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Old 2nd July 2013, 10:26 AM   #781
AndrewT is offline AndrewT  Scotland
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Originally Posted by owdeo View Post
......................... unless I happened to live under a TV or FM broadcast tower (which I don't, I'm at least 20km from the nearest). ....................
How many radio transmitters are there in your house?
How close are your neighbours' radio transmitters?
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Old 2nd July 2013, 11:18 AM   #782
Bonsai is offline Bonsai  Taiwan
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You are all talking as if anything with a BIP front end is hobbled sonically and clearly inferior.

Nonsense!

If you are in an area where your system is demodulating RF, you are going to be getting all sorts of other problems. It's not just the front end JFET but all those other BIP junctions in the opamps and discrete circuitry that are going to be an issue as well. Fix the root cause and sort your screening and grounding out etc.

The ONLY way to make an assertion that JFETs sound better than BIP is through a DBT. I am 100 % with the objectivists on this.

Well designed BIP input amplifiers sound wonderful and it has nothing to do with whether its JFET or BIP.

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Old 2nd July 2013, 11:37 AM   #783
AndrewT is offline AndrewT  Scotland
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I'm siding with Bonzai.
Most of my amplifiers are BJT front end.
I have no RF issues, none.
Even my uncased prototype amplifiers do not get interference that becomes audible.
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Old 2nd July 2013, 12:01 PM   #784
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Its a little more nuanced than simply BP vs JFET. BP nput opamps (LM6172 for example) without LTPs still sound pretty good to my ears in the presence of RF. Better than what should (on paper) be a fairly decent JFET opamp (AD8066) which imparts a strange HF colouration
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Old 2nd July 2013, 12:22 PM   #785
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Originally Posted by Bob Cordell View Post
Hi ivanlukic,

I prefer JFET op amps in general, but especially at the front-end of equipment. I doubt it is because of noise masking of distortion, since they are quite adequately low in noise. Moreover, many circuits that people use may not be optimized for the very best noise, and even BJTs in those circuits with BJTs will have as much noise as a well-designed JFET-based circuit.

I believe that the higher RFI immunity of the JFET is partially responsible for the better sound. Bear in mind that the signal entering a BJT op amp goes into a forward-biased junction (base-emitter) eager to rectify. The signal going into a JFET op amp goes into a junction that is reverse biased (gate-source), sometimes by a volt or more, and much less close to the region where it might rectify.

Cheers,
Bob
Hi Bob,

This is perfectly good explanation from an engineer's viewpoint. But there is also taste involved here. Even I must admit that j-fets sound better, if better means free from any nasty moments, aggressiveness, sharpness, edgy quality. But they are too polite, too bland for my taste. If you want to sooth yourself with music j-fets are way to go. But if you want drama (even if the price is occasional aggressiveness) and excitement, nothing beats bipolars. Great music performance involves a range of emotions, and performance sometimes contains anger, aggression, and negative emotional energy. J-fets seem to reduce everything to beauty. Listener remains calm all the time, unmoved enough by the musical performance. J-fets seem to be lacking in utmost realism, while bipolars sound thinner, sharper and more aggressive.
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Old 2nd July 2013, 12:38 PM   #786
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Originally Posted by Mooly View Post
I would go along with the "rf theory" too. In fact, this has been put forward as one reason why bjt's (such as 5532 etc) might have earned a poor reputation. This noise could apparently be "demodulated" in a non linear way (think of an old fashioned RF diode demodulator/detector) wheras FET input stages are essentially immune. It seems a very plausible theory given that the 5532 and similar was extensively used in DAC I/V conversion and filtering, a location that invariably does have a lot of hf hash present. And it was precisely these kind of applications that were seeing big sonic gains when switching to FET devices.
I changed NJM5532 in an old Philips CD player with OP275 because some people suggested to me that the sound will improve with j-fets. But in spite of the so called "midrange grit" I prefer 5532. Yes, the sound is softer with j-fets, more analog-like, but lacking in detail and resolution. I used small ESP P88 preamp board fitted with IC sockets for evaluation of opamps because pot is between two amplifying stages (or buffer and amplifying stage). Tried many "audio" opamps (j-fet and bipolar) and overall I found 5532 (or improved version NJM2114) the best choice. In general, I prefer bipolars. One that proved to be very good is OP27 in spite of the fact that slew rate and bandwidth are not so impressive.
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Old 2nd July 2013, 01:27 PM   #787
redjr is offline redjr  United States
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What kind of high frequency sources would I typically have to worry about coloring the sonic characteristics of my pre-amp sitting in my living room? How much of a real audio concern is this and should I run out and buy 20+ new OP-amps to replace all my 5532? Aren't we really talking about such fine nuances of the sound, that at some point it becomes a moot point - unless one is solely intent on chasing audio nirvana?
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Old 2nd July 2013, 01:43 PM   #788
AndrewT is offline AndrewT  Scotland
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Motors, both while running and during power ON/OFF.
Wireless gadgets, eg. mobile phone, WiFi, wireless house alarm, wireless landline, bluetooth, television
Dimmer switches, fluorescent lighting, LED drivers, SMPS.

It can be a very long list in most households !
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Old 2nd July 2013, 02:55 PM   #789
redjr is offline redjr  United States
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Originally Posted by AndrewT View Post
Motors, both while running and during power ON/OFF.
Wireless gadgets, eg. mobile phone, WiFi, wireless house alarm, wireless landline, bluetooth, television
Dimmer switches, fluorescent lighting, LED drivers, SMPS.

It can be a very long list in most households !
Maybe I should have emphasized 'coloring the sonic characteristics'. None that I can tell anyway.
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Old 2nd July 2013, 03:00 PM   #790
AndrewT is offline AndrewT  Scotland
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I don't see that emphasising that phrase changes my reply.
Those sources of interference still leave lots of potential to "colour the sonic character" of your equipment.
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