# AD797 now sounds like it should



## NelsonVandal

*EDIT:* This thread has become a bit longer than expected. In short. I implemented AD797 in a bad way and found the sound to be colored. Now it's better implemented and it sounds very neutral, and it has become my favourite opamp. Very smooth and unfatiguing, maybe there's a lack of aggressiveness.

 I bought some AD797AR (SOIC) from eBay, and they don't sound as I expected from the reviews by others. I thought they would sound dark and bassy. I've tried them in 3 different amps. Buffered and unbuffered, Jung multiloop and normal multiloop. 9, 12 and 18 V supply. I've tried to add small caps in the feedback loop as suggested in the data sheet. I've burnt them in over night. There's no excessive current draw, noise, hum or clicks to indicate malfunction.

 To my ears they have a coloration in the lower treble that make them sound bright. This coloration is similar to AD823, but AD797 sounds much cleaner and more sofisticated. They're not the least bassy. I find them very neutral in bass and mid.

 I've only read one review of AD797 that correlates to my findings and that's from Majkel: "AD797 - is like more analytical version of AD825, less impactful and with some glaze over highs." Are the eBay AD797 from another batch or even fakes?

 As I understand AD797 seems to go through a revival, used in Zero DAC and D1. Please comment your impressions of AD797.


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## TzeYang

wow, you managed to tame a BJT AD797 even with multiloop?

 please share your resistor values!!!


 AD797 is used in RSA's top end amps IIRC. They shouldnt sound too bad 
	

	
	
		
		

		
			





. I think, from observation, the Apache is AD797 ---> Push Pull Output stage driven at centre point of two diodes, of course biased to Class A.


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## NelsonVandal

Shopper, you should try AD797 since you like AD823. Regarding the Linear amps, I just haven't got around to order any samples yet. If you have "too many" LT1364 or 1363 lying around, I'll be glad to trade for AD797.

 I haven't got that many opamps left, since many of them have been fried in various experiments and placing them the wrong way on sockets, but the best balance is with LM6171 in ground channel. OPA2134/AD797 is too dark and dull and AD825/AD797 or AD829/797 is a bit bright. I'm awaiting a batch of opamps bought from a fellow Head-fi'er (only dual, I'm afraid).

 AD797 can be unstable. It oscillated in the LISAIII-clone until I added 10 pF caps in the local loop. In the PINT-style 18 V amp it's totally stable with or without such caps. In the 9 V three ch amp with LISAIII buffers it's also totally stable, Jung multiloop or "normal" closed loop, with or without capacitors.

 I can't remember the exact resistor values. In the LISAIII-clone, I think it's more or less the same values proposed by Walt Jung in his original article. In the other buffered amp, the values are a bit lower, but I think it's about the same proportions. In the PINT-style amp, I think it's about the same values as in PINT, with something like a 6 or 8 Ohm "output resistor" in the loop.

 Have you heard AD797? What do you think of it? I don't think it will become a favourite for me, if I can't find a perfect match for ground channel (should be dark sounding yet powerful and detailed). AD797 is a fine sounding opamp in every aspect, but it's far to colored for my taste.


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## majkel

OPA211 is what I'd call "dark AD797". After another bunch of listening sessions I think OPA211 is good, similar to OPA637, the latter being a bit laid back and "confined" in direct comparison.


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## NelsonVandal

I think it's funny to compare the "PINT" amp to "LISA". All this talk about capacitors and "the right" resistor values. The coloration of AD797 is exactly the same in these two amps. The LISA-clone with it's Jung multiloop and isolating JFETs on the rails and discrete buffers, expensive OS-CONs. The PINT-style amp with no electrolytics at all right now, only small ceramics like in RA-1. LISA is slightly better, the soundstage is very special, and it's a bit more detailed, but the major difference is the opamp. It's not easy to be sure either. It could be placebo since I only have one AD829 and one LM6171, and I have to roll opamps while comparing them. I have two NE5534. I think I'm going to compare the amps with the same opamps.

 Majkel, you should do a new list of opamps, like an updated version of this: http://www.head-fi.org/forums/f6/bes...2/#post3032335
 Sound is very subjective, but I think your comments are very accurate. I'm eagerly awaiting two more AD825 to be able to use it in all channels and ADA4841-2 amongst some others.


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## NelsonVandal

I did the comparison AD797/NE5534 in the two amps mentioned above. The LISA-clone is better, no doubt about it. I guess AD797 isn't good driving headphones unbuffered. The tonality was quite allright, since NE5534 is dull and dark. The combination with LM6171 is still better, and it's a better opamp than NE5534 in every aspect. I could live with this combination. I have two PIMETA boards and a lot of discrete buffers. I think I'll make an amp of it.


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## Filburt

I personally like the AD797, but my experience has been (and I'm told my knowledgeable engineers) that it is a somewhat difficult chip to use properly (for reference, I don't consider the AD8397 "difficult"). It cannot just be casually inserted into a circuit; you have to build around it (which means no using SOIC-to-DIP adaptors, especially Browndog!). The topology makes it very sensitive to a variety of environmental factors that you can be much more casual towards with many other chips. If it isn't used properly, you will get substantially rising harmonic distortion with frequency at the least, along with probably other distortion products. My experience has been that it is not suitable for driving headphones directly.

 What resistor values did you use for jung multiloop? The bias current requirement is several thousand times that of, say, the AD744 that ppl seems to like. 

 AD825 is a great chip. One of my favourites to use if I need a JFET-input op-amp, especially if it needs to go over 12V.


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## NelsonVandal

Quote:


  Originally Posted by *Filburt* /img/forum/go_quote.gif 
_I personally like the AD797, but my experience has been (and I'm told my knowledgeable engineers) that it is a somewhat difficult chip to use properly (for reference, I don't consider the AD8397 "difficult"). It cannot just be casually inserted into a circuit; you have to build around it (which means no using SOIC-to-DIP adaptors, especially Browndog!). The topology makes it very sensitive to a variety of environmental factors that you can be much more casual towards with many other chips. If it isn't used properly, you will get substantially rising harmonic distortion with frequency at the least, along with probably other distortion products. My experience has been that it is not suitable for driving headphones directly.

 What resistor values did you use for jung multiloop? The bias current requirement is several thousand times that of, say, the AD744 that ppl seems to like. 

 AD825 is a great chip. One of my favourites to use if I need a JFET-input op-amp, especially if it needs to go over 12V._

 

As far as I can remember, I used basically the same values as suggested by Walt Jung except for a 10k pot and 100k (not 10M) from input to ground, and of course since the buffers are unity gain, there's no local feedback loop for them. Rs = 1k. I don't use output resistors outside the loop.





 Filburt, how does AD797 sound to you? Do you find it "perfect" without any flaws at all? Do you find it colored, and if so in what way?

 And Filburt, are you one of the few who think there is a JFET and a bipolar sound? I do.


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## NelsonVandal

And about BrownDogs, what's so bad about them? I often solder the caps and some of the resistors directly on them. If you take "good" amplifier boards, there are often small ceramics close to the opamps, but the electrolytics are far away. I've seen some measurements of doing this (read it on Diyaudio, not measured myself), and the result is worse than using just electrolytics close to the opamps.


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## NelsonVandal

After some more listening time, I've been more habituated to the coloration, and I can appreciate the very dynimic, detailed but most important musical sound of AD797. It's very engaging. I think the coloration I hear is what people report as tube-sounding, more pentode than triode. Like Majkel said, a glaze over the treble. If you like AD823 you must love AD797. It's like an AD823 but in every single aspect better and "bipolar-sounding" (= non grainy). I'm still using it with LM6171 and LISAIII buffers, multi loop and with 10 pF caps in the local loop.


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## NelsonVandal

Quote:


  Originally Posted by *Shopper* /img/forum/go_quote.gif 
_Pity for the stability concerns, especially mounted on adapters, as mentioned by Fliburt._

 

I have no oscilloscope. I don't know if it's unstable. There's no indication of it with regards to current draw, offset, pops, clicks, interference, noise etc.


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## Filburt

Quote:


  Originally Posted by *NelsonVandal* /img/forum/go_quote.gif 
_As far as I can remember, I used basically the same values as suggested by Walt Jung except for a 10k pot and 100k (not 10M) from input to ground, and of course since the buffers are unity gain, there's no local feedback loop for them. Rs = 1k. I don't use output resistors outside the loop.



_

 

Hey there! Sorry about the delay in replying. You know, holiday festivities and all 
	

	
	
		
		

		
		
	


	




 Anyhow, be careful about the multiloop topology. You need to balance the bias currents. I haven't checked those values to see if they match, but the AD823 is JFET input so it's not as big a deal; the 797 has several thousand times the Ib.

  Quote:


 Filburt, how does AD797 sound to you? Do you find it "perfect" without any flaws at all? Do you find it colored, and if so in what way? 
 

It should sound a lot like the 8599, if that's any help to you. The 8599 is two re-compensated 797s, much like how the 5532 is a recomp'd 5534. The 797 isn't unity stable without external comp; the 8599 is (likewise 5534/5532). I don't find it particularly coloured, and it has a touch of what people call warmth, although in reality I think people are used to output stages which have some third or fifth harmonic distortion problems and so 'neutral' has shifted such that what is actually very low distortion is now termed "somewhat warm" or something of that sort. I think the 797 is better overall, though it is the more difficult of the two to use.

  Quote:


 And Filburt, are you one of the few who think there is a JFET and a bipolar sound? I do. 
 

Not in a specific sense (or "house sound" of sorts as seems to be the popular kind of term on head-fi), but the physical characteristics (and respective performance parametrics) of each type of device presents different challenges for a designer and may lead to different distortion spectra in a particular application.


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## NelsonVandal

AD797 doesn't sound a bit like AD8599. AD8599 has recessed mid and a warmer than neutral tonality.

 Filburt, or anybody else, how should I make AD797 sound it's best? Are there any "known to work" schematics out there?


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## Filburt

Quote:


  Originally Posted by *NelsonVandal* /img/forum/go_quote.gif 
_AD797 doesn't sound a bit like AD8599. AD8599 has recessed mid and a warmer than neutral tonality.

 Filburt, or anybody else, how should I make AD797 sound it's best? Are there any "known to work" schematics out there?_

 

Honestly, since I don't know what your circuits look like, it's pretty difficult for me to help you on your troubles. I'll reiterate, however, the topology is such that these are very temperamental devices that require care in application. Performance can degrade in these chips, relatively speaking, especially rapidly absent proper application.

 AD's own application notes should give you some insight into what you need to do. In order to obtain specified performance, you will probably have to use professionally made PCBs with proper layout, in addition to the schematic requirements.


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## NelsonVandal

I've read the data sheet, and I found an article by Walt Jung http://waltjung.org/PDFs/ADI_2002_Se..._Drivers_I.pdf and now this opamp sounds like it should. I just crumpled the paper and stuffed it in the amp
	

	
	
		
		

		
		
	


	




.

 No, I added a capacitor from pin 8 to pin 6 for "distortion cancellation". I had no 50 pF plastic, so I used 100 pF ceramic. Now the heavy coloration in the lower treble is gone, and it sounds just like in most reports - smooth and even a tiny bit on the dark side. It even sounds OK driving headphones without buffers, and even used unity gain in the ground channel. Why wasn't this cap built in since it seems to be mandatory?

 I won't show pictures of it since the cap I use, a SMD1206, is soldered directly on the opamp pins. People allergic to hardwiring and BrownDogs would get a rash.


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## majkel

So, what did you do with the AD797 after reading that document? 
	

	
	
		
		

		
			





 Gotta know if I need to do something more but I think the AD797 worked as it should in my circuit. It's good but not among my favourite. 

 Here is something more comprehensive:
http://focus.ti.com/lit/an/slod006b/slod006b.pdf


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## NelsonVandal

I just added the recommended capacitor from pin 8 to pin 6 for "distortion compensation". Jung says it's even better to put this capacitor between the buffers output to pin 8 to get a "distortion reduction" in the whole circuit. Maybe I'll try this if I build a dedicated amp for AD797.

 I've put two of these in my LISAIII clone, so they are matched with AD829 in the ground channel. I use the cap mentioned above and 10 pF in the local feedback loop, but I've removed the resistor for the local loop, so there's no Jung multiloop at the moment. Now this amp has a more neutral tonality than with AD744 and there's not the typical JFET graininess or "Analog snap" anymore, for good and for bad. I think it softens the sound a bit, loosing some bite and aggressiveness. Maybe adding 100 pF instead of 50 pF "overcompensates" it, or it's the lack of multiloop. After the hollidays I'll try to find some better caps. Maybe it's the AD829, I've always found it a bit soft.

 It still mates well with LM6171 as ground channel in the other amp only fed with 9.6 V and used with Jung multiloop. For some reason this amp is a bit brighter.

 No doubt about it, AD797 is one of the best opamps.

 Edit: I added local feedback to get the Jung multiloop, and it could be placebo but I think it's more neutral now = less soft.


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## NelsonVandal

Shopper, I always thought you're after some kind of coloration to get a "meatier" sound, yet you want all the details. I'm more a neutrality freak. AD797 is more neutral, very transparent. If I add this amp (the LISAIII-clone with AD797/AD829 with multiloops) between another amp and the phones, it's very hard to hear any difference. It adds very little, all to my liking. I have to give it some time, but I think this is a keeper, better than the original LISA. AD744 is a little lean and has that JFET sound. I think there'll be only bipolars in my "final" amp.

 I've never heard OPA627 or 637. From what I've read, I might like the 637. I've heard OPA2107 which is supposed to sound like OPA627, and I think it's too colored and lacks details. I guess you should like OPA6*3*7. Why not try AD797? 7+9+7=23 so there's no reason for you not to try it.


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## Filburt

2227 isn't JFET input, it's bipolar. 797 has lower distortion than any of the three you listed.


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## Filburt

Quote:


  Originally Posted by *Shopper* /img/forum/go_quote.gif 
_Ops, true. In fact, the OPA2134 is more musical sounding than the OPA2227 (as if it had a more ear-friendly type of distortion); yet both have that typical (full, smooth, without any apparent artificialness) Burr-Brown sound. I guess that probably the house sound thing has greater relevance than the FET/bipolar thing.


 I'm sure that the AD797 does have (even) lower distortion. The LM4562 also has super low distortion on paper but I don't like it better than the OPA627, as it lacks some naturalness and body (some serious deficiencies in my book). The LME49720 is somewhat better.

 I'd still really like to try the AD797, and I probably will even with the concern if it's going to be stable._

 

The 2227 isn't a particularly good op-amp for audio, IMO, but not because it's bjt input. The LM4562 is OK, although not great; I'd rather use the 797. AFAIK the 49720 and 4562 are the same chip; the data on them is identical.

 BB doesn't have a "house sound" that I'm aware of (and I've used a lot of op-amps); that appears to be another one of those unifying principles that are popular on head-fi that I guess has managed to propogate itself, probably because the same core group of op-amps have been used and so there is sampling error due to inadequate set. JFET-input chips involve particular challenges in implementation that can perhaps produce some common distortion problems, although I haven't noticed a more "musical" sound as some sort of general rule. Then again, it's rather unclear just what that means.


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## 12Bass

Quote:


  Originally Posted by *Filburt* /img/forum/go_quote.gif 
_The 2227 isn't a particularly good op-amp for audio, IMO, but not because it's bjt input. The LM4562 is OK, although not great; I'd rather use the 797. AFAIK the 49720 and 4562 are the same chip; the data on them is identical._

 

Have you tried the AD8599? If so, how does it compare in sound to the AD797? I've found the AD8599 to be warmer, detailed, but somewhat less so and less immediate sounding than the LM4562. I'm wondering if these characteristics also transfer to the AD797? If I were to guess, I would say the LM4562 has less distortion and less coloration. What is it about the LM4562 that you don't like? How about the LME49710 - any experience with that one?


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## 12Bass

Quote:


  Originally Posted by *Shopper* /img/forum/go_quote.gif 
_LME49720 is highly recommended by me 
	

	
	
		
		

		
		
	


	




 Intersting - the AD8599 sounding less immediate than the LM4562 somehow justifies my lack of interest for this chip so far. The much trashed AD823 is a chip I like because it sounds immediate._

 

I didn't like the AD823 much at all.... found it sort of bright and brash, but lacking in true high frequency detail.... not very hi-fi.


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## 12Bass

!Why can't I delete my double post!


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## NelsonVandal

AD797 doesn't have any of the "Analog house sound". It's liquid smooth and unlike other high quality bipolar amps the mids don't sound recessed. I prefer it to AD8599. I'll have to see how it stands up for long time listening. Maybe I'll find it to be lacking aggressiveness (it takes longer to find out there's too little than too much aggressiveness), but at the moment this is the new champ. I hope I'll get some more AD825 soon to find out if they're even better.

 The noise level is very low, and there's no problem listening to IEMs. The AD744 I used before is the opposite. I guess it's the noisiest HiQ opamp out there. The amp looks like a rats nest now and still the noise level is just slightly above Mini3 at the same gain.

 About AD8599, I've thought of it as a JFET input opamp, but it's probably not if it's a compensated AD797. They don't tell which it is in the data sheet, but it's a bit grainy in comparison to LM4562 and AD797. It's warmer than neutral and the mids are a bit recessed just like in LM4562 but the latter has a brighter and somewhat clearer treble. I don't find it sounding less "immediate" than LM4562. LM4562 is a bit uninvolving, it's very apperent if you use it in all three channels, then it's really boring. I find AD8599 to be better in this aspect, more involving and warmer.


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## 12Bass

Interesting........ maybe the LM4562 is boring because it doesn't add much coloration (or distortion)? Some people like a bit of grit to liven up the sound. I agree that the AD8599 is warmer - it sounds a bit rounder in the lows to me as well. 

 As for the AD825, so far it is my favorite FET op amp. It's decently quiet, but still quite clear on top and clean and even overall, yet not harsh like a TLE2072 or AD823. It sounds quite uncolored to me. The TLE2072 seems to add some unnatural, somewhat brittle highs which sound impressive at first, but become fatiguing after a while.

 Tonight I spent some time comparing the AD823, LT1057, OPA2604, OPA2132, OPA2134, AD825, TLO72, OP249, and TLE2072. Of these FETs, the AD825 sounds the best overall, with the OPA2132 coming in second. The LT1057 is kind of interesting in the midrange, but lacks openness in the highs. As for the OPA2134, I'm puzzled about why people say it sounds just like the OPA2132, because I clearly hear more detail and less veiling with the OPA2132. In comparison, the OPA2134 sounds kind of "phased" and rolled-off on top.


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## NelsonVandal

LT13xx is on my wishlist.

 I think LM4562 _is_ colored. The coloration is recessed mid. I also find the treble colored but not grainy or lacking details, just a bit artificial. It's not because it's too neutral I find it uninvolving. I think AD797+AD829 is more neutral, and AD8599+AD825 is also more neutral, but these combinations are more involving and sound more alive.


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## majkel

Shopper, I guess I would choose AD845 over the AD797 but honestly I wouldn't use any of them anywhere. For my today's needs they are both too far from being neutral. 
 OPA2107 does not sound like the OPA637, the latter is more neutral but sometimes "slow" and boring. OPA2107 has got great soundstage but not so great timbre and impact.
 Op-amps which still matter to me are:
 ADA4841-x, OPA1632, OPA(2)211, AD825, AD811, AD8045, AD8599, LM4562, AD8022, OPA(2)604
 And the LT's which I haven't tried.


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## majkel

I heard the best Linear op-amp ever was LT1028. Gotta try. This one being not so new should be better suited for stand-alone devices providing high supply voltages, so maybe this one? 
 AD845 is warm and dark (whoaaa, dark AD op-amp 
	

	
	
		
		

		
		
	


	




 ), AD825 is warm and rather bright, and has got very interesting bass.


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## majkel

Quote:


  Originally Posted by *Shopper* /img/forum/go_quote.gif 
_The core difference being that I have the AD845 and not the AD825. 
	

	
	
		
		

		
		
	


	




 Which is the more transparent of the two, btw?_

 

AD825 IMHO, gives better sound differentation while AD845 gives a bit of one-note sound presentation IMHO.


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## Filburt

Quote:


  Originally Posted by *12Bass* /img/forum/go_quote.gif 
_Have you tried the AD8599? If so, how does it compare in sound to the AD797? I've found the AD8599 to be warmer, detailed, but somewhat less so and less immediate sounding than the LM4562. I'm wondering if these characteristics also transfer to the AD797? If I were to guess, I would say the LM4562 has less distortion and less coloration. What is it about the LM4562 that you don't like? How about the LME49710 - any experience with that one?_

 

Seems like folks associate 'neutral' with something _other_ than low distortion. The 797 is more neutral and seems to have better settling characteristics than the 8599, and its distortion is lower, so it's overall the superior of the two. The LM49710 is just a single channel version of the 4562/49720. It's fine, but nothing extraordinary. I'm not a huge fan of that series. I think the NE5532 might sound a bit better. 

 Shopper - I don't know what you mean by "house sound"; I've not experienced such a thing amongst the 40+ op-amps I've used from BB, AD, NatSemi, LT, etc. Haven't found the 8058 to be harsh, either; you probably implemented it wrong. Your comments remind me of (resemble those of) former member Andrea.


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## NelsonVandal

Quote:


  Originally Posted by *Filburt* /img/forum/go_quote.gif 
_Seems like folks associate 'neutral' with something other than low distortion._

 

To me neutral is neutral = not adding or subtracting anything. Not adding "musicality", not widen or deepen the soundstage, not giving a more powerful bass etc.

 Speaking of good opamps. I just got ADA4841-2 amongst some other opamps. Majkel's right. This is a very good opamp (totally not burned in), very transparent, almost neutral. If it's adding something it's adding some kind of nice glow or sparkle. This is very close to AD797. I'm going to let it burn in for a while. There's one major drawback, and I'm not thinking of the rated maximum voltage supply, but DC-offset. It's slightly above 90 mV. Using tangents calculator it should be closer to 130 mV in this amp, so I don't think it's oscillating or behaving bad, just high bias current. I guess it should be used with input caps and balancing the input bias currents.

 I also got some more AD825s, and it's less neutral. This is an opamp for mid-freaks. I can see why it mates well with AD8599. The sound is good though, just a bit forward and a slightly exaggerated mid.


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## NelsonVandal

Quote:


  Originally Posted by *Shopper* /img/forum/go_quote.gif 
_But the music is musical. 
	

	
	
		
		

		
			



_

 

Yes, thats exactly what I mean. There should be nothing more or nothing less.

 You should try AD4841-x, just beware of the DC-offset, and the limited max voltage supply.


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## amb

Quote:


  Originally Posted by *Shopper* /img/forum/go_quote.gif 
_House sound is a sound you recognize as belonging to a particular semiconductor maker. Sorry if you haven't experienced it._

 

There is no such thing as a "house sound" associated with a particular semiconductor brand. Each company, be it TI/Burr-Brown, Analog, Linear, National, whatever., have hundreds of models of opamps, each of which are different in design, and 99% of them were not even intended for audio. Some happened to work well as audio amps. If a few opamps from a particular company sounded alike, it's pure coincidence, not by design. I am sure if the engineers at Analog or TI were reading this they would be quite amused about the "house sound" theory.


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## Filburt

Quote:


  Originally Posted by *Shopper* /img/forum/go_quote.gif 
_e.g.: LT opamps have great tonal quality; BB opamps have a peculiar softness; AD opamps have a peculiar aggressiveness; National's opamps a certain coldness. Then again, nothing too definitive or so clear cut as it could seem from my poor attempt at generalisation.

 I'm just trying to say that different things sound different._

 

My and amb's point, though, is that this is a _false_ generalisation. Someone who would rely upon this generalisation would be misled about the nature of each company's products. If you are encountering a house sound, it is probably due to sampling error or cognitive bias (or both).

 Aside from this, it seems as though people rather casually introduce various op-amps to a circuit and then pass judgment based upon this. High speed op-amps in particular need a substantial body of supporting topology in order to function properly. If you do not have this, you will get distortion; sometimes a lot of it.


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## Filburt

Quote:


  Originally Posted by *Shopper* /img/forum/go_quote.gif 
_"sampling error" 
	

	
	
		
		

		
		
	


	




 And a "cognitive bias" (or just a serious hearing limitation) may be a problem with you, not with me. I know what I hear and I'm not so stupid as to let myself be influenced by "what they say I should be hearing"._

 

Such errors don't have to be due to the words of others. However, it sounds like you're going into each of your trials with some notion of house sound, and that could bias your results. Secondly, you mentioned you were looking at what was noted for audio use either explicitly or by what people used, which points towards sampling bias.

  Quote:


 I have tried high speed opamps in amps where a lot of attention was paid to the problem (for instance the bandwidth of the opamp had been limited, etc.). How do you say it was "distortion" and not the opamp's own unnaturalness I was hearing? 
	

	
	
		
		

		
		
	


	




 Unlike you (so I suspect), I'm particularly sensitized to sonic naturalness - or lack of it. 
 

I'm ear trained for very subtle changes in response, including distortion spectra, since I helped tune psy models as well as have worked on other audio-related projects. I doubt that's the problem here. If you have a wide bandwidth spectrum analyser, or perhaps a scope if you know how to use it properly, you can see for yourself that improper implementation leads to out-of-spec performance. Obtaining optimum performance from a particular chip sometimes comes down to a case-by-case basis rather than having a generic circuit that you can simply plug everything into. Furthermore, most op-amps are not designed to drive a load such as a headphone directly, and the result can be a rather large rise in distortion.

  Quote:


 Btw, Fliburt, you're my perfect embodiment of the limitation of the scientist attitude. 
	

	
	
		
		

		
		
	


	



 

You're wedded to ungrounded notions of "house sound" and other subjectivist traits of inherent character in your descriptions of op-amps, and that seems to be encumbering your ability to approach this issue objectively. Responding to such comments with a critical approach and a concern for proper implementation and optimisation is not somehow deprived and obtuse to the concerns of subjective response.


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## 12Bass

Quote:


  Originally Posted by *Filburt* /img/forum/go_quote.gif 
_The LM49710 is just a single channel version of the 4562/49720. It's fine, but nothing extraordinary. I'm not a huge fan of that series. I think the NE5532 might sound a bit better._

 

Hmmm...... I've found what seems to be cleaner sound with more resolution with the LM4562 as compared to the NE5532. In comparison, the 5532 seems a bit lacking in detail in the highs, along with greater DC offset. LM4562 seems better in this regard.....


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## Filburt

Quote:


  Originally Posted by *Shopper* /img/forum/go_quote.gif 
_No I don't have any "notions of house sound"; I heard this expression being used here and just related it to my prior impressions. No prejudice, you see.


 As you may tell at this point, regarding subjectivism, and individualism, I'm a committed advocate of it as an objective trait of the human being - probably the only one we can tell. 
	

	
	
		
		

		
		
	


	




 In particular, I'm fully conscious of being subjective and individual in my hearing (ok, well...sometimes I would need to remind it to myself 
	

	
	
		
		

		
		
	


	




 )


 So I'm proud and shameless in being wedded to my subjective and individual traits. Not that opening yourself up to 'the rest of the world' is substantially denied, not really! But firstly you need to fully realize, and come to terms with, your own peculiarity - or you can only remain caged in your own subjectiveness of perspective (and subsequent intolerances). Ok I've drifted a bit. 
	

	
	
		
		

		
		
	


	


_

 

It seems like what's really going on here is that you're unhappy that I criticised your evaluative methodology, and so are responding by insinuating I simply lack the ability to make relevant analysis of the suitability of one chip or another for audio purposes in order to argue that somehow your methodology is sound and your evaluations accurate. This is a pretty unconvincing argument, overall, and is mostly just an ad hominem argument instead of a substantive defense of your methodology and does very little to address the issue of accuracy. I'm not sure what to make of your tangent on subjectivity and individuality but perhaps you dislike this 'scientific' approach because it appears to contain underlying deterministic elements which, when fused with a sensitivity to subjective performance, undermines an idea of people carrying individual, exclusive, and perhaps unique ownership of their preferences. Since what you're posting is almost patently incoherent at times, it's rather difficult to be sure this is the case, but that's the impression you've given me. 

 Science is fundamentally about mastery of the empirical universe, which includes subjective phenomena. Thus an analytical approach that involves science is relevant on the issue of subjective response. It's a matter of abstracting it to analysable data which can be used to obtain the desired results, not a matter of substituting something akin to my written response to you for the somatic elements of my hearing when I listen to music. It is simply not useful data or discourse for me to bother with using unclear subjectivist terms to describe amplifier performance, nor is it particularly useful or productive to act as though my senses will somehow transcend the physical limitations of these devices such that I can sense some (fictitious) essential character and render forth a description for all to bare witness to.

 Thus, it remains the case that op-amps are sensitive devices, and some of them may have their performance shifted dramatically by environmental factors that seem negligible, or simply don't occur to the user, and may not necessarily impact the performance so dramatically with other chips. Responding by telling me that you're just relaying what you're hearing and that you have confidence in the designs of the Xenos and Go-Vibe products doesn't change that and, looking at those respective designs, doesn't provide a particularly compelling case that this issue is of negligble relevance. Responding by telling me I'm being too analytical and insinuating that I'm completely obtuse to the matter at hand simply insults the integrity of our discussion and essentially forces us to discuss irrelevant matters.

  Quote:


  Originally Posted by *12Bass* /img/forum/go_quote.gif 
_Hmmm...... I've found what seems to be cleaner sound with more resolution with the LM4562 as compared to the NE5532. In comparison, the 5532 seems a bit lacking in detail in the highs, along with greater DC offset. LM4562 seems better in this regard....._

 

The Ib on the 4562 _is_ lower, so sure you'd probably get lower offset. The NE5532 is quirkier to work with than the 4562 and is more sensitive to your decoupling/bypassing configuration, so it may be of some benefit to check that first before passing final judgment. Also, which 5532 did you use? There are a few variants out there and, due to some differences in the manufacturing process, performance is shifted somewhat as a result. I've found the TI part to work the best, although I know a lot of people seem to like the old Philips/Signetics (which I have, but have found kind of fuzzy sounding; possibly due to poor settling characteristics onset by a less refined manufacture process). Overall, though, I'm still mostly undecided between the 5532 and 4562 on which sounds better.


----------



## Filburt

Quote:


  Originally Posted by *Shopper* /img/forum/go_quote.gif 
_My way of proceeding is something you don't seem to grasp. Contradiction? It is inherent of the human nature, and me being just a human being I accept & welcome it. 
	

	
	
		
		

		
		
	


	




 The human knowledge is bipolar -- that is, it proceeds by a troubled experience of the opposite poles, rather than by taking one stance and remaining obstinately coherent whatever happens around you.

 How true. Do you think it all ends there, with the "empirical universe"? Ultimately it's just a matter of how articulate and complex is your own perception of things; hence my mentioning synaesthesia.

Baudelaire: "Je me resigne à la modestie"


 Oh that's it for me because I'm getting bored answering your totalitarian scientific discourse. 
	

	
	
		
		

		
		
	


	


_

 

Well, I guess a muddled reference to dialectic along with a misunderstanding of what constitutes 'empirical universe' is as good a way as any to end the conversation.


----------



## 12Bass

Quote:


  Originally Posted by *Filburt* /img/forum/go_quote.gif 
_The Ib on the 4562 is lower, so sure you'd probably get lower offset. The NE5532 is quirkier to work with than the 4562 and is more sensitive to your decoupling/bypassing configuration, so it may be of some benefit to check that first before passing final judgment. Also, which 5532 did you use? There are a few variants out there and, due to some differences in the manufacturing process, performance is shifted somewhat as a result. I've found the TI part to work the best, although I know a lot of people seem to like the old Philips/Signetics (which I have, but have found kind of fuzzy sounding; possibly due to poor settling characteristics onset by a less refined manufacture process). Overall, though, I'm still mostly undecided between the 5532 and 4562 on which sounds better._

 

The 5532s in my possession are a Signetics NE5532 from my NAD 3150 integrated amplifier and an old Exar XR5532 which I had lying around. From what I recall, neither seems to have the openness of the LM4562, but it has been a while since I have given them a critical listen. Also, note that I've been using them in either the preamp stage of my NAD or in my Eden WT-500 bass amplifier, NOT in a headphone amplifier, although I have made sure to employ careful decoupling in both circuits. I'm planning to build a variant of the CMOY sometime in the near-future. The particular applications under study may explain some of the differences I'm hearing....


----------



## Filburt

Quote:


  Originally Posted by *12Bass* /img/forum/go_quote.gif 
_The 5532s in my possession are a Signetics NE5532 from my NAD 3150 integrated amplifier and an old Exar XR5532 which I had lying around. From what I recall, neither seems to have the openness of the LM4562, but it has been a while since I have given them a critical listen. Also, note that I've been using them in either the preamp stage of my NAD or in my Eden WT-500 bass amplifier, NOT in a headphone amplifier, although I have made sure to employ careful decoupling in both circuits. I'm planning to build a variant of the CMOY sometime in the near-future. The particular applications under study may explain some of the differences I'm hearing...._

 

Ah, okay. Your description definitely made me wonder if you were using the Signetics chips; I'd probably describe them similarly. I mostly compared the chips in an LPF or buffer stage, so I think we're getting fairly similar circumstances in our comparisons. I didn't get the opportunity to compare the TI and Signetics NE5532s as much as I would have liked, but I did compare the respective 5534s considerably, and found that the differences appeared to be of the same nature. The Signetics are less clear, have a narrower soundstage, and an overall warmer character. When I ran them on an analyser, I did notice more distortion in the Signetics overall.


----------



## Filburt

Quote:


  Originally Posted by *Shopper* /img/forum/go_quote.gif 
_I'd like it if you'd develop just a little why you consider my "reference to dialectic" as muddled, and why I'm misunderstanding "empirical universe" (which I may be), but then again if your proudness needs leaving it at it... 
	

	
	
		
		

		
		
	


	





 Okay I just read "...which includes subjective phenomena". No problem with that. Nut that's not my point, which you definitely don't grasp._

 

'Empirical universe' refers to the sum total of those things observable, which includes things such as "this sounds like ____ to me." I called your reference muddled because that's essentially the concept you're describing, but you chose to use a circuitous and ultimately unclear method of conveying it. Secondly, just because I don't endorse your view of the issue doesn't mean I don't _understand_ it. On the contrary, I understand it, and find it lacking. Mi spiace che non mi capisce....;D


----------



## Filburt

Quote:


  Originally Posted by *Shopper* /img/forum/go_quote.gif 
_I have edited my post. Now it should give you a glimpse on why your "empirical universe" is so subjective (and as such, your science). Essentially, it is so subjective because it takes a hopelessly objectivist approach (since true objectivity is not in any way in the reach of purely rationalist-determinist means such as the traditionally scientific).

 And, the concept I was illustrating before lies at a more fundamental level than dialectic; dialectic (which is internal to every individual firstly) is already a consequence of the inherent bipolarity of man and of his/her knowledge. Do you understand me? I was trying to rationally address the subject of the broken unity of feeling and understanding (which is somewhat pertinent since you've proven to lack synaesthesia - which is a definite symptom of it). 
	

	
	
		
		

		
		
	


	


_

 

Synaethesia is the misexcitement of one sense in place of or simultaneous to the excitement of another. e.g., synthesis of aesthetes, or synaesthesia. That really isn't relevant here, and you've done very little to show that I somehow lack the capacity to do useful analysis of subjective response in amplifier performance other than a bunch of hand-waving and digression. Giving me watered down greek, cartesian, and existentialist philosophy along with ad hominem arguments doesn't make the problem go away; it just makes our conversation look silly and takes up a bunch of space with irrelevant banter.

 Anyhow, I'm not going to subject the DIY forum to more of this. I get it; you think I'm somehow obtuse to the fundamental nature of audio, and that's your defense to your test methodology and your results. Have at it; buona notte.


----------



## NelsonVandal

I think I agree with the statements above. So far AD797 is my favourite opamp as well. It's tame but not clinical like eg LM4562. It's warm, comfortable as an old pair of jeans and "natural" sounding even though it's colored - weird. Compared to AD744 it lacks some energy/aggressiveness and I also find it a bit less 3D, but I combine it with LM6171 which isn't the best opamp. From your description it should be a perfect match with LT1363 in ground channel.

 How did you implement AD797? Are you using a capacitor from pin 6 to 8 for distortion compensation? If so, what value and type do you use? Are you using caps in the feedback loop as recommended in the data sheet? Local or global?


----------



## majkel

I know it's not easy to satisfy myself and I have to admit that the AD797 is a very good op-amp that I can't stand. It's the same case as with the OPA637 - it's very good but there is something wrong and frustrating in the sound. The OPA637 lacks attack, sounds begin to slow, with compressed impact. In the AD797 I hear that lower treble glaze, maybe it helps for rock but it's too obvious and pronounced that I perceive it as a residual addition to the sound which I would like to get rid of but I cannot. I don't think it's due to stability issues because no symptoms of that have appeared in my circuit - normal power consuption and no weird behaviors while turning the volume knob or plugging the headphones. 
 As I mostly agree with the description comparing the AD797 to the AD8397 (which I refused to use any more many months ago), I have to say that there are op-amps that in spite of being audibly imperfect, they are likeable, i.e. AD825 single or AD8022 dual, and on the other side, there are chips being almost perfect, with one but nasty imperfection. Maybe it's because this imperfection is not well hidden behind the others but I'd rather say this is more because of their inacceptability to a certain individual like me. Ending this elaborate write-up, I think the OPA211 is worth direct comparison with the AD797, they are not far from each other IMHO, with the OPA211 providing better soundstage and no artificial treble shine.


----------



## majkel

I tried to try yesterday, but IE7 in my office doesn't work with the Linear Shopping Basket correctly. It does not update. I have to remember ordering the LT1364's when at home where I have more internet browser options and access rights.


----------



## NelsonVandal

Quote:


  Originally Posted by *majkel* /img/forum/go_quote.gif 
_In the AD797 I hear that lower treble glaze, maybe it helps for rock but it's too obvious and pronounced that I perceive it as a residual addition to the sound which I would like to get rid of but I cannot. I don't think it's due to stability issues because no symptoms of that have appeared in my circuit - normal power consuption and no weird behaviors while turning the volume knob or plugging the headphones._

 

Majkel, are you sure you have a small capacitor (the data sheet recommends 50 pF) from pin 6 to 8 on the AD797? It seems to be mandatory. It changed the sound dramatically in my amps, and there wasn't an increased current draw, noise, clicks, interference, high DC-offset or anything else indicating instability. That cap should probably simply just be there. There's still some sort of coloration in the treble like before but lower by a magnitude.

 Since you like the sound of ADA4841-x, you should like AD797. It's a bit drier and lacks some of that colorful sparkle, but I think it's more neutral and does everything better.


----------



## Filburt

I'd like to reiterate that the AD797 is _NOT_ something you can just casually drop into a circuit. It can, and will, incur substantial rise in distortion absent proper implementation, and it will do so to a degree that exceeds that of most other chips. You cannot properly evaluate its performance absent proper implementation, as the overall sound characteristic will be substantially altered otherwise, and there is no "common thread" or what have you that will render an impression, in the presence of improper implementation, as being somehow representative of the performance in the presence of proper implementation.

 As for the OPA211, I think it's OK, but the AD797 does seem better overall to me. The 211 has more gain stages and more degeneration, I think, so it gets a better 1KHz THD+N figure, but the 20KHz figure isn't really any better and I do wonder if perhaps TIMD or aharmonic products may be higher due to what may be a less optimal feedback structure and overall topology.

 Nelson - "coloured" as compared to what, exactly?


----------



## majkel

No, I wasn't using any capacitors between the pins but I remember such eperiments with other AD op-amps and placing the compensation capacitors was degrading the sound - it was loosing immediacy and speed, leaning towards boring sound while preserving the tonal balance. You have to keep in mind that I've been testing the op-amps in a buffered configuration with a global negative feedback loop. This changes the frequency/phase relationships due to the characteristic of the buffer, and all direct datasheet recomendations become invalid. I can tell you that in my circuit the AD8099 is stable at gain of 1 and produces top notch sound, say amongst the few best. And again, what I am writing about is just a slight efect but my ears seem to be sensitive to this. The same with the OPA637, it's similar to OPA1632, where the latter sounds like a sweet spot between the OPA211 and the OPA637. They are actually close to each other, the OPA637 being the slowest, the most airy and the least precise, the OPA211 a tad too dry with OK speed, the OPA1632... could be more colorful but in this field is still better than the AD744. 
 Finally, our observations might differ because of different accompanying equipment like sources, headphones and the rest of the amp. Refer to my signature for some info.


----------



## NelsonVandal

Quote:


  Originally Posted by *Filburt* /img/forum/go_quote.gif 
_I'd like to reiterate that the AD797 is _NOT_ something you can just casually drop into a circuit. It can, and will, incur substantial rise in distortion absent proper implementation, and it will do so to a degree that exceeds that of most other chips. You cannot properly evaluate its performance absent proper implementation, as the overall sound characteristic will be substantially altered otherwise, and there is no "common thread" or what have you that will render an impression, in the presence of improper implementation, as being somehow representative of the performance in the presence of proper implementation._

 

I wish you or just somebody could tell me how it should be implemented. You could also tell me how it should sound, in what way it colors the sound. I wont believe you if you say it's the only amp on earth with a totally pure sound without the slightest imperfections. If you do know a way to get this to sound totally transparent, you ought to tell us so we could stop all this tweaking and upgraditis and just enjoy good music. How have you implemented it, or is it a family secret?

 AD797 sounds good in my amps now. It has less coloration than other opamps I've tried.

 Are you hinting that fewer active components make a better amp? I also have this feeling, and I've started to explore simple discrete amps with fewer parts and I hope I eventually can leave opamps behind.

  Quote:


 Nelson - "coloured" as compared to what, exactly? 
 

Compared to nothing. I've already told you so. CDP>amp>amp to be evaluated>phones vs CDP>amp>phones. Or DAP>amp to be evaluated>phones vs DAP>phones. When I speak of neutrality, I don't mean "inner details" or esoteric nuances. I mean tonality and if it sounds soft or hard.


----------



## majkel

I've read the datasheet of the AD797 focusing on pin 8 and it says that you should start using this pin around a gain of 10. I tried at unity gain so it doesn't apply. This is quite possible that in a different design the AD797 will shine. It's all about the synergy and I agree that transparent op-amps don't exist.


----------



## Shoewreck

I've finally assembled a headamp based on AD797. That's a revelation, sincerelly. I hear no colouration, just loads of smooth detail. Of course, I've thoroughly read the datasheet, so Cn was installed before the first listening.
 I haven't used any output buffer, that's not good considering my K501 are only 120 Ohms. I'll probably add one later, but for now I'm almost fully content with the amp.
 One trick I've done was adding a 470 Ohm resistor inside feedback loop. If you check Fig.19 of the datasheet you'll see that something strange happens to AD797' open-loop output impedance. It grows a lot once the load resistance falls below 200 Ohms. I know that sounds odd, but additional resistor seems to lower closed-loop impedance. I may be wrong here, but at least the resistor should also make driving a headphone cable (capacitance!) easier.


----------



## NelsonVandal

I'm glad you like AD797. Have you read http://www.sg-acoustics.ch/analogue_...distortion.pdf. This confirms the sonics
	

	
	
		
		

		
		
	


	




.

 I don't really understand where you put that 470R resistor. What values do you use for feedback resistors etc? What virtual ground concept do you use?

 One thing I've found out is that AD797 is happier with low impedance at it's input, but using something like a 1k pot has it's drawbacks loading down the source.

 This is what I'm running at the moment. A discrete JFET input, class A output "AD797". Sounds very good.


----------



## Shoewreck

Quote:


  Originally Posted by *NelsonVandal* /img/forum/go_quote.gif 
_I don't really understand where you put that 470R resistor. What values do you use for feedback resistors etc? What virtual ground concept do you use?_

 

The 470R resistor is connected between output pin of the opamp and the point where feedback resistor meets the phone output. I haven't yet moved the Cn - I'm not sure if I should. "Real" ground and dual power supply (+- 19V - just a bit beyound maximum ratings). Non-inverting connection. 470R feedback, 120R to ground (gain is about 4.9).

  Quote:


 This is what I'm running at the moment. A discrete JFET input, class A output "AD797". Sounds very good. 
 

The output buffer is close to what I'm going to add to my AD797 headamp, except JFET current sources in the driver stage - I'd simply set idle current with resistors.


----------



## NelsonVandal

I use my AD797s with CCS loaded diamond buffers and active ground channel (AD829 or AD825). The amp is battery powered by two 8.4 V batteries. I think AD797 is slightly dry and a bit bright, but it's the best opamp I've ever heard.


----------



## majkel

Quote:


  Originally Posted by *NelsonVandal* /img/forum/go_quote.gif 
_I think AD797 is slightly dry and a bit bright, but it's the best opamp I've ever heard._

 

Because you're using cheaper ANZ or ARZ series. Try BRZ and you'll lose admiration for discrete voltage stages for some time.


----------



## Shoewreck

Quote:


  Originally Posted by *majkel* /img/forum/go_quote.gif 
_Try BRZ and you'll lose admiration for discrete voltage stages for some time._

 

I just checked the DS. AD797B has generally higher open-loop gain.


----------



## NelsonVandal

Quote:


  Originally Posted by *majkel* /img/forum/go_quote.gif 
_Because you're using cheaper ANZ or ARZ series. Try BRZ and you'll lose admiration for discrete voltage stages for some time._

 

I didn't know they sound different. The circuit in A and B have to be the same. It seems to me that the B's are picked out with regards to lower DC offset, and better matched inpupt transistors should give a slightly higher OLG. It's funny the B's PSRR is worse. I don't think I'll loose admiration for discrete amps when they sound as close to perfect as they do, and there's still room for improvements with CFP and/or cascode input stage, better output transistors, better caps, higher supply voltage etc.


----------



## NelsonVandal

Majkel, to start a little discrete vs. monolithic opamp battle - have you ever used SA1016/SC2362. The difference using them vs. SA970/SC2240 or BC550/BC560 is like comparing AD797 to NE5532 or OPA2134.


----------



## majkel

Oops. I know the latter, SA970/SC2240 and SK170/SJ74. Good to know. The AD797BRZ are truly better, also the P vs. PA series gives better sound, or BP against AP, the LT1028ACN8 sound different and better than the CN8 series. I tried it out and I'm telling what I heard. Just another legend revised.


----------



## Filburt

Nelson, where do you get your 2SA1016/2SC2362? bdent has some but some posts on diyaudio seem to indicate they only stock the "F" grade which has the lowest beta. bdent's site doesn't specify what grade they have other than it's the "K" type, where K seems to just specify a different Vcbo and Vceo.


----------



## NelsonVandal

Quote:


  Originally Posted by *Filburt* /img/forum/go_quote.gif 
_Nelson, where do you get your 2SA1016/2SC2362? bdent has some but some posts on diyaudio seem to indicate they only stock the "F" grade which has the lowest beta. bdent's site doesn't specify what grade they have other than it's the "K" type, where K seems to just specify a different Vcbo and Vceo._

 

I bought them from bdent.com. SA1016 Hfe 300 - 330 and SC2362 200 - 300. I've got some from a member at diyaudio.com that he had bought from profusion. The Hfe of those were slightly higher. Lowish Hfe or not, they sound much better than the other small signal transistors I've tried.


----------



## majkel

Which BC550's are you referring to? I have very nice memories with those from Fairchild. Not yet tried from NXP but their BC337/BC327's sounded worse.


----------



## Filburt

Quote:


  Originally Posted by *NelsonVandal* /img/forum/go_quote.gif 
_I bought them from bdent.com. SA1016 Hfe 300 - 330 and SC2362 200 - 300. I've got some from a member at diyaudio.com that he had bought from profusion. The Hfe of those were slightly higher. Lowish Hfe or not, they sound much better than the other small signal transistors I've tried._

 

I was thinking of using them in my CKKIII build I'm doing. I picked up some 2SA968/2SC2238 for output; not sure if those will work well or not.


----------



## Pars

Quote:


  Originally Posted by *NelsonVandal* /img/forum/go_quote.gif 
_I bought them from bdent.com. SA1016 Hfe 300 - 330 and SC2362 200 - 300. I've got some from a member at diyaudio.com that he had bought from profusion. The Hfe of those were slightly higher. Lowish Hfe or not, they sound much better than the other small signal transistors I've tried._

 

Anyone know what the 2SA1016K-AA is that bdent carries as well? Same price, not shown in datasheet. The -AA version of the 2SC2363K is cheaper.


----------



## NelsonVandal

Quote:


  Originally Posted by *majkel* /img/forum/go_quote.gif 
_Which BC550's are you referring to? I have very nice memories with those from Fairchild. Not yet tried from NXP but their BC337/BC327's sounded worse._

 

I've tried both Fairchild, NXP and noname. There's no major difference between them.


----------



## Pars

I found that the -AA version is tape and reel.

 I've seen mention in this thread as well as on diyaudio of Profusion? WHo are they? Google didn't find a website. I take it they only do large orders (100 pieces or more)?

 When changing out transistors (this in an I/V stage) are only the transistors in the signal path of interest, or should all of them (CCS, etc.) be changed? Design is rbroer's less simple, and so far I have only changed Q4 and Q6 in the attached schematic. I may just do the rest of them; they are currently 2SA970/2SC2240.


----------



## looser101

Quote:


  Originally Posted by *Pars* /img/forum/go_quote.gif 
_I found that the -AA version is tape and reel.

 I've seen mention in this thread as well as on diyaudio of Profusion? WHo are they? Google didn't find a website. I take it they only do large orders (100 pieces or more)?_

 

Profusion

 I assume that's what you are looking for.


----------



## NelsonVandal

Quote:


  Originally Posted by *Pars* /img/forum/go_quote.gif 
_I found that the -AA version is tape and reel.

 I've seen mention in this thread as well as on diyaudio of Profusion? WHo are they? Google didn't find a website. I take it they only do large orders (100 pieces or more)?

 When changing out transistors (this in an I/V stage) are only the transistors in the signal path of interest, or should all of them (CCS, etc.) be changed? Design is rbroer's less simple, and so far I have only changed Q4 and Q6 in the attached schematic. I may just do the rest of them; they are currently 2SA970/2SC2240._

 

I think Q4 and Q6 (and the SK389) are the most influential transistors in this circuit. If I understand the circuit right, it's a single end folded cascode topology, where Q4 is input and Q6 the cascode and SK389 is a buffer stage. Do you know at what currents the transistors run?

 Does it sound good? Have you already rolled transistors?


----------



## Pars

Quote:


  Originally Posted by *NelsonVandal* /img/forum/go_quote.gif 
_I think Q4 and Q6 (and the SK389) are the most influential transistors in this circuit. If I understand the circuit right, it's a single end folded cascode topology, where Q4 is input and Q6 the cascode and SK389 is a buffer stage. Do you know at what currents the transistors run?

 Does it sound good? Have you already rolled transistors?_

 

I'm not using the buffer, though I do have 389BLs and 170BLs. I had already changed Q4 and Q6. I completed changing the other 3 BJTs and am listening to it right now. It sounds great (but it did with the sa970/SC2240s as well).

 IIRC, Q3 has 9-10mA thru it (+/-15V PSU, TL431s drop 2.5V). About 10mA was the highest I could get the 970/2240s to be stable (stage has no feedback). From my reading, it would appear that the SA1016/SC2362s don't really iike higher currents either.

 The hFe on these transistors is a bit low (my SC2362s were measuring 190s to just under 300; SA1016s were low 300s), and I got them from bdent so they are F grade.


----------



## NelsonVandal

Yes, the Sanyos don't like too much current. I feed mine not more than 1 - 2 mA. Didn't you notice any difference?


----------



## Pars

Quote:


  Originally Posted by *NelsonVandal* /img/forum/go_quote.gif 
_Yes, the Sanyos don't like too much current. I feed mine not more than 1 - 2 mA. Didn't you notice any difference?_

 

It seemed quite stable at the present currents, even without the servo installed. I did quite a bit more listening, but recollection being fickle, I can't say which sounds better. I was rather pleased with what I was hearing however. Typo in my previous response also (2SC2240 when I meant 2SC2362).


----------



## xslavic

hi,i know that this post is old but i wanted to ask where do you put the 10pf capacitor, between pin 6 and 2 =


----------



## rds

Quote: 





nelsonvandal said:


> If you take "good" amplifier boards, there are often small ceramics close to the opamps, but the electrolytics are far away. I've seen some measurements of doing this (read it on Diyaudio, not measured myself), and the result is worse than using just electrolytics close to the opamps.


 

 Not very convincing without seeing the measurements or the circuit measured.  Regardless, there's a reason why op-amps makers recommend "fast" ceramic caps close to the op-amp.  This picture tells the story if you understand how non-deal capacitors behave as a function of frequency:
   

   
  PS that's from the opa627/637 datasheet
   
   
*Edit: Just realized I replied to a comment from over 3 years ago :$*


----------



## xslavic

why ceramic? isnt better using polypropylene or polyester capacitors ?


----------



## holland

Quote: 





xslavic said:


> why ceramic? isnt better using polypropylene or polyester capacitors ?


 


  for what?
   
  decoupling?  no.
  signal?  yes....and no.
   
  for decoupling, it's hard to beat ceramic, low ESR, low ESL, and temperature stable.
  for AD797 decompensation I would personally use mica, for temperature stability and stable capacitance over a high bandwidth instead of plastics.
   
  as to where to put the cap, read the datasheet.


----------



## 00940

Oh, come on, forget ceramic or mkp and just follow the example of all the Chinese "audiophiles" designers : put as many wima mkt caps near your opamps as you can.
   
  But they have to be red for the magic to work. 
	

	
	
		
		

		
			




   
   
   
  Am I kidding ? I ? Never....


----------



## holland

You're right, what was I thinking!  red FTW!
   
  Retired
  Extremely
  Dangerous


----------



## xslavic

i agree with ceramic but why mkp,those the film are the same with wima,or mkt that are good for power supply filters(self healing)


----------



## holland

Quote: 





xslavic said:


> i agree with ceramic but why mkp,those the film are the same with wima,or mkt that are good for power supply filters(self healing)


 


  He's making fun of designs for audiofools.  In other words, "ooh, MKP/MKT, let's put them everywhere, it's so boutique".  The "proper" engineering design will use the appropriate caps necessary, taking into account the function the capacitor is supposed to play in that particular position, and why.


----------



## piotrekfronc

I have a one question, can you have a look at the ad797 on the board:
  

  
 ?
  
 I have bought balanced card based on 4 AD797 for my MA9 and... I can hear hiss (ground noise!) in my IEMs (JH16),
  
 I am sure that genuine AD797 should have almost ZERO noise! Is it possible these are fake AD797???
  
 Im thinking on ordering from mouser genuine 4 AD797BRZ and replacing those


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