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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 2nd March 2013, 05:30 AM   #36071
john curl is offline john curl  United States
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It is somewhat more complicated than whether a low Rbb' bipolar transistor is available.
Difficulty in biasing, is one reason that bipolars are not so good.
With either jfets or bipolars, you can get the same input VOLTAGE noise. It just takes more current to achieve the same noise with jfets, and the input capacitance can be VERY high.
It has been known how to use either jfets or paralleled bipolars since the mid '60's. The problem then was the available product. Most bipolar transistors have fairly high Rbb' from 40-200 ohms, only a few have Rbb' of 2-4 ohms, and I don't know how available they are today.
All else being equal, the jfet is more linear, equally low noise, and easily self biased to allow doing without any coupling cap.
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Old 2nd March 2013, 07:05 AM   #36072
Esperado is offline Esperado  France
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Quote:
Originally Posted by john curl View Post
My biggest worry today, is using a digital delay for 'preview' rather than the old way of putting a reproduce head a few feet ahead to capture the signal and tell the control electronics in the disc cutter how much to widen the groove.
This is used most of the time since decades. Makes-me smile with people allergic to Digital :-)
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Old 2nd March 2013, 08:36 AM   #36073
abraxalito is offline abraxalito  United Kingdom
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+1 - similar argument goes for the BBC's stereo FM broadcasts, they've been digital (13bit companded) for decades too...
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Old 2nd March 2013, 08:45 AM   #36074
PMA is offline PMA  Europe
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John Curl's Blowtorch preamplifier part II
As well as all the files used for vinyl cut preparation
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Old 2nd March 2013, 09:51 AM   #36075
jan.didden is offline jan.didden  Europe
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You guys are mean

Do you know you can buy plug-ins for your digital audio workstation to emulate vinyl sound? I wonder what the algorithms are...
They do take in account a LOT of parameters, like:

iZotope VinylThe ultimate lo-fi weapon, iZotope Vinyl uses 64-bit processing and advanced filtering, modeling and resampling to create authentic "vinyl" simulation, as if the audio was a record being played on a record player.
You have complete control over the following parameters:
Mechanical Noise: The amount of turntable motor rumble and noise
Wear: Control how worn out the record is, from brand new to played a few thousand times
Electrical Noise: Internally generated electrical noise, such as 60 Hz grounding hum
Dust: The amount of dust on the record
Scratch: The number and depth of scratches on the record
Warp Depth: The amount of warping and the warp shape for the record—from no warp to the edges totally melted and warped


jan
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Last edited by jan.didden; 2nd March 2013 at 09:54 AM.
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Old 2nd March 2013, 10:45 AM   #36076
fas42 is offline fas42  Australia
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Might be pertinent to mention this little 'expose': http://www.soundonsound.com/sos/feb1...oguewarmth.htm. They've been fooling us for years ...!!

Frank
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Old 2nd March 2013, 11:41 AM   #36077
SY is offline SY  United States
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John Curl's Blowtorch preamplifier part II
Quote:
Originally Posted by john curl View Post
Difficulty in biasing, is one reason that bipolars are not so good.
With either jfets or bipolars, you can get the same input VOLTAGE noise. It just takes more current to achieve the same noise with jfets, and the input capacitance can be VERY high.
...
All else being equal, the jfet is more linear, equally low noise, and easily self biased to allow doing without any coupling cap.
Thanks, John. Let me follow up with a few more:
1. Does that input capacitance really matter, again restricting ourselves to low output MCs?
2. How important is the linearity for the first stage considering the tiny amount of signal involved at that point in the circuit?
3. What about gain comparisons? At the end of the day (as they say in MBA-speak), we're interested in s/n. More gain = higher s/n, with all else equal.
4. Is it useful to make the s/n better than the limiting s/n due to the cartridge itself (i.e., the output versus Johnson noise)? If so, why?
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Old 2nd March 2013, 01:16 PM   #36078
Pano is offline Pano  United States
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John Curl's Blowtorch preamplifier part II
Jan, have you ever tried those vinyl plug-ins? I have - in the hope that emulating some of the defects of vinyl might give it "that sound". I.E., is it the flaws of vinyl that we like?

I found the effects awful. Maybe I just wasn't good at using the software, but it never sounded better than a crude gimmick to me. Was wondering if anyone else had better luck.
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Old 2nd March 2013, 02:04 PM   #36079
jan.didden is offline jan.didden  Europe
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No I never tried it, and it's just one example I found.

But in general, with these type of effects and others like room reverb simulation, you must tread VERY softly.
Adjust it to the point that you think you switched it off, and with longer listening you do hear the effect. Don't overdo it; I can very well understand it can sound terrible.

But it's an interesting technology, like the plugins that emulate tube sound, where you can sometimes even select different tubes and/or the biasing point and overload.

jan
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Old 2nd March 2013, 02:41 PM   #36080
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by Chris Hornbeck View Post
Excellent! I find myself transferring vinyl to digital about as often as simply playing it these days, and "overs" is a nuisance that even two (well, one's in pieces) Keith Monks machines don't always eliminate.

Thanks,
Chris
You can remove them by hand and you would be surprised how inaudible the result is. At 24 bit I was surprised at how few actually hit the rails. A soft clipper still leaves the pop and my preamp recovered very fast, so fast that you usually can see the grove wall sag and tip resonance on the falling edge.

I noticed on the 24/96 files I recorded in Austin there were a few activations of the Fostex's soft clipper, only during the start of SY's VERY entusiastic applause (he was sitting directly next to the mic).
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