New Doug Self pre-amp design...

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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.

:)
 
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.
 
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.
 
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? :D 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? :)
 
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. :D
 
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.

Interesting points. In the spectrum of devices, JFETs are more like tubes than BJTs, and some of what you say can be said about tubes. Some people prefer tubes, some people prefer solid state.

Cheers,
Bob
 
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 !

I hear sonic signature of j-fets in any application including input stages of power amps, not only in opams. I remember when a friend of mine had Audio Analogue Paganini CD player. The sound was very soft and warm, like some old turntable, very analog-like. We opened it and in the analog section there was some TI TLE Excalibur j-fet. But that was the sound that reminded me of QUAD 34 preamp that I had 30+ years ago (with a lot of TL071 inside) and than there was no CD DACs, mobile phones, WiFi, SMPS, etc., to pollute audio signals. I never really liked the sound of that preamp and it took me a long time to understand that I am not a fan of j-fets.
 
Several comments have been made as to being "more analog sounding"

I know what they mean ;) but apart from Digi Synths etc, Everything else is Analog originally. I sure don't want to be exposed to "digi sounding" products !

The problem is, that are so Many variables involved i reproduction. The exact same gear in different rooms/locations WILL sound better or worse !

I've used & replaced combinations of Bipolar & Jfet OpAmps in mixers & other Pro gear over the years to improve performance. Jfet's "can" be beneficial in for eg usually higher impedance stages such as tone controls, to lower noise ;) They all sounded great :)

*

Originally Posted by Bob Cordell

Maybe we just shouldn't be making preamps with 35-year-old op amps

741's would do it :D
 
ivanlukic, I agree absolutely with both your recent posts - I think I can pick a jfet opamp easily, and same goes with power amps with jfet inputs (eg AEM6000). The smoothness is nice at first but gets boring quickly. So you were right, we're absolutely on the same page :)

Have you tried the OPA604 though? To my ears this is a nice compromise subjectively - it has the smooth "open" sound of fets while still maintaining some of the bipolar "drama".
 
They might have the 'potential', but it's been my experience - with my gear and ears - none of them do to the extent my listening experience is compromised, or diminished.

redjr you've already stated that your preamp is the only high quality audio component in your system, so you would be extremely unlikely to hear any issues. I suggest you get yourself some decent speakers, power amp and source and another good preamp to compare to if you want to contribute to this discussion meaningfully.
 
ivanlukic, I agree absolutely with both your recent posts - I think I can pick a jfet opamp easily, and same goes with power amps with jfet inputs (eg AEM6000). The smoothness is nice at first but gets boring quickly. So you were right, we're absolutely on the same page :)

Have you tried the OPA604 though? To my ears this is a nice compromise subjectively - it has the smooth "open" sound of fets while still maintaining some of the bipolar "drama".

owdeo
Then why on earth are you still playing around with opamp based designs with their incredibly high open loop gain, when you could be further improving your discrete David Tilbrook based design from quite a few years back ?
Let's do a comparison between a couple of discrete preamps and the recent designs using 35 year old opamps. ;)

Regards
Alex
 
Maybe we just shouldn't be making preamps with 35-year-old op amps, whether they are JFET or BJT.

Hi Bob,

With all due respect I don't see any reason why not, if they are as good as or better than, objectively or subjectively, modern devices. Self has already argued the case for the objective reasons to use 5532s, but I have my own subjective ones also...

I bought some more LM4562s the other day so that I had enough to replace all the opamps in the main signal path of the Precision Preamp. I had a listen last night and oh dear, it's awful. Talk about a preamp that kills enjoyment of the music. It's hard to describe exactly why this is so, and presumably the distortion and noise would now be slightly lower than before. I don't understand why it's so bad, but I'm putting the 5532s back in - at least they are relatively harmless. The LM4562 might be regarded as "progress" for the test instruments, but as a device to faithfully reproduce music they are a big step backwards to my ears. At least in this design. And before anyone asks, I did check waveform with the scope and it appears stable so it's not that.

Cheers,
owdeo