Greg, hopefully my explanation adequately explains why the headphone impedance is typically not much of a factor in this type of device/purpose. As I mentioned, I think many people are fooled by the volume control being at a different setting. 300 ohms could be pushing it though, so we'll see how that goes.

In relation to the power, this is still considered "mains powered", even though the power supply is external to the device. Manufacturers increasingly do this when manufacturing low powered devices, for various reasons that probably aren't all that important here. Some big disadvantages for the consumer however are that, in my opinion anyway, the external power supplies are just butt ugly. However more a factor is that when internal, the main power switch is normally on the AC side of the power supply, so kills the whole power. In this case the power supply is clearly not even inside the unit, so is powered 24/7. Even when "idling" like this, they still consume some power, so it's neither environmentally friendly and does potentially pose a fire hazard if it malfunctions while nobody was around.

As far as the potential to run this from batteries, I'll resist the temptation to ask "why?", instead suggest that it may not be quite as easy as you may imagine. The 12V into this unit is regulated to be at this figure reasonably accurately. A battery is by definition unregulated and varies quite a lot in voltage depending on type/charge/etc. I think many people seeing 12V envisage powering in auto type scenarios ... maybe banging out some tunes as they're cruising down the M5 I really don't know. But I could pretty much guarantee that attempt to run the unit on an unregulated 13.8V battery like that would almost certainly result in the release of the smoke genie. If you wanted to power off batteries, be sure there is a voltage regulator in that setup to give true 12V regulated power.

Pete

What about something like this? Think that may work?

http://accessories.musiciansfriend.com/p...ELAID=578549420

Pete,
Did you read my post where I stated that my HD570s, that are LESS sensitive than my AKG601s (97dB vs 101dB), are louder?

I am in no way convinced that impedance is NOT an issue, even at 64 ohms and 120 ohms.

Also, it appears that my multmedia headset has a sensitivity of 98dB, which is less sensitive than the AKG601s, yet it is MUCH louder. (I will attempt to make sure of that 98dB spec with Verbatim)

I await your HD650 opinion.

RE: the battery idea, I thought it might be handy for busking or similar applications. Yes, 13.8V might be pushing it a bit though. If I try it, I'll report back. ;^)

Greg.

Maybe, but I think it would require a splitter cable, because these Casios have two seperate pedal inputs - not a dual input.
(yes, it ALSO has a seperate proprietry input for the Casio 3-pedal unit)

Greg.

Ok, my Sony headphones are MDR-P1

I've also tried el cheapo earphones that came with a free mp3 player and they produce plenty of noise too, so there must be some sort of issue with your machine's output.

Fingers,
You would need to buy the CASIO pedal if you want the half pedal option. That is what connects to the pedal jack under the piano.You will have a hard time mounting and stabilizing the Casio pedal without the wood stand. It is propertiary. I recommend the m-audio SP2 pedal for your Casio. I believe you said you are just starting out. This is a good pedal and is really all you need.

Thanks for checking this. I don't think we can come to that conclusion yet though. As I said, I also have two pairs of headphones (the multimedia headset and the ear buds) that ARE loud with the PX-330. If I didn't have two OTHER pairs that were NOT loud, I would not have brought this up in the first place.

I haven't been able to find the specs on the MDR-P1 headphones yet.

Greg.

Greg, yes I have read all your posts. Having re-read this part of the thread again I can see I may have caused some unintended confusion. While I was replying to one of your initial posts about headphone impedance's you posted again. Now reading them in order I feel this leads to a false "story". So I'll try again from the top

Though I cautioned about being lured in by the setting of the volume control and drawing conclusions about a headphone's efficiency, it seems that is precisely what has happened. Basically when you use headphones of different impedance you may indeed need to adjust the volume control, in fact probably will. However the volume control on consumer electronic devices is not a calibrated device, at best it will have numbers around it, but typically simply min/max. For that reason you can't draw any conclusions about either the headphone's sensitivity/impedance from the relative setting of the volume control. As you found yourself Greg, you can have an inverse relationship, with the impedance winning out

At the point I came into this discussion you were discussing headphones in the range 30-120 Ohms, and around this (relatively low impedance) range the Casio shouldn't have any difficulty in achieving sufficient peak-peak voltage to achieve quite high sound pressure levels. I emphasise shouldn't because sometimes theory and practice are two different things. All decent headphone amps should have an output impedance of 120 Ohms, and be capable of driving headphones up to 300 Ohms without difficulty. Without getting too much into the technicalities, a typical op-amp (as almost certainly used in this) can normally be driven to within a couple of volts of the rail voltage. The engineers have a 12 v rail available, so in theory that would be MORE than adequate for a headphone amp to drive very high impedance headphones. BUT, that's just the theory. I'm currently using some Sony MCR-CD770 headphones (ie low 32 Ohm impedance/high sensitivity), yet I too noticed I needed a relatively high volume setting even on these.

So the bottom line is that the headphone impedance in relation to modern amps is largely immaterial (except as we may well find out when you get to the extremes). If you're swapping between different headphones you may notice you'll need to adjust the volume control somewhat, but it was never set on any particular value to begin with. Greg I'm very surprised you're having difficulty driving a 120 Ohm headphone, as there is no technical reason that I can see for this to be the case. I do vaguely recall some limitation on the maximum SPL that could be delivered by portable electronic devices (to protect people's hearing). Now it could be that's been implemented in this DP, either by design or by accident, I honestly have no idea. When designing a device, engineers very typically simply lift an entire circuit design from something else and simply copy it, especially in this part of the circuit as it's pretty basic.

Hopefully that clarifies this somewhat.

Pete

PS as far as your device being "faulty" as suggested by some others, I very much doubt it. Most modern headphones are low impedance and relatively efficient, since the main market is in portable music devices. Given these devices are battery powered by just a few volts, they don't have much headroom to play with. Op-amps designed specifically for portable devices can go much closer to the rail voltage for that reason, nevertheless they still won't typically be able to deliver much p-p voltage output. It would be extremely foolish for a headphone manufacturer to produce a relatively high impedance headphone priced such that it may appeal to that market. Indeed just glancing through specs, it almost seems as if somewhere around 32 Ohms has become the de-facto "standard" for headphones these days, simply due to the intended market.

Thanks Pete. Yes, I agree/understand that the efficiency of the headphones is important, and there would only be some correlation to impedance if the headphone output was being maxed out. (which I still think is entirely possible in the case of this PX-330)

I think you are starting to accept that the headphone amp in the PX-330, just maybe, is not as good as it might be. ;^)

Note that my laptop computer is also unable to drive the AKG601s loudly. (haven't tried the HD570s yet) My smartphone is the worst of the bunch. ;^)

I have been doing a bit of digging, though, and it appears that there are good quality headphones that have a low impedance, assuming I am right in that the PX-330 is best suited to low impedance headphones.

Greg.

Errr, I don't recall claiming that the headphone amp in this was particularly good. I DO however recall saying that I thought the headphone amp is crap and I was considering stripping it out and rebuilding it, to which several posters here cautioned against that. The reason for that had nothing to do with headphone impedance, it was because I could both hear it was crap and as an electronics engineer myself, had a pretty good idea of how it would be designed (ie cheaply!). Since then I've decided to get an external mixer (again for quite different reasons) and probably won't be bothered to fool about with the Casio's headphone circuit. The mixer I'm now waiting on is nothing special, Behringer 502, but I chose that as it's simple, cheap, and I've looked through the schematics of some of their mixers, and they're all the same basic design, so the 502 can be easily "frankensteined" should I get a sudden rush of blood to my head one afternoon and decide I want to upgrade its audio performance.

I'm still hobbling around largely one armed, but if I get a chance in the next few days I'll try to drag my oscilloscope up from the workshop (though "portable" I wouldn't want it dropping on my head!) and let you know what the p-p voltage output is on the Casio. Whether it's a worthwhile exercise I don't know, as if you're saying the Casio won't drive a headphone of 120 Ohms, then that's basically the end of the story.

Pete

Pete,
Sorry - I knew you were thinkig of trying to improve the outputs, but I didn't know you had already noticed any deficiencies. (and I hadn't thought about whether you were interested in the line-outs, headphone outs, or both)

Yes, not only is it having trouble driving 120 ohms, but it is also having trouble (but less so) driving 64 ohms.

That would be interesting if you did the p-p measurement. I don't have anything that can measure at audio frequencies, and I'm loathe to use mains frequency. ;^)

Greg.

Ok, well I dragged the CRO up here. Not a terribly scientific test, but striking a variety of keys (mainly middle C) as hard as one would, I got roughly 1.0 V p-p output, and I think that was being generous. That's somewhat lower than I'd expect for a headphone amp, indeed now I'm REALLY curious to see the circuit. As mentioned above though, keep in mind that the biggest selling headphones are in the 32 Ohm range, maybe even 16 Ohm! If you design a circuit that can cope with quite high impedance headphones, the majority of the population will be fiddling about trying to adjust the volume over a small range towards the bottom of its travel. That's really the only reason I can think of as to why the output should be this low.

Yes I'm always keen to improve the performance of audio products, but at this price point you basically know what you're getting before you even listen to it. For 99.9% of the population they honestly couldn't care less, but for A-R's like me, I care. Indeed I recall some years back sitting down and listening to a live compilation CD recorded in OZ. Not only was the compression outrageous, but I could distinctly hear digital clipping (which sounds horrible!) on the tracks. I ran it through some audio analysis software and sure enough, over 1,500 points of digital clipping per channel on each track. I wrote to the record company asking why their full retail priced CD was so poorly mastered. Their response? "We have sold over 150,00 copies of that CD and you're the first to complain about this". ... BTW, my retort was that McDonalds sells millions of hamburgers a day too, based on "the more we sell, the better it must be" standard of the record company executive, McDonalds must be a 3 star Michelin restaurant! Needless to say, that was the end of that email exchange

Anyway, the bottom line of all this has been that the Casio PX-330 is probably only suitable for driving low impedance headphones. Why? Who cares, but that fact could be a good thing for potential purchasers to know.

Pete

Thanks for doing the measurement - much appreciated!

Yes, I have read that clipping is quite common now.

You think you're an A-R. I can't believe I did this, now, but I actually complained about the impulse response of a consumer CD player. I took the unit in, and showed them the impulse response output of the player. Can you believe that? I think I'm a bit healthier now. Just a bit.

I'm curious about battery operated headphone amps. One day I might try one but I can get by without one at the moment.

Greg.

Really???!!! Pffft, well that just really bugs me, because there's no reason for it other than trying to simply be louder than the next song. Sad!

Anyway, last post OT as I better actually use this thing for its designed purpose. If you or anyone reading this buys the Casio and feels the need for an external headphone amp, I just went through the process of looking at quite a few different designs. If you're handy with a soldering iron, I felt the kit offered by Jaycar here in Australia, as published by Silicon Chip magazine some years back, was pretty much as good as any I saw. http://www.jaycar.com.au/productView.asp?ID=KC5417&keywords=headphone+amplifier&form=KEYWORD In addition to this you'll need the power supply, some form of volume control, and of course an enclosure. I haven't built the circuit myself, but it certainly looks quite good on paper, and if you exchanged some higher grade components I'm quite confident would be suitable for even quite high-end audio systems in addition to being used with this DP.

Pete

Good point galaxy. Thinking it over, the m-audio sp2 will probably be all I've ever need. I think I'll snatch that and be done with it. Thanks for your input. Appreciate it!

Just on the Australian warranty issue again, I forgot to mention that the 5 year warranty is provided by the distributor - NOT Casio. (that's what the document I received from the distributor seems to say very clearly, anyway)

Greg.

The FiiO E5 looks like a VERY VERY cheap battery operated headphone amp that may well produce sufficient volume through high impedance and/or low efficiency headphones. Seems to get positive reviews too. I might get one of these for my laptop and smartphone.

Greg.

Greg, my little Behringer 502 mixer arrived, but the HD-650s are still in transit ... somewhere. The mixer is a bit disappointing I have to say. I will try different inputs as at the moment it's basically just rigged up with the leads I had available, but the audio quality does seem to affected from what I can hear and it has quite a lot of noise for somebody used to even half reasonable equipment. Ok, maybe I was expecting a bit much, and it's not THAT bad, but I know it's also not that difficult to make it much better. At 0200 the other morning (the joys of pain killers wearing off) I pulled it apart and it won't be an easy rebuild and I'm not sure I'll be bothered messing with it. The bottom line is it sounds "ok" and I have absolutely no doubt it will happily drive those Sennheisers.

Messing about with the line outs on the Casio was a bit of a revelation, again maybe something for those considering purchase. Firstly the line out level is controlled by the volume control. Of course I have no experience with other DPs so maybe that's normal for them, but I have never come across any line level signal in any other equipment that is affected like that. The "gotta" is if you turn the volume control right down, no signal will come out ... in which case you may spend a few minutes scratching your head wondering quite why you can't hear anything through the mixer In other words if you were using this as a stage piano using the speakers to hear yourself, adjusting the volume on the DP will also affect the level going to the mix. I have no experience or even interest in using a DP in that scenario, but maybe some will, and it just seems bizarre to me.

As far as a headphone amp, I decided to build the kit as sold by Jaycar here in Australia, the UK and other places I believe. The design has quite a following, particularly amongst this group who call it the SCHA (Silicon Chip Headphone Amp, as it was initially published in Silicon Chip magazine) http://rockgrotto.proboards.com/index.cgi?board=chitchat The design is basic enough that somebody with even basic soldering and electronics skills should be able to construct it.

I hadn't seen the portable amp you suggested until now. Indeed it does get quite good reviews, but it's really designed more towards an application where people want a headphone amp on their iPods or phones. I haven't been able to find a schematic diagram as yet, but looked at the components they're using and one can normally somewhat deduce performance from that. Since it's designed to run on batteries, both the voltage output (for high impedance headphones) and current draw is a big consideration in design. This is a "review" by a poster on head-fi that I think pretty much sums it what I would expect from it:
.


Pete

Pete,
FWIW, my professional stage piano (Kawai MP9000) also has a variable output level on it's unbalanced line-outs, but if I recall correctly, the balanced outs have a fixed level. (never used them)

Yes, I imagine your kit amp would be better than this little E5 thingy. IF I get one, I'll let you know whether it actually boosts the signal of the PX-330 enough to use with my AKG headphones or not. The reason I mentioned it is that it actually states in the specs that it can be used with headphone impedances up to 300 ohms. (I know this is no guarantee though) The two negatives I am aware of with the E5 so far are: a) some hiss in some situations, and b) a slightly reduced channel seperation.
I'm sure it's overall specs would not be as good as more expensive units either.

Greg.

Greg, the 300 Ohm HD-650s headphones arrived and I've tried them on the PX-330. Whether something is loud enough for an individual is a very personal thing, what may be adequate for one person could be considered way too quiet for another. The HD-650 worked fine as far as I was concerned, BUT to get to the volume level I would normally like to use I needed to have the volume control "flat out", and even then I think they were somewhat softer that the Sony's I had been using. I definitely wouldn't place any money on the latter however, as the Sennheisers in situ would be somewhat lower distortion, with the corresponding affect on perceived loudness. All in all though, I wouldn't want the volume to be less and I don't think the two were a good combination without an intervening headphone amp.

It's probably not a deal-breaker for anyone considering purchasing this DP, 300 Ohm headphones are not particularly common these days, and if you did have only this type available it's not like it won't work at all. Furthermore, a DP doesn't place huge fidelity demands on any headphone, and it would be quite inexpensive to source some quite reasonable headphones in a more popular impedance and high sensitivity if you lean more towards loud reproduction.

Pete,
Thanks for the feedback, and I agree totally - it's not a show stopper by any means. I was merely posting it as a "heads up".

Just as an aside, I have some in-ear ear-buds on order which I am hoping will work on EVERYTHING I have. These are mainly for mobile use (laptop & phone), but it will be nice if they are also loud enough on the Casio. (I am almost certain they will be).

Greg.

You'd think I'd have learnt my lesson about saying what "should be" by now, but once again I'll go out on a limb and say the majority of bud-style headphones are 16/32 Ohm and will work just fine. I have some other Sony MDR-EX71 buds I use with pretty much all my portable stuff and they worked just fine on the Casio. The quality isn't great, but you'll certainly get your volume :P

Further to my previous comments, as I suspected, the way I had the little Behringer mixer wired it was indeed affecting the audio quality. I have now re-wired it correctly, and the line-out of the Casio seems to give a noticeably better quality audio output, even into that POS mixer, compared to coming straight from the Casio's headphone output. So in my opinion, if you have the Casio DP, good quality headphones (irrespective of whether they are high impedance), and are looking to improve the audio quality a tad, try feeding a headphone amp with the line-outs. I could hear that even with the Sony MDR-CD770s ... but the HD-650s were really quite nice

Yes - they are 16 ohms. Can't remember the sensitivity at the moment but they are Creative EP 630.

I haven't compared fidelity between line-out & headphone out yet......

Greg.

In most cases all outputs are variable in the same way.
That has a simple reason: There is no dedicated internal volume adjustment at all.
To change the volume simply the PCM values are changed before they go into the DAC or maybe the DAC's amplification is modified.
That is much cheaper to produce.

Ah is that right! Ok thanks for that, I guess I'm showing my age here as to how stuff "used to be done" I'm glad you told me that though as I noticed a couple of interesting things with the Casio volume control. The first was that it didn't seem to be properly logarithmic, and the difference in gain in the top 1/3 of the control wasn't all that much. I noticed it even on the oscilloscope, so it wasn't just my ears failing me. The other thing is that even with the volume at maximum the output doesn't get pushed into clipping. It's something one would expect to see if it was an analogue control, but makes perfect sense now you've explained that to me, so thanks again!

On a completely different note, a couple of other things I've noticed on this DP that I don't know how they compare to similarly priced competition, but I was somewhat shocked Casio bothered to model it at this price point. I've been reading a lot about real piano actions in the past week or so, and the guys on the tech forum helped steer me the right way. When I was looking at this DP I noticed the action was a bit different in regards to when a key isn't allowed to come fully up. I've since found out this is (at least audibly) simulating the double escapement action of a grand piano, where the hammer can re-strike the key without the damper having to touch the strings between the key strokes. I noticed that one at the store, but until today had no idea what it was called. The other thing is that apparently the highest strings on a real piano aren't damped. This I'm afraid I can only go by what I've read, so maybe others with experience can confirm this? Indeed I just noticed when I was testing these headphone/amps/etc that the top 1 1/2 octaves have indeed been modelled with no damping on the strings. So from 2nd top F up, if you strike the key hard it will continue to resonate. It is probably quite "ho-hum" information to you experienced people here, but it was an attention to detail I think many of the target market simply wouldn't have noticed if it wasn't there.

Pete

Pete,
I think the undamped upper strings thing is quite common now, however the double escapement is not as common, and yes, it's great that Casio have implemented this. To the best of my knowledge, Yamaha were the first to do the double escapement, but we now have Roland and Casio as well.

Greg.

I have noticed something else on this DP I'm hoping others could help me with as it's causing a bit of grief for me. Sometimes (particularly if my hands are a bit warm and moist) I find my third finger is dragging down adjacent black keys when I play. For example, playing an Eb triad in the root position, I tend to pull down the Ab key with the G. Some of it surely my crappy technique however ....

In the end I grabbed my digital callipers out and started looking at the actual key spacing and this is where things started getting strange. Firstly, there is a huge difference in spacing between the 2 black keys versus the 3 black keys (maybe 1-2 mm, and that's more than enough to get one's finger "stuck" v playing normally). Secondly, there is a difference in spacing between black keys depending on where they are on the keyboard. I think the latter is simply a QC issue at this end of the price range. Indeed if I move the black keys from side to side, some are quite tight, while others have quite a lot of lateral movement, and presumably it's this lateral movement that is manifesting itself as a difference in spacing. However what I don't know is if there is a difference in spacing between the 2/3 black keys on a decent acoustic piano?

Pete

FWIW I have not noticed any problems with neighbouring notes being dragged down yet. The only potential problem with mine is that the strip of red felt above the keys does not seem to be actually in contact with the keys. I'm pretty sure on every digital piano I've seen, and real pianos, the keys push up against that strip of felt, don't they? Doesn't seem to be causing any problems yet - just looks a bit strange to see the gap.

Greg.

It must however be considered that these double escapement MIDI sequences can make some serious trouble with sequencers, piano libraries and external sound modules or MIDI tools when these are not prepared for it. Unfortunately it is only a minority that is prepared for these MIDI sequences.

Therefore, if a stage piano, that is also be used as a generic MIDI controller, has this feature, then there should be a possibility to disable it ;-)

This is an issue of a controller sending (for a particular note)

3 sensor: note-on, note-on, note-off

instead of

2 sensor: note-on, note-off, note-on, note-off

correct?


Percussion controllers don't generally send note-off, do they?