Help - All the gear but no idea !

Well, I've had decent speakers for years and never really paid much attention to headphones until recently. I have started doing a lot of transatlantic flights so bought some Sennheiser PXC450 noise reduction cans and have got a bit hooked. Oops.

The PXC450's are a balanced design - they come with a replaceable cable that has a TRRS connector at the can end to allow the cable to be switched out to use a balanced amp.

So. My dilemma is what bits to upgrade (cans, source, DAC, amp), to what (who knows?), and in which direction (single-ended or balanced).

I'm intrigued and somewhat bewildered as where to go next. The PXC450's sound great in active mode, and sound similarly great in by-pass mode (i.e. bypassing all the in-can electronics). This could mean a number of things

1. The in-can electronics are uber-perfect,
2. The source or amp I am using to feed them is not as good as the electronics and I will gain from upgrades there,
3. My hearing isn't good enough to tell the difference, but I know I can tell the difference between tiny tweaks, so we can eliminate that,
4. The drivers are not actually that good after all, and I can gain by upgrading the headphones.

Right now I am using any of the following:

Arcam AV8 DAC & pre-amp + PXC450. Sounds OK, but not as good as the floorstanders.

Arcam AV8 + Arcam P1000 + Pro-ac 2.5. Sounds better than with the PXC450's.

This comparison suggests either the AV8 headphone amp is wanting, or the PXC's are not much good (but they do sound better on the Sansa)

SanDisk Sansa Fuze MP3 player. Sounds great (better than the AV8). How to make it better? I am using the 3.5mm jack. It is possible to suck a line-out signal from this unit but I do not have the wires to do so and there are mixed reports whether it makes any difference above placebo effect.

Dell Studio 1747. Sounds rubbish. Loose and boomy bottom end. Probably not very surprising. It has USB and HDMI.

So... new headphones? New headphone cable? New DAC? New headphone amp? Balanced amp? all-in-one DAC & amp?

I have seen things like the Mistral HP509, Litte Dot Q Tube, Little Dot DAC, Little Dot amps, Little Dot balanced amps, Bravo 6922, Bravo 12AU7, Arcam DAC, and, well, pfft.... Gotta say, without any steer (which is what I am asking for), I'd probably plump for a Bravo 12AU7 to play with until upgraditis gets the better of me and go for a Little Dot VII+ balanced, then also add a DAC. Probably the LD one.

And... if I stick a single-ended signal into the LD VII, do I get a balanced signal out?

Cheers

DefLugs.

Thanks for the interest, and a good clarifying question.

For plane use the PXC450's are just great and I will continue to use them for that.

I am looking for something superior for desk use, where noise reduction is not needed. On the face of it, it seems to make sense to get the best out of the 450s...

Ah, yes, and mostly at home, so open should be fine, as should exposed valves.

Quote:

Originally Posted by elwappo99 

I did a little research into the PXC450 a little time ago. That cable is not replaceable at all. The only way to change it is with another stock cable. 

Hmm, yes and no. Your comment prompted me to dismantle them for a look and a probe with a voltmeter. The TRRS socket is wired up with Tip L+; Ring1 R+; Ring2 to solder pad; Sleeve to Gnd and another solder pad. It appears possible to rewire them to balanced by cutting the LGnd wire and soldering it to the Ring2 pad. The socket is in the left can, so the operation is trivial. The headphones would have to be used in passive mode and would lose their noise cancelling abilities. As a curiosity, the two pads are labelled +&- rather than L&R.

As I am not in the mind-set of turning an excellent pair of noise cancelling phones into passive balanced phones, let's move forwards on the basis that these headphones are not going to be balanced, and now I just need steer on which unbalanced DAC and amps to get.

(Or until I go to RadioShack/Maplin and buy a TRRS and two TRS plugs and wire them up to prove to myself that I can or cannot use either mode by putting each TRS in my MP3 player one at a time)

(There's another option - I could add a switch that switches the L- connection between Gnd and Ring2. Seems easy on the face of it, but I am not ready for that)

(It is possible that I missed a connection between Ring2 and the microphones. I have already reassembled them and did not check for this whilst they were apart. I can test that with the TRRS - 2xTRS cable that I have yet to make and a microphone socket)
 

OK then, the plot thickens (see - said I was hooked!)

I was pretty sure I had some old Sennheisers in a box somewhere that I bought in 1995/6. Hadn't used them for years because the foam had rotted off. Anyway, I've been digging around and I found them. An HD435 Vegas and an HD435 Manhattan.

In a back-to-back test they destroy the PXC450. Takes about 5 seconds of listening to prove that. They may just have the edge over the Proac 2.5, too, (but do not have the ability to fill a room)

So, I have a new set of plans.

1. Leave the PXC450 alone and use them on 'planes, which was always the original plan.
2. Find some new foam pads for the HD435.
3. Get a headphone amp. I suppose a Bravo will do for starters.
4. Get upgraditis. It's inevitable. HD600, Little Dot amp, HD800, DAC, Balanced wiring...

Right. Replacement pads ordered.

Next stop, a headphone amp.

Updates - Bravo amp,  Laptop settings,  Senn HD650

Might be speaking to myself, and if so then maybe this'll just help me choose things in my own head. Replies would be most welcome.

Amp

I put a bunch of snipes on eBay until I won/bought a Bravo amp at $10. Ended up with the V3. Would've preferred a V2, but who cares for ten bucks? My understanding of the tone controls is they are all passive attenuators, so I am just leaving them all turned up full, which should be close to flat, or bypassing them. They do have a mid-point notch that visually and tangibly feels like it should be the mid-point, but from the circuit layout, this seems misleading. As the tone controls are turned down (and the volume up to compensate), the sound feels claustraphobic and constrained. When up full (and less volume to compensate) the sound is open and relaxed.

The Bravo amp is a better than the HP/out on my laptop with my Senn HD435, but nothing to shout about. Of course, one can argue that the laptop HP/out is the limiting thing in this setup, and the amp is just reproducing a mediocre source perfectly. That's a story for another day. When the wife's not looking, I'll pull out the hifi find a proper line out from the Arcam AV8.

There's a nasty spike as the amp is turned off, so I have learned to unplug the 'phones before turning it off. FWIW, the connection is a Cambridge Audio Pacific 3.5 to RCA cable that probably cost more than the amp.

Headphones

The HD435 pads arrived and were fitted, which made them seem like new. Took them and the PXC450 on a 5 hour train journey (10 hour return) with my Sansa Fuze. Whilst the HD435 are better in my quiet study, the PXC450 are much, much, much better on a noisy train (in the same way that I loved them transAtlantic last month).

I had the opportunity of new HD650s at £199. So I took them. The Sansa Fuze sounds muddy through them, which is a disappointment, but perhaps not too surprising. The laptop to Bravo to HD650 sounds absolutely amazing. Surprisingly, the laptop does a reasonable job with them, but the bass gets loose and the mid- and upper-presence and definition is lacking.

Source

Massive improvement here! Separate from the Windows audio mixer, there is an IDT Control in Windows Control Panel. It is colouring the audio. I can turn it off which gives a big improvement, but every time the computer is restarted and/or every time I plug headphones in and out, it is automatically turned back on and I have to go into Windows Control Panel to turn it off again. No updates are available, and there is no obvious option to disable it. I need to experiment with deleting drivers and seeing how to keep the audio ports working without this annoying "feature."

Of course, you should all be screaming at me for using a laptop headphone-out as my source, and I am digging through reviews and pros/cons to move forwards. My only digital-outs are HDMI & USB. Unfortunately this laptop does not have an optical SPDIF buried at the end of a 3.5 TRL socket.

My shortlist based only on reviews is as follows, each with pros & cons (bearing in-mind that my main source is likely to be USB, both the HD435 and HD650 can become balanced, and I may one day get a balanced amp)

Matrix Cube

   +ve ASRC as 2/4x multiples; small; cheap; line in

   -ve max USB 16/48; no XLR out

Matrix mini-i

   +ve small; great reviews, XLR out; track names show on screen

   -ve noASRC; max USB 16/48; no line-in

Yulong D100

   +ve ASRC; USB to 24/96; XLR out; great HP amp; best reviews.

   -ve most expensive; no line-in; ASRC is not to complete multiples of source, which bugs me - taking a 44KHz signal and upsampling to 110KHz must introduce temporal offset similar to jitter, but that is not random so cannot be called jitter. Moire would probably be a better term. It must impart a delay of 1s/220K, or 4us, to every second pulse. I guess this is adding a 44KHz frequency modulation (FM) signal to a 110K carrier signal. This artefact is absent from either Matrix implementation. There is a more complicated artefact added with input signals of 48, 88 or 96KHz that I cannot be bothered to work out. In all cases the offset should not be more than 4us between pulses and reviews seem to show that the end result works, but knowing there is a hidden cludge is always going to bug me. Hmm, I just scribbled it out on paper for both 44 & 88. Looks bad. For 20 pulses of 110KHz signal, the actual music signal is as follows

Carrier 110KHz 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20
Signal 44KHz   00    02       05    07       10    12       15    17       20
Signal 88KHz   00 01 02    04 05 06 07    09 10 11 12    14 15 16 17    19 20

See how the pulses that start at 44 or 88 get upsampled into an uneven spacing? That wouldn't happen either if not upsampled or if upsampled to a multiple of the original frequency. Still, the reviews are great and this is the model I am currently leaning towards. Maybe another bit of electronics in the signal path compensates for this patterning. Or maybe points are interpolated rather than just resynchronised. I don't know. I'm speculating. More reading required.

Panic over. I read this tutorial at DIYAudio that explains the stuffing, interpolation & decimation.

Yulong is looking a pretty likely acquisition.

Hah! Fair challenge. Mostly just getting my own thoughts in order, I suppose. Always interested in being pointed in a useful direction, such as "Have you considered X because of the way it'll do Y?", but I have never been one for asking the question "Should I get DAC A, B, or C?" to which there can only be subjective answers.