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Post by rossman on Apr 30, 2008 9:27:15 GMT
sandyk, kittenyberk, you have pm
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Post by PinkFloyd on Apr 30, 2008 21:04:23 GMT
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Post by PinkFloyd on Apr 30, 2008 21:23:59 GMT
Ouch! AD8066 running a wee bit too hot for my liking, possibly oscillating, (must go read the spec sheet!) back in with the AD843s on B-dog and (again) a huge improvement across the board from the AD843 pre tweaks..... will try the 4562 again..... let's see how the 843 develops overnight.
Shit, this is ONE GOOD amp for the money Alex isn't it?
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Post by Deleted on Apr 30, 2008 21:52:43 GMT
Mike
There is no point in me doing this. You are reaping the benefits of further lowering the PSU impedance in the higher part of the audio spectrum. The additional JLH board takes care of that, and then some !
IMHO,this amplifier has the potential for experienced modders, to make it better than most of the expensive, well known Headphone Amplifiers, although it obviously won't suit all headphones without tweaking. The extra headphone socket provided, but not used, could be,for example, connected to the existing one via a couple of resistors, to build the total output resistance out to 120 ohms, to suit some of the much higher sensitivity recent headphones. This would allow for the use of 2 very different types of headphones.
Alex
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Post by jelosno on Apr 30, 2008 22:46:20 GMT
Hmmm,
I might order one of these kits as well. I just have to check the shipping costs. Might be cheaper to send it to Europe and then have someone bring it down here when they visit...
Is it ONE board that is needed for the amp?
Is there still one or two available?
MIKE,
could you later some time provide a bag with all the goodies you have changed from the original BOM?
Stefan
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Post by Deleted on Apr 30, 2008 22:51:42 GMT
Jelosno
There are presently no JLH PCBs available. You would need to etch and construct your own.
It isn't a commercial product, but an expansion of a design that appeared in ETI magazine many years ago, and almost forgotten.
BTW, using a JLH board should get around the need for all those more expensive capacitors, as it's output impedance is considerably lower than that of the capacitors, and much better than even the best of capacitors to >100KHZ.
What Mike is doing, however, would be the next best option to fitting a JLH board.
Alex
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Post by jelosno on May 1, 2008 0:22:56 GMT
You would need to etch and construct your own. Alex, Rather not! I've never done this before and learning another skill and purchasing the equipment isn't worth it. From what I've read in this thread it kinda seems that without the JLH thingy there is something relevant missing in the amp. So I'll skip this kit  ciao stefan |
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Post by Deleted on May 1, 2008 0:29:53 GMT
Stefan
Why don't you wait and see what Mike comes up with , without using that JLH PCB ?
Mike seems pretty happy with what his changes to the original have achieved already.
Perhaps what you guys need from Mike is some kind of reference against the performance of other amplifiers that he has ?
Alex
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leo
Been here a while! 
Team wtf is it?
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Post by leo on May 1, 2008 0:58:49 GMT
I'd say in standard form the output stage of the amp is too slow for a device like the LM4562 which is fairly quick, it'll just drag it down. Alex's is a lot quicker than the standard unit + the improved PSRR, probably why the LM's work so well in his You folks are making my fingers itch, I'm trying to resist the temptation  |
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Post by canjunkie on May 1, 2008 9:04:56 GMT
You would need to etch and construct your own. Alex, Rather not! I've never done this before and learning another skill and purchasing the equipment isn't worth it. From what I've read in this thread it kinda seems that without the JLH thingy there is something relevant missing in the amp. So I'll skip this kit ciao stefan Stefan, I'm 'tooling up' to etch a few boards, including a few JLH's. Let me know if you're tempted ;D. |
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bullpup
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Post by bullpup on May 1, 2008 9:21:20 GMT
Perhaps what you guys need from Mike is some kind of reference against the performance of other amplifiers that he has ? Alex Excellent idea Alex, perhaps an amp we are fairly familiar with like a tweaked x-can? |
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Post by PinkFloyd on May 1, 2008 11:24:12 GMT
I'd say in standard form the output stage of the amp is too slow for a device like the LM4562 which is fairly quick, it'll just drag it down. AD843s on on single to dual convertor a completely different story! These have settled in overnight and I am over the moon with the results..... your typical organic AD signature with bass to die for..... analytical yet warm, let's liken these to a hybrid of LM6171 / OPA627..... everything the LM6171 has to offer (speed, spaciousness, detail, seperation, air) but with a large sprinkling of much needed "soul"...... you know the way the LM6171 can be clinical to the point of sounding cold and exact but, at the same time, able to extract every last ounce of detail as if it were a microscope homing in on every last ounce of minutiae...... well, in this application let's just say the AD-843 does all that but has a heart and actually manages to convey all the information "musically" instead of clinically. AD843 has a tendancy to drift from cold and IMO needs a good few hours to stabilise..... once stabilised this is one fantastic chip to use in the Jaycar and that's "without" the JLH we are hearing so much about..... god only knows what it would sound like with a JLH onboard. This really is (as the Americans would say) a "no brainer".... get your wallets out, pay the man his £8.95, put this thing together and sit back and enjoy a right royal aural treat. I've only been playing about with her for a couple of days but it's already clearly evident that this amp has MAJOR potential! In stock guise it's very good but throw a few different components / opamps into the mix and it's potentially a giant killer..... no shit, it really is. Each board is a 30 second job to strip from the enclosure so tweaking isn't a "Shit it's gonna take me an hour to strip all that down I can't be bothered" kind of thing it's more a case of "right. I'll whip that board out and try XYZ in it... it'll only take me a couple of minutes" a fantastic little amp to fiddle about with. Alex, please don't ask me to compare this to some commercial amps..... I really don't want to embarrass some of the guru manufacturers who are charging an arm and a leg................ |
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Post by PinkFloyd on May 1, 2008 11:52:22 GMT
Must incorporate this into the circuit using AD843..... will try later   |
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Post by Deleted on May 1, 2008 13:18:01 GMT
Mike
I only suggested that, as a couple of members were wondering if it was really worth constructing without the JLH installed.
We both already know that it is ! Even if it had turned out to be very average, it would still be a great project for people to start out with.
Alex
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Post by PinkFloyd on May 1, 2008 14:38:40 GMT
Must incorporate this into the circuit using AD843..... will try later AD suggest a 2u2 tantalum and a 100nF ceramic disc in parallel from +vs / -vs to ground but I'm thinking more along the lines of mama honker 2u2 polyprop and 100nF polyprop..... any observations you guys would like to make on this? Obviously the tant and ceramic don't take up much board estate and can be neatly implemented onto the board.... the 2u2 polyprop will span from each pin (4 & 7) to ground with minimal lead inductance..... just a case of suck it and see I suppose. I tried the tant / ceramic combo with the 843 in the WNA amp but much prefered the sound with polyprops fitted here.... any comments most welcome. |
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leo
Been here a while!
Team wtf is it?
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Post by leo on May 1, 2008 14:54:38 GMT
Got to be worth a try, tants are extremely good for local decoupling, I know some folks don't like them but used in the right places in moderation their hard to beat IMO.
Main thing to watch with big polypropylenes is if too big physically they add too much inductance especially if the leads are long and too far away from the chip pins.
If it sounds squeaky bright check for instability, the onboard regs are quite a long way from the chip so the low esr may not cause ringing
I'd avoid any ceramics unless they are NPO/COG
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Post by PinkFloyd on May 1, 2008 16:53:24 GMT
I'll try a few more opamps anyway before deciding on which one is the keeper.... just rolled in the OPA2111 and it is also, surprisingly, good!
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Post by PinkFloyd on May 1, 2008 18:43:02 GMT
Any of you guys know what this chip is? I got them from David White a few years ago and they sound absolutely awesome in the Jaycar.... thing is they run a bit "hot" and I'd like to know exactly what they are before running them for too long..... I know it sounds daft but I've forgotten what they are!   |
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Post by PinkFloyd on May 1, 2008 18:44:51 GMT
..................... yes, you do have a tendency to forget what's what when you have a bundle like this to sift through   |
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Post by PinkFloyd on May 1, 2008 19:04:35 GMT
Next to be hot rolled (ie: rolled with amp switched on) is the THS4032CD kindly supplied by Miguel...... very promising, spacious, good bass extension and detailed..... deffo put onto the second audition list:  |
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Post by holland on May 1, 2008 20:52:31 GMT
looks like some opamp in sot23-5 packaging. I can't make out the markings. 8a8? ba8? 8ab? hab?
what's the bandwidth of the buffer stage?
Edit: If HAB, it might be the AD8067.
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Post by PinkFloyd on May 1, 2008 21:37:16 GMT
Just a few more I've tried this evening: OPA602  Very similar to the OPA627 signature but not too hot in the Jaycar..... thought they may shine but, nope, didn't get me tenting at all. OPA227  Funnily enough pretty unstable as a direct roll in..... most surprising as these chips are usually not cranky.... but as a direct drop in replacement not recommended. IS55002  Very nice.... on the second listen list.... quite an airy sound very much the same sort of presentation in the bass as listening to a pair of AKG K-501.... this chip has potential. AD744 biased into class A mode  Without a shadow of a doubt the BEST so far as a direct drop in... everything where it should be, nothing over nor under estimated just beautifully flowing, organic and classy sounding..... I reckon they'd sound even better if they were mounted onto the B-Dog direct and not on the 2 dip8 socket "tower" I've mounted them on... these are the best direct drop ins I have yet tried in the Jaycar and, obviously, can be tuned further to extract the ultimate performance out of them.... as a direct drop in though, SUPERB! The "god knows what they are" chips: Fantastic, very much LM6171 with a touch of NE5523 thrown in to the bottom end...... they were running a bit hot so, until I find out exactly what they are I won't leave them in circuit "just in case" 12V is too much for them or something is causing them to oscillate. THS4032 Lightweight presentation but extremely detailed yet flowing and mellifluous.... this would be a nice chip for classical lovers..... again, I am only talking direct drop in here.... with a bit of offboard tweaking this could turn out to be a totally different sounding chip.... certainly fit for audio duty though! AD843... Second to the AD744 and takes first place if you like your music on the warmer side of neutral. More to come........................ |
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Post by PinkFloyd on May 1, 2008 21:43:04 GMT
Mike There is no point in me doing this. You are reaping the benefits of further lowering the PSU impedance in the higher part of the audio spectrum. The additional JLH board takes care of that, and then some ! IMHO,this amplifier has the potential for experienced modders, to make it better than most of the expensive, well known Headphone Amplifiers, although it obviously won't suit all headphones without tweaking. The extra headphone socket provided, but not used, could be,for example, connected to the existing one via a couple of resistors, to build the total output resistance out to 120 ohms, to suit some of the much higher sensitivity recent headphones. This would allow for the use of 2 very different types of headphones. Alex Can't wait to try the JLH.... what about whacking an andante straight onto the board..... I have a spare williams hart andante board somewhere. |
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Post by Deleted on May 1, 2008 21:59:16 GMT
Mike
I haven't seen the schematic of the Andante, only photographs. Going by the photos, I wouldn't expect a great deal of improvement.
Alex
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Post by holland on May 1, 2008 22:00:41 GMT
If I read the package markings correctly (picture is blurry), it's the AD8067. It's not stable at gains below 8 unless compensated.
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