Talking to my 'tech' friend about the benefits of upgrading op amps in the output stages of CD players (such as the LM833 to NE5532 change I made in my Philips CD620), he wondered if video op amps have ever been considered for upgrade use in audio applications?
After having a wee search through here I didn't come across any mentions of them and I'm just wondering why they have been ignored?
Excuse if there is a blatently obvious reason... they cost a fair bit more, so cost vs benefits perhaps? Or is there a more technical reason they're not considered?
After having a wee search through here I didn't come across any mentions of them and I'm just wondering why they have been ignored?
Excuse if there is a blatently obvious reason... they cost a fair bit more, so cost vs benefits perhaps? Or is there a more technical reason they're not considered?
video versus audio op amps
Video chips are viable for audio. I like the AD811 for example.
It may not be suitable for upgrading an existing product since it is a high bandwidth current feedback amp. There are a number of possible problems that could lead to oscillation.
Internally, the LM7171 is current feedback amp with a buffer on the inverting input; so it is a voltage feedback amp with the speed of a CFB amp. (It can be a drop in replacement for VFB amps, if the circuit can handle the high bandwidth.)
I think there is a subjective preference. I "imprinted" on video amps and think they give a realistic sound. Others might say that they are harsh or noisy and that audio amps are more musical. It is really hard (or at least faulty) to make generalizations since the application of the amp can affect the sound quality so much.
Video chips are viable for audio. I like the AD811 for example.
It may not be suitable for upgrading an existing product since it is a high bandwidth current feedback amp. There are a number of possible problems that could lead to oscillation.
Internally, the LM7171 is current feedback amp with a buffer on the inverting input; so it is a voltage feedback amp with the speed of a CFB amp. (It can be a drop in replacement for VFB amps, if the circuit can handle the high bandwidth.)
I think there is a subjective preference. I "imprinted" on video amps and think they give a realistic sound. Others might say that they are harsh or noisy and that audio amps are more musical. It is really hard (or at least faulty) to make generalizations since the application of the amp can affect the sound quality so much.
They haven't. I have a Micromega DAC1 which uses the LT1227 for the unbalanced analogue outputs.
I think the circuit needs to be designed to take video opamps. I tried the pin-compatible OPA627 in place of the LT1227 but noticed they got very hot (they did work, though). I had adjusted the DC-offset to 0.0 mV with nothing connected to the outputs (outputs of the DAC1 have no DC-blocking caps). Once I connected my headphone amp the DC offset jumped to > 130 mV (despite the fact that the headphone amp does have DC-blocking caps at the input).
The offset-shift after connection was gone when I reinstalled the LT1227.
BTW, my headphone amp actually had some oscillation-issues with the DAC1 in combination with short interlinks that I fixed by adding some HF bypassing on the headphone amp (http://www.diyaudio.com/forums/showthread.php?s=&threadid=135900 ).
I for one prefer using video opamps when using such devices for audio. I find them to sound more transparent than normal audio ones. Some measures have to be made if the video opamps are much faster and make sure they arent oscillating. While experimenting between various opamps I noticed that the ones I prefered all had faster settling times and this was always the case with the video opamps. Some of the commercial highend gear do go this route but mid Fi usually stick with the normal audio ones. Video opamps arent necessarily current feedback, look at ad826, ad827 and ad829.
looking at the thread
felt like making a joke .....
imagine one amplifier that in the ltp stage uses a video IC as mentined above ..... then for drivers use a TDA8177 (clasic vertical television amplifier ) and then for outs something like BU508 ir even better S2055
(dumper diode included ) !!!!!
ha ha ha this will be called amplivision ha ha ha
felt like making a joke .....
imagine one amplifier that in the ltp stage uses a video IC as mentined above ..... then for drivers use a TDA8177 (clasic vertical television amplifier ) and then for outs something like BU508 ir even better S2055
(dumper diode included ) !!!!!
ha ha ha this will be called amplivision ha ha ha
Thanks for all the replies so far, has been very enlightening...!
In general, the only reason my electronic engineering mate brought up video op amps are for the faster settling times and better slew rates. Going with what homemodder said, to me I'd expect the better specs in those areas to translate to better transparency... but ones persons transparency and realism can always equate to someone elses trashy, harsh and noisy! ...And of course, what's on paper might not work out so well in different real life uses.
"More musical" to many people seems to mean what I class as warm, a very British thing apparently.
I have a Denon PMA-255UK integrated amp that was apparently tuned for that "warm British sound". I, on the other hand want to try and undo that (Elna Tonerex capacitors need to get ripped out lol!)
Of course, the extra bandwidth of a video op (up to what 50MHz?!) is hardly going to improve a CD recording that's freqeuncy response ends at 20KHz!
As I'm learning, in these fields everything is subjective and down to very personal taste in most cases...
There is of course all the problems of trying to place a video op amp into where an NE5332 once sat in a CD player even if on the surface it looks like a pin-for-pin replacement (have been reading a pdf about the differences in implementation between voltage feedback and current feedback op amps) but nevertheless, it's something else worth knowing about!
The AD826 looks interesting, has anyone had any experience dropping one of these into where something like an NE5532 was? There are also what gets called 'Precision' op amps that seem to offer better than audio grade op amps specs in settling and slew, but not as 'fast' as video op amps.
Most op amps are reasonably priced to buy and try... I think I really need to do that more to practically see what happens!
In general, the only reason my electronic engineering mate brought up video op amps are for the faster settling times and better slew rates. Going with what homemodder said, to me I'd expect the better specs in those areas to translate to better transparency... but ones persons transparency and realism can always equate to someone elses trashy, harsh and noisy! ...And of course, what's on paper might not work out so well in different real life uses.
"More musical" to many people seems to mean what I class as warm, a very British thing apparently.
I have a Denon PMA-255UK integrated amp that was apparently tuned for that "warm British sound". I, on the other hand want to try and undo that (Elna Tonerex capacitors need to get ripped out lol!)
Of course, the extra bandwidth of a video op (up to what 50MHz?!) is hardly going to improve a CD recording that's freqeuncy response ends at 20KHz!
As I'm learning, in these fields everything is subjective and down to very personal taste in most cases...
There is of course all the problems of trying to place a video op amp into where an NE5332 once sat in a CD player even if on the surface it looks like a pin-for-pin replacement (have been reading a pdf about the differences in implementation between voltage feedback and current feedback op amps) but nevertheless, it's something else worth knowing about!
The AD826 looks interesting, has anyone had any experience dropping one of these into where something like an NE5532 was? There are also what gets called 'Precision' op amps that seem to offer better than audio grade op amps specs in settling and slew, but not as 'fast' as video op amps.
Most op amps are reasonably priced to buy and try... I think I really need to do that more to practically see what happens!
I too am a guitarist, and completely understand the love of the 'valve sound'.
I just find that I prefer having my music presented to me when I'm listening through my system with all the harshness warts and all that might be inherent in a recording, rather than trying to slightly gloss over what might be a trait of a recording with syrupy warmness...
At least, that's what I think I think LOL
I just find that I prefer having my music presented to me when I'm listening through my system with all the harshness warts and all that might be inherent in a recording, rather than trying to slightly gloss over what might be a trait of a recording with syrupy warmness...
At least, that's what I think I think LOL
I mentioned those opamps because I drop them in everywhere, you might need a little compansation cap. They arent too expensive and no 5532 can come near the sound of it. A little while back I changed some friends who insisted me changing their cdplayers and amps ad826s I had put in for them for the new super duper but slower national lme parts, they were back within a week asking for the ad parts back.
There are many advantages into using fast parts, wide bandwith brings advantages, you can read up some technical papers. Why do you think hi end manufacturers use them if there was no point.
Which precision parts are you thinking of ???
There are many advantages into using fast parts, wide bandwith brings advantages, you can read up some technical papers. Why do you think hi end manufacturers use them if there was no point.
Which precision parts are you thinking of ???
Well, looking back at the RS website, the precision op amps hardly seem as good as I thought they were when I quickly looked at them last night when I was half asleep...! lol
But you have now got me very intrigued by the AD826, I will definitely be picking up a couple of these to try out.
Just tonight I have taken out from my old Sony CD-PXE330 2 JRC 4558D op amps (many people on here consider them as truly evil!) replaced them with 2 TI NE5532Ps I had kicking about... Now, I've not got to hear the AD826 as yet, but damn the improvement is pretty astonishing... (I'm pretty sure taking out the muting transistors which I did at the same time won't contribute much to that change in sound) so if the NE5532 makes this much of an improvement, how good will it be if I get a couple of AD826's in there?
lolBut you have now got me very intrigued by the AD826, I will definitely be picking up a couple of these to try out.
Just tonight I have taken out from my old Sony CD-PXE330 2 JRC 4558D op amps (many people on here consider them as truly evil!) replaced them with 2 TI NE5532Ps I had kicking about... Now, I've not got to hear the AD826 as yet, but damn the improvement is pretty astonishing... (I'm pretty sure taking out the muting transistors which I did at the same time won't contribute much to that change in sound) so if the NE5532 makes this much of an improvement, how good will it be if I get a couple of AD826's in there?
Taking out the mute tranny makes quite a difference, I suggest you get schematics for the amp or cdplayer first and carefully study them or come ask here at the forum for someone to check if they can be direct replaced. There are other opamps but youll have to try them, only way you can find out which one you prefer.
Unfortunately can't get a hold of the schematics for this particular CD player but am willing to use it as experiment bench
Luckily my tech friend can figure things out without much hassle so if I do run into trouble dropping op amps into places they shouldn't be he should be able to figure out what's going wrong and how to compensate for it
Luckily my tech friend can figure things out without much hassle so if I do run into trouble dropping op amps into places they shouldn't be he should be able to figure out what's going wrong and how to compensate for it
Completely understand that, I definitely don't intend on dropping in a video op amp with 2500v/uS slew into where a 9V/uS audio op amp was! It's just unnecessary and overkill for me to try and come up against the problems that would cause vs the possible benefits of trying to figure it out.
But something like the AD826 is plausible surely, and if required a slight adjustment of circuit it would be going into is not impossible, I'm not expecting things to go smoothly, but the only way is to try and see I guess!
Please excuse my ignorance on this matter but op amp oscillation... it's something I've yet to experience in my hi-fi tweaking so far, would there be any lasting damage to the surrounding circuit if this was to occur? I take it that running an output from an oscillating op amp isn't a wise thing to do if you value the speakers that would be on the recieving end of the oscillations?!!!
But something like the AD826 is plausible surely, and if required a slight adjustment of circuit it would be going into is not impossible, I'm not expecting things to go smoothly, but the only way is to try and see I guess!
Please excuse my ignorance on this matter but op amp oscillation... it's something I've yet to experience in my hi-fi tweaking so far, would there be any lasting damage to the surrounding circuit if this was to occur? I take it that running an output from an oscillating op amp isn't a wise thing to do if you value the speakers that would be on the recieving end of the oscillations?!!!
Bleachershane
Where exactly are you suggesting replacing the opamp, if its in cdplayer is it the IV converter or the amplification of this. Either way it is a big improvement. Study the datasheet carefully and see what is necesary for it being stable, for the ad826 the supply lines must be bypassed properly. With just this it is probable that it will be stable, if not an additional small value cap of around 22pf will do this but its hard to tell without schematic. What you must do is see whether the opamp has dual supply as sometimes the manufacturers use these junk opamps with single supply, in that case theres a little more youll have to do. What player and model is it, I have quite a library of service manuals. Keep in mind that a VFB opamp should be replacing a VFB, one can change to CFB but not for some applications. Dont just rush in and do it, if done properly youll have no problems.
Nania video opamps are commonly used in high end gear to improve performance, manufactures with equipment costing thousands of dollars dont use cheap 5532 s, I cannot understand your fear. Its simply a matter of using whichever opamp in the way it was intended to be used and the datasheet always has info on this. I suggested this AD part because of its stability, its a folded cascode topology wich has very good high frequency stability already because of its topology, and a very good candidate to just drop in for 5532. Theres no need for opamps with slewrates of 2500 v us but a faster than your average 20 v us opamp is a big improvement, as I said earlier opamps with reduced settling times sound better and more accurate regardless of the slewrate in my honest opinion. If a lm6172 was to be used extra care would have to be taken appropriately and in accordance with datasheet but this opamp is also a major improvement over 5532. Wide bandwith and speed actually helps get rid of RF and other interferances present in a cdplayer
Where exactly are you suggesting replacing the opamp, if its in cdplayer is it the IV converter or the amplification of this. Either way it is a big improvement. Study the datasheet carefully and see what is necesary for it being stable, for the ad826 the supply lines must be bypassed properly. With just this it is probable that it will be stable, if not an additional small value cap of around 22pf will do this but its hard to tell without schematic. What you must do is see whether the opamp has dual supply as sometimes the manufacturers use these junk opamps with single supply, in that case theres a little more youll have to do. What player and model is it, I have quite a library of service manuals. Keep in mind that a VFB opamp should be replacing a VFB, one can change to CFB but not for some applications. Dont just rush in and do it, if done properly youll have no problems.
Nania video opamps are commonly used in high end gear to improve performance, manufactures with equipment costing thousands of dollars dont use cheap 5532 s, I cannot understand your fear. Its simply a matter of using whichever opamp in the way it was intended to be used and the datasheet always has info on this. I suggested this AD part because of its stability, its a folded cascode topology wich has very good high frequency stability already because of its topology, and a very good candidate to just drop in for 5532. Theres no need for opamps with slewrates of 2500 v us but a faster than your average 20 v us opamp is a big improvement, as I said earlier opamps with reduced settling times sound better and more accurate regardless of the slewrate in my honest opinion. If a lm6172 was to be used extra care would have to be taken appropriately and in accordance with datasheet but this opamp is also a major improvement over 5532. Wide bandwith and speed actually helps get rid of RF and other interferances present in a cdplayer
homemodder
My caution was for drop in replacements that many diy'ers frequently presume to do because they see the replacement chip has the same pinout as the original. Yes, I agree that video op-amps can be useful in certain audio applications and my earlier post in this thread mentions where I think they are most suitable. I am not saying that it cannot improve a CD source output but I am saying that it is probably not the best avenue to take when looking to improve your sound. I say that from both from a risk/reward and net improvement perspective. All the components in a stereo system have a part in the final result and here is how I break them down in order of significance:
70% amp/speaker
15% control (ie: preamp/buffer)
10% sources
5% interconnects and other miscellany
I would recommend all budgets to follow these guidelines for the most probable route to audio satisfaction. I say this because too many people will make a $100 effort on a CD source player and expect to hear a huge improvement when they play it out of a JVC integrated chip amp and Radio Shack speakers.
My caution was for drop in replacements that many diy'ers frequently presume to do because they see the replacement chip has the same pinout as the original. Yes, I agree that video op-amps can be useful in certain audio applications and my earlier post in this thread mentions where I think they are most suitable. I am not saying that it cannot improve a CD source output but I am saying that it is probably not the best avenue to take when looking to improve your sound. I say that from both from a risk/reward and net improvement perspective. All the components in a stereo system have a part in the final result and here is how I break them down in order of significance:
70% amp/speaker
15% control (ie: preamp/buffer)
10% sources
5% interconnects and other miscellany
I would recommend all budgets to follow these guidelines for the most probable route to audio satisfaction. I say this because too many people will make a $100 effort on a CD source player and expect to hear a huge improvement when they play it out of a JVC integrated chip amp and Radio Shack speakers.
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