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Post by PinkFloyd on Oct 26, 2009 17:19:00 GMT
Simply a case of snipping one leg off and bending another over I'll take a pic of the process. Mike I agree that the AD744 is a nice chip, as I ordered a tube of 20 some time ago, and used them in an earlier preamp with a "booster " O/P stage. Would you also be able to check please if there is any change to the DC OUT, after the modification ? The simplified schematic suggests that there should be around 600mV, but it may not be the complete schematic, and if inside the feedback loop, it may possibly get corrected ? Alex With AD-744 biased in class A the DC measurements are: L/C 1.7mV R/C -2.3mV So, pretty much negligble Alex.
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Post by Deleted on Oct 26, 2009 19:04:45 GMT
Stop whinging man and HOP to it ;D
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Post by PinkFloyd on Oct 26, 2009 20:38:39 GMT
I agree that the AD744 is a nice chip In this particular application it's a very nice chip indeed Alex, and biased into Class A even nicer as it gives more clarity like nice clean mountain water... you can really appreciate the air between instruments and pick out each indivdual element with pinpoint accuracy. And..... all this from the stock DC wallwart! It promises to get even better with a regulated supply. I am going to try a couple of PSU's, one of my DC Pinkies and also the Velleman Kit from Rapid.... the beauty of the Velleman is you have 4 volts (or so) to play with and can adjust for best SQ.... it's also only £7 won't break the bank.
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Post by PinkFloyd on Oct 26, 2009 20:39:41 GMT
Not quite yet, but I must say it seems to have affected my tap dancing. Cut your other leg off and you can bounce up and down on your stumps ;D
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matt7941
100+
Mmmmmmm... Pork scratchings.....
Say cheese!!!!!
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Post by matt7941 on Oct 26, 2009 20:57:23 GMT
Good evening Mike.
Bounce might be a little optimistic, I'll just sway in the breeze!
Am I right that to output bypass the AD744 pin 6 is removed from the opamp and pin 5 bent across to contact pad 6 (if using soic)? Just checking t'interweb there's talk amongst the chattering classes that to actually make it class A a 2K2 resistor also needs to be placed twixt pads 6 and 7. Is this: a) correct; and b) worth doing?
BTW, I jumped the gun a little this afternoon and bought the Velleman kit. It has been redesigned from the pictures on the Rapid website. The board layout has changed quite a bit, but I presume the circuit is still largely similar. The large axial cap has been replaced by a 2200uf 35v radial and the two WIMA polys have been replaced a 1uf 50v electrolytic and a 10uf 50v electrolytic. The switch to radial for the main cap I suppose gives more options to use better caps, the problem is you're going to want to change them as they are everybody's favourites ......................................... JAMICON. Sorry, I just uttered an unforgivable profanity, I am away now to birch myself thoroughly as a pennance.
Matt
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Post by PinkFloyd on Oct 26, 2009 21:17:17 GMT
Am I right that to output bypass the AD744 pin 6 is removed from the opamp and pin 5 bent across to contact pad 6 (if using soic)? Correct! I, personally wouldn't want to be the one doing it with a soic chip though..... they are very small things.... a lot easier with a DIP chip..... just snip off the leg and bend the other one over to take it's place.... I will take pictures so you'll get the idea, give me a couple of days. I've heard talk of this but haven't actually implemented it... as yet.... I've always run my AD-744/A without the resistors..... I'll try the 2K2 thing next time I'm under the hood...... if you have a look at Xin's site there is quite a lot there about it www.fixup.net/talk/pop_printer_friendly.asp?TOPIC_ID=1231I ordered one from Rapid, it will be interesting to see if I receive the one in the photo
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Post by PinkFloyd on Oct 27, 2009 20:48:44 GMT
The Velleman 1 amp power supply kit arrived today and it took me about 15 minutes to put together, it's so easy a child could do it, I have replaced certain parts of the kit with other alternatives which I will detail: Comes in a nice plastic box Containing PCB, instruction manual and parts Another pic of the parts The kit comes shipped with 1N4007 diodes, I replaced these with ultrafast UF4001 types which have a faster response Fit the 120ohm resistor The kit comes with a 100nF ceramic capacitor, I have replaced this with a 220nF polyester type I replaced the two 1uF electrolytic capacitors with WIMA 3u3 (3.3uF) film types Fit the trimpot I decided to keep the stock Jamicon 2200uF capacitor for the time being (I'm sick of looking at Panasonic FM 2200uF ) Regulator fitted I didn't bother fitting the terminal blocks as I prefer to hard wire to the pads. You could build one of these cheaper on stripboard but the kit makes it ever so simple and @ £7 it's really very reasonable. Right, all I have to do now is hook up a transformer and that's it.... hopefully a cheap as chips PSU for the Aune.... I will post again once I have put it all together
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toad
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Post by toad on Oct 28, 2009 9:43:19 GMT
It'll be interesting to see if you get the same marked improvement that I did over the stock PSU Mike. We are not talking subtle differences, we're talking more of everything by the bucket load.
Ian
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Post by PinkFloyd on Oct 28, 2009 14:10:50 GMT
It'll be interesting to see if you get the same marked improvement that I did over the stock PSU Mike. We are not talking subtle differences, we're talking more of everything by the bucket load. Ian I'm just putting her together now Ian, cramming it all into one of my Pinkie enclosures.... I'll start off at 20V and see how she sounds
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Post by PinkFloyd on Oct 28, 2009 15:04:47 GMT
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matt7941
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Mmmmmmm... Pork scratchings.....
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Post by matt7941 on Oct 28, 2009 16:32:52 GMT
Good afternnon Mike.
Just wondering what voltage the transformer is and what the VA rating is? I was thinking of using a 25V 30VA or 24V 30VA, or would a 50VA be more appropriate?
I see you've used a 1nf polyprop. across the secondary, does this make a worthwhile difference? I've got a couple of spare X2 caps so I'll be using one across L and N on the way in.
Cheers
Matt
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Post by PinkFloyd on Oct 28, 2009 19:44:08 GMT
Good afternnon Mike. Just wondering what voltage the transformer is and what the VA rating is? I was thinking of using a 25V 30VA or 24V 30VA, or would a 50VA be more appropriate? I see you've used a 1nf polyprop. across the secondary, does this make a worthwhile difference? I've got a couple of spare X2 caps so I'll be using one across L and N on the way in. Cheers Matt Hi Matt, The transformer I used was poached out of a Mascot 8930 www.mascot.no/?CatID=1181 It's 31VA which is more than adequate for the job. The voltage is 24V AC. A suitable one for you would be part number 88-3495 or if you prefer a doughnut part number 88-3792 You can also fit a MOV across L/N part number 26-3255 If you really want to go to town you can fit one of these over the output lead or thread a few of these over each output wire part number 23-0730I normally use a 470nF EVOX class X2 cap, if you'd like one (and an EPCOS MOV for that matter) send me a PM with your details and I'll send you them in the post. Mike.
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Post by PinkFloyd on Oct 28, 2009 21:53:55 GMT
I've been listening to the aune / Velleman concoction for a few hours now and, boy, what a difference over the aune / wallwart.... at first the improvement was pretty subtle but the more the "Velleman" has cooked the more the SQ has blossomed.... bags more air around instruments, better bass extension, a greater degree of clarity, wider soundstage.... you name it, the Velleman gives you more of each component in spadeloads The PSU runs quite warm but nothing wrong with that.... the transformer takes a good couple of hours to get up to "full" temperature and all this definitely plays it's part on the SQ..... a cold transformer doesn't "sound" as good as a hot one..... I'll give her another 24 hours in the oven and report back but, at the moment, this is absolutely SUBLIME sound quality.... the AD744/A on Bdogs are lapping this up and delivering the sonics BIG time
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matt7941
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Post by matt7941 on Oct 29, 2009 0:59:25 GMT
Thanks for that Mike, much appreciated. PM sent.
Cheers
Matt
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Post by PinkFloyd on Oct 29, 2009 21:05:23 GMT
Thanks for that Mike, much appreciated. PM sent. Cheers Matt I'll get the bits and bobs in the post tomorrow mate though I doubt they will go anywhere till this bloody postal strike is over ;D
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Post by clausdk on Oct 29, 2009 23:55:45 GMT
Does it work as a standalone DAC ?
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Post by PinkFloyd on Oct 30, 2009 22:03:29 GMT
Does it work as a standalone DAC ? Not as far as I'm aware (but I may be wrong).... seems an obvious question but if you're looking for a standalone DAC then why not go for a dedicated standalone DAC? ;D
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Post by clausdk on Oct 30, 2009 22:26:29 GMT
Does it work as a standalone DAC ? Not as far as I'm aware (but I may be wrong).... seems an obvious question but if you're looking for a standalone DAC then why not go for a dedicated standalone DAC? ;D then it would be easier deciding what is the good stuff, amp or DAC or both, in the aune that is. also if it is a good DAC at the price, it is interesting.
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Post by PinkFloyd on Oct 30, 2009 22:29:54 GMT
Not as far as I'm aware (but I may be wrong).... seems an obvious question but if you're looking for a standalone DAC then why not go for a dedicated standalone DAC? ;D then it would be easier deciding what is the good stuff, amp or DAC or both, in the aune that is. also if it is a good DAC at the price, it is interesting. BOTH.
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Post by clausdk on Oct 30, 2009 22:33:35 GMT
Is the Amp, better than an V8 ?
Then I will have to order one tomorrow.
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Post by proximo on Oct 30, 2009 23:41:02 GMT
Does it work as a standalone DAC ? Hi, first time user here I believe it does. Here's a comment I found on head-fi.org describing the input/ouputs and the use of the A/D switch: "The rca output on the back is hardwired to the lpf filter/dac meaning no matter what switches you use, the connector always outputs the the usb/spdif source. The a/d switch decides what source the headphone amp part should use, D uses the dac as source while A uses the rca input at the back. I'm using it with a little chinese tube buffer, i connect the out to its in, and its out back to the aune. A/D switch is in the A position." If I read that correctly, you should be able to use the Aune as a standalone DAC by connecting the RCA analog outputs to a preamp.
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Post by PinkFloyd on Oct 30, 2009 23:50:56 GMT
Does it work as a standalone DAC ? Hi, first time user here I believe it does. Here's a comment I found on head-fi.org describing the input/ouputs and the use of the A/D switch: "The rca output on the back is hardwired to the lpf filter/dac meaning no matter what switches you use, the connector always outputs the the usb/spdif source. The a/d switch decides what source the headphone amp part should use, D uses the dac as source while A uses the rca input at the back. I'm using it with a little chinese tube buffer, i connect the out to its in, and its out back to the aune. A/D switch is in the A position." If I read that correctly, you should be able to use the Aune as a standalone DAC by connecting the RCA analog outputs to a preamp. Nice first post! Thanks
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matt7941
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Post by matt7941 on Nov 3, 2009 18:40:46 GMT
Good evening folks.
Thanks Mike, the bits arrived today and I'll fit them soon. The power supply's built before I've got the amp!
Has anyone tried replacing the opa2134 yet as I've got a metal can LME49720 or AD8066 to try and just wondered whether it makes an improvement?
Mike, I'll let you know how the AD744s sound in class A, I've also output bypassed them. Those SMD resistors (1.6mm long!) are a bit fiddly mind, serves me right for buying SOIC.
Cheers
Matt
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Post by Deleted on Nov 3, 2009 21:36:19 GMT
Matt Only one way to find out ! Just remember though, not to exceed +-12V with the AD8066. Alex
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matt7941
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Post by matt7941 on Nov 3, 2009 22:10:01 GMT
Sorry Alex. I'm just jumping the gun a little as my Aune doesn't arrive until 25th Dec. I wish I'd settled for socks for Xmas now, I could have bought one myself and had it playing by now. All I've got is the power supply to look at, it doesn't sound very good on its own!!! Matt
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