Date: Thu, 2 Mar 89 11:37 CST From: ihlpb!miklyd (Michael Lloyd +1 312 979 5541) Subject: Re: TL074 op amps Bob Rogers asked about comparable or better parts than the TL074 op amp. I had a similar question myself once and rounded up the following information. Hope it helps. By the way Bob, the TL074 is not a bad part at all! It is orders of magnitude better than a quad 741, especially with regard to parameters importatnt to audio circuit use! Michael Lloyd Notes: According to the data I've seen, these parts have identical pinouts, so you can play "musical op amps" until you find what you want in the sound. TI = Texas Instruments HA = Harris Semiconductor, etc. (they merged recently) BB = Burr Brown AD = Analog Devices PM = Precision Monolithics, Inc. I don't use any quad op amps in any of my audio gear (homebrew preamp, amp; mods to cd player, tuner, tape deck), but the singles and duals I like are: Harris HA5147, Analog Devices AD711, AD712, AD744, Burr Brown OPA606, OPA37. I had read someplace (maybe Walt Jung's Op Amp Book) that the National Semiconductor (and second source) versions of the LM347 and similar parts (LM356, LM353, etc.) exhibit an perculiar type of frequency dependent distortion that may make these parts not preferred for use in high performance audio systems. National makes a LM4xx series (I don't know if it includes quads) that maybe doesn't have this problem. Maybe somebody out there can comment more; I don't want to shoot myself in the foot anymore than I already have! Manufacturer | Part Number | Comments TI TL074 Good general purpose BIFET for audio TI TL054 New and improved version of above PMI OP471 Low noise, bipolar PMI OP470 Quieter, slower version of above BB OPA404 Low noise, high speed, DIFET AD AD713 High speed, BIFET HA HA5104 Low noise, bipolar HA HA5114 faster (decompensated) version of above Michael Lloyd ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ A Moderate Note There's a new op-amp available from Analog Devices some of you might be interested in: the AS846. AD calls it a "450V/us precision current-feedback Op Amp". It was designed for, among other things, high speed DAC buffer and high performance audio circuitry applications. Here's a few of the features: Small signal bandwidth: 46 MHz (Av=-1) Slew rate: 450V/us Full power bandwidth: 6.8 MHz at 20V pp, Rl=500 ohms THD: .0005% @ 100 kHz Input voltage noise: 2nV / root Hz Quiescent supply current: 6.5 mA max These impressive specs hold true over a range of gains from -200 to 200, and since it is a transimpedance amplifier, is especially suited for DAC output buffering. Cost in 100s is $6.25US. It is a single op-amp in a 741 compatible package. If you wish more information, send me a mail message or call AD at (617) 329-4700. The 12 page data sheet is full of specs and schematics; there is a schematic showing this op-amp as an output buffer for the AD568 DAC. - Tom ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ------------------------------ Date: Tue, 5 Dec 89 01:57:07 EST From: "Edmund C. Lam" Subject: Op-amp Games With 14 Bit Philips I just popped some TI TL287's to replace the 5532. No one has reported using Ti's newest fet-opamps. I have not heard the Ad712 or the 5535. The first thing I noticed was a exagerated sound stage. Everything was pushed forward. The high end was much cleaner and more relaxed (with the stock 12V supply with safety resistors removed). I then applied 4.7K to force about 8mA draw out of each op-amp (Jung's does this with the 5535). This seemed to push the stage back a little, but still nowhere near my reference player (Onkyo DX7500). My question is: has any noticied this effect?? Second question, nowhere in the TL287's or AD712's spec is there mention of effects of output bias. What then is Jung's 3.92K or 4.75K doing between the op-amp output and -Vcc? My general option of the 287 is favorable. It certainly generates a more relaxed sound. My comparison between the 14bit philips and the DX7500 is very unfair (DX7500 has tweaked neglex on 14K tiffany running on unfiltered out). I would like to investiage the use of opto-coupler to isolate the laser's output to the DAC and the DAC to the analog section. Also, has anyone tried jumping the 3rd Bessel and running with the 176KHz band? What effects are introduced with the 176KHz band and are they worst than what is introduced by the 3rd Bessel? By the way, I think the TDA1541A (16bit philip chip) has problems dealing with sibilance. [Ed sends this addendum... -tjk] I re-read Jung's article in AA/88 and discovered that the resistor between the op-amp output and -Vcc exists to force the op-amp to draw higher currents at idle. This has the effect of providing a higher internal bias point. Jung argues that this brings the op-amp out of its AB operation and into A. In a reply letter (also in AA/88), Jung insists that the bleed resistor be metal film, but they aren't in the signal path so why does he insist? Back the to the op-amp biasing, Jung suggests an idle current of 6-10mA, so any value resistor giving this will do. ------------------------------ Date: Thu, 18 Jan 90 11:26:53 EST From: kludge@pyr.gatech.edu (Scott Dorsey) Subject: New Op Amps Spring is here! Even though it's still January, the new op-amps are coming out. Today's batch of datasheets includes an improved AD712 from analog devices, called the AD748. Bandwidth and slew rate are improved somewhat, though I am not sure of the noise figure because the sheet I have is rather preliminary. Overall it looks like it might be worth a try, and they tell me that samples will be available soon. The other neat beastie is something from National called the LM6118. Also a dual part, also compatible with the LM833 pinout so you can put it in your Magnavox CD player. This is another very-wide-bandwidth chip, even wider than the MC34082 (which is presently in my CD player and also serving as a video distribution amp so that my VCR can drive an old Conrac hires monitor). Ft is 17 MHz which is fairly respectable for something unity-gain-compensated. The slew rate is given as a pair of numbers: for decreasing (Av=-1), it's 140 V/uS, and for increasing i(Av=1), it's 75 V/uS. Not bad overall, though drive capability is pretty limited. Strange PNP output stuff that I don't understand, but they are sampling it (regretfully only in plastic packages), so get some and try them. Even at list price it's cheaper than a 6DJ8. --scott From: miklyd@ihlpb.att.com Date: Fri, 26 Jan 90 10:42 CST From: ihlpb!miklyd (Michael Lloyd +1 708 713 5497) Subject: More Op Amps And A Power Amp Design Question Greetings: To add to Scott Dorsey's list of new and maybe useful op amps, PMI has a new dual part that may be of interest. The part number is OP249. It is a Bi-Fet part, designed to be an improved replacement for the Analog Devices AD-712. I think I remember seeing from the spec sheet that the dc and noise specs are similar, and the BW and Slew rate are somewhat improved. One major point that PMI makes is that the OP249 has a more linear input stage and a very symmetrical slew rate. The include a few comparative scope photos to try to make their points. Obviously, this is from memory, so consult PMI for more info. They are sampling now. And these are pin to pin compatible with the National LM833, Signetics NE5532, Analog Devices AD712, etc. so you can substitute to your heart's and ears' content! Burr Brown has a couple of new high performance parts of interest well. The part numbers are OPA627 (unity gain stable) and OPA637 (stable at gains >5). I THINK (memory is really foggy on these!) are Bi-Fet parts with similar noise & dc specs and improved ac specs to their bipolar counterparts the generic OP27 and OP37. These parts are also available now for sampling. Contact your Burr Brown distributor. These are single parts, not duals. I have datasheets on all three of these and if there is interest, I could type in a few of the relevant specs. We may have to ask our friends that prefer tubes and discrete semiconductors to scroll past that part of the newsletter though :-) <---that is a smiley, OK!! Ona different topic, now that op amps have gotten to the present high level of performance, has anyone toyed with using some of the newest models as driver stages in power amplifiers? A few years ago, Accoustat marketed a couple of power amps that used the Hitachi series of Power MOSFETs as an output stage with voltage as well as current gain. The driver stage ran on lower supply rails (plus and minus 23 volts) than the output stage (plus and minus 70 volts). The topology applied some clever or weird (depending on your point of view) schemes for applying whatever negative feedback was needed. I always thought the driver portion of their circuit could be substantially improved, and thereby improving the design as a whole. Of course, an op amp (with a buffer to drive power MOSFET gate capacitances if needed) may not necessarily be a substantial improvement, but I was just kicking the idea around. Any comments??? Michael From: miklyd@ihlpb.att.com (Michael Lloyd +1 708 713 5497) Date: Mon, 30 Apr 90 12:49 CDT Subject: new op amp; specs look good! For those who may be interested: I recently obtained a data sheet and samples of a new, "ultra low noise, low distortion, audio op amp" from Linear Technology. The part number is LT1115. Here is a quick summary of the key specs.: Voltage noise: 0.9nV/root Hz typ (1.2nV/root Hz max !!) at 1KHz Wideband Noise (DC to 20KHz): nV RMS Current Noise: 4.7 pA/root Hz typ at 10Hz, 2.2 pA/root Hz max at 1KHz GBW Product: 70MHz typ (40 min) Slew Rate: 15V/uS typ (10 V/uS min; no comments about SR symmetry, I may call LT and ask) THD (Av=-10, Vo=7V RMS, RL=600 ohms <--!!!): < 0.002% IMD (CCIF, Av=10, Vo=7V RMS, RL=600 ohms): < 0.0002% Large Signal Voltage Gain (RL>,= 600ohms, Vo=+/-10V): 10V/uV typ, 1.0v/uV min Offset Voltage: 50 uV typ (200 uV max) Input Bias Current (Vcm=0): +/-50nA typ (+/-380 nA max) Supply current: 8.5 mA typ (11.5mA max) Supply Voltage: Testing done at +/- 18V (abs max is +/- 22v) The data sheet contains lots of data in graphical form and applications hints that may be of interest to DIYers like us. Here are some highlights from my quick scan of the data sheet: 1. Low voltage noise is acheived by running the input transistors at 1mA. To my knowledge, this is much higher than other parts! 2. This part is generally NOT applicable for unity gain followers/ inverters. 3. Circuits included are: RIAA equalizers for MM and MC, microphone preamps and ultra low THD sine wave oscillator. 4. Several of the circuits hang a current source from the output to the negative supply rail. This is a fancy implementation of Walt Jung's (or whoever started that business) hanging a resistor from the output to the negative rail to bias the output stage more into class A operation. The data sheet uses a jfet and resistor to implement the current sink function (they recommend pulling out ~2mA). Looking at pictures of the new ADCOM 565 circuit boards from the magazine advertisements, it appears that they use use the same approach! Has anybody tried this with other op amps? Did you notice any improvements? Does it harm the op amp or change any of its parameters (e.g. offset voltage, etc.) 5. Several of the circuits feed the output of the op amp into a LT1010 buffer for driving low impedance loads (including feedback loops). According to Stereophile (oh oh, do I hear the flame throwers warming up?), the ADCOM 565 does this also. Again, looking at the ads showing the circuit board, it appears that they might be using the Elantec EL2008 (or maybe EL2009). These are high speed (SR > 3000V/uS), high power (~1A drive capability) devices in a TO-220 case. This seems a bit of overkill, but who am I to say? I was looking at using one of the xx0033 type buffers to fill this role; they are roughly half as fast & drive about 200 mA, in a mdip package. As an aside, the Elantec 1990 Data Book has some good applications hints on using buffers (not just their own) to drive cables. Linear Technology's telephone number is 408-432-1900. Elantec's telephone number is 408-945-1323. DISCLAIMER: I have no stock in, nor do I work for either of these companies. But if they want to give me any free parts, I will certainly take them! By the way, what are you other DIYers doing out there? Construction type articles have dropped in quantity lately. Michael Lloyd Date: Fri, 28 Jun 91 18:21:22 pdt From: prls!max@uwm.UUCP (Max Hauser) Subject: The maligned 5534 op amp (Was: Chesky's 128x oversamp) In article <13391@uwm.edu>, Mithat F Konar (who recently called me a god) writes: | | My gut feel (I've never actually run any tests on any pro digital gear) | is that the easiest and best way to improve the sound of many pro digital | recorders would be to simply get those wretched NE5532 dual ops or NE5534 | singles out of the signal path. Replacement with TL07x (yup, that's right), | AD711/712/746 or 845, or Motorola MC3408x series would probably work | wonders. For some reason I simply cannot phathom, lots of engineers think | the 5532 is well suited to audio amplification. I know it was designed for | that purpose, but it's really not very good. In the case of a boom-box, it | probably would not be a limiting factor on sound quality ... This is the first time I've heard such a perspective. On a recent visit to Caltech, I discussed audio op amps with a couple of people who had been in the audience, and who have in fact run tests on pro digital gear. One was the principal engineer of Sheffield Labs and the other a classical musician who runs a high-end independent record firm that everyone seems to like. Both spoke highly of the Signetics 5534 series, specifically for pro gear, and they told me that lots of professional audio hardware is actually being retrofitted with 5534s although designed originally with other op amps. I asked what was desirable about the 5534 (in view of the competition, which Mithat cites) and they said that it sounds good, in careful listening tests. Of course, it could be that they're wrong. M. Hauser, obnoxious analog gadfly (OAG) and sometimes opamp designer (OAD) (No, I didn't design the 5534, I think Ralph Lovelace did.) From: konar@lennon.SRC.Honeywell.COM (Mithat F Konar) Subject: Re: The maligned 5534 op amp (Was: Chesky's 128x oversamp) Date: Mon, 8 Jul 91 20:35:06 GMT In article <13887@uwm.edu> prls!max@uwm.UUCP (Max Hauser) writes: > [stuff deleted] > >On a recent visit to Caltech, I discussed audio op amps with a couple of >people who had been in the audience, and who have in fact run tests on >pro digital gear. One was the principal engineer of Sheffield Labs and >the other a classical musician who runs a high-end independent record firm >that everyone seems to like. Both spoke highly of the Signetics 5534 >series, specifically for pro gear, and they told me that lots of >professional audio hardware is actually being retrofitted with 5534s >although designed originally with other op amps. I asked what was >desirable about the 5534 (in view of the competition, which Mithat >cites) and they said that it sounds good, in careful listening tests. > >Of course, it could be that they're wrong. What? High-end tweako-philes be wrong? More seriously, perhaps the closer truth is that the 5534 may sound alright, but there are other devices that work much, much better. I have noticed marked improvments in some line level electronics when 5534's were replaced by lowly AD711's. This assessment is based purely on my subjective empirical evaluation as I don't have access to the sophisticated instrumentation needed to produce a meaningful quantified analysis. My ears have proven generally reliable, however. [This is certainly no substitute for proof, however.] This is (unfortunately) my only experience retrofitting the 5534. I have much more experience retrofitting the 5532 and the LM833. I was very close on one occasion to replacing many, many 5534's on a very well respected studio recording console. The owners wanted to see what difference replacing the op amps would make as they were growing increasingly dissatisfied with the sound of the console. The idea was to swap a bunch out, and try a variety of chips to see if there would be any marked improvement. Alas, the bean counters gave a firm thumbs down to the project when they were presented with the projected cost of the adventure. Too bad. The results would have been quite instructive. -Mithat Konar From: franko@juliet.caltech.edu (Filipanits, Frank J.) Subject: Re: The maligned 5534 op amp (Was: Chesky's 128x oversamp) Date: 9 JUL 91 09:47:23 In <13918@uwm.edu>, konar@lennon.SRC.Honeywell.COM (Mithat F Konar) writes... >In <13887@uwm.edu> prls!max@uwm.UUCP (Max Hauser) writes: >> {stuff deleted} >> >>On a recent visit to Caltech, I discussed audio op amps with a couple of >>people who had been in the audience, and who have in fact run tests on >>pro digital gear. One was the principal engineer of Sheffield Labs and >>the other a classical musician who runs a high-end independent record firm >>that everyone seems to like. Both spoke highly of the Signetics 5534 >>series, specifically for pro gear, and they told me that lots of >>professional audio hardware is actually being retrofitted with 5534s >>although designed originally with other op amps. I asked what was >>desirable about the 5534 (in view of the competition, which Mithat >>cites) and they said that it sounds good, in careful listening tests. >More seriously, perhaps the closer truth is that the 5534 may sound alright, >but there are other devices that work much, much better. I have noticed >marked improvments in some line level electronics when 5534's were replaced >by lowly AD711's. This assessment is based purely on my subjective empirical >evaluation as I don't have access to the sophisticated instrumentation needed >to produce a meaningful quantified analysis. My ears have proven generally >reliable, however. [This is certainly no substitute for proof, however.] [more stuff deleted] I have done some preamp design working closely with Professor Jim Boyk here at Caltech and receiving some tips from his connections in pro audio; what I have found is that the 5534 has superb sound WHEN OPERATED IN A CERTAIN RANGE. To maintain maximum clarity and low noise, the 5534 seems to like running around 20 dB of gain, in inverting mode. Try to run it with more gain and the high end becomes harsh; less gain and the noise floor comes up. There are other circuit specifics it seems to prefer... Basically, my point is that ANY device has a certain set of conditions under which it obtains maximum performance; I propose that in certain circuits, the 5534 may be unhappy and an AD711 may sound better. However, I prefer designing with the 5534 and feel it offers the best combination of noise/transient/price performance when used properly. I would say the only way to know what operates best in an existing system is to try different things and see what sounds best. After all, that's the only thing that matters. As always, this is just my opinion... Frank Filipanits, AIT (Audiophile In Training) franko@juliet.caltech.edu PS> Just a word about "meaningful quantified analysis"... in doing alot of measurement and listening tests with Prof. Boyk, we've found that there are alot of times where two pieces of equipment will bench almost identically, but will sound entirely different... even a full gamut of testing on sophisticated equipment doesn't tell you what you really want to know --- how does it SOUND? ------------------------------ From: francis@heruka.adelaide.edu.au (Francis Vaughan) Subject: Re: The maligned(?) 5534 op amp Date: 10 Jul 91 03:36:49 GMT In article <13918@uwm.edu>, konar@lennon.SRC.Honeywell.COM (Mithat F Konar) writes: |> |> In article <13887@uwm.edu> prls!max@uwm.UUCP (Max Hauser) writes: |> > [stuff deleted] Both write about 5534/5532 in audio applications. My younger brother and I have had some experience with these beasts and have found that a major problem with them has been their low input impeadance. The design of active filters, be they RIAA, active crossover, or digital reconstruction filters with them, runs into trouble. Their impeadance is sufficiently low to distort the filter charateristics noticably. Designing around this is significantly more difficult than assuming infinite impeadance as one like to do with op-amp designs. In particular comparing j-fet opamps (like AD711 etc) in the same circuit is not possible. We have removed 5534/2s from a number of systems after the event for this reason alone. We designed assuming higher impeadance than we got. People who play musical op-amps (especially those that mess with the reconstruction filters in their CD players) may be listening to slight changes in frequency response as much as anything to do with inherent superiority of the device. That said, there is no doubt the 5534/2 is getting quite old now, and that newer devices have significantly better perfomance. Better CMRR (Common Mode Rejection Ratio) better slew rates, better noise immunity. The 5534 does however have a better noise figure than the j-fet variety, and is still very useful for this reason. Remember one of the reasons professional audio gear used 5534s was that they are capable of driving straigth into a 600 ohm load, which makes life much easier for the designer. Just how well it performed in this role is open to some dispute. Francis Vaughan From: strong@tc.fluke.COM (Norm Strong) Subject: Op Amps for Audio Date: Thu, 18 Jul 1991 15:09:03 GMT Since there seems to be considerable interest in opamps for audio use, I thought I would mention the extensive line of audio IC's from SSM, a small company subsequently bought out by PMI. They have low distortion, low noise opamps, as well as differential mike amps, etc., all designed for professional audio applications. Since PMI is now a part of Analog Devices, you can get a very nice catalog of the SSM line from AD, complete with 19 app notes. It's called the "Audio Handbook, Vol. I" . -- Norm Strong (strong@tc.fluke.com) 2528 31st S. Seattle WA 98144 USA ------------------------------ Date: Thu, 8 Jul 93 18:18:38 EST From: stacy@trc.com (Robert Stacy) Subject: op amps I have known: LM318 It's fast, but watch out in unity- or low-gain applications; if you're using a feedback resistor, make sure you've got some compensation capacitance across it to flatten out the gain peak caused by the input capacitance and FB resistance pole. I had a voltage follower stage, with matched DC offset equalization resistors on both inputs (input buffer for an electronic crossover), take off on me and never come back -- it oscillated to destruction. The same circuit is now served quite civilly by an AD712, with only minimal compensation (5 pF, I think). AD712 A good, quiet device with adequate GBW and very low DC offset -- ideal for direct coupled circuits and DC offset correction circuits. I've used quite a few in CD player upgrades to good effect. LM412 Another low-offset device, similarly good for DC offset correction (aka "servos" [sic]). Worked well in the line amp stage of my FET Leach preamp (and oh, what a difference eliminating two steenking electrolytics from the signal path made!). OPA2604 I put one of these into the reconstruction filter/output stage of a Nakamichi CD Player 4 recently. (An interesting compromise between cost and performance, this player has one of the more intelligent [single-sided] board layouts I've seen for a dual DAC [an AD1864], and individual [zener/pass-transistor] regulators for the DAC [low] and op amp [high] rail voltages.) The sound was slightly smoother, with a small improvement in image stability, but I think losing the output coupling cap and upgrading the supply regulators would make these improvements far less subtle. My only other application of these devices so far has been in the GIC reconstruction filters of a DSP loudspeaker crossover. The filters were based on an app note from Burr-Brown (Application Bulletin AB-026, February 1991). Computer simulations -- and actual measurements -- showed that the most important feature required of an op amp, in order to perform well in this circuit, is BW and lots of it. With their 20MHz spec, the B-B devices are more than up to the task. AD847 Upgrading the high-pass output stage of the aforementioned electronic crossover (see LM318 above -- not the DSP crossover also mentioned) with the AD847 allowed the R-C values to be reselected for lower Rs; this, as a result of the increased current drive capability. This same current drive also accounts for the '847's ability to source (with appropriate precautions) capacitive loads unflinchingly. Some component value juggling was necessary to balance the criteria of lower noise and precision components available (Wima MKP 10 caps), but a workable compromise was reached. --Bob ------------------------------ From: p26005@hac2arpa.hac.com Subject: Re: Replacements for LM301 op amps? Date: 5 Oct 93 17:10:13 GMT In article 28p783INNdgn@uwm.edu, jpmakela@cc.helsinki.fi (J Pekka Makela) writes: > > > I would like to know if there is lower-noise/more-headroom > replacement op amps for LM301's. As I have no desire to > modify the rest of the circuit, those should be direct drop-in > replacements. And, preferably, cheap. I don't know about lower noise/more headroom info, but there are industrial/military versions of the LM301A's which have better characteristics over a wider temperature range (LM201/LM101 respectiveley). That is, input offset voltage and offset current are specified lower than commercial devices. The slew rate of this device is spec'd at 10V/us. If you go to a higher bandwidth part, you may introduce other undesirable problems. Note that these ind/mil parts are more expensive. > The whole code of the op amps is " /8051 LM 301AN", if that > makes any difference. The /8051 usually means the device was manufactured on the 51st week of 1980. ------------------------------ From: vision@netcom.com (Aitech Intern'l Corp) Subject: Better Op-amps than AD8xx ? Comlinear Date: Tue, 12 Oct 1993 22:57:08 GMT Hi, Some time ago there were discussion regarding the relative sound quality of op-amps, with Analog Device's AD8** series winning.... I've come across a data book from Comlinear products that features some excellent specification op-amps: eg, Dual Op-amp CLC412, $5.90 (@1k) Specs: 250Mhz -3dB bandwidth, when gain=2, 1300V/uS slew rate, 70mA output current Anyone have any experience? Casey ------------------------------ Date: Thu, 14 Oct 93 11:37:13 EDT From: Scott Dorsey Subject: Better Op-amps than AD8xx ? Comlinear The Comlinear op-amps are very strange... many of them are current-input devices instead of voltage-input, and are a bit odd to work with. They also are amazingly fast and as a result are tricky to keep stable. However, they might be worth trying in audio circuits. I would personally recommend the Motorola MC34081, which is the best sounding op-amp that I have ever heard. It's fast and it's inexpensive, although the noise level isn't the best. Give it a try. --scott ------------------------------ From: mlloyd@ihlpm.att.com Date: Wed, 1 Dec 93 09:50 CST Subject: Re: CD-mods and op amp problem Regarding the question on this thread, the AD811 is NOT a drop-in replacement for the xx5534. The AD811 is one of those "newfangled" current feedback op amps. I STRONGLY suggest the original poster of the question contact Analog Devices and get the data sheets and app notes for the device (and any general information on how current feedback op amps work and how to use them) and study those before applying the device. A few points: 1. (Usually) Current mode op amps will oscillate in circuits where there is a capacitor connected directly between the output and the inverting input. In a recent "The Audio Amateur", Walt Jung discussed ways of using the AD811 in these types of circuits. I don't remember the issues numbers, it was the ones regarding modifying the Philips player. Maybe this is happening in your application. 2. The data sheet for the AD811 suggests that the AD811 be heatsinked when used with supply rails above +/- 12 volts. 3. If your AD811 is drawing 80mA, I suspect it is oscillating, as a previous poster suggested. Hopefully, the heat hasn't damaged it. 4. I am not a big fan of just putting sockets in a CD player and plugging all kinds of op amps in. Most op amps that could be used for this kind of thing are different enough that they would benefit by having the circuit optimised for their specific characteristics. 5. Having made point #4, if someone held a loaded gun to my head to force me to plug in a different op amp for the xx5534 without touching the circuit otherwise, I would spend big bucks (last time I looked, on the order of $13.00 each) and try Burr Brown's OPA637 or OPA637. A good op amp for audio, as a poster to the recent digitally controlled preamps thread suggested. Does anyone know if Max Hauser is still around?? Maybe he could be enticed into writing a couple of points (from an IC designer's point of view) on using op amps in audio design. Walt Jung's op amps for audio book should be on most tinkerer's shelves too! Michael Lloyd disclaimer: these are my own opinions.... mine .... mine .... mine .... all mine .... ha, ha, ha, ha, ha........................... ------------------------------ Date: Wed, 1 Dec 93 15:51:04 EST From: Scott Dorsey Subject: AD811 >According to my data book on the AD811, it should only draw 16.5 mA. >Granted that this number will vary with frequency and load, however, 80 >mA seems a bit high. An alternative may be the AD847 which typically >draws 5.3 mA. Its slew rate is 300 V/us versus 2500 V/us on the AD811. >Good luck with your mod. I'm also about to make a mod to a >Magnavox(Phillips) CDB-472. I strongly recommend trying out the MC34082 op-amp from Motorola. It doesn't have the best specifications around, especially in terms of noise, but it's one of the cleanest-sounding op-amps that I have used. Motorola also tends to be more promiscuous with free samples than other companies, as well. I have been using these things since 1985 in audio circuits, and while I have found some that performed better in particular circuits, I have never found as good an overall general purpose op-amp part. Try it. --scott ---------------------------------------------------------------------- From: moskowit@panix.com (Len Moskowitz) Subject: Re: AD811 Date: 2 Dec 1993 09:35:24 -0500 Scott Dorsey wrote: :I strongly recommend trying out the MC34082 op-amp from Motorola. It doesn't :have the best specifications around, especially in terms of noise, but it's :one of the cleanest-sounding op-amps that I have used. Motorola also tends :to be more promiscuous with free samples than other companies, as well. I :have been using these things since 1985 in audio circuits, and while I have :found some that performed better in particular circuits, I have never found :as good an overall general purpose op-amp part. Try it. Just be aware of it's 30 nV/root-Hz equivalent input noise voltage and the fact that it's not made for single supply operation. Get the "A" version if you can find it. -- Len Moskowitz Core Sound moskowit@panix.com ------------------------------ From: shumaker@eisner.decus.org Subject: Re: NE5534 replacements (Was AD811) Date: 2 Dec 93 14:18:26 -0500 In article <2dksm3$26q4@introl.introl.com>, Scott Dorsey writes: > I strongly recommend trying out the MC34082 op-amp from Motorola. It doesn't > have the best specifications around, especially in terms of noise, but it's > one of the cleanest-sounding op-amps that I have used. I'm not sure that the MC34080-series units would be really suitable as replacements for NE5534s _in existing equipment designed for the '5534s_. The '34080s are FET-input amps, with much higher (nearly 9X) input noise voltage than the '5534s and an associated much lower (1/40) input noise current -- they should be very useful in high-input-impedance applications (like at the wiper of a pot). However, in the single-amp 8-pin minidip units (the MC34081P) the offset null connections are to pins 1 and 5, which are one 'balance' connection and one compensation connection respectively on the NE5534. If the existing equipment has connections to these two pins, the effect on the 34080 will be unpredictable (likely none, but...). ------------------------------ Date: Thu, 19 May 94 18:00:34 EST From: stacy@trc.com (Robert Stacy) Subject: Jung op amp books In HiDi 22/91, carter@sst10c.lanl.gov (Michael J. Carter) asks: > 5) Books: Is Jung's 'Audio Opamp Applications' book really > out of print? My local bookshop says so. Is his 'Opamp Cookbook' a > good replacment? Second question first: No, in general the _IC Op-Amp Cookbook_ does not cover the same material as _Audio IC Op-Amp Applications_. The latter covers some of the basic stuff dealt with in the former, regarding the care and feeding of op-amps in general -- power supply bypassing, offset correction, input protection, stability requirements, etc. -- but quickly focusses on specific audio applications. The former of the two covers more historical background/evolution and general operating requirements, then segues into general purpose applications such as voltage references, signal processing, multipliers, comparators . . . good stuff to have around if you're involved in general analog design, but not strictly targetted toward the amateur audio hobbyist. If that describes you, I'd look for _Audio IC Op-Amp Applications_. Last I was aware, both books had gone into their Third Edition. Pertinent hard data follows: Jung, W. G., _IC Op-Amp Cookbook_, 3rd Ed., <, Howard W. Sams & Co., Ind. IN, 1986, ISBN 0-672-22453-4, Sams #22453. Jung, W. G., _Audio IC Op-Amp Applications_, 3rd Ed., Howard W. Sams & Co., Ind. IN, 1987, ISBN 0-672-22452-6, Sams #22452 Howard W. Sams & Co. A Division of Macmillan, Inc. 4300 West 62nd St. Indianapolis IN 46268 Old Colony Sound Labs used to carry the audio book in their listing. You might try giving them a call at (603) 924-6371 to see if it's still available. --RSt ------------------------------ Date: Thu, 19 May 94 18:00:34 EST From: stacy@trc.com (Robert Stacy) Subject: Jung op amp books In HiDi 22/91, carter@sst10c.lanl.gov (Michael J. Carter) asks: > 5) Books: Is Jung's 'Audio Opamp Applications' book really > out of print? My local bookshop says so. Is his 'Opamp Cookbook' a > good replacment? Second question first: No, in general the _IC Op-Amp Cookbook_ does not cover the same material as _Audio IC Op-Amp Applications_. The latter covers some of the basic stuff dealt with in the former, regarding the care and feeding of op-amps in general -- power supply bypassing, offset correction, input protection, stability requirements, etc. -- but quickly focusses on specific audio applications. The former of the two covers more historical background/evolution and general operating requirements, then segues into general purpose applications such as voltage references, signal processing, multipliers, comparators . . . good stuff to have around if you're involved in general analog design, but not strictly targetted toward the amateur audio hobbyist. If that describes you, I'd look for _Audio IC Op-Amp Applications_. Last I was aware, both books had gone into their Third Edition. Pertinent hard data follows: Jung, W. G., _IC Op-Amp Cookbook_, 3rd Ed., <, Howard W. Sams & Co., Ind. IN, 1986, ISBN 0-672-22453-4, Sams #22453. Jung, W. G., _Audio IC Op-Amp Applications_, 3rd Ed., Howard W. Sams & Co., Ind. IN, 1987, ISBN 0-672-22452-6, Sams #22452 Howard W. Sams & Co. A Division of Macmillan, Inc. 4300 West 62nd St. Indianapolis IN 46268 Old Colony Sound Labs used to carry the audio book in their listing. You might try giving them a call at (603) 924-6371 to see if it's still available. --RSt