Wavebourn said:
Not too far from how HDCD works. Keith Johnson built a system around the DBX compressors that did essentially track input to output with a control signal. It was used for a CCD delay line to overcome the noise problems. Not good enough for primary audio.
1audio said:
If all CDs had information about compression at least I would be able to restore original dynamics. 😉
1audio said:
Yes you are right. There are two Lundahl compensation circuits. The one that cancels the primary DC resistance (the cause of the distortion) is identical to the AP circuit. This 'zero field' one appears to me to do the same but at the secondary. Note that they specify that the pos feedback resistor value should be the same as the secondary DC resistance (160 ohms in the app note). That to me makes it conceptually the same as the primary cancellation circuit.
BTW Is a transformer with 'zero field' going to work??
Jan Didden
Hi Jan
Yes there is an American patent about curing butan, but I was talking about a German patent...
I looked at the url you provided, it seems it only shows Amarican patent. How do you use it to search for patents from other counties?
And the "zero field" is mareketing speach, the idea is getting close. Lars Lundal once told us that there might be granular effects due to magnetics if you get too close.
Sorry Mr Curl if this is getting too offtopic...
örjan
Yes there is an American patent about curing butan, but I was talking about a German patent...
I looked at the url you provided, it seems it only shows Amarican patent. How do you use it to search for patents from other counties?
And the "zero field" is mareketing speach, the idea is getting close. Lars Lundal once told us that there might be granular effects due to magnetics if you get too close.
Sorry Mr Curl if this is getting too offtopic...
örjan
This is interesting, but I think most here don't appreciate -R or negative resistance, caused by positive current feedback, which is key in this case. The basic concept has been around a long time, and is sometimes used to damp loudspeakers as an adjustment in power amps.
orjan said:
I don't think www.pat2pdf.org can get non-US patents, I thought your number WAS a US patent, sorry.
Jan Didden
The AP technique explained here (>page 29):
http://waltjung.org/PDFs/ADI_2002_Seminar_Ch6_Audio_Drivers_I.pdf
http://waltjung.org/PDFs/ADI_2002_Seminar_Ch6_Audio_Drivers_I.pdf
Actually, I have posted the AP output drive diagram on diyaudio.com, maybe even in this thread, but don't know exactly where or when.
As the frog said, time's fun if you're having flies 😉
Jan Didden
As the frog said, time's fun if you're having flies 😉
Jan Didden
john curl said:
I saw some ancient schematic of a microphone feedback. It used positive feedback by current in output transformer. I don't remember which one.
"Everything new is well forgotten old". -- folklore wisdom
Also, motor speed stabilizers used positive feedback by current.
Loudspeaker control such a way has a long white beard.
I would like to point out that most of what we have discussed on this thread, recently, has little or nothing to do with the BLOWTORCH preamp, which was the original subject of this thread. First of all, the BLOWTORCH deliberately avoids bipolar transistors, coupling transformers, and coupling caps in the audio path. This is on purpose, not an accident.
The BLOWTORCH uses only fets in the audio path and the best switches, volume controls, wire, and connectors that we could buy, and we put it in a very heavy, shielded case.
Why we did this was based on years of trying things out, and needing something to use at CES and at home. We didn't skimp, we didn't make a big profit, and we tried to make the design 'buildable' at some level, so it would not be unreliable or difficult to get right.
The distortion measurements are only OK, BUT they are low order, lower order than just about any IC I have ever seen tested, and the thru-path is minimum.
The only thing that could have beat what we did, in our opinion, was no preamp at all, but that actually was found to be compromised, because the pot should be buffered, if possible, and it's a hassle to change connectors in order to use another source.
Most of the insides of the BLOWTORCH have been described on this thread, somewhere, but it must be re-iterated that the soldering, wiring, and component pre-cleaning before soldering was just as necessary, as a 'slick' topology.
This is the 'essence' of the BLOWTORCH and hopefully we can get back on track.
The BLOWTORCH uses only fets in the audio path and the best switches, volume controls, wire, and connectors that we could buy, and we put it in a very heavy, shielded case.
Why we did this was based on years of trying things out, and needing something to use at CES and at home. We didn't skimp, we didn't make a big profit, and we tried to make the design 'buildable' at some level, so it would not be unreliable or difficult to get right.
The distortion measurements are only OK, BUT they are low order, lower order than just about any IC I have ever seen tested, and the thru-path is minimum.
The only thing that could have beat what we did, in our opinion, was no preamp at all, but that actually was found to be compromised, because the pot should be buffered, if possible, and it's a hassle to change connectors in order to use another source.
Most of the insides of the BLOWTORCH have been described on this thread, somewhere, but it must be re-iterated that the soldering, wiring, and component pre-cleaning before soldering was just as necessary, as a 'slick' topology.
This is the 'essence' of the BLOWTORCH and hopefully we can get back on track.
To change the subject to something 'productive' relating to the BLOWTORCH, I want to re-introduce the bypass capacitor, and why it seems to be so important in simple discrete designs. You will find that most hi end manufacturers use similar, if not the same type and brand of bypass capacitor. Why is this? Is there a good reason?
One of the best caps out there is the Reliable .1 uf RT polystyrene cap. What is the 'quality' that makes this cap so successful?
One of the best caps out there is the Reliable .1 uf RT polystyrene cap. What is the 'quality' that makes this cap so successful?
john curl said:
But it is obvious John. At $12/pc. they are expensive enough to make it in a high end audio product.
I pay a dollar or two, but that is not the reason. There IS a reason that they cost some extra money, that is where the answer is.
This is just like having expensive tires on a Porsche or Mercedes. Why not cheaper tires? Could it be, that expensive tires are made better, out of better materials, and have less compromises?
When it is a matter of life and death, it matters more, but what about performance?
When it is a matter of life and death, it matters more, but what about performance?
Branding. Brand names are very, very important to high end purchasers.
(yes, John, I saw you called- I'm traveling, will get back to you as soon as I return)
(yes, John, I saw you called- I'm traveling, will get back to you as soon as I return)
Not really. WE select the parts, and the purchasers usually don't know what we select. In fact, REL parts are slightly plain looking, but we use them anyway. There are many prejudices shown here, by the cynical. It is not that way, in reality.
The high end magazine reviews I see call out the fashion parts brands. Not that any of those guys would know a capacitor from a bilateral frammistat...
http://forum.stereophile.com/photop...20/password//sort/1/size/medium/cat/501/page/
Even the brand of power plugs!
From a couple of recent reviews:
"The 16-bit, digital shunt-control –based volume control uses Vishay Bulk Metal resistors to provide 140 steps of 0.5dB each. "
"serious, well-thought-out designs of considerable originality, in which are found such high-quality parts as Solen capacitors, Alps potentiometers, and fast-recovery diodes."
Even the brand of power plugs!
From a couple of recent reviews:
"The 16-bit, digital shunt-control –based volume control uses Vishay Bulk Metal resistors to provide 140 steps of 0.5dB each. "
"serious, well-thought-out designs of considerable originality, in which are found such high-quality parts as Solen capacitors, Alps potentiometers, and fast-recovery diodes."
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