audiofool opamps - Page 1
Forum section: electronics / general

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 27, 2018, 03:07:28 pm
content: https://www.bursonaudio.com/products/supreme-sound-opamp-v5i/They apparently don't want to admit how poor their noise performance is when it's not listed in the datasheet.

author: BrianHG
author_rank: Super Contributor
timestamp: May 27, 2018, 04:05:05 pm
content: Yes, that's a pitifully inept spec sheet...

author: Kleinstein
author_rank: Super Contributor
timestamp: May 27, 2018, 05:09:20 pm
content: A bias current in the 2 µA range is also more typical for a BJT based OP than a JFET design. With such a high bias quite a few circuits made for FET based OPs will not work. In addition input current noise is also likely rather high with so much bias - so higher impedance circuits would likely be rather noisy.There is essentially no way a single OP can replace so different OPs as listed: they are just to different in GBW. When replacing a slow one it might oscillate. Higher GBW is not always better.Another point is the common mode range: especially with a discrete input stage it is hard to get rail to rail performance and some of the OPs listed work to at least one rail.Even when designing a circuit around that OP - the data-sheet is telling enough to reliably use that amplifier.

author: David Hess
author_rank: Super Contributor
timestamp: May 27, 2018, 05:45:46 pm
content: Based on the specifications, it looks something like an ADA4898 followed by a buffer.The list of operational amplifiers which it is suppose to replace however is ludicrous as it includes both JFET and low noise bipolar parts.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: May 27, 2018, 07:21:47 pm
content: In any event, passive components contribute more hiss than the transistors. Especially any high value resistors in the inputs, if they are not bypassed by a lower impedance such as a mic or guitar pickup. This is why non-inverting preamps are generally quieter - an inverting stage must have series resistors. The quality of resistors in such positions also makes a huge difference. Cheap carbon film types can be very noisy, a top brand metal film type far less so.The TL071-4 series, designed by audio guru John Linsley-Hood, are very inexpensive and good enough even for professional gear. So, why pay silly money?

author: David Hess
author_rank: Super Contributor
timestamp: May 27, 2018, 11:16:36 pm
content: Quote from: IanMacdonald on May 27, 2018, 07:21:47 pmAnother place to see this is in power amplifiers which use emitter degeneration (resistors in series with the emitters) in their differential input stage to lower transconductance. See below why this is necessary.Since power amplifiers are usually intended for a high level input, the added noise is usually not a problem but it sure is annoying if are close to a high efficiency speaker at low volume levels.QuoteAnd there are even much better JFET input parts now which do not cost a lot more.Originally the big advantage in audio applications of JFET operational amplifiers besides low input bias current was lower first stage transconductance which allows higher gain-bandwidth product, slew rate, and full power bandwidth. Early bipolar operational amplifiers used emitter degeneration to trade higher input voltage noise for the same things so they had as much if not more voltage noise anyway and there was no reason not to use a JFET part. The old noisy LM318 is a good example of this kind of bipolar part and it is common with modern "video" amplifiers where low input noise is not required.

author: james_s
author_rank: Super Contributor
timestamp: June 03, 2018, 05:48:14 pm
content: You could probably put a 741 in a fancy can and people would buy it and write glowing reviews.

author: David Hess
author_rank: Super Contributor
timestamp: June 03, 2018, 06:59:58 pm
content: Quote from: james_s on June 03, 2018, 05:48:14 pmStart a line of operational amplifier substitutes for the authentic 741 sound.

author: Yansi
author_rank: Super Contributor
timestamp: June 03, 2018, 07:02:25 pm
content: I think uA709 wold get more crispier sound with honey-like mids...

author: Brumby
author_rank: Unknown
timestamp: June 04, 2018, 02:11:52 am
content: You have to go with the technology of the day to match the media of the day. Anything to do with vinyl records can only be properly processed with op-amps using the mighty 741!Do you think it's onlycoincidencethat the hey-day for both ran through the 70's and 80's?!!!

author: Cyberdragon
author_rank: Super Contributor
timestamp: June 04, 2018, 05:18:28 am
content: Disgusting solid state crap!Tubes rule!

author: innkeeper
author_rank: Unknown
timestamp: June 25, 2018, 10:27:00 pm
content: WHERE ISNwAvGuyIEEE Spectrum article:https://spectrum.ieee.org/tech-history/silicon-revolution/nwavguy-the-audio-genius-who-vanishedNwAvGuy's blog (still up):NwAvGuy - Northwest Audio & Video Guy BLOG

author: Bassman59
author_rank: Super Contributor
timestamp: June 28, 2018, 12:36:55 am
content: Quote from: innkeeper on June 25, 2018, 10:27:00 pmThe IEEE article is four years old. Any update?

author: innkeeper
author_rank: Unknown
timestamp: June 28, 2018, 12:51:59 am
content: All I know is his domain name was renewed, and his website is still up. So everyone is assuming he is still alive, whoever he is.

author: 0xFFF0
author_rank: Regular Contributor
timestamp: July 14, 2018, 10:34:04 am
content: Wima caps for $5. Did a virgin urinate about that? I bought the same MKP type for 20 cents some weeks ago. To the OPs: The values given in the data sheet are worse by a factor of 10-15 than in a very good OP for $2.

author: julianhigginson
author_rank: Frequent Contributor
timestamp: July 16, 2018, 04:25:38 am
content: eh. people have been fooling about with opamp replacements in pro audio gear forever.people take the opamps out of a perfectly functioning bit of gear, put in new ones with no idea how the opamp's specs match the rest of the circuit, and have a listen. if they like it, there's a win for serendipity. if they hate it, they chuck it out and find another one to put in... people with old mixing desks sometimes load different channels up with different opamps just to have them all a bit different.It's kind of like car hot-rodding but based entirely with audio performance as measured with the users ears, and subjective taste. because that's the thing with audio electronics... if it sounds good, or you can convince someone it sounds good, then it is good. For something, at least.though normally they're at least fully discrete opamps in the vein of original parts used in old neve designs when you spend that much $.https://jlmaudio.com/shop/jlm99v-opamp-/-16v-to-/-24v.html?display_tax_prices=1it's a bit funny if you ask me, but way less offensive than the actually out of touch with reality hoo-ha of one-way audio cables, or even $1000 IEC power cables.

author: GregDunn
author_rank: Frequent Contributor
timestamp: July 16, 2018, 07:11:25 pm
content: When building stuff for my own use I typically design around TL07x series or maybe NE553x series, depending on what I'm actually using the amps for. On the output of my preamp, I actually have TL072 gain stages with an LH0002 buffer inside the feedback loop; the advantage is that I can drive arbitrarily low impedances without compromising performance - and it has come in handy once or twice. Pretty much any good op amp with a low noise spec can be made to work in hi-fi applications.What I can't get my head around is why people are now praising single-ended triode amps with way too little feedback, poor impedance characteristics and practically no output capability. I built amps back in the 60s which outperform them by miles, and I didn't spend $2000 on them either - more like $20.But yeah, the real nutters are the ones who spend more than a few pennies per foot for audio cable. Though I'd save a place at the table for the ones who claim demagnetizing their LPs improves the sound.

author: David Hess
author_rank: Super Contributor
timestamp: July 16, 2018, 07:12:32 pm
content: At least they are not using oldK2-W operational amplifiers.

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 16, 2018, 08:02:24 pm
content: In the compact disc’s heyday, some people would dunk them in liquid nitrogen.Digital Audio guru Ken Pohlmann, actually bet that he would fill his pool with LN2, and jump inside if someone could provide proof of the improvement.

author: GregDunn
author_rank: Frequent Contributor
timestamp: July 16, 2018, 09:15:00 pm
content: Quote from: David Hess on July 16, 2018, 07:12:32 pmSshhhhhhh... the tweakers are probably rushing to their benches right now to build up some expensive new preamps based on these...