More audiophoolery: discrete op-amps better than ICs! - Page 1
Forum section: electronics / general

author: Zero999
author_rank: Super Contributor
timestamp: September 20, 2014, 11:12:10 pm
content: I found this when I was researching op-amp design and couldn't believe the stupidity and ignorance!http://www.bursonaudio.com/creations/discrete-opamp/

author: c4757p
author_rank: Super Contributor
timestamp: September 20, 2014, 11:26:18 pm
content: Quote

author: miguelvp
author_rank: Super Contributor
timestamp: September 21, 2014, 01:20:09 am
content: Quote from: c4757p on September 20, 2014, 11:26:18 pmWhat's wrong with matched pair transistors?http://www.nxp.com/products/bipolar_transistors/general_purpose_bipolar_transistors/matched_pair_transistors/

author: Marco
author_rank: Super Contributor
timestamp: September 21, 2014, 01:22:12 am
content: QuoteAnd everyone wins buzzword bingo.

author: miguelvp
author_rank: Super Contributor
timestamp: September 21, 2014, 01:24:19 am
content: I get that, and I didn't read the article until now, but I don't know why the matched paired transistors claim is soo funny.

author: tautech
author_rank: Super Contributor
timestamp: September 21, 2014, 07:16:47 am
content: Quote from: miguelvp on September 21, 2014, 01:24:19 am"Perfectly matched" was the claim....is there such a thing?Depends in how good your test gear is, no doubt.

author: miguelvp
author_rank: Super Contributor
timestamp: September 21, 2014, 07:33:24 am
content: Quote from: tautech on September 21, 2014, 07:16:47 amTo me it does sound the same, but I guess it has some marketing flare in a more common non electronic language.But matched transistors will make a difference and as far as "perfectly" one could say that's the design intent.

author: PE1RKI
author_rank: Regular Contributor
timestamp: September 21, 2014, 07:39:54 am
content: someone should buy one and test it against a 741

author: German_EE
author_rank: Super Contributor
timestamp: September 21, 2014, 09:55:25 am
content: One of my side hobbies is collecting weird audio stuff, forget expensive cables, some guys claim that you can affect the sound by changing the knobs on the front panel.However............................If you are building a low-level amplifier you have a choice of either using an IC (such as an op-amp) or using discrete transistors. For example:http://sound.westhost.com/p66-f1.gifThat transistor configuration on the front looks just like an op-amp and I'm guessing that the good Mr Elliott knows what he's talking about,this simple design has very low noise, close to the theoretical minimum, high hum rejection and variable gain with a single rotary potSo, if we try to ignore the wank word bingo we may find that these guys are right.

author: tszaboo
author_rank: Super Contributor
timestamp: September 21, 2014, 10:17:49 am
content: Well, transistor based amplifier circuits have their benefits. Like driving high loads. Or working with higher voltages. Also, a cheap single transistor works easily at higher frequencies than a more expensive opamp. So it is not all bullshit what they say.But there are thing that you cannot replicate with discrete design. Like temperature coupling, compensation, and tolerances. The truth, as always are in the middle.But again, this is for audio. Does it matter? No. That sound went 50 times through a 5532 before the recording was made.

author: timb
author_rank: Super Contributor
timestamp: September 21, 2014, 10:20:59 am
content: I bought a nice mid-range headphone amp a few years back that has socketed op-amps. The idea being you can change them out to match your listening style. Different OpAmps have different characteristics, OK, makes sense I guess. But going all discrete? These guys just like throwing away money.By the way, go onto HeadFi or so other forum and bring up DBT; see how long it takes for your post to be removed. That's how far down these guys have their heads buried in the sand.Sent from my Smartphone

author: dannyf
author_rank: Super Contributor
timestamp: September 21, 2014, 10:23:04 am
content: QuoteIt takes stupidity / ignorance to not see that a discrete opamp ****CAN**** out-perform an IC opamp.Whether this particular discrete opamp out-performs an IC opamp is a separate discussion.

author: Circlotron
author_rank: Super Contributor
timestamp: September 21, 2014, 10:32:27 am
content: So you fit these things and finally have the perfect amplifier.Only trouble is, nothing is going to fix the  sonic contribution of dozens of opamps upstream in the recording chain....Except the magic power cords I sell.

author: David Aurora
author_rank: Frequent Contributor
timestamp: September 21, 2014, 11:03:36 am
content: Quote from: timb on September 21, 2014, 10:20:59 amThis is why we can't have nice things.

author: timb
author_rank: Super Contributor
timestamp: September 21, 2014, 11:13:44 am
content: Quote from: dannyf on September 21, 2014, 10:23:04 amSomehow I doubt a modern high performance OpAmp from TI, AD or LT isn't going to be better than what 99.9% of people will be able to produce discreetly.First, you need access to the equipment to characterize and match the transistors. Then you need the knowledge and talent to build a layout that minimizes noise and interference. They requires using simulators and a lot of time.Finally, in terms of using it for audio, the human auditory system is pretty shitty. There's no way you can hear the benefit of something like this.That said, for something like use in very specialized instrumentation, sure, a discrete OpAmp could perform better.Sent from my Smartphone

author: Zero999
author_rank: Super Contributor
timestamp: September 21, 2014, 11:18:35 am
content: Quote from: dannyf on September 21, 2014, 10:23:04 amYes of course, a discrete design can beat some monolithic op-amps, in certain applications. For example, it's easy to design a discrete op-amp with lower noise and a higher bandwidth than the 741 but the idea that just simply ripping out all the op-amp ICs in a design and replacing them with discrete op-amps will magically improve the performance is utter nonsense.

author: dannyf
author_rank: Super Contributor
timestamp: September 21, 2014, 11:20:51 am
content: QuoteThat's probably true and not contradictory to what I said earlier.My statement can be further demonstrated by these two statements:1) for any given IC Opamp, you can make a discrete Opamp that will outperform the IC opamp on at least one measurement.2) for any given discrete Opamp, you can make an IC Opamp that will outperform the discrete opamp on at least one measurement.The two statements are not mutually exclusive and 99.99% of the time, they are true at the same time for any two discrete / IC opamps.

author: dannyf
author_rank: Super Contributor
timestamp: September 21, 2014, 11:44:02 am
content: QuoteAgreed.

author: c4757p
author_rank: Super Contributor
timestamp: September 21, 2014, 11:53:33 am
content: Quote from: miguelvp on September 21, 2014, 01:20:09 am"Perfectly"

author: penfold
author_rank: Frequent Contributor
timestamp: September 21, 2014, 12:17:17 pm
content: Well, a pair of transistors matched within 2% isn't anywhere near as good as I can get using an analogue multimeter (because they sound better) and adjusting my head to get the best view on on the needle hovering exactly over the right value! I'm sure that perfect matching is possible if they use my soon-to-be-patent-pending measurement technique

author: German_EE
author_rank: Super Contributor
timestamp: September 21, 2014, 12:28:04 pm
content: Circlotron mentioned magic power cables, ask and thou shalt receivehttp://www.amazon.com/AudioQuest-NRG-WEL-Signature-Series/dp/B0055OM9WS/ref=rec_dp_1$6900 USD for a six foot power cable. Make sure you read the reviews because they have a high comedy content.

author: VK5RC
author_rank: Unknown
timestamp: September 21, 2014, 12:42:29 pm
content: Thanks for the link to the NRG-WEL, only 10 left so we had better be quick, I think I might lock up my wife after reading one of the reviews! Priceless.

author: miguelvp
author_rank: Super Contributor
timestamp: September 21, 2014, 05:04:23 pm
content: Quote from: penfold on September 21, 2014, 12:17:17 pmThat link was just for reference, didn't look too much into it and used the first hit, but for example these ones are 0.5% typical.http://www.analog.com/en/special-linear-functions/matched-transistors/mat12/products/product.htmlBut I didn't search too deep.

author: dannyf
author_rank: Super Contributor
timestamp: September 21, 2014, 05:26:53 pm
content: QuoteAside from "what parameters are you trying to match?" and "Are you matching point to point or along a curve?", there is also a question of "do you need to match them?".I would submit that with sufficient degenerative resistors, a random pair of transistors is practically no different from a well matched pair of transistors, discrete or integrated, in an opamp.

author: denelec
author_rank: Regular Contributor
timestamp: September 21, 2014, 05:52:56 pm
content: I guess it's a matter of nostalgia.If you're old enough, vacuum tubes amplifiers will deliver the best sound to your ears.Followed by germanium transistors, silicon transistors and finally IC's.Similarly, a vinyl record will sound better than a CD.The best electric guitars amps are made with tubes and the best fuzz pedals are made with germanium transistors. Nostalgia...http://www.guitarplayer.com/guitar-player/1011/all-about-germanium-transistors/25357Beauty is in the ear of the beholder

author: denelec
author_rank: Regular Contributor
timestamp: September 21, 2014, 06:11:10 pm
content: But any claim of better sound must be validated in a "double blind trial".If you can't tell the difference, it doesn't exist.How often do "better sound" claims are said to be validated by a double blind trial?There's a lot of placebo effect and cognitive dissonance going on with audio equipments.

author: SeanB
author_rank: Super Contributor
timestamp: September 21, 2014, 06:29:28 pm
content: Major advantage of the IC amplifier is that if you make 10k of them, then you can do very fast and simple testing to ensure that all are within the parameters desired, and you can get low noise, good gain and very similar performance with almost unmeasurable difference in the performance between any randomly selected units.The discrete amplifier requires adjustment and selection of parts that have to be matched for each unit, and making 100 will take longer than what it takes to have the 10k of integrated circuits go from raw metallic silicon to finished, packaged, labelled and tested units ready to ship out.The IC makes it near trivial to ensure matching, and this will hold true over a larger range than for any discrete transistor in almost every case. Unless you cut them from the die as a unit and keep them bonded together until casing they will vary. In that case you might as well use an integrated circuit differential pair, or a IC array.

author: dannyf
author_rank: Super Contributor
timestamp: September 21, 2014, 06:30:22 pm
content: QuoteWhy?QuoteIf a tree fell in the forest but you didn't hear it, did the tree fall?If someone committed a crime but you didn't see it, did he commit the crime?....

author: dannyf
author_rank: Super Contributor
timestamp: September 21, 2014, 06:32:49 pm
content: QuoteNot sure if they deliver the best sound but tubes do deliver better than than solid state amplifiers when over-driven.That is well understood.

author: GreyWoolfe
author_rank: Unknown
timestamp: September 21, 2014, 06:59:19 pm
content: If that cable got my wife pregnant, I would be suing everyone in sight since my wife has had a full hysterectomy. Then, I would make Jerry Springer pay us 10 million dollars to come on his show to tell our story. I bet we could be even bigger reality TV stars than Snooki and Kim Kardashian!

author: denelec
author_rank: Regular Contributor
timestamp: September 21, 2014, 07:09:32 pm
content: Quote from: dannyf on September 21, 2014, 06:30:22 pmBecause of the placebo effect. If someone expect an equipment to sound better, it probably will to his ears.And the trial must include a statistically significant number of participants.But the subject is complex. For some people, lower distortion, lower noise and higher dynamic range doesn't necessarily means better sound. "Better" for someone may mean "worse" for another.

author: denelec
author_rank: Regular Contributor
timestamp: September 21, 2014, 07:20:10 pm
content: Quote from: dannyf on September 21, 2014, 06:30:22 pmI should have said: "It doesn't matter."Ideally, when choosing between several audio equipments, you should listen to each without knowing which one you are listening to. If you can't tell the difference between two equipments, then you should base your choice on other criteria.

author: dannyf
author_rank: Super Contributor
timestamp: September 21, 2014, 07:34:42 pm
content: QuoteSo?And the trial must include a statistically significant number of participants."must"?

author: Circlotron
author_rank: Super Contributor
timestamp: September 22, 2014, 02:12:45 am
content: Quote from: denelec on September 21, 2014, 05:52:56 pmWith a musical instrument amplifier the situation is different to a hifi amp. A solid state guitar amp for example sounds much the same as the volume goes up and up till finally (and suddenly) it hits the brick wall of hard clipping. Truckloads of negative feedback add to this sudden onset of grating distortion and clipping. With a vacuum tube amp, generally the distortion climbs gradually with the volume, and then right at the end it gets worse(?) quicker, but nowhere near as sudden as with a solid state amp.The benefit of this is that the musician can use thisgradualdrift into distortion as an extra dimension of expression, much the same as a softly played piano has a gentle sound, but a firmly played piano has a much more urgent sound because of a different harmonic structure. The amp contributes to the timbre of the sound at the whims of the artist. Definitely desirable with a musical instrument. Really bad news for a hifi. It's horses for courses. Each device has it's own benefits and drawbacks.

author: Galenbo
author_rank: Super Contributor
timestamp: September 22, 2014, 10:37:57 am
content: Quote from: denelec on September 21, 2014, 07:09:32 pmThe subject isn't complex, but the uninformed religious fundamentalists are."better sound" is simply how close output and input signals are related. This can be measured and compared by people who are schooled to do that. The other ones can go discuss about their emotions, what they say is important for psychiatrists, not for technicians.

author: David Hess
author_rank: Super Contributor
timestamp: September 22, 2014, 12:13:38 pm
content: Quote from: dannyf on September 21, 2014, 05:26:53 pmDegeneration will lower gain and increase noise significantly. They go to great lengths to lower the Rbb and Rbe resistance in low noise differential pairs. Large area discrete transistors may be even lower noise but require higher currents.

author: David Hess
author_rank: Super Contributor
timestamp: September 22, 2014, 12:19:23 pm
content: A discrete design may have the advantage of preventing thermal feedback between the output and input transistors which among other things limits open loop gain but the same thing may be accomplished by adding a discrete buffer stage to the output of an integrated operational amplifier. This is especially the case when an audio design may use low impedance feedback networks to keep noise down.I would be more impressed in a discrete design using integrated matched input transistors like the SSM2220/SSM2212 or LSK389/LSK489

author: Bassman59
author_rank: Super Contributor
timestamp: September 22, 2014, 05:44:20 pm
content: Quote from: NANDBlog on September 21, 2014, 10:17:49 amTHIS.

author: Bassman59
author_rank: Super Contributor
timestamp: September 22, 2014, 05:48:00 pm
content: Quote from: timb on September 21, 2014, 10:20:59 amTheir heads are buried somewhere else, much darker.

author: dannyf
author_rank: Super Contributor
timestamp: September 22, 2014, 10:57:24 pm
content: QuoteLowering gain would be a good thing for audio amplification.As to increasing noise significantly: how significant is your "significantly"? is it 0.1db significantly or is it 10db significantly? is the noise in an amp going from -300db to -200db due to degeneration?One person's "significantly" can differ significantly from another person's "significantly".

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 23, 2014, 02:19:39 am
content: Quote from: David Hess on September 22, 2014, 12:13:38 pmDegeneration doesn't need to be resistive, see "noiseless feedback" for example.Also, to be clear: dynamic range will drop (gain / noise ratio) for increased degeneration, but total noise (output v_n) will drop. I think I'd want to run some numbers before making a more precise statement, like how dynamic range varies over chained stages, at different gain settings (and for different approaches, resistive / noiseless feedback, local vs. global, etc.), but I seem to recall it's best for fairly small ratios (a gain of 3 or thereabouts being just enough to get the first stage out of the noise floor of the subsequent stages, so signal grows exponentially while noise grows additively for N stages). Which is also best for bandwidth.Tim

author: VK5RC
author_rank: Unknown
timestamp: September 23, 2014, 11:16:55 am
content: One interesting low noise pre-amp I built was using paralleled op Amps from a design by Self, by paralleling the noise reduces by the sq-rt 2. IIRC.

author: daqq
author_rank: Super Contributor
timestamp: September 23, 2014, 01:51:54 pm
content: Discrete-better-than-integrated seems to be a belief shared by the audionuttery community:http://www.6moons.com/audioreviews/totaldac3/1.htmlAs I see it, a DAC is made up from a load of precision resistors. Are they actually being driven by the 74HC574 next to them? Even if that is not the case I wonder how they'd achieve 24 bit resistor driver matching...

author: dannyf
author_rank: Super Contributor
timestamp: September 23, 2014, 01:56:03 pm
content: QuoteDepending on the specific topology. Many are - most were, but many aren't.

author: alpaca
author_rank: Newbie
timestamp: September 23, 2014, 02:38:30 pm
content: This stuff is quite normal in the world of audio woo-woo. You REALLY want to see nutso? Try this:http://www.machinadynamica.com

author: calexanian
author_rank: Super Contributor
timestamp: September 23, 2014, 03:17:52 pm
content: I love this sort of nonsense and messing with the people who believe it! I want to make the suggestion to Wendell and Lenora at evil mad scientist to make a discrete 741 kit like they make the 555 kit. They already have the legs and such! Good learning type kit.

author: dannyf
author_rank: Super Contributor
timestamp: September 23, 2014, 03:23:49 pm
content: QuoteYou are trying to bring too much "rationality" to human comprehension.A few points for you to consider:1) the fact that something is unlikely to be useful doesn't mean it is not useful: what's "useful" is highly subjective and dependent on the individual perception / definition of "use" and knowledge at that point in time and the context. A bottle of water is useless for a person drowning but a life saver for the same individual dying of thirst in the middle of a dessert.2) the fact that something is not explainable today doesn't mean it is explainable: our knowledge will advance over time and a silly mystery today may be common knowledge tomorrow.3) individual freedom vs. imposition of "intelligence" onto others: however rationale / optimal you may think your position is, you have no right to project it onto others. Everyone of us should be free to make our own decisions, however silly it may seem to you.4) "religionize" science: science is ***one*** of many possible ways to understand our world. The key to science is the presumed assumption that science as we know it today is always wrong: something better and more comprehensive will come along tomorrow and revolutionize our understanding.To follow that spirit of science, you have to keep an open mind - what's "un-scientific" today may be "scientific" tomorrow, and vice versa, however unlikely.What you often see, unfortunately, are "scientists" who treat scientific discoveries with absolutism: what's science today will always be true and what's not science today will never be science.By doing that, they have violated the fundamentals of science.

author: miguelvp
author_rank: Super Contributor
timestamp: September 23, 2014, 04:13:44 pm
content: Quote from: dannyf on September 23, 2014, 03:23:49 pmYou should watch or even just listen to MindWalk 6 minutes into this part about a view of science as a religion:Edit: hmnm the time set in the link is not working, start at 6 minutes exactly.Actually you should watch the whole movie, it's pretty good for thinkers.

author: ConKbot
author_rank: Super Contributor
timestamp: September 23, 2014, 05:33:16 pm
content: Quote from: VK5RC on September 23, 2014, 11:16:55 amShhh, dont mention paralleling, you'll bring around stuff likeParalleling DAC IC's to sound gooder.

author: wraper
author_rank: Unknown
timestamp: September 23, 2014, 06:04:16 pm
content: Quote from: daqq on September 23, 2014, 01:51:54 pmI really doubt that this dac can do even 12-13 bit with monotonicity of output. Not to say that analog and digital is highly mixed all over the board.

author: coppice
author_rank: Super Contributor
timestamp: September 23, 2014, 06:07:28 pm
content: Quote from: German_EE on September 21, 2014, 09:55:25 amYou've never tried changing a volume control? The effects are really profound.

author: David Hess
author_rank: Super Contributor
timestamp: September 23, 2014, 06:13:01 pm
content: Quote from: dannyf on September 22, 2014, 10:57:24 pmEmitter degeneration will decrease the open loop gain and not the closed loop gain.QuoteThis depends somewhat on circuit details but 60 millivolts added to the difference in Vbe is typical from what I found online although I have typically used more. Just winging it, if the collector current is raised to make up for decreased transconductance, then 22 ohm emitter degeneration resistors will more than double voltage noise in the input stage and the doubled collector current will double it again so that is a 6 dB increase right there without even including the doubling of bias current which will double the voltage noise through the input resistance if it is not lowered. That is a 9 dB increase total.Meanwhile if I have a matched input pair, I can throw all of that out and get a lower input bias current as well.This link does not cover noise but gives some idea of the issues:http://www.douglas-self.com/ampins/dipa/dipa.htmQuoteFor designs which are not limited by input noise this would not be an issue.Quote from: T3sl4co1l on September 23, 2014, 02:19:39 amWithin the context of an operational amplifier, I was referring to emitter degeneration of the input differential pair and I was unable to find any noiseless feedback examples which would apply.QuoteIf resistors are used for emitter degeneration presumably to ameliorate the effects of mismatched transistors, then input referred noise has to go up.

author: coppice
author_rank: Super Contributor
timestamp: September 23, 2014, 06:17:26 pm
content: Quote from: wraper on September 23, 2014, 06:04:16 pmBack when DACs had to be made in ways like that, the good ones were ovenised. You can trim something up to 16 bits or so, but you can't easily do it over a reasonable temperature range.

author: SirNick
author_rank: Frequent Contributor
timestamp: September 23, 2014, 07:12:18 pm
content: I've been a fan of Radiolab for a while, listening to whatever I happened to catch on the radio. Decided to begin at episode 1 and work my way up (it's good company while tied up at the bench). This parallel-to-improve-noise thing reminds me a lot of the episode entitled "Emergence". They consider ants, neighborhoods, and society as a whole, and find that individually we are dumb, but en masse, we average out to be rather smart. Examples given include a game where a group of random folk are asked to guess the weight of a large animal. Most of the guesses were way off, but the combined average of all of them was within a couple pounds.Interesting stuff. The best part for me is that, for every ridiculous audiophile concept or product that numbs the mind to consider, there's an episode of Radiolab that restores my faith in humanity's combined intelligence.

author: hamster_nz
author_rank: Super Contributor
timestamp: September 23, 2014, 09:04:32 pm
content: Quote from: calexanian on September 23, 2014, 03:17:52 pmWhat like "The XL741 Discrete Op-Amp Kit" (http://shop.evilmadscientist.com/productsmenu/762)?

author: Unknown
author_rank: Unknown
timestamp: September 23, 2014, 09:30:23 pm
content: This thread reminds me of a high end Hi-Fi store where a friend of mine works (lovely guy). I went in there to grab a decent set of speakers (probably going to settle for a set of Focal's, but I digress).One of the other employees was talking absolute nonsense, but I just let him go, didn't want to lead on that I knew more than he did. I also had to laugh at the $200+ price tag for a few metres of speaker cable.Don't get me wrong, they had some very nice, reputable gear among all that 'sales-pitchy' marketing bullshit, but still.

author: David Hess
author_rank: Super Contributor
timestamp: September 23, 2014, 10:53:49 pm
content: Quote from: daqq on September 23, 2014, 01:51:54 pmAll of the HC logic outputs will match each other closer than their absolute value of about 25 ohms so it is possible that the R-2R ladder resistance is an insignificant load or at least taken into account. I do not see how they could get 24 bit monotonic resolution though. I might believe 16 bits.Quote from: coppice on September 23, 2014, 06:17:26 pmThat thing is insane. I imagine some of the old hybrid DACs from Analog Devices looked a little like it but without the extravagance and more realistic specifications.With all of those 0.01% Vishay resistors per channel I could see getting into the 16 bit range if they were graded but I assume it does some sort self calibration. You used to be able to buy precision R-2R networks but offhand I do not know of anybody who makes one good enough.

author: SeanB
author_rank: Super Contributor
timestamp: September 24, 2014, 05:33:47 am
content: Even a 12bit network is best as a hybrid with laser trim for the voltage ( not per digit, that you design in and test that you deposit the film evenly) and then drive with something that has good matching. Doing it with random resistors will not work for monotonicity, unless you match resistors to at least 6 decimal places. Even then it will drift due to power dissipation differences.

author: dannyf
author_rank: Super Contributor
timestamp: September 24, 2014, 10:42:00 am
content: 8-bit is the practical limit for typical 1-5% resistors;10-bit is the practical limit for 0.1% resistors;beyond that it is practical not possible to do with even precision resistors.

author: tszaboo
author_rank: Super Contributor
timestamp: September 24, 2014, 08:38:59 pm
content: Quote from: dannyf on September 24, 2014, 10:42:00 amWell there is always the bulk metal foil, which they make with 0,001% accuracy. For a price.But in any case, R-2R networks have an absolute huge code change glitch. I dont see how it would be practical for audio. Probably much more practical to take an industrial DAC and connect it to I2S / DSD with some glue logic.//The TotalDAC is absolute bullshite. The amount of effort put into a fundamentally wrong concept is just creepy.

author: calexanian
author_rank: Super Contributor
timestamp: September 24, 2014, 10:16:20 pm
content: Quote from: hamster_nz on September 23, 2014, 09:04:32 pmExactly like that one. hahahaha.. I actually visited them a few weeks back when I was in the area. Great people.

author: VK3DRB
author_rank: Super Contributor
timestamp: September 25, 2014, 10:47:03 am
content: You'd have to have rocks in your head to believe this rubbish...http://www.machinadynamica.com/machina31.htmThese clowns should send Dave some rocks for a review...Genuine reviews?http://www.machinadynamica.com/machina19.htm

author: G0HZU
author_rank: Super Contributor
timestamp: September 25, 2014, 11:23:08 am
content: Have they started on food products yet?eg special £££ chewing gum that stimulates the ears and improves the soundstage and all the usual guff. You could have different flavours designed to improve the perception of classic music or pop or heavy metal.The really expensive versions would come in a gold wrapper that seals all the cleverness inside.

author: Richard Crowley
author_rank: Super Contributor
timestamp: September 25, 2014, 11:45:57 am
content: But those magic crystals are so sensibly priced! They could have charged 10x and the true-believers wouldn't have thought twice about it.That 741 kit is an educational tool, of course. Nobody proposes that a discrete retro-discrete implementation of that antique design is practical. Even if you implemented it in a DIP package.OTOH, the pro audio world has a major case of retro-philia. Back in the mid-20th century they were making 1.25 inch square potted modules of discrete op-amps because the monolithic products at the time (the 709 and 741 typ.e parts) had major problems with high-quality audio. So API (Automated Projects Inc.http://www.apiaudio.com/) started making the 2520 module in the same form-factor as the modules used by the analog computing people back in the day.API is still selling audio gear, but I think they have moved on from the old discrete opamp modules. However you can still buy clones and even kits from companies like CAPI (Classic Audio Products of Illinoishttp://classicapi.com/) and SLL (http://www.scottliebers.com/)And a highly respected home-built mic preamp (John Hardy,http://www.johnhardyco.com/) still makes his own 3rd generation discrete audio op-amp, the 990, designed by Deane Jensen of Jensen Transformers. (US Patent #4,287,479) Last year Mr. Hardy was forced by parts availability to finally switch to SMD construction to continue using the SSM2212 super-matched transistor pair that is the heart of the design. He publishes a very interesting and comprehensive document about the 990 discrete opamp. Recommended reading:http://www.johnhardyco.com/pdf/990.pdf

author: dannyf
author_rank: Super Contributor
timestamp: September 25, 2014, 12:00:04 pm
content: QuoteThe 990 is, by the numbers, a very unremarkable opamp. Nothing about it stands out and many modern amps, at a tiny fraction of the 990's cost, can out perform the 990 on the numbers.Yes, people who have listened to them love them - I am one of them.I have multiple amps in my possession, from the el cheapos to some of the more expensive ones (Signature and Parasound). I spend the most time listening to a set of JLH1969 -> 4 transistors, single-ended input, all npn (n-ch) output and good for 5w on a good day.Yet, I always liked how it sounds.Human perception is very interesting, let alone rationale. It makes no sense to take a pure academic approach to it. Whatever floats other's boats...

author: David Hess
author_rank: Super Contributor
timestamp: September 25, 2014, 12:56:49 pm
content: QuoteThe 990 input noise has only relatively recently been matched by monolithic operational amplifiers. Before amplifiers like the LT1028 became available, the LM394 and MAT02 were used to make low noise input stages in combination with monolithic amplifiers which were unmatched by monolithic amplifiers used alone and you can find the designs and specifications in old application notes for the LM394 and MAT02. High open loop gain, CMRR, PSRR, bandwidth, and slew rate tend to go along with this. You can still get lower input noise than is available in a monolithic amplifier by paralleling LM394s or MAT02s which might seem unreasonable but that was included in the old application notes as well.Considering that it takes an LT1028 style operational amplifier to equal some of the specifications of the discrete 990 (chiefly input noise) and the LT1028 has not been around as long as the 990, I would not consider the 990 useless. My preference though would be an LT1028 or similar at less than 1/5th the cost with a discrete output stage to increase drive capability and ameliorate thermal effects. I usually get along with LT1007 style amplifiers though when input noise is not critical which is usually the case and I still have a whole tube full of LM833s that I am working through.I am surprised though that there is not a JFET input version of the 990 using something like an LSK389 or LSK489 monolithic dual JFET in place of the LM394 or SSM2212.

author: diyaudio
author_rank: Frequent Contributor
timestamp: September 25, 2014, 03:19:14 pm
content: Quote from: dannyf on September 21, 2014, 10:23:04 amBuilding a discrete pre-amp stage and comparing it to an IC package (LM833N, NE5532 ect..) has no benefits to the ear for analogue playback material (sound), both these "audio circuits" will employee a dominant pole to force loop gain stability, high performance figures will be attenuated to meet the attenuated criteria to prevent self oscillation and reduce gain considerably at high frequencies.Measurement equipment and figures renders a different and valid story, unfortunately we don't listen with measurement equipment, but with our ears.Discrete stages are more valued in class-d comparator stages, which yields faster slew rates dv/dt for quantization and noise reduction where ultra high speed events are taking place, this is of benefit and relevant.

author: daqq
author_rank: Super Contributor
timestamp: September 25, 2014, 03:40:13 pm
content: QuoteAnd then you need just as matched push/pull drivers... 24 of them. Per channel. At those levels, even PCB traces might add something... but I'm sure it's OK, a trained ear is sure to hear that if it's OK or not.

author: SeanB
author_rank: Super Contributor
timestamp: September 25, 2014, 05:54:10 pm
content: Opamp labs.........Or a regular opamp and a discrete power output stage, which is enclosed inside potting resin in a steel can with an octal base. Took me a day to get one out of the can to replace the output transistors. Claiming 100ma drive capability and using 2N3907 transistors. Turns out they are not happy doing that with video though, though they supposedly are rated for it, or it was the 32 150R loads attached to the opamp. Replace with 2N2219 and 2N 2905 with clip on heatsinks and all is well again, though it would not fit back into the remains of the can though.

author: dannyf
author_rank: Super Contributor
timestamp: September 25, 2014, 06:35:37 pm
content: QuoteAn opamp + a diamond buffer is pretty much the ideal amp, only exceeded by a CFB xDSL driver -> incredibly fast, high current capabilities, huge slew rate, and no gain-bandwidth limitation.The price you pay is poor DC performance.

author: atferrari
author_rank: Frequent Contributor
timestamp: September 25, 2014, 11:55:07 pm
content: Quote from: alpaca on September 23, 2014, 02:38:30 pmParticle Accelerator Ion GunAmazingly cheap, I think!

author: coppice
author_rank: Super Contributor
timestamp: September 26, 2014, 01:54:55 am
content: Quote from: atferrari on September 25, 2014, 11:55:07 pmMust be German technology. It looks like its from Herr Dryer.

author: Zero999
author_rank: Super Contributor
timestamp: September 27, 2014, 07:33:38 pm
content: The hair dryer really made me laugh.I understand how some people prefer technically inferior technology, such as liking the sound of an old track, played on vinyl, through their ancient valve amplifier but no one should allow themselves to get brainwashed by that bullshit.Quote from: Circlotron on September 22, 2014, 02:12:45 amThank you for explaining that to me. My usual response to those who say valves amplifiers don't give nasty distortion when overdriven, like solid state amplifiers, is to never allow your amplifier to go into clipping but now I can see why some people do this.How about a hybrid amplifier, designed so the valve stage goes into clipping long before the ultra low distortion solid state stage clips? Then the guitarist can get the best of both.

author: dannyf
author_rank: Super Contributor
timestamp: September 27, 2014, 07:44:14 pm
content: QuoteYou can never assure yourself of that, unless you know the music before you hear it.You can do some basic math but assuming a reasonable crest factor, you need tremendous amount of headroom for a solid state amplifier to play the same music than you do with a valve amplifier.Another way to say the same thing: a comparably rated valve amplifier sounds much better than a solid state amplifier playing the same music.

author: wraper
author_rank: Unknown
timestamp: September 27, 2014, 07:50:35 pm
content: Quote from: dannyf on September 27, 2014, 07:44:14 pmTo be fair. For a comparable size or price you can get a solid state amp with at least an order of magnitude more output power.

author: free_electron
author_rank: Super Contributor
timestamp: September 27, 2014, 08:14:00 pm
content: Quote from: denelec on September 21, 2014, 06:11:10 pma doubleblind listening test proved that coathangers work better than expensive oxygen free interlinks

author: Zero999
author_rank: Super Contributor
timestamp: September 27, 2014, 09:16:54 pm
content: Quote from: wraper on September 27, 2014, 07:50:35 pmExactly, solid state amplifiers are cheap!Clipping can also occur in the speakers which sounds nasty, regardless of what amplifier you're using. If clipping occurs, just adjust the volume control.

author: VK5RC
author_rank: Unknown
timestamp: September 28, 2014, 05:11:44 am
content: A bit of silly question, has anyone ever seen any data that looks at the effect of ageing on speaker performance?I have some nice but old (20+ yrs) "Richard Allen HP12B Super" bass drivers.I would think that age may be not nice on some of the 'plastics/foam' surrounds etc. The surrounds look intact and do not appear brittle to gentle touch.

author: Richard Crowley
author_rank: Super Contributor
timestamp: September 28, 2014, 05:54:32 am
content: Your fellow countrymen, A. Neville Thiele of the Australian Broadcasting Commission, and Richard H. Small of the University of Sydney devised a method of measuring electro-mechanical parameters of loudspeakers some 40 years ago. The Thiel/Small Parameters.http://en.wikipedia.org/wiki/Thiele/Small.If you could get the Thiel/Small parameters for the loudspeaker drivers, you could measure your specimens and compare the numbers to actually characterize the deterioration.Particularly vulnerable are the foam-rubber molded surrounds which don't fare well in many environments. I have some JBL drivers (and passive radiators) which have been re-coned more than once because of environmental deterioration.The cited Wikipedia article also includes a brief overview of: "Lifetime changes in driver behavior".http://en.wikipedia.org/wiki/Thiele/Small#Lifetime_changes_in_driver_behavior

author: SeanB
author_rank: Super Contributor
timestamp: September 28, 2014, 07:06:40 am
content: Speakers do age and the supports and the foam become stiff and lose elasticity. A lot of high end speakers have an active business in replacing the foam rubber and the cone supports, along with the big car audio units.

author: VK5RC
author_rank: Unknown
timestamp: September 28, 2014, 08:17:36 am
content: Thanks Richard and Sean, just what I was looking for, many thanks.

author: Circlotron
author_rank: Super Contributor
timestamp: September 28, 2014, 10:38:07 am
content: Quote from: Richard Crowley on September 28, 2014, 05:54:32 amSome time ago I fiddled about a lot with all that stuff. After trying a number of unsatisfactory ones I ended up writing my own spreadsheet to do the calcs. All you need is an amplifier, oscillator, resistor, meter and a lump of blue tac of known mass.http://www.diyaudio.com/forums/attachments/multi-way/23875d1079781945-best-ever-t-s-parameter-spreadsheet-best-ever-ts-parameter-calc.zipMake sure you put the back of the speaker against a large mass e.g. lengthwise 100x100x300mm post otherwise the speaker vibrates in anti-phase to the cone and gives inaccurate Q measurements. don't cover any vent holes on the back of the magnet though.

author: dannyf
author_rank: Super Contributor
timestamp: September 28, 2014, 11:08:06 am
content: QuoteMuch less so.QuoteThat's assuming that the T/S model can capture the effect of aging. Without knowing the mechanism of aging that you are trying to study, that's not a sure thing.I tend to think that the lack of information on that is fairly indicative of aging's impact, or lack of.On a broader topic, speakers are one of the most impactful, if not the most impactful, elements on sound quality. Yet, many people would buy speakers without first listening to them, and spend the most on the least impactful elements, like cables, power conditioners, or amplifiers...

author: VK5RC
author_rank: Unknown
timestamp: September 28, 2014, 12:30:24 pm
content: Thanks Circlotron, I had found diyaudio forum but you have spurred me on to register, the diyaudio site has some data on the T/S parameters of the Richard Allan drivers , so I have some data to compare. Unfortunately I might not get to it for a week or so as my wife is about to go away so I will be busy with the carpet commandos.I suppose I am lucky they are bass drivers as I suspect compliance issues are probably less critical at lower frequencies.@dannyf, I fully agree that speakers (drivers,cabinet) are THE most important aspect of a good "HiFi" system, room acoustics probably next.

author: oldway
author_rank: Super Contributor
timestamp: September 28, 2014, 04:50:34 pm
content: In my younger years, I was projecting and building hi-fi and guitar tubes amplifiers.For guitar amplifiers, musicians were seeking for amplifiers with high distortion for "coloring" the sound of their musical instrument.I then chosed universal low quality output transformers and I biased tubes (mostly EL34) for low quiescent current (working nearby class B)For Hi-Fi stereo, I chosed expensive and high end output transformers as the most important components in a tube amplifier are the output transformers. (with push pull EL84 / 9W or EL34 / 25W)What whe were looking for is just what we obtained later with the transistorized amplifier performance.But there is a big difference between a tube amplifier and a transistor amplifier : the damping factor. (low for a tube amplifier, high for a transistor amplifier)On this point, the best is the enemy of the good.With a tube amplifier, loudspeakers operate more freely in their natural resonant frequency, which gives a more pleasing sound to the ear.I think that's why music lovers say the sound of a tube amp is more enjoyable than a transistor amplifier. (with the same speakers)NB: I also fully agree with dannyf about speakers and room acoustics...

author: Zero999
author_rank: Super Contributor
timestamp: September 28, 2014, 05:23:50 pm
content: Quote from: oldway on September 28, 2014, 04:50:34 pmNot everyone likes that.The main advantage of a solid state amplifier is lower output impedance and a high damping factor to give a more flat frequency response, rather than the horrible peaks at the resonant frequency of the speaker.Fortunately, if you like that, it's easy to ruin the damping factor by adding series resistors or more than one speaker in series, without having to resort to expensive valve amplifiers.

author: oldway
author_rank: Super Contributor
timestamp: September 28, 2014, 05:52:08 pm
content: My choice: MARANTZ 2285B with KEF speakers.You see that I am NOT a tube amplifier fan !They are only very useful in the winter...

author: dannyf
author_rank: Super Contributor
timestamp: September 28, 2014, 06:51:09 pm
content: QuoteIt would reduce output power significantly.However, some headphone amps do that deliberately, as power ratings there are of minimum concerns.

author: Zero999
author_rank: Super Contributor
timestamp: September 28, 2014, 07:37:50 pm
content: Quote from: dannyf on September 28, 2014, 06:51:09 pmIt's still cheaper to buy a solid state amplifier 10 times more powerful (than the same valve amp) and add series resistors.

author: dannyf
author_rank: Super Contributor
timestamp: September 28, 2014, 08:20:38 pm
content: You don't have the headroom then.