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Post by Deleted on Feb 13, 2010 22:53:21 GMT
Mike You could also fit a 7809 instead of the 7812 for those who want to use 9V. This would then be useable from a 12V battery on a vehicle. Alex
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Post by PinkFloyd on Feb 13, 2010 23:13:10 GMT
Mike You could also fit a 7809 instead of the 7812 for those who want to use 9V. This would then be useable from a 12V battery on a vehicle. Alex Yes.... a lot of possibilities 7824..... in fact 78** (whatever)..... it has outputs for a LED too... pretty "bog standard" (1000uF / 470uF 'lytics / 100nF film caps) but good for small enclosures and enough spare "estate" on the board for tweaks
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leo
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Post by leo on Feb 14, 2010 8:29:32 GMT
What about something based around LME49600? If its anything too complex or expensive to build I really can't see many wanting it tbh
If you want something like discrete classA you may as well go for the SC 15w classA and convert it to a classA HA like in Alex's mods
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Post by clausdk on Feb 14, 2010 8:49:50 GMT
Claus If we did that we would keep getting requests for superb sounding results using whatever headphones were available, using low voltage supplies, where it just isn't possible. The requests would gain momentum, but there would then be no likelihood of anything special ever getting constructed. I haven't had a chance to lookthrough all recent posts, as I haven't even had breakfast yet, but has there been ANY interest shown by the 2 EEs here that know much more than I do? ( at least technically) Or are they steering well clear ? Alex I see your point Alex, I was just shooting from the hip.. I have read somewhere that there is a standard of 150 ohms, if that is something that the industry picks up it, we should go for that.. Again speaking without really knowing ;D ;D also seeing that if they agree on that it would take years to come into the "real world". We could however tune it to xxohms and then make some "pods" for those headphones that are "to easy" to drive, just an idea..
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Will
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Post by Will on Feb 14, 2010 11:12:10 GMT
I'll throw these in to the mill. Jon's suggestion = j310 schematic is attached below. Very simple, and apparently sounds best at 16v. Not tried it myself, but it's here to stimulate, if nothing else. Leo's suggestion, the LME49600. Page 11 has a headphone amplifer application note, based on lme49720/lm4562 front end. How about a discrete front end? Could the thermally balanced long tail pair front-end from the Class A be adapted to 'fit' the lme49600? I know this entails close matching of the componenets for both hfe and vbe for very best best results, but we do know that we can get hold of the linear systems matched transistors to make this easier. I like Mike's idea of a simple PSU, there is no need to do much more as a starter. It's been mentioned that you could have different grades of kit - basic/normal/full-blown. This could be related to the PSU being a separate board. This way you could use normal regs, JLH PSRR or shunts. Anymore ideas?
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Post by Deleted on Feb 14, 2010 11:21:30 GMT
Will I wouldn"t count on it ! A friend of mine is still waiting, many months later ! They may go very nicely as replacement devices in an RIAA Phono preamp though ? Alex
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Will
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Post by Will on Feb 14, 2010 11:33:39 GMT
Based on our previous experience, we'd be fine, a two week wait. Are these the higher gain devices for the current mirror? If he has two spare when they come, let me know.
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Post by derekrumble on Feb 14, 2010 11:49:18 GMT
In the first instance I would like to take part in building something simple. Battery power would be good as this would minimise the build time (?) and cost.
And then if those who are up for creating the designs can stand it.. then follow on with a real hi-fi bit of kit; but I'd need plenty of hand-holding.
I listen to radio in bed at night frequently - I know that if I take the line-out from my Pure Dab receiver and run it inot my X-CANv3 then the sound is much much better than when I use the Pure's built-in headphone output. But my X-CAN lives downstairs - so a 'phone amp for bedside use that doesn't compromise too much on SQ would be great.
So I'd like to see an 'easy to build, but better than your average headphone-out circuitry'. I'd have a use for that and would enjoy building it. I have already, successfully, built a Velman kit pre-amp using an op-amp plus the few necessary passive components - and it worked!
Derek
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Post by andy on Feb 14, 2010 12:19:43 GMT
Derek, I use a bravo next to the bed from a portable CD player, sounds great. So you could try one of them.
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Post by derekrumble on Feb 14, 2010 13:07:05 GMT
Derek, I use a bravo next to the bed from a portable CD player, sounds great. So you could try one of them. I like that idea - and the Bravo is not expensive - but am inspired to do a DIY project. As I have an X-CAN i can't see me getting permission to buy another amp - but a DIY projuct may creep in below the radar.
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Spirit
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Post by Spirit on Feb 14, 2010 13:18:32 GMT
i can't see me getting permission to buy another amp Remind me to set some hard and fast rules before I get another girlfriend/get married ;D
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robertkd
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Post by robertkd on Feb 14, 2010 15:17:38 GMT
The LM49600 looks like a beast to tame with all that current gain, interesting to note the output stage of the SCHA is essentially a discrete version of this chip I have even implemented similar current limiting function. Of course you wouldn't get the same bandwidth using the discrete circuit but that increased bandwidth is in itself a mixed blessing.
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Will
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Post by Will on Feb 14, 2010 15:44:58 GMT
I've read a bit more about this LME49600, and it does look quite interesting.
Should drive just about anything, bandwidth can be altered with one resistor. Balanced as an option. You have to use 1 per channel, so Chris gets his dual mono, which is no bad idea. It is classed as SMD, but it isn't ridiculously small, and quite doable, I think. A discrete front end would stop it being a implementation of the datasheet, also. Anymore interest in this from anyone else?
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robertkd
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Post by robertkd on Feb 14, 2010 16:04:10 GMT
you guy's with the class A amp might want to have a look at the DC servo arrangement in the example headphone solution in the LME49600 data sheet An op amp (single or dual) would give the ability for op rolling for added flavour ;D
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jonclancy
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Post by jonclancy on Feb 14, 2010 17:27:55 GMT
Just wanted to point out that the J310 idea was one floated, by Juma, over at DIYA on the JFET BOZ thread. I wanted to try it (and haven't yet), but Will and I did get the best part of an EAGLE layout done. So, not my work, can't be used commercially etc etc. www.diyaudio.com/forums/pass-labs/103050-jfet-boz-15.html#post1832806Have a read, it's pretty interessting, and a simple circuit. Cheers Jon
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Post by Deleted on Feb 14, 2010 20:50:48 GMT
you guy's with the class A amp might want to have a look at the DC servo arrangement in the example headphone solution in the LME49600 data sheet An op amp (single or dual) would give the ability for op rolling for added flavour ;D Robert The present offset corrector was found to give virtually no colouration in comparison with a friend's otherwise identical preamp,(capacitor input) but without the servo. The dual time constant at the input was used to help minimise the effects of the typical attenuator when changing positions.(DC offset variations) This wasn't a problem with a normal Alps Blue Velvet potentiometer. I will revisit the data sheet though. Alex
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Post by PinkFloyd on Feb 14, 2010 23:39:43 GMT
I am happy to allocate funds to this project (for parts, development costs etc.) so if you've got something to contribute to this "joint venture" amp then please indicate an express desire to participate and we'll take it from there.
Mike.
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Sol
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Post by Sol on Feb 15, 2010 12:13:00 GMT
As a Official Resident Electronics Numpty I can offer nought in the way of technical input - as I know you all know .... but my ears are always available, and I'll happily give an opinion.
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Post by Deleted on Feb 15, 2010 21:50:23 GMT
Like Sol said! One area I may be able to help, I've been eyeing up various case possibilities (non specific) and already have an expanding shortlist of cheap options from the unlikliest of sources. Some I reckon would be really nice with minimal tinkering. Once we know the internal dimensions required I can rejig the list. We just need a design to fill the case! Oh, nearly forgot. Please, no tiny SMD work. I was looking at the PFM effort until it went that way, total turn off for those with dodgy eyes
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leo
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Post by leo on Feb 15, 2010 22:16:59 GMT
loads of interest ;D Once a circuit has been got together its a case of knocking up on vero first to see if it works Keep the idea's coming in
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Post by PinkFloyd on Feb 15, 2010 22:23:06 GMT
Be sure that a Rock Grotto headphone amp would FLY Leo Mike.
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leo
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Post by leo on Feb 15, 2010 22:32:53 GMT
Problem is finding something to have a big enough appeal. lots of options, its just finding something suitable, not too hard so anybody can build it and not too expensive or nobody will bother
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Post by PinkFloyd on Feb 15, 2010 23:11:17 GMT
Problem is finding something to have a big enough appeal. lots of options, its just finding something suitable, not too hard so anybody can build it and not too expensive or nobody will bother Well....... I'm a "boring old bastard" and only require an amp to have one set of inputs, a volume control and a 6.3mm headphone socket so I am very easily "satisfied". Your average, modern day punter obviously wants the damn thing to make tea at the same time..... it's all a matter of finding the right "balance" and not getting carried away designing an all singing, all dancing "bells and whistles" type wankfest.... What do I want? "the best sound quality possible at the lowest price".... I am more than happy to forgo unnecessary "ad ons" to achieve that. Everything has to be compromised and, the more features you add, the more the SQ is compromised. We are either going to design the best sounding "desktop size" amp in the WORLD or we are going to arse about pandering to every request for "USB Dacs", "diamond buffers", "ipod docks" etc. and ending up with a Christmas tree ;D Me, personally, I will only get involved in this if the end result equates to the BEST sounding amp in it's class.... I may be old fashioned but sound "quality" is paramount to me. Mike.
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Post by Deleted on Feb 15, 2010 23:34:58 GMT
I think this is the main stumbling block at the moment, what "class" are we going for? So far, on a quick count, we only have 14 members who have voiced the slightest interest As an old holiday ad. used to say [put on a thicko accent] "Where is everybody". Chime in folks, we need a target to aim for.
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Post by PinkFloyd on Feb 15, 2010 23:59:11 GMT
I think this is the main stumbling block at the moment, what "class" are we going for? The best sounding headphone amp on the planet..... what else IS there to go for?..... "shitty sounding but lots of features"?...... Keep it simple (input / volume knob and head-out) and I believe we can (as a combined effort) make the finest headphone amp on the planet at a price that suits ALL pockets.... To be totally honest, though (as I usually am!) it will have to be BLOODY special as the majority of amps on the market sound very good. The Little bravo / Indeed amps (IMO) sound better than some £700 amps and you can pick them up from ebay for £50..... I have listened to many many amps in my time and have reached the conclusion that "there's not a lot in it" between a £50 ebay special and a £3,000 headphone amp apart from the bullshit talked by the punters who have forked out £3,000..... they have to "justify" that outlay and can only do it by talking / quoting bullshit. So, as I say.... a "Rock Grotto" amp would have to be "bloody special" and would have to make me hear things I have never heard before..... a VERY hard thing to achieve ;D I don't want to put the dampeners on the idea but, seriously guys, you won't get much better "sonically" than the likes of the Bravo / Indeed / SCHA / MF amps.... forget the "specs" and forget the "valve V SS" argument..... listen to them all, they all sound much the same ;D Mike.
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