Owen, that is truly spectacular! Kudos to you and the guys at National, i dont think ive seen anything quite like that before. i find it intriguing that the THD is actually lower at 7v than 1V, is this simply due to less attenuation/higher DNR of the signal source?
the SE-SE amp with psu is a real bargain if looking for an SE amp. the phase plots are crazy
the SE-SE amp with psu is a real bargain if looking for an SE amp. the phase plots are crazy
It's THD+N. The noise remains constant, thus contributing less to the figure with higher drive level.
yeah i though about that after, thanks. given opc said he was bouncing against the AP signal generator noise floor i thought perhaps that was what was staying constant vs the signal amplitude; basically in the same way as you describe the self-noise THD+N.
its just not that common to see a loaded amplifier with signal input thats noise/distortion doesnt increase with amplitude, let alone the opposite
edit: except that there is no gain increase here, just signal amplitude
btw ive got a long reply to your massive post to me yesterday, but i might just PM you with it as its a 'bit' OT
its just not that common to see a loaded amplifier with signal input thats noise/distortion doesnt increase with amplitude, let alone the opposite
edit: except that there is no gain increase here, just signal amplitude
btw ive got a long reply to your massive post to me yesterday, but i might just PM you with it as its a 'bit' OT
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. a piece of wire!
Order add on...
Hi Owen - your measurements just convinced me to do something I've always dreamed of! I would be most appreciative if you could please *add* the following to my existing order (if it isn't asking too much):
3 x BAL-SE full kits
1 x BAL-SE bare PCB
If you don't have the parts to fulfill the above as full kits, then please feel free to "downgrade" them to just bare PCBs. My diy studio IEM system is going to sound world class thanks to you!
Hi Owen - your measurements just convinced me to do something I've always dreamed of! I would be most appreciative if you could please *add* the following to my existing order (if it isn't asking too much):
3 x BAL-SE full kits
1 x BAL-SE bare PCB
If you don't have the parts to fulfill the above as full kits, then please feel free to "downgrade" them to just bare PCBs. My diy studio IEM system is going to sound world class thanks to you!
Hi, a quick question regarding the transformer, getting a Antek AN-0115 shipped to the UK is a bit costly. As long as I sauce a transformer with the same specs [115V/230V 10VA 2x15V 0.33A] there shouldn't be any problems!
But, so far UK stock of a toroidal is proving hard to find [main parts retailers]. I did find this http://uk.rs-online.com/web/p/products/3472622/ isolation pcb mounting transformer in stock. Should this be OK?
I know, a basic, stupid question, but being a newbe I just want to be double sure.
Paul.
But, so far UK stock of a toroidal is proving hard to find [main parts retailers]. I did find this http://uk.rs-online.com/web/p/products/3472622/ isolation pcb mounting transformer in stock. Should this be OK?
I know, a basic, stupid question, but being a newbe I just want to be double sure.
Paul.
Paul,
in the UK, you can obtain excellent toroids suitable for audio apps here:
Canterbury Windings Home
in the UK, you can obtain excellent toroids suitable for audio apps here:
Canterbury Windings Home
You could also go up to 15VA without any issue. I am running a 15VA on my original Wire without issue. In any case, that gives a few more options.
115/230:
Buy Toroid Transformers Toroidal transformer,15VA 2x15V o/p Nuvotem 91938-P2S2 online from RS for next day delivery.
230 only:
Buy Toroid Transformers Toroidal transformer,15VA 2x15V RS 81526RS online from RS for next day delivery.
115/230:
Buy Toroid Transformers Toroidal transformer,15VA 2x15V o/p Nuvotem 91938-P2S2 online from RS for next day delivery.
230 only:
Buy Toroid Transformers Toroidal transformer,15VA 2x15V RS 81526RS online from RS for next day delivery.
Reading through this got me to wonder about DC protection.
Is there a danger of a potentially damaging switch on or off off-set voltage spike from 'the wire' amps?
What happens if a connecting wire or contact from the PSU breaks or goes 'high resistance'? Will it damage the voice coils?
That will cost in the order £700 to replace the HD800 diaphragms so I'd rather take no chances.
Thanks.
Hi Guys,
Sorry for the delay in posting the rest of the measurements... it has been yet another busy week. I'll get them up tomorrow for sure.
As a side note, I think the crosstalk measurements I posted for the SE-SE amp the other day are a little suspect. I'm going to re-run them tomorrow and verify. I wasn't getting a number that high with the BAL-SE and the output stages are almost identical, so I think something may have been amiss when I took those. Everything else seems to be good though.
Q&A time
sek:
I think those measurements are taken with a dScope and not RMAA. The serious problem with RMAA is that it relies entirely on the sound card for good performance and that's not really acceptable when you're trying to measure something that is way beyond the capabilities of most sound cards. If I did use RMAA what you would see is the performance of whatever sound card I used, and not the headphone amplifier itself.
The dScope is a whole other thing though, and is a very capable piece of measurements equipment. What I would be more than happy to do is swap the SE-SE version of The Wire for an 02 amplifier, and we could both check each others work. If someone wants to arrange for that, I'd be more than happy to supply a completed Wire amp.
BuildMeSomething:
Several others have already answered with some excellent advice, but I just want to confirm that the transformer suggested is merely a suggestion, and there would not be a problem with going to a higher VA unit, especially if you're having trouble sourcing the 10VA part I mentioned. Larger VA transformers will work just as well in general, but the reason I suggested not going overboard is that the larger the transformer gets, the more stray magnetic field it has. That means you'll need to keep it farther from the circuit which can quickly turn into a pain.
The links you posted above would be fine, and you can safely go as large as 25 VA without worrying at all.
IanAS:
I can assure you there is absolutely no on or off transient with the wire. I can capture a few scope shots of startup and shutdown if it would put your mind at ease.
As far as DC protection goes though, there is nothing on The Wire natively, except perhaps the current limit on the buffer.
There will always be a scenario in which you could potentially cause damage to your headphones, but you'd have to be pretty careless in this case. Hooking up the supplies in reverse polarity would cause problems, and so would hooking it up to a source with a large DC offset. That, however, would be a problem with any DC coupled amplifier, not just this one.
This may sound a bit harsh, and it's in no way directed at you, but my general take on any audio protection circuitry is that it's mostly meant for idiots, and I try my best not to design to the lowest common denominator. If you're foolish enough to build this amp, hook it up to a source that has a huge DC offset, and then plug in a pair of very expensive headphones without checking for DC on the output, then you really are going to be out of luck. This amplifier wasn't designed for people like that though. I have been using it for more than a year now, with a immense number of different sources, headphones, and systems, and not once have I had a problem with it. I'm very confident that it is a safe and reliable amplifier for any type of headphone.
Regards,
Owen
Sorry for the delay in posting the rest of the measurements... it has been yet another busy week. I'll get them up tomorrow for sure.
As a side note, I think the crosstalk measurements I posted for the SE-SE amp the other day are a little suspect. I'm going to re-run them tomorrow and verify. I wasn't getting a number that high with the BAL-SE and the output stages are almost identical, so I think something may have been amiss when I took those. Everything else seems to be good though.
Q&A time
sek:
I think those measurements are taken with a dScope and not RMAA. The serious problem with RMAA is that it relies entirely on the sound card for good performance and that's not really acceptable when you're trying to measure something that is way beyond the capabilities of most sound cards. If I did use RMAA what you would see is the performance of whatever sound card I used, and not the headphone amplifier itself.
The dScope is a whole other thing though, and is a very capable piece of measurements equipment. What I would be more than happy to do is swap the SE-SE version of The Wire for an 02 amplifier, and we could both check each others work. If someone wants to arrange for that, I'd be more than happy to supply a completed Wire amp.
BuildMeSomething:
Several others have already answered with some excellent advice, but I just want to confirm that the transformer suggested is merely a suggestion, and there would not be a problem with going to a higher VA unit, especially if you're having trouble sourcing the 10VA part I mentioned. Larger VA transformers will work just as well in general, but the reason I suggested not going overboard is that the larger the transformer gets, the more stray magnetic field it has. That means you'll need to keep it farther from the circuit which can quickly turn into a pain.
The links you posted above would be fine, and you can safely go as large as 25 VA without worrying at all.
IanAS:
I can assure you there is absolutely no on or off transient with the wire. I can capture a few scope shots of startup and shutdown if it would put your mind at ease.
As far as DC protection goes though, there is nothing on The Wire natively, except perhaps the current limit on the buffer.
There will always be a scenario in which you could potentially cause damage to your headphones, but you'd have to be pretty careless in this case. Hooking up the supplies in reverse polarity would cause problems, and so would hooking it up to a source with a large DC offset. That, however, would be a problem with any DC coupled amplifier, not just this one.
This may sound a bit harsh, and it's in no way directed at you, but my general take on any audio protection circuitry is that it's mostly meant for idiots, and I try my best not to design to the lowest common denominator. If you're foolish enough to build this amp, hook it up to a source that has a huge DC offset, and then plug in a pair of very expensive headphones without checking for DC on the output, then you really are going to be out of luck. This amplifier wasn't designed for people like that though. I have been using it for more than a year now, with a immense number of different sources, headphones, and systems, and not once have I had a problem with it. I'm very confident that it is a safe and reliable amplifier for any type of headphone.
Regards,
Owen
This concern about fault DC output stems from using it with a battery supply.
If one supply rail drains quicker than the other, which – in case of batteries – it will, the imbalance in the DC supply will inevitably cause a DC offset on the output.
This problem is not inherent to the O2. It's something to be kept in mind with The Wire too, just in case someone considers battery drive.
IMO, at least the BAL-BAL could possibly be capable of suppressing this, as both output stages would exhibit the same offset during turn on or turn off. Thus, the differential between both outputs could remain zero.
I'd put it like this:
If you ruin an expensive headphone during building or testing of a new project, you're doing it wrong.
If a user you gave it to ruins their expensive headphone during normal use, your project wasn't ready for release yet.
That, or you did target the wrong group of users.
