I would doubt it, but look for my new review of the Parasound JC-2 in the next issue of 'The Absolute Sound'. IF and WHEN, I can make IC's sound as good, I will use them more frequently. As I have already tried to tell you, I am TRYING to make YOUR IC sound good.
Many years ago, I believed that you had the answer when I put your AD712 in the front end of the Parasound HCA-2200 MK1. It FAILED the independent listening tests. I had to remove your IC and any other IC in the audio path and I got a B rating in the same magazine that failed it the first time. Sorry about embarrassing you and your company, then. I had to do what I had to do, in order to get the amp to pass the listening tests. As I remember, Walt Jung was ordered by AD to send me a serious letter about it.
Once burned, twice shy. However, I do think that you are one of the best IC designers out there, and I use your stuff in my test equipment and hopefully, even in some of my products, if I can get away with it.
Also, I got most of what I needed about microphone capacitance distortion in the B&K handbook. Not everything, but they quote a factor of 5 in distortion, if you are not careful with the load capacitance. Also, THEIR mic preamp as a rated input capacitance of 0.2pf. How about that?
Many years ago, I believed that you had the answer when I put your AD712 in the front end of the Parasound HCA-2200 MK1. It FAILED the independent listening tests. I had to remove your IC and any other IC in the audio path and I got a B rating in the same magazine that failed it the first time. Sorry about embarrassing you and your company, then. I had to do what I had to do, in order to get the amp to pass the listening tests. As I remember, Walt Jung was ordered by AD to send me a serious letter about it.
Once burned, twice shy. However, I do think that you are one of the best IC designers out there, and I use your stuff in my test equipment and hopefully, even in some of my products, if I can get away with it.
Also, I got most of what I needed about microphone capacitance distortion in the B&K handbook. Not everything, but they quote a factor of 5 in distortion, if you are not careful with the load capacitance. Also, THEIR mic preamp as a rated input capacitance of 0.2pf. How about that?
john curl said:
Be serious, your memory fails you.
You obviously don't want to discuss some different circuit approaches for low noise. BTW I found in the B&K technical literature that they were using 10G resistors already in 1971.
I might read TAS if someone lent me a free copy.
Scott -
I download TAS now and then. Very convinient and I like to have the mag in digital form.
One can also download old reviews.
http://www.avguide.com/the-absolute-sound/
Sigurd
I download TAS now and then. Very convinient and I like to have the mag in digital form.
One can also download old reviews.
http://www.avguide.com/the-absolute-sound/
Sigurd
scott wurcer said:
scott wurcer said:
Scott,
WRT virtual gnd capsule load, that's what I saw, but thought that's
not right... and moved on.
Are there any other advantages of running the mic like this?
cheers
Terry
john curl said:
The variable distorsions due different stylus shapes are a main factor imho , because cartridges with the usual cantilever systems works different than the cutting head .
Cutting is pretty much tangential , but a cantilever changes his angles with the groove modulations .
I ended up with an very exactly handmade MC , (the MicroMagic Diamond) using a spheric tip , because this one has always the same diameter in the groove , compared with an elliptical shape which changes the diameter with modulation due movement .
Also this is lesser sensitive to surface noise and scratches .
BTW : I am somewhat familiar with the Swiss made McKinnie Phonostage using your designs , 25 years ago i had to handselect FETs 😀
Uh , my turntable and phonostage are also not the worst
John,
as the IC version will sell for 1/10th of the price of the discrete version, is the AD797 really exessively priced?
One could could even say that it is cheap 😉
The cost is about the same as for one TX2352 resistor....
Personally, I am not using the AD797 but instead use the AD745 (K-version) for RIAA front ends. But maybe it is too noisy for your needs.
Combined with superb capacitors and resistors and separate PS for the AD745 and the next stage OPamp, it can sound marvellous. As good as or even better in some ways than a fully discrete RIAA amplifier with good caps and resistors (but not superb passive components).
Sigurd
as the IC version will sell for 1/10th of the price of the discrete version, is the AD797 really exessively priced?
One could could even say that it is cheap 😉
The cost is about the same as for one TX2352 resistor....
Personally, I am not using the AD797 but instead use the AD745 (K-version) for RIAA front ends. But maybe it is too noisy for your needs.
Combined with superb capacitors and resistors and separate PS for the AD745 and the next stage OPamp, it can sound marvellous. As good as or even better in some ways than a fully discrete RIAA amplifier with good caps and resistors (but not superb passive components).
Sigurd
john curl said:
Terry Demol said:
Lots of interesting avantages noise wise, like instead of padding for high SPL you just make the feedback cap bigger than the capsule cap. Also I mis-spoke yesterday, if you do the simple Q=C*V model of a capacitor and go through the equations of the open circuit vs short circuit situation the first order non-linearity is eliminated. The biggest advantage is that you can take a mike with 1.58mV/PA sensitivity and make it 110mV/PA and still fit everything in the head. This means you can buy an inexpensive CF card recorder and do some nice nature phonography.
B&K makes traceable to standards instruments, noise is a secondary issue. They have an excellent noise overview in the 1972 technical notes. It is clear that their instrument mikes are 8-12dBA worse than equivalent recording mikes from Sennheiser, etc. The problem is actually similar to the MM/MC cartridge situation. When they set out to make an ultra-low noise acoustic survey mike they brought the diaphram resonance down and used some equalization. That's also in a very informative paper.
The graphs and data are all there make up your own minds, I'm not going to argue with JC anymore.
Groove-T said:
Elsewhere someone mentioned line contact stylii. As technology goes I would have thought our compulsive drive to make better and better machines would have resulted in perfect ones. I was told that actually a stylus that matched a cutting head would simply destroy your LP's after a few plays. I have no knowledge of this one way or the other???
MikeW said:
I thought "Why does he have a picture of Doris Day"
Killer is right here in Medford, I hear he's hurtin' these days but still going.
Now there's a smart man, especially if you use a MM. There's a National app note on phono noise that shows how much improvement you get from a FET amp vs. bi-polar. I once put a Shure body in my Quantec as a source resistance and plotted the noise of 1nV bi-polars vs FET's, quite interesting.
Normally I would use a fet IC, but I need low noise for MC cartridges. That leaves the AD797 and the LT1115 as contenders. The LT is cheaper, but slightly slower.
I needed a DUAL, unity gain compensated, fet input IC for the input stage of the HA2200. I had already designed AD711's into my Vendetta Research servos with good result, and even designed whole CD playback systems with AD712's. I still think that it is a good IC (for an IC) but it did not pass independent subjective tests. It is NOT my fault. It might not be anyone's fault, but it does show that overconfidence in measurement can get one into trouble. THAT is what I continually try to point out.
Now, when it comes to microphones. The cap divider concept looks good on paper, BUT is the added capacitance 'toxic' or does it actually keep the microphone output linear? This question is not easily proven, at least by me, at this point.
I really found the B&K website to be a goldmine of information. I must have saved several hundred pages from it. Please, any of you really interested, look up Erling Fredricksens's 1996 paper on using negative capacitance to NULL microphone distortion in the B&K Tech Notes. You will never regret it, and might begin to understand my concern, and questions.
I needed a DUAL, unity gain compensated, fet input IC for the input stage of the HA2200. I had already designed AD711's into my Vendetta Research servos with good result, and even designed whole CD playback systems with AD712's. I still think that it is a good IC (for an IC) but it did not pass independent subjective tests. It is NOT my fault. It might not be anyone's fault, but it does show that overconfidence in measurement can get one into trouble. THAT is what I continually try to point out.
Now, when it comes to microphones. The cap divider concept looks good on paper, BUT is the added capacitance 'toxic' or does it actually keep the microphone output linear? This question is not easily proven, at least by me, at this point.
I really found the B&K website to be a goldmine of information. I must have saved several hundred pages from it. Please, any of you really interested, look up Erling Fredricksens's 1996 paper on using negative capacitance to NULL microphone distortion in the B&K Tech Notes. You will never regret it, and might begin to understand my concern, and questions.
john curl said:
... and OPA211 :
http://focus.ti.com/lit/ds/symlink/opa211.pdf
The datasheet was updated April 2008.
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