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Post by PinkFloyd on May 17, 2011 21:01:44 GMT
Israel..... if you are wanting absolute "honesty" from a recording then there is only one chip in my opinion.... the LM6171 (or 6172 in a dual channel version).... only thing is it is NOT a direct "roll in" type chip and can be extremely problematic unless the circuit is optimised to accept it.... motorboating, oscillation, overheating, smoke.... it is a VERY cranky chip and ESSENTIAL that it is implemented correctly.
Still, to this day, the most revealing chip I have ever heard.... I spent ages with Dr. White helping to tune it for use in the WNA MKll / MKlll amps.... it's also a very clinical listen and a true microscope on the proceedings.... if it's "on" the recording the LM6171 will show it up, warts and all.
The AD-843 is a lot more forgiving, warmer in nature and (to a certain degree) easier to live with but if you want "all out" warts and all then the LM6171 is pretty hard to beat in my opinion.
Mike.
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Post by Deleted on May 18, 2011 0:32:35 GMT
Israel..... if you are wanting absolute "honesty" from a recording then there is only one chip in my opinion.... the LM6171 (or 6172 in a dual channel version).... only thing is it is NOT a direct "roll in" type chip and can be extremely problematic unless the circuit is optimised to accept it.... motorboating, oscillation, overheating, smoke.... it is a VERY cranky chip and ESSENTIAL that it is implemented correctly. Still, to this day, the most revealing chip I have ever heard.... I spent ages with Dr. White helping to tune it for use in the WNA MKll / MKlll amps.... it's also a very clinical listen and a true microscope on the proceedings.... if it's "on" the recording the LM6171 will show it up, warts and all. The AD-843 is a lot more forgiving, warmer in nature and (to a certain degree) easier to live with but if you want "all out" warts and all then the LM6171 is pretty hard to beat in my opinion. Mike. Hi, Mike It sounds interesting, but I don't think I have the amplifier that can handle it. From what I can tell (perhaps I am wrong ) the chip requires a pretty high voltage to be stable, which the Neco portable may not have. The Neco Bossfet, which I have does have an 18V power supply, but I am not sure about wanting to mess with it either. :-/The Bossfet has the AD843's in it, and I am very happy with it. I would be willing to experiment, but not at the expense of damaging any of the Neco amps that I have (the above two). The other two SS amps that I have are the Little Dot Mk1 with a 14.8V power supply, and a cheap Mini RA-1 with a 9V battery power supply made by AW Audio in China. The other headphone amps that I have are 5 Chinese hybrids that do not use op amps. Thanks for your suggestion, and if you think that an experimental change in the circuitry for the sake of op amp rolling such as this is worthwhile and doable without too much pain on any of the amps that I have, then I may be willing to try and modify the circuitry, provided that it is reversible. From what you say, however, it looks like it is not. Although I would love to be able to use the AD843's on the Neco portable, which is impossible because the supply voltage is too low, I am pretty happy with the AD8610's in it. I have a pair of AD843's in my Little Dot Mk1, and they work OK, but the amp does not have the quality of the Necos, so I may not use it that much. All the Best! Israel
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Post by Deleted on May 18, 2011 7:16:33 GMT
Hi Israel,
I had a look on good old Google regarding these opamps and one reviewer who did some comparisons mentioned what I think I find difficult at times with the AD8610:
When paired with an aggressive or very revealing system, this chip can be unpleasant. This chip is at its best complementing a smooth, laid-back system.
That's where I think I have a problem with it and why I turned to opa227. Especially if you put something like a K701 on it. However, it's probably better with HD600/650 if you are running full sized headphones with it.
However, he also goes on to say it's one of his favourites for portable applications.
Burr-Brown OPA227 Cost, single: n/a Vmin, 0.5V into 33 Ù: 5.4V Cost, dual: $3.53 (OPA2227PA) Vmin, 2.0V into 330 Ù: 8.2V
This family of opamps sounds very similar to the OPA132 and OPA134 families. The main difference is that the 227 isn't as tubby on the bottom end as the 132. The 227 will run to slightly lower supply voltages than the 132 family.
Digi-Key only carries the dual versions in DIP packages. The 'A' versions are the right ones for audio, as the non-A version simply has better DC specs, which is not useful for audio.
Bottom Line: This is a good alternative to the OPA132. It is arguably even a significant upgrade.
Analog Devices AD8610/AD8620 Cost, single: $8.00 (AD8610) Vmin, 0.5V into 33 Ω: 5.7V Cost, dual: $13.33 (AD8620) Vmin, 2.0V into 330 Ω: 7.6V
This is quite possibly the best chip for battery-powered amps, period. Its voltage tolerance is among the lowest of all the chips I mention here, it has good output current abililty, it has among the lowest supply current of any chip reviewed here, and above all it sounds good.
What does it sound like? Well, take the AD823, and remove some of the aggressive harshness. Add a bit of detail and smoothness from the AD843. That's the 8610. It's not a smooth chip, just not harsh. It's not the most detailed chip, but not heavily veiled, either.
This chip is rare in that it is only rated for a 26V supply. (Absolute maximum is 27.3V.) Another oddity is that it is only available in SOIC versions, so you need to mount it on a Brown Dog adapter to use it in amps that use DIP chips.
Bottom line: This is a contender for my favorite chip of all time, especially in battery-powered amps. When paired with an aggressive or very revealing system, this chip can be unpleasant. This chip is at its best complementing a smooth, laid-back system.
Analog Devices AD843 Cost, single: $8.56 (AD843JN) Vmin, 0.5V into 33 Ω: 8.2V Cost, dual: n/a Vmin, 2.0V into 330 Ω: 12.2V
When I went into this test, I was hoping to find a chip to dethrone the OPA627 which is expensive and requires a lot of voltage. The 627 also has the characteristically mellow Burr-Brown sound, which is not always a good thing. Analog Devices chips tend to be a little snappier and more aggressive, which can help balance some systems. I wanted a chip that would fit all of these criteria while still maintaining the OPA627's incredible level of resolution and clarity. The AD843 doesn't completely fit these criteria, but it does come close.
What this chip gets right: First, the AD843 is definitely cheaper. Like the 627, the cheaper grade is fine for audio, so a pair of 843s is about half the cost of a pair of 627s. Second, this chip does have that Analog snap and verve.
The downside is that the AD843 requires more voltage than the OPA627. And like the 627, the sound gets very nasty very quickly when it starts clipping.
The AD843 seems to trade smoothness for resolution relative to the OPA627. In some cases the more detailed OPA627 might be preferrable, and in others the smoother AD843 could be helpful. I'm torn on what to make of this real difference. The OPA627 isn't hyper-revealing, and the AD843 isn't over-smooth. The OPA627's detail seems genuine; it isn't grain or overemphasized real detail. I don't mind the way the AD843 ignores these details, but at the same time I don't resent the OPA627 for presenting them. The OPA627 can be accurate to a fault, if your recording has unpleasant detail in it that another op-amp would ignore or deemphasize. If you have flawed recordings, you may prefer the pleasant lie told by the AD843.
Bottom Line: This is a serious contender with the Burr-Brown OPA627 for the title of "best op-amp I've ever heard". I view these two chips as rough equals; they're both in the same audio class, but each chip has strengths lacked by the other. Taste and system matching will be the largest factors in choosing one over the other.
National Semiconductor LM6171 Cost, single: $2.83 Vmin, 0.5V into 33 Ω: 6.1V Cost, dual: $3.80 Vmin, 2.0V into 330 Ω: 9.5V
Digi-Key carries the LM6171BIN single-channel version, and the LM6172IN dual version in the DIP package.
This is a very high-speed op-amp with bipolar input transistors. Translated, that means this op-amp is hard to use. However, it has exemplary audio performance for such a low price, so experienced builders should at least consider using it. If you decide to give it a shot, you must design the amp around the chip: you cannot just pop the chip into an existing circuit and expect it work. (For info on what's necessary to make this chip work, see the companion article, "Working with Cranky Op-Amps".)
I made another test amplifier according to that article's principles in order to test this chip. To assure myself that the necessary design changes didn't impact the sound, I tried some of the other chips in it. This brings up an important point: the changes necessary to make chips like the LM6171 work in a CMoy amp do not prevent less picky chips from working. If you think you might want to try a chip like this someday, you might make the design changes from the start so you're free to use most any chip in the amp.
Sonically, this chip is significantly more revealing than the OPA132/134 series, and the bass is a touch more impactful as well.
With a high supply voltage (15V), the difference between the LM6172 and the OPA134PA is subtle, but real. At lower supply voltages, the LM6172 can greatly outshine the OPA132/134 series. The clipping numbers above don't tell the full story; when this chip clips, it does so in a very soft, rounded way, instead of the harsh clipping you get with other chips. This means you can often run the chip to lower voltages than my tests indicate by accepting a mild form of distortion.
Bottom Line: This chip is not for tyros, but it's cheap, it performs very well at low voltages, and at higher voltages it still outshines many other chips in its price class. It requires more external components to achieve that performance, however.
Ian
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Post by PinkFloyd on May 18, 2011 8:11:04 GMT
Ian, I will send you some OPA228 to try, they should be fine in the NECO
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Post by Deleted on May 18, 2011 10:08:15 GMT
Thanks Mike ........if you do, could you also send a little Pinkie fuse? I've blown one again and rubber feet for Bp. Bigg Pinkie!! I'll get you some fags. BTW - I keep meaning to ask - can you remember which opamp you put in the V-Can that you modded for me? It's the one that had the long volume knob. That is unbelieveably good sounding on the K701. (Pink'ed up of course!!) Ian
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Post by Deleted on May 18, 2011 15:20:15 GMT
Hi Israel, I had a look on good old Google regarding these opamps and one reviewer who did some comparisons mentioned what I think I find difficult at times with the AD8610: Ian Hi, Ian Thanks for posting the information! I am familiar with it. I find that this excellent article, entitled 'Notes on Audio Op-Amps', written by Warren Young www.tangentsoft.com , is very helpful in searching for improved audio op amps. After reading his comments in general, it is easy to conclude, however, that there indeed is no ideal op amp chip. According to Warren Young, they all seem to be less than perfect in one way or the other -- a balance of compromises, so to speak. Luckily, what the scopes and other measuring instruments show, while most helpful in designing a good audio circuit, is not always perceivable by the human ear, but sometimes detectable in AB comparisons. Cheers! Israel
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Post by Deleted on May 18, 2011 16:19:53 GMT
I had a look back through posts and I think it may be opa4227. That's why I like it so much!!! Looking back, I can see why you may have used that one - to rid it of the toppiness that it had new!! Probably why I'm keen on opa227 in the Neco. Ian
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Post by PinkFloyd on May 18, 2011 19:46:42 GMT
I had a look back through posts and I think it may be opa4227. That's why I like it so much!!! Looking back, I can see why you may have used that one - to rid it of the toppiness that it had new!! Probably why I'm keen on opa227 in the Neco. Ian Hi Ian, I started you off with the OPA4227 and then sent you the OPA1644: Is that the one you have in your V-CAN at the moment? I soldered them onto Winslow adaptics adaptors... IMO a much nicer overall sound than the OPA4227 BUT the OPA4227 will generally be more sympathetic to poor recordings.... have a look under the hood and see what opamp you are running in the V-CAN.
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Post by Deleted on May 18, 2011 21:01:52 GMT
Thanks Mike, I opened up and sure enough ..... opa1644. It's a great sounding op amp. It really is and works incredibly well with the K701. Funnily enough, I'd kept the AKG away from it, but I was missing a trick. It's superb. But then, you Do know what you're doing eh? It sounds so good that I cleaned the casing up with WD40. Now it looks smart too!! Ian
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Post by Deleted on May 20, 2011 3:10:10 GMT
<snip> From a technical point of view (if I were selling them) I would insert a 10 Ohm resistor between the output of the amp board and the output connector. There is a technically quite sound reason for doing this. As the opamps output is directly connected to the output plug, the feedback loop is vulnerable to the capacitance of the headphone cable which can cause instability with certain opamps, ringing or overshoot that may even enter the audible domain. Adding this small resistor (I thing Ian heard correctly by adding the 38) makes the opamp more stable and less dependent on the capacitance of the headphone cable, which can be high with the thin wiring (wires close together) of certain buds / ie's. Neco has limited the bandwidth of the amp which helps a bit in stability issues but could be improved markedly this way. Anyway... it's what I would do... if it were mine. 10 Ohm is actually quite low (about the minumum that should be used) and wouldn't affect the sound much but increase stable operation. 16 Ohm HP's max SPL would drop 4 dB, 32 Ohm about 2dB which is hardly noticeable. higher Ohmic resistors are not recommended for general use execpt for the 18V portable versions. Hi, Frans Yesterday I added the 10 Ohm resistors in my Neco portable, and it noticeably improved the SQ, especially with my Senn ie8's. A couple of hours ago I did the active bass boost circuitry that you designed, and managed to install the switch on the front plate of the Neco portable. It was a really tight squeeze, but it worked! I thought about moving the rear LED to the front and install the switch in the back, but, keeping in mind that the wires must be kept as short as possible, I measured carefully the size of the sub-mini switch, and managed to fit it in just to the right of the blue LED, barely clearing the volume control knob. I ended up using 330nF caps, because the 270nF that they sent me are way too big, and they simply will not physically fit. It worked out great, however. The booster is now working more toward the sub-woofer range. Of course, I will not use it with the ie8's, for they have plenty of bass, but switching it on when playing with the Etymotic R-4s, gives them the much needed bass, and now they are a completely different pair of ie's. Fantastic improvement, and I have you to thank for your generous and immensely helpful expert guidance! You are one of the people who make this forum one of the best on the planet! Thank You, Thank You, Thank You!!! All the Best! Israel Added on 5/20/2011
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Post by Deleted on May 20, 2011 5:18:55 GMT
Hi Israel, Glad it all worked out. the designed bass booster is an approximation of the 'wanted filter' especially on the mid bass it deviates. If you replace the 330nF for 220nF the bass lift will lean a bit more towards the mid bass range. the filter is designed to be used with the said earphones only.
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Post by greenstiles on May 21, 2011 11:28:53 GMT
"Neco has already SOLD 18V portables. We've discussed them already on the forum, but no one here has bought one so far ""................hey guys i posted a couple of pages back about my recent 18v i got off Neco with pics, no one notice ? Page 10
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Post by Deleted on May 21, 2011 13:41:54 GMT
"Neco has already SOLD 18V portables. We've discussed them already on the forum, but no one here has bought one so far ""................hey guys i posted a couple of pages back about my recent 18v i got off Neco with pics, no one notice ? Page 10 Hi, I did notice it, and am very interested in reading more about your impressions. Neco told me about it a while back, and I have been on the waiting list for one since then. In his last email, Neco told me that the 18v (new version of it) won't be available until early July. I will use the AD843 op amps in it, since the 18V power supply is of high enough voltage for them. Which op amps does yours have?
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Post by greenstiles on May 22, 2011 12:39:08 GMT
Hi, i got the upgraded op amps that Neco offers. Here is what I thought.....(please note i owned a Mosfet v2 not 2.1) Hi Neco here are my thoughts after listening to 18v Dual pro compared to Mofset v2 (by memory). Using full sized CD player and familiar recordings as source, the dual sometimes seems to have a larger scale than the mofset ! and at other times much smaller ! Voices seem to be a bit more up front and open. Left and right chanel seperation is really really good (perhaps new mofset is too, with seperate supplies now etc ) Detail on the dual pro is sometimes more than the V2 mofset , but on a smaller scale if music is busy. Emotion seems more with dual pro (i noticed this instantly when i briefly had earlier dual (non pro) before getting mofset The mofset was big , rich and relaxed most of the time and great for long listening, but i like the dual pro more in lots of ways, but not completly. Sorry if sounds strange. I have briefly listened to the dual pro for it's intended purpose with an i-pod and all i can say is that it is far far better in every way than without, really different, but i am really enjoying it a lot with full sized CD player at the moment, ( lot's of room for phono to 3.5 jack adaptor next to phones out too, which is great. Cheers Neco. kind regards
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Post by Aragon on May 27, 2011 9:53:58 GMT
new here ,just wondering if you could recommend an opamp to replace my 8610s ,dont get me wrong its an amazing sound but the sflo2/neco/hfi780 chain is just a little bright sometimes with some music (although the bass is still very present). I sold my caffine ultra amp and that tamed highs a little more but i felt it was a class below the neco v2 (gain 4) would the opa627 have the power needed ? oh and errrr any tips on my amp to player joining device ?
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Post by Deleted on May 27, 2011 10:07:54 GMT
Hi, I changed my opamp to opa 227 for the same reason. Ian
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Post by elysion on May 27, 2011 16:23:29 GMT
Welcome, aragon!
Maybe OPA134 could be also an option, but I must admit that I didn't hear it. At least, it's a rather cheap opamp and it works well with the portable.
I don't know much about the Ultrasone HFI-780. It has 35 Ohms impedance and I'm almost sure the portable should drive it well.
BTW: We don't have much informations about Ultrasone headphones on the RG forum. IMO it could be very interesting if you would share your knowledge about Ultrasone headphones.
Christian
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Post by elysion on May 27, 2011 17:01:53 GMT
Aragon, can you tell me the diameter of the Ultrasone HFI-780 pads (at the base and on the top of the pads)?
I've seen on pics that they use a similar pad system like AKG/Superlux use for some of their headphones. I'm just curious if Ultrasone pads work with other headphones and vice versa.
If the diameter is similar to AKG K240, I'd suggest you to try AKG K240 velours pads with them. AFAIK it's a kind of leather/pleather that Ultrasone uses with the stock pads.
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Post by Aragon on May 27, 2011 17:29:34 GMT
thanks for the suggestions ,both those seem very cheap to try ,the pads are eliptical and they seem to measure 95mm by 85mm.(edit maybe 90 by 80) yes the hfi 780s are driven very easily ,but i find the sound is much better through the neco than the headphone socket ,i have the ultrasone demo cd and there is an ear shaking sub bass rumble on it that has an amazing impact on the neco but none through the hp. I do love the 780s though,the vocals are very very intimate if thats the right word ,and every breath and detail is there but most of the other instruments are outside of the head ,to me its not a massive soundstage ,maybe more like inside a big space helmet! the bass has alot of impact but i dont think it drowns out anything else
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Post by mrarroyo on May 27, 2011 23:05:50 GMT
The Beyer DT250 earpads fit very nicely in the HFI780.
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Post by Deleted on May 28, 2011 19:15:20 GMT
<snip> I can see you changing the cable next Israel because you're not a quitter!!! I am curious about a silver based cable in case it helps to tidy up the bass without an amp. I'm not generally fussed about cables on a headphone since I have had some of these 'exotic' things and if I'm honest, I couldn't detect a massive difference. I felt kind of conned at the price levels charged for them. However, if it works for you, then that's fine, but I must admit a curiosity about a silver cable for these just in case it helps the bottom response a tad. Ian, The OFC cable (2 OFC silver plated + 2 OFC wrapped in teflon), which I ordered from Hong Kong for the ie8's arrived today, and my first impressions are that it tightens the bass, and as a result, seems to open up the highs a little more without boosting them. I did a 'back and forth' a few times with the original cable, and the difference to my ears is clearly apparent. At first try I didn't like the sound at all, for I was missing the bass, but then I noticed that in my hurry to change the cable, I didn't ascertain that the connectors are all the way in, but when I did, the bass was all there, and considerably tighter than with the original cable. Also, this cable is much more comfortable to the ears than the original. A fault that I can live with is that the cable is somewhat microphonic, which will probably bother someone that jogs with these phones on. I don't use them when I exercise so it is not an issue for me. The price of the cable is a quite reasonable 24.99 GBP with free shipping, and here is the link: cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250818608233&ssPageName=STRK:MEWNX:IT#ht_1917wt_928 Oh, and for those that wonder, I have no financial interest connected with the above eBay seller. ;D Cheers! Israel
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Post by PinkFloyd on May 28, 2011 19:45:45 GMT
OPA227 is a good allrounder... you could also try OPA228, I have tested them in my Neco and they are fine.... Ian, sorry to be such a slow arse but if you PM me your details again I will get those feet and a couple of OPA228 over to you on Tuesday mate..... it's been hectic here with all this redecorating and I need constant reminders at the moment so PM me in CAPS something along the lines of "SEND ME THOSE FEET AND OPAMPS YOU BASTARD!!"
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Post by Deleted on May 28, 2011 21:37:49 GMT
;D ;D No worries Mike. I know you're upside down. It's not a big deal. Tell you what, those power supplies really kick ass!! I love the new Little Pinkie. Quiet as a mouse and powerful. Ian
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Post by Deleted on May 28, 2011 21:41:48 GMT
Hi Israel,
Really weird .... I was thinking about you today!!
Glad you like the cable. If it is changing the sound there may be a different impedance that the amp sees? (Although you have a 10 ohm resistance in in the Neco don't you?) My goodness, you get stuck in.
It's a cheap cable too. It's getting better all the time!!!
Ian
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Post by Deleted on May 28, 2011 22:19:35 GMT
Hi, Ian I was also thinking that the impedance may be different with the replacement cable, and I will at some point measure the resistance of each cable to see if they are different, but I simply don'y know how to measure impedance of a cable. Perhaps there is a difference also because the replacement cable is stranded and twisted; maybe the OEM one is just stranded. I don't know whether that will affect performance. And, yes I have the 10 Ohm output resistors installed in the Neco portable. Perhaps Frans can give us some insight here. Frans, if you are reading this: Theoretically speaking, with all things being equal, does a stranded and twisted, or pleated cable have a different impedance than one with that is just stranded without being twisted or pleated? Thanks! Israel
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