Supposedly 'up there' with the HD650 and cheaper.

 

The thing is at this price range I am already 'all out' so if the HD650s are worth the extra I may as well!!!

 

EDIT - It's interesting to note what the same writers say about each headphone (DT880 and HD650) and also how they have basically ruled out the K702


Edited by sidepartings26 - 2/1/12 at 4:06pm
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