On Monday, May 15, 2017 at 8:15:36 PM UTC-4, Phil Allison wrote:> George Herold wrote: > > ------------------------- > > On Monday, May 15, 2017 at 10:49:56 AM UTC-4, Dave M wrote: > > > Has anyone used any of the consumer-grade audio power amps such as the > > > LM1825, TDA2030, or TDS7297 as a basic DC power opamp? > > > Any reason they shouldn't be used as power supply regulators, TEC > > > controllers, etc? > > > > > > Dave M > > > > Only the TDA2030 comes up in a search (as obsolete) check your part numbers. > > > > ** Dave's list is full of typos. > > It should read: LM1875, TDA2030 and TDA7294 > > > .... PhilThanks Phil, The schematics for the LM1875 looks like the LM675. Which is an oldie, but I still use it. (Again as you say it wants to run at a gain of 10 and above.) George H.> > > I'm guessing the DC performance is not as good as it could be. > > Lots of DC offset perhaps. > > > > George H.
Using consumer-grade power amp as Power opamp
Started by ●May 15, 2017
Reply by ●May 16, 20172017-05-16
Reply by ●May 16, 20172017-05-16
krw@notreal.com wrote...> > Winfield Hill wrote: >> Dave M wrote... >>> Has anyone used any of the consumer-grade audio power amps ... >> >> Sorry, but these days "consumer-grade audio power amps" >> are all class-D. In general most of these can perform as >> well as a linear amps. I have my favorites. Especially >> high-performance ICs that are well represented in complete >> PCBs from China, available at rock-bottom prices on eBay. > > Define "consumer grade". Class-AB amplifiers are the > norm in automotive applications.The high-power amps I mentioned are clearly consumer grade; they're not studio amps, SFAIK, although the specs may be good enough. As for automotive systems, I imagine they've pretty much all moved to class D. Using parts like TI's tpa3116 family of dual 15 to 50-watt BTL amps. These are "filter free", have "AM Avoidance" with PLL-based multiple switching frequencies (to 1.2MHz), and with SpeakerGuard. 50W part, $2 qty 10k. http://www.ti.com/product/tpa3116d2 Four channel and up are available, like the TAS5414C. Class D provides OK sound quality, is cheap and doesn't get hot - these issues are important to designers, no? -- Thanks, - Win
Reply by ●May 16, 20172017-05-16
Chris Jones wrote: ------------------> > >> Has anyone used any of the consumer-grade audio power amps such as the > >> LM1825, TDA2030, or TDS7297 as a basic DC power opamp? > >> > > > > > > ** Generally they are not unity gain stable. > > > > Audio power amps have a voltage gain of 10 to 50 times in most cases. > > > > Yes, that is a consideration. The "noise gain" needs to be high but not > necessarily the gain from the input of the circuit as a whole. You can > of course lower the gain back to unity by attenuating the input, or a > number of other tricks. >** A low impedance between the + and - inputs does the trick. Say 100hms plus a 22nF cap in series. Leaves the DC condiitons in place. .... Phil
Reply by ●May 16, 20172017-05-16
On Tuesday, 16 May 2017 12:54:40 UTC+1, Chris Jones wrote:> On 16/05/2017 09:59, Phil Allison wrote: > > Dave M wrote: > > > > ---------------- > >> Has anyone used any of the consumer-grade audio power amps such as the > >> LM1825, TDA2030, or TDS7297 as a basic DC power opamp? > >> > > > > > > ** Generally they are not unity gain stable. > > > > Audio power amps have a voltage gain of 10 to 50 times in most cases. > > > > Yes, that is a consideration. The "noise gain" needs to be high but not > necessarily the gain from the input of the circuit as a whole. You can > of course lower the gain back to unity by attenuating the input, or a > number of other tricks. > > The TDA2030 and similar ones also need a series R-C from the output to > ground, I think it is called a "Zobel network". Usually the capacitor is > 100nF or so, and the resistor 1 Ohm or so. Without this it can oscillate. > > The DC offset voltage is also pretty terrible and unstable with temperature. > > The quiescent supply current of the TDA2030 is also quite high and could > be a problem in some applications. > > I have used TDA2030 chips in electroplating power supplies, configured > as Howland current sources. I also used similar ones in voice coil > drivers using an old hard driver voice coil as an actuator, and for > driving power LEDs with a controlled current waveform. The reason why I > used these audio amplifier chips is because they were very cheap and > quite powerful. > > The TDA2030 is discontinued now. It was one of my favourite parts, not > because it was easy to use but I guess because I got a lot of use out of > them (e.g. as a kid I connected one to my crystal radio for driving a > speaker) and they were very cheap so they seemed like a good deal.The Zobel is only needed when driving an inductive load. NT
Reply by ●May 16, 20172017-05-16
On a sunny day (16 May 2017 05:53:25 -0700) it happened Winfield Hill <hill@rowland.harvard.edu> wrote in <ofeso501uek@drn.newsguy.com>:>krw@notreal.com wrote... >> >> Winfield Hill wrote: >>> Dave M wrote... >>>> Has anyone used any of the consumer-grade audio power amps ... >>> >>> Sorry, but these days "consumer-grade audio power amps" >>> are all class-D. In general most of these can perform as >>> well as a linear amps. I have my favorites. Especially >>> high-performance ICs that are well represented in complete >>> PCBs from China, available at rock-bottom prices on eBay. >> >> Define "consumer grade". Class-AB amplifiers are the >> norm in automotive applications. > > The high-power amps I mentioned are clearly consumer grade; > they're not studio amps, SFAIK, although the specs may be > good enough. As for automotive systems, I imagine they've > pretty much all moved to class D. Using parts like TI's > tpa3116 family of dual 15 to 50-watt BTL amps. These are > "filter free", have "AM Avoidance" with PLL-based multiple > switching frequencies (to 1.2MHz), and with SpeakerGuard. > 50W part, $2 qty 10k. http://www.ti.com/product/tpa3116d2 > Four channel and up are available, like the TAS5414C. > > Class D provides OK sound quality, is cheap and doesn't > get hot - these issues are important to designers, no?Looks like an interesting chip, but all those switch mode wall warts already kill the shortwave band here. Seems a bad idea on say a boat that also needs SSB short wave say for sendmail or whatever. Are we just sacrificing parts of a useful spectrum just for power sake? Actually I had some sort of switching power amp from ebay, not that chip, it died in a very short time, don't even remember why, used the inductors for something else. It all depends...
Reply by ●May 16, 20172017-05-16
On Mon, 15 May 2017 11:18:36 -0700, John Larkin wrote:> On Mon, 15 May 2017 12:48:08 -0500, Tim Wescott > <seemywebsite@myfooter.really> wrote: > >>On Mon, 15 May 2017 09:49:45 -0500, Dave M wrote: >> >>> Has anyone used any of the consumer-grade audio power amps such as the >>> LM1825, TDA2030, or TDS7297 as a basic DC power opamp? >>> Any reason they shouldn't be used as power supply regulators, TEC >>> controllers, etc? >>> >>> Dave M >> >>If the super-est best-est performance isn't an issue, a plain old op-amp >>driving an emitter follower stage often works well, particularly in a 1- >>quadrant amplifier such as a regulator or TEC controller. > > Or an opamp driving the adjust pin of a 3T regulator. That has some nice > points.Current limit and thermal shutdown not least among them. What else? -- www.wescottdesign.com
Reply by ●May 16, 20172017-05-16
On 16 May 2017 05:53:25 -0700, Winfield Hill <hill@rowland.harvard.edu> wrote:>krw@notreal.com wrote... >> >> Winfield Hill wrote: >>> Dave M wrote... >>>> Has anyone used any of the consumer-grade audio power amps ... >>> >>> Sorry, but these days "consumer-grade audio power amps" >>> are all class-D. In general most of these can perform as >>> well as a linear amps. I have my favorites. Especially >>> high-performance ICs that are well represented in complete >>> PCBs from China, available at rock-bottom prices on eBay. >> >> Define "consumer grade". Class-AB amplifiers are the >> norm in automotive applications. > > The high-power amps I mentioned are clearly consumer grade; > they're not studio amps, SFAIK, although the specs may be > good enough. As for automotive systems, I imagine they've > pretty much all moved to class D.Nope. The classics are still class-AB from ST, NXP, and Toshiba. There are some class-Ds used but it's not the norm. They're too expensive and not needed.>Using parts like TI's > tpa3116 family of dual 15 to 50-watt BTL amps. These are > "filter free", have "AM Avoidance" with PLL-based multiple > switching frequencies (to 1.2MHz), and with SpeakerGuard. > 50W part, $2 qty 10k. http://www.ti.com/product/tpa3116d2 > Four channel and up are available, like the TAS5414C.Power is limited by speaker impedance and Vcc. In a car, for practical purposes that's 2-ohms and 14V, which gets close to 50W. It doesn't matter what the class.> Class D provides OK sound quality, is cheap and doesn't > get hot - these issues are important to designers, no?Cheap matters. Class-D is not. Heat doesn't matter much. You're not really pumping 600W into a car cabin.
Reply by ●May 16, 20172017-05-16
Don Y wrote:> On 5/15/2017 7:49 AM, Dave M wrote: >> Has anyone used any of the consumer-grade audio power amps such as >> the LM1825, TDA2030, or TDS7297 as a basic DC power opamp? >> Any reason they shouldn't be used as power supply regulators, TEC >> controllers, etc? > > Consider how they handle (highly) reactive loads?The reason for my interest in these parts is because I came across a half-full bag of them while helping a friend clean out his recently deceased dad's garage, and while I'm not really interested in building audio stuff anymore, I wondered if they could be useful in other applications. Since their main purpose was to drive speakers, which are pretty reactive over the audio range, Zobel networks are commonly used with them. So I'm sure they don't like to see a lot of reactance. Operating at DC, if they're not asked to handle a lot of AC power, then compensation might not be too difficult. That should be an interesting experiment. I might give a shot at using one as a DC power supply regulator, or maybe to drive a power transformer or audio output transformer to make an AC voltage reference. I've wanted one of those for a long time. Hmmm... I wonder how they would like being run as BTL amps? Thanks for all the suggestions and advice!! Dave M
Reply by ●May 16, 20172017-05-16
George Herold wrote:> On Monday, May 15, 2017 at 8:15:36 PM UTC-4, Phil Allison wrote: >> George Herold wrote: >> >> ------------------------- >>> On Monday, May 15, 2017 at 10:49:56 AM UTC-4, Dave M wrote: >>>> Has anyone used any of the consumer-grade audio power amps such as >>>> the LM1825, TDA2030, or TDS7297 as a basic DC power opamp? >>>> Any reason they shouldn't be used as power supply regulators, TEC >>>> controllers, etc? >>>> >>>> Dave M >>> >>> Only the TDA2030 comes up in a search (as obsolete) check your part >>> numbers. >>> >> >> ** Dave's list is full of typos. >> >> It should read: LM1875, TDA2030 and TDA7294 >> >> >> .... Phil > Thanks Phil, The schematics for the LM1875 looks like the > LM675. Which is an oldie, but I still use it. > (Again as you say it wants to run at a gain of 10 and above.) > > George H. >> >>> I'm guessing the DC performance is not as good as it could be. >>> Lots of DC offset perhaps. >>> >>> George H.Yep, sorry for the typos... I had a visit to my opthalmologist that day and looking at anything that emitted light was like staring into the sun, so please forgive. Right about the gain... that caution is mentioned on the first page of the LM1875. DC offset coltage & current are only specified at 25C, and isn't great, for sure. Dave M
Reply by ●May 16, 20172017-05-16
On Tue, 16 May 2017 10:08:44 -0500, Tim Wescott <tim@seemywebsite.really> wrote:>On Mon, 15 May 2017 11:18:36 -0700, John Larkin wrote: > >> On Mon, 15 May 2017 12:48:08 -0500, Tim Wescott >> <seemywebsite@myfooter.really> wrote: >> >>>On Mon, 15 May 2017 09:49:45 -0500, Dave M wrote: >>> >>>> Has anyone used any of the consumer-grade audio power amps such as the >>>> LM1825, TDA2030, or TDS7297 as a basic DC power opamp? >>>> Any reason they shouldn't be used as power supply regulators, TEC >>>> controllers, etc? >>>> >>>> Dave M >>> >>>If the super-est best-est performance isn't an issue, a plain old op-amp >>>driving an emitter follower stage often works well, particularly in a 1- >>>quadrant amplifier such as a regulator or TEC controller. >> >> Or an opamp driving the adjust pin of a 3T regulator. That has some nice >> points. > >Current limit and thermal shutdown not least among them. What else?That's mostly it. C-load stability is good, too. And cost. I tried every imaginable way to destroy an LM1117 by abusing the Vadj pin, and it survived. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
