Hi JPV,
I will try and answer most of your questions (even though I get no benefit from it as my last paycheck from National just arrived in the mail today.)
The LME49811 is a mono version of the LM4702 with a few minor layout changes that Bob Pease suggested. The LME49710 is a whole other animal! Both parts sound great and all my listening comparisons were done on the same ckt board inside of the same mono block amplifiers for both parts.
The pole being higher in freq for the 811 is because an extra A/B output stage was added to the 810 to get the 50 ma of output current, which of course changes the loop response. I believe that is the reason I slightly prefer the sound of the 811 to the 810 with identical bipolar output stages. I don't like sound of FET outputs so let's not even talk about the 830.
Someday I could relate a long story of a test at Wilson audio with coupling cap removal in a 4702 amplifier but suffice to say even the very best/most expensive caps in the world are very, very audible in the signal path!!!!! Servos are the way to go where there is a DC problem but better to make a pure signal path with no offsets... which I know is hard to do.
The extra compensation circuit for the 4702 and 49811 is actually a noise gain compensation circuit not an extra compensation circuit. I did not know that either and one of our Masters Stanford grads pointed out to several of us the difference. Young college kids actually can be of use sometimes! It is mandatory for that 75pf and 3.3k resistor to be there!!! You will have osc problems coming out of clipping if it is not there.
Also the 4702 and 49811 share the same soft clipping circuit that is virtually a Baker Clamp but the clamp in the 49811 IS a real Baker Clamp. Sonically both parts are very easy on the ears when in clipping. So use the 810 if you need the clipping flag or need the 50ma to get more than 300 watts. Use the 811 for the highest sound quality if the power needs are 300 watts or less.
I did not design the chip so I can't talk about the output stages in any of the parts.
Not sure about your bias questions either, as we did not have time to try other bias schemes. We only used the Vbe multiplier circuit that is in the schematic/ap note for the 4702.
The mute and shutdown circuits can be used in the manner you described for protection. I know that others are doing the same thing successfully.
Hope this all helps! Wish me luck in my job search and buy a lot of these parts so National might bring some of us back to make more.
Be sure and try the LME49710 VFB and LME49713 CFB opamps in the metal cans in all your low level circuits.
Best DIY Audio Regards,
Mark / audioman54
I will try and answer most of your questions (even though I get no benefit from it as my last paycheck from National just arrived in the mail today.)
The LME49811 is a mono version of the LM4702 with a few minor layout changes that Bob Pease suggested. The LME49710 is a whole other animal! Both parts sound great and all my listening comparisons were done on the same ckt board inside of the same mono block amplifiers for both parts.
The pole being higher in freq for the 811 is because an extra A/B output stage was added to the 810 to get the 50 ma of output current, which of course changes the loop response. I believe that is the reason I slightly prefer the sound of the 811 to the 810 with identical bipolar output stages. I don't like sound of FET outputs so let's not even talk about the 830.
Someday I could relate a long story of a test at Wilson audio with coupling cap removal in a 4702 amplifier but suffice to say even the very best/most expensive caps in the world are very, very audible in the signal path!!!!! Servos are the way to go where there is a DC problem but better to make a pure signal path with no offsets... which I know is hard to do.
The extra compensation circuit for the 4702 and 49811 is actually a noise gain compensation circuit not an extra compensation circuit. I did not know that either and one of our Masters Stanford grads pointed out to several of us the difference. Young college kids actually can be of use sometimes! It is mandatory for that 75pf and 3.3k resistor to be there!!! You will have osc problems coming out of clipping if it is not there.
Also the 4702 and 49811 share the same soft clipping circuit that is virtually a Baker Clamp but the clamp in the 49811 IS a real Baker Clamp. Sonically both parts are very easy on the ears when in clipping. So use the 810 if you need the clipping flag or need the 50ma to get more than 300 watts. Use the 811 for the highest sound quality if the power needs are 300 watts or less.
I did not design the chip so I can't talk about the output stages in any of the parts.
Not sure about your bias questions either, as we did not have time to try other bias schemes. We only used the Vbe multiplier circuit that is in the schematic/ap note for the 4702.
The mute and shutdown circuits can be used in the manner you described for protection. I know that others are doing the same thing successfully.
Hope this all helps! Wish me luck in my job search and buy a lot of these parts so National might bring some of us back to make more.
Be sure and try the LME49710 VFB and LME49713 CFB opamps in the metal cans in all your low level circuits.
Best DIY Audio Regards,
Mark / audioman54
opps!
One error I just saw in my reply needs to be corrected. The 810 has the real baker clamp not the 811. The LME49811 and LM4702 have something very close to but not pure baker clamps. All the parts sound very good when driven into clipping compared to other solutions. Of course it is ALWAYS better to have tons of headroom never go into clipping! But that does tend to increase costs just a bit!
Mark / audioman54
One error I just saw in my reply needs to be corrected. The 810 has the real baker clamp not the 811. The LME49811 and LM4702 have something very close to but not pure baker clamps. All the parts sound very good when driven into clipping compared to other solutions. Of course it is ALWAYS better to have tons of headroom never go into clipping! But that does tend to increase costs just a bit!
Mark / audioman54
Mark,
Thank you for your answers.
First, I am a diyer and designing this for myself so I will be of little help in raising the sales of NS .
As I understand it must have been an exceptional environment for an audiophile and engineer beeing part of a project like the one you were in. Your experience is unique and you are invaluable for a lot of companies in the audio industry.
You are in better shoes than all these fake wallstreet traders/ dealers/lawyers.
Sorry to insist but still two points:
do you believe that the ouput current at the bias pin is constant with operation voltage.
Did you experienced the sonic effect of twin pole compensation ( two capacitors with an in between resistor to ground)
Thanks
JPV
Thank you for your answers.
First, I am a diyer and designing this for myself so I will be of little help in raising the sales of NS .
As I understand it must have been an exceptional environment for an audiophile and engineer beeing part of a project like the one you were in. Your experience is unique and you are invaluable for a lot of companies in the audio industry.
You are in better shoes than all these fake wallstreet traders/ dealers/lawyers.
Sorry to insist but still two points:
do you believe that the ouput current at the bias pin is constant with operation voltage.
Did you experienced the sonic effect of twin pole compensation ( two capacitors with an in between resistor to ground)
Thanks
JPV
Hi again JPV,
Hey I am just a DIY'er now too! ...and I started out as a DIY'er over 30 years ago so never say "Just" a DIY'er, be proud of it!
#1) I do not know if the ouput current at the bias pin is constant with operation voltage, sorry. That is a good question for the apps guys who were able to keep their jobs at National.
#2)- I thought you were asking about the noise gain comp circuit we used on the 4702 and the 49811 boards we designed, which in addition to the normal 30pf comp cap is a 3.3k resistor in series with a 75pf cap to ground from the comp pin. Not the same as what you are talking about but "NECESSARY" for the best operation. I don't think we ever published the noise gain compensation circuit on the web? But to directly answer your question I have not used the type comp circuit topology that you are talking about. Sounds interesting though. Actually both of your questions would be good ones for Bob Pease.
Let me know how your amplifier turns out.
Mark / audioman54
Hey I am just a DIY'er now too! ...and I started out as a DIY'er over 30 years ago so never say "Just" a DIY'er, be proud of it!
#1) I do not know if the ouput current at the bias pin is constant with operation voltage, sorry. That is a good question for the apps guys who were able to keep their jobs at National.
#2)- I thought you were asking about the noise gain comp circuit we used on the 4702 and the 49811 boards we designed, which in addition to the normal 30pf comp cap is a 3.3k resistor in series with a 75pf cap to ground from the comp pin. Not the same as what you are talking about but "NECESSARY" for the best operation. I don't think we ever published the noise gain compensation circuit on the web? But to directly answer your question I have not used the type comp circuit topology that you are talking about. Sounds interesting though. Actually both of your questions would be good ones for Bob Pease.
Let me know how your amplifier turns out.
Mark / audioman54
I'm so dismayed to hear your story, Mark.
What really gets me, is that it's you older guys who are the ones who really have the clue. Training and education these days in electronics is sorely lacking I think. I refer to myself and people of my generation as "the chip generation"... whereas you guys would probably solve a problem with discrete design, people nowadays would look for an IC or two to do it. If that fails, program a micro.
Discrete electronics is something i would sorely like to be better at. I did apply to study electronics at college when i was 16, but they cancelled the course because of too few applicants. To go to university to study it, well first i'd have to find a uni that offers it, then pay a fortune.
(For those wondering, i'm 28 now)
A friend of mine's dad worked for a long time for the MoD here designing electronics for mostly things he can't even talk about (He's worked on the Westland Sea King helicopter though). He once told me about what his colleagues referred to as "the milk run" - basically visit all the good uni's, and find out whose graduating and whos hot to hire. He told me that for the past few years, the prospective talent "didnt know anything".
It's a sad state of affairs that companies like National and HP are letting the old talent go... no doubt decisions made by young execs who haven't a clue!
What really gets me, is that it's you older guys who are the ones who really have the clue. Training and education these days in electronics is sorely lacking I think. I refer to myself and people of my generation as "the chip generation"... whereas you guys would probably solve a problem with discrete design, people nowadays would look for an IC or two to do it. If that fails, program a micro.
Discrete electronics is something i would sorely like to be better at. I did apply to study electronics at college when i was 16, but they cancelled the course because of too few applicants. To go to university to study it, well first i'd have to find a uni that offers it, then pay a fortune.
(For those wondering, i'm 28 now)
A friend of mine's dad worked for a long time for the MoD here designing electronics for mostly things he can't even talk about (He's worked on the Westland Sea King helicopter though). He once told me about what his colleagues referred to as "the milk run" - basically visit all the good uni's, and find out whose graduating and whos hot to hire. He told me that for the past few years, the prospective talent "didnt know anything".
It's a sad state of affairs that companies like National and HP are letting the old talent go... no doubt decisions made by young execs who haven't a clue!
Hi Jaycee,
I am still very "bummed out" (that phrase dates me) about the whole thing. Everything these days is about turning a quick buck and the patience needed to develop and then market basic analog building blocks and wait for the market to accept the parts is not there. They (the entire industry) want a 2 year payback and that does not happen with these kinds of parts which is why we did not get any new great opamps for the past 10-15 years or so.
Even though myself (apps guy), the chip designer, marketing people and techs are all gone now at least we were able to get the parts out. Since I am really an audio equipment designer having the opportunity to specify some of these new parts was a great blessing and actually getting them made in metal cans is awesome! I hope that National sells a ton of the LME parts so we will have them for many years to come. In the mean time I am working on an upgrade of the Eiger D/A I designed 15 years ago using the LME parts. If anything else it keeps my mind off the poor job market that seems to get worse every day, i.e. Circuit City gone now! Dang!
Audioman54 / Mark
I am still very "bummed out" (that phrase dates me) about the whole thing. Everything these days is about turning a quick buck and the patience needed to develop and then market basic analog building blocks and wait for the market to accept the parts is not there. They (the entire industry) want a 2 year payback and that does not happen with these kinds of parts which is why we did not get any new great opamps for the past 10-15 years or so.
Even though myself (apps guy), the chip designer, marketing people and techs are all gone now at least we were able to get the parts out. Since I am really an audio equipment designer having the opportunity to specify some of these new parts was a great blessing and actually getting them made in metal cans is awesome! I hope that National sells a ton of the LME parts so we will have them for many years to come. In the mean time I am working on an upgrade of the Eiger D/A I designed 15 years ago using the LME parts. If anything else it keeps my mind off the poor job market that seems to get worse every day, i.e. Circuit City gone now! Dang!
Audioman54 / Mark
jaycee said:
I know what you mean. I'm a 2nd year electrical engineering student, and I have helped the guys who are about to graduate out more than once, some of them had never even heard of Analog Devices!!! The labs we get in our circuits classes are pretty lame. We get some discreet design information in the lower div classes, bu after that, its all about the microcontroller and programing.
You make a valid point about the young execs; they (and so do young engineers for that matter) think they are up on the latest and greatest and so eager to make a ripple in the corporate pond so they ca climb the ladder, they forget to take a moment and think what will happen on a more long term basis, i.e. 5-10-15 years from now.
@Mark
National will feel the pain for cutting you. This whole 2 year ROI thing is biting the world in the butt starting two years ago, or at least that's what I think.
I have two questions for you one about the LME49725 and second is a more general question. How does the single supply set up work? Do I have to have split the rail with a virtual ground and then use that virtual ground as my signal gnd? My second question is does the metal can package make the sound more open and smooth compared to the SO packages?
QUOTE
@Mark
National will feel the pain for cutting you. This whole 2 year ROI thing is biting the world in the butt starting two years ago, or at least that's what I think.
UNQUOTE
I could not agree more. The stock mkt people only understand quick profits and fat bonuses - to hell with the consequences and who gets chewed up in the process.
The whole world economy is screwed, and , so is our industry. I am eally pissed off that financial dicks can come, take a company over, and then make the same company pay for the loan these guys take out to buy that same company: Private Equity.
Freescale: screwed and in deep **** - paying $800m a year on the Private Equity loan of $11Bln
NXP: screwed - paying $500m a year on the Private Equity loan of 6Bln
Then we've got the guys in Wall Street that caused all this crap ordering their corporate jet last week on goverment bail out money.
We really need some rules and regulations to kick these pricks into touch.
@Mark
National will feel the pain for cutting you. This whole 2 year ROI thing is biting the world in the butt starting two years ago, or at least that's what I think.
UNQUOTE
I could not agree more. The stock mkt people only understand quick profits and fat bonuses - to hell with the consequences and who gets chewed up in the process.
The whole world economy is screwed, and , so is our industry. I am eally pissed off that financial dicks can come, take a company over, and then make the same company pay for the loan these guys take out to buy that same company: Private Equity.
Freescale: screwed and in deep **** - paying $800m a year on the Private Equity loan of $11Bln
NXP: screwed - paying $500m a year on the Private Equity loan of 6Bln
Then we've got the guys in Wall Street that caused all this crap ordering their corporate jet last week on goverment bail out money.
We really need some rules and regulations to kick these pricks into touch.
HA vs MA or SO
Hi Jeff,
Why do you want to use a single supply? It involves DC blocking caps, which will screw up the signal quality. Usually single supplies are used on portable devices where signal quality is not a priority and single batteries are being used. (Also large consumer companies also do not want to spend more than a few cents on opamps in their hand held devices.)
The metal can devices (in split supply DC circuits) exhibit a more open and spacious sound quality with a little more detail (sorry for the non-technical audiophile terms). In our single blind tests everyone choose the metal can devices over the identical internal die dip packages every time! (Not a ton of tests though. Usually 5 to 10 subjects.) We used two identical D/A preamps I designed loaded with the two different packages (HA vs MA) and then measured them on the AP2/192 and saw no differences with the standard tests. More investigation is warranted and hopefully Bob Pease will attack this question at some point. I would really like to know for sure (measurements!) why the metal can devices sound a bit better…even in the power supplies!
audioman54 / Mark
Hi Jeff,
Why do you want to use a single supply? It involves DC blocking caps, which will screw up the signal quality. Usually single supplies are used on portable devices where signal quality is not a priority and single batteries are being used. (Also large consumer companies also do not want to spend more than a few cents on opamps in their hand held devices.)
The metal can devices (in split supply DC circuits) exhibit a more open and spacious sound quality with a little more detail (sorry for the non-technical audiophile terms). In our single blind tests everyone choose the metal can devices over the identical internal die dip packages every time! (Not a ton of tests though. Usually 5 to 10 subjects.) We used two identical D/A preamps I designed loaded with the two different packages (HA vs MA) and then measured them on the AP2/192 and saw no differences with the standard tests. More investigation is warranted and hopefully Bob Pease will attack this question at some point. I would really like to know for sure (measurements!) why the metal can devices sound a bit better…even in the power supplies!
audioman54 / Mark
Hi Bonsai,
One of those team members is from Japan and he is the chip designer who actually did almost all of the LME parts. He was also laid off.
If you like the 4562 (i.e. LME49710) get some of the metal can parts and try those. Also try the LME49713 current feedback device sometime. It is my favorite part...in metal can of course! (Some might say it is my favorite because I specified it!)
Cary audio is using these parts in metal cans in their new headphone amplifier.
audioman54 / Mark
One of those team members is from Japan and he is the chip designer who actually did almost all of the LME parts. He was also laid off.
If you like the 4562 (i.e. LME49710) get some of the metal can parts and try those. Also try the LME49713 current feedback device sometime. It is my favorite part...in metal can of course! (Some might say it is my favorite because I specified it!)
Cary audio is using these parts in metal cans in their new headphone amplifier.
audioman54 / Mark
Re: HA vs MA or SO
Mark, my device is technically a portable device. It was originally just going to be a buffer on a circuit I've already designed and tested, but then it got caught up in feature bloat.
I wanted to use a single supply so that I wouldn't have to design a negative rail and positive rail supply system on top of making it work with batteries, wall worts from 3.3V to +48V, and phantom power. (this thing went from a simple buffer circuit to a 6 page monster in no time at all).
Thanks!
audioman54 said:
Mark, my device is technically a portable device. It was originally just going to be a buffer on a circuit I've already designed and tested, but then it got caught up in feature bloat.
I wanted to use a single supply so that I wouldn't have to design a negative rail and positive rail supply system on top of making it work with batteries, wall worts from 3.3V to +48V, and phantom power. (this thing went from a simple buffer circuit to a 6 page monster in no time at all).
Thanks!
audioman54 said:
Would it be possible that the metallic package modifies the parasitic capacitance of the input pins and so modifies the open loop bandwith, or do you think that it has more to do with shielding?
You mentionned that the compensation requires a resistor to ground that is not published in the AN.
Could you elaborate on this?
Thanks again
JPV
Answers to questions
JPV, Nelson and apache405,
The Resistor / Cap series ckt from the comp pin to ground on the LM4702 and the LME49811 are a 3.3k resistor and a 75 pf cap. (Bob Pease actually came up these values and they are actually a “Noise Gain Comp” circuit.) These parts are in addition to the normal 30pf comp cap. The LME49810 is a different animal and does not require these parts.
If everyone buys a ton of LME series parts in metal cans maybe I can get my apps job back at Nat Semi someday...maybe not?
I heard a great DAC chip on an interview last week. After some more tests in my lab at home I will report further on that in a week or two. Need to compare it with the new AK4399 that I am installing in my best D/A right now. Need an AP2 for my lab at home also. Anyone know of a beat-up, used one for sale?
Also JPV, your guess on why the metal cans sound better is one we considered...along with a bunch of other thoughts but we never had the time to prove any of them out. Everyone write Bob Pease and ask him why he thinks metal can devices sound better.
Nelson, I was told a little about the topology but yes my lips are sealed. Suffice to say there were some new wrinkles put into the 49710 VFB and 49713 CFB opamps that I believe contribute to their great sonic qualities. But then again the process these parts were built on, that makes the NPN and PNP parts identical in terms of carrier flow and dimension, may be the main reason for the great sound of this series of parts. I like to think though that the process, design, layout and metal can packages all contribute to the great sound of these parts. (And… let’s not forget the lowly apps guy that specified the 49713 CFB part for audio and pushed hard to get both parts made in metal cans!)
and Lastly...apache405, I know how simple projects can get out of hand real fast! But if your project requires reasonable signal quality then find a way to go with the dual supplies.
Best Regards Everyone and hope you all have a good day at work tomorrow… while I am at home/online sending out more resumes.
Audioman54 / Mark
JPV, Nelson and apache405,
The Resistor / Cap series ckt from the comp pin to ground on the LM4702 and the LME49811 are a 3.3k resistor and a 75 pf cap. (Bob Pease actually came up these values and they are actually a “Noise Gain Comp” circuit.) These parts are in addition to the normal 30pf comp cap. The LME49810 is a different animal and does not require these parts.
If everyone buys a ton of LME series parts in metal cans maybe I can get my apps job back at Nat Semi someday...maybe not?
I heard a great DAC chip on an interview last week. After some more tests in my lab at home I will report further on that in a week or two. Need to compare it with the new AK4399 that I am installing in my best D/A right now. Need an AP2 for my lab at home also. Anyone know of a beat-up, used one for sale?
Also JPV, your guess on why the metal cans sound better is one we considered...along with a bunch of other thoughts but we never had the time to prove any of them out. Everyone write Bob Pease and ask him why he thinks metal can devices sound better.
Nelson, I was told a little about the topology but yes my lips are sealed. Suffice to say there were some new wrinkles put into the 49710 VFB and 49713 CFB opamps that I believe contribute to their great sonic qualities. But then again the process these parts were built on, that makes the NPN and PNP parts identical in terms of carrier flow and dimension, may be the main reason for the great sound of this series of parts. I like to think though that the process, design, layout and metal can packages all contribute to the great sound of these parts. (And… let’s not forget the lowly apps guy that specified the 49713 CFB part for audio and pushed hard to get both parts made in metal cans!)
and Lastly...apache405, I know how simple projects can get out of hand real fast! But if your project requires reasonable signal quality then find a way to go with the dual supplies.
Best Regards Everyone and hope you all have a good day at work tomorrow… while I am at home/online sending out more resumes.
Audioman54 / Mark
For Audioman54
Audioman I feel your frustration with the corporate world. I've recovered and you will too. Thanks for your great work bringing good sounding parts to market!!! I use LM4562's in everything I can (except my tube gear of course) and have a question if you don't mind. I recently acquired a QSC RMX 850 to drive the tweeters in a small rig I am building.
http://www.qscaudio.com/support/library/schems/Current/RMX Series/rmx850.pdf
Build like a tank, sounds like crap... I upgraded the PS caps to Gold Tune, upgraded the electrolytic coupling caps before the volume controls and bypassed with 1uf film caps - so far so good! Much clearer overall and has some stereo width. On to the opamps. The opamps (5532) are 8 dip in sockets. Installed a set of LM4562's and heard power buzzing through the speaker outputs and weird intermittent audio. Installed OPA2132P's, sounded perfect. Well as good as 2132's can sound... Installed AD8032N's, audible squealing! Installed LT1361's, clear audio but audible clipping. Next I soldered 100uf Pany FMs and .1 films onto pins 4/8 of the LM4562 but still no change. Soldered .01 ceramics to the opamp + and minus to ground caps still no change. Did the same with the OPA2132's and they now sound quite good but not close to the LM 4562's which work perfectly in my PC soundcard of all things!
Any suggestions?
Pat Semeraro, Orlando, FL
Audioman I feel your frustration with the corporate world. I've recovered and you will too. Thanks for your great work bringing good sounding parts to market!!! I use LM4562's in everything I can (except my tube gear of course) and have a question if you don't mind. I recently acquired a QSC RMX 850 to drive the tweeters in a small rig I am building.
http://www.qscaudio.com/support/library/schems/Current/RMX Series/rmx850.pdf
Build like a tank, sounds like crap... I upgraded the PS caps to Gold Tune, upgraded the electrolytic coupling caps before the volume controls and bypassed with 1uf film caps - so far so good! Much clearer overall and has some stereo width. On to the opamps. The opamps (5532) are 8 dip in sockets. Installed a set of LM4562's and heard power buzzing through the speaker outputs and weird intermittent audio. Installed OPA2132P's, sounded perfect. Well as good as 2132's can sound... Installed AD8032N's, audible squealing! Installed LT1361's, clear audio but audible clipping. Next I soldered 100uf Pany FMs and .1 films onto pins 4/8 of the LM4562 but still no change. Soldered .01 ceramics to the opamp + and minus to ground caps still no change. Did the same with the OPA2132's and they now sound quite good but not close to the LM 4562's which work perfectly in my PC soundcard of all things!
Any suggestions?
Pat Semeraro, Orlando, FL
Re: Answers to questions
I've used the LM4562 in a "re-do" of a Crown IC-150 -- with a Jung Super Regulator -- and folks can't understand why it sounds so good. (All the RCA jacks were replaced and the internals cleaned up.)
I have another Crown IC-150 just in which will use the LME49600 power driver for a regulator and get some of the LM4562 with their little tin hats.
(fwiw, I have also gutted several crown amps and retrofitted the innards with LM4702 both LME49830 -- I just buy the amps for their power transformer, heat sinks and cases.)
audioman54 said:
I've used the LM4562 in a "re-do" of a Crown IC-150 -- with a Jung Super Regulator -- and folks can't understand why it sounds so good. (All the RCA jacks were replaced and the internals cleaned up.)
I have another Crown IC-150 just in which will use the LME49600 power driver for a regulator and get some of the LM4562 with their little tin hats.
(fwiw, I have also gutted several crown amps and retrofitted the innards with LM4702 both LME49830 -- I just buy the amps for their power transformer, heat sinks and cases.)
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