Phil Allison wrote:> > "Michael A. Terrell" > > ** Go eat shitNo one wants your lunch.> - you rabid pile of ASD fucked Septic garbage.You're still at the six year old level of half assed insults, I see. You're the one with a reputation for gay sex. -- You can't have a sense of humor, if you have no sense.
Audio Amp Crossover Distortion?
Started by ●January 12, 2012
Reply by ●January 12, 20122012-01-12
Reply by ●January 12, 20122012-01-12
On Wed, 11 Jan 2012 20:14:05 -0800, Bill Bowden wrote:> I see excessive crossover distortion with this audio amp not shown with > LTspice. It simulates ok, but the wired circuit produces about a 50uS > dead time step as the signal crosses the mid point. I tried increasing > the bias with no help. Both inputs to the op-amp look good with no > distortion. Any idea what is going on? >If you look at the opamp output in the simulation you'll see that it has some near-vertical segments at crossover -- this means you're working the amp pretty hard, and it's an opportunity for Bad Things to happen. Make sure that the slew rate, DC gain, and gain-bandwidth product of your "universal" op-amp matches the data sheet for what you're using. You may want to check the real op-amp's output impedance, if it's even listed. If not, try tossing a 600 ohm resistor in series with your op-amp's output, see what that does. And take a look at your real op-amp output in your real circuit; see what it's doing. Beyond that -- I dunno. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
Reply by ●January 12, 20122012-01-12
"Fred Abse" Phil Allison wrote:> >> ** You need to post a schematic - dickhead. >> >> Totally SMARTARSE of you to post only a Spice list on SEB. > > What he posted *is* a schematic. >** Fuckwit, pedantic twaddle .
Reply by ●January 12, 20122012-01-12
"George Herold" I was going to say it's a push-pull.... but it's flipped about. Here's a pic http://imageshack.us/photo/my-images/708/crossover.jpg/ ** Than schem looks horribly familiar, maybe from the same idiot OP before. It's the sort of thing you find repeated on many hobby sites that cannot possibly work. As drawn, it only works if the output transistors are biased for class A operation PLUS it cannot possibly drive an 8 ohm load. 50 ohms might be about the limit. The twin rail splitters are an abortion. Bias and load driving ability depend on the + DC rail voltage, which is not shown. ... Phil
Reply by ●January 12, 20122012-01-12
On Thu, 12 Jan 2012 08:45:44 -0800 (PST), George Herold <gherold@teachspin.com> wrote:>On Jan 11, 11:55�pm, "Phil Allison" <phi...@tpg.com.au> wrote: >> "Bill Bowden" >> >> I see excessive crossover distortion with this audio amp not shown >> with LTspice. It simulates ok, but the wired circuit produces about a >> 50uS dead time step as the signal crosses the mid point. I tried >> increasing the bias with no help. Both inputs to the op-amp look good >> with no distortion. Any idea what is going on? >> >> ** You need to post a schematic �- �dickhead. >> >> Totally �SMARTARSE of you to post only a Spice list on SEB. >> >> ... �Phil > >I was going to say it's a push-pull.... but it's flipped about. > >Here's a pic >http://imageshack.us/photo/my-images/708/crossover.jpg/ > >Does this output have a name? > >George H.Unstable ?:-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●January 12, 20122012-01-12
On Jan 12, 11:18=A0am, Tim Wescott <t...@seemywebsite.com> wrote:> On Wed, 11 Jan 2012 20:14:05 -0800, Bill Bowden wrote:> > I see excessive crossover distortion with this audio amp not shown with > > LTspice. It simulates ok, but the wired circuit produces about a 50uS > > dead time step as the signal crosses the mid point. I tried increasing > > the bias with no help. Both inputs to the op-amp look good with no > > distortion. Any idea what is going on?> > If you look at the opamp output in the simulation you'll see that it has > some near-vertical segments at crossover -- this means you're working the > amp pretty hard, and it's an opportunity for Bad Things to happen. > > Make sure that the slew rate, DC gain, and gain-bandwidth product of your > "universal" op-amp matches the data sheet for what you're using. =A0You may > want to check the real op-amp's output impedance, if it's even listed. > If not, try tossing a 600 ohm resistor in series with your op-amp's > output, see what that does. > > And take a look at your real op-amp output in your real circuit; see what > it's doing. > > Beyond that -- I dunno. > Yes, slew rate may be the problem. I was using a LM358 which may not be the best. I thought anything would work at audio freqs. The book shows 10uS to move 3 volts into 2K with a 15 volt supply. The output impedance also appears high since adding a 560 resistor in series with the output doesn't change things much. The distortion is present at the op-amp output and looks about the same as the main output. The thing I don't understand is how the feedback signal from the distorted output looks so good at the (+) input to the op-amp. It's a 10K resistor with a distorted waveform on one side and a clean signal on the other. -Bill
Reply by ●January 12, 20122012-01-12
On Fri, 13 Jan 2012 08:51:48 +1100, Phil Allison wrote:> "Fred Abse" > Phil Allison wrote: >> >>> ** You need to post a schematic - dickhead. >>> >>> Totally SMARTARSE of you to post only a Spice list on SEB. >> >> What he posted *is* a schematic. >> >> > ** Fuckwit, pedantic twaddle .Time to pretend you live in the same universe as the rest of us Phil, or at least take your meds. LTSpice schematics are text files, and that's what that was. I cut it and pasted it into a text file and it worked _just fine_ in LTSpice. Because it _is_ a schematic. I'll leave the conclusions about what that says about _your_ intelligence, wit, and state of mind to the general audience. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
Reply by ●January 12, 20122012-01-12
"Tim Wescott = FUCKING IDIOT "> >> "Fred Abse" >> Phil Allison wrote: >>> >>>> ** You need to post a schematic - dickhead. >>>> >>>> Totally SMARTARSE of you to post only a Spice list on SEB. >>> >>> What he posted *is* a schematic. >>> >>> >> ** Fuckwit, pedantic twaddle . > > Time to pretend you live in the same universe as the rest of us Phil,** I do NOT live in the same narcissistic hell you do - pisshead.> LTSpice schematics are text files,** FFS - I want to see the **ORIGINAL** schematic. That means a link to the site where the fuckwit OP got it.> Because it _is_ a schematic.** Absolute FUCKWIT INSANITY .... Phil
Reply by ●January 12, 20122012-01-12
"Bill Bowden = RETARD " Yes, slew rate may be the problem. I was using a LM358 ** ROTFLMAO. Will this tenth wit moron never learn ANYTHING !!
Reply by ●January 12, 20122012-01-12
On Jan 12, 6:09=A0pm, "Phil Allison" <phi...@tpg.com.au> wrote:> "George Herold" > > I was going to say it's a push-pull.... but it's flipped about. > > Here's a pichttp://imageshack.us/photo/my-images/708/crossover.jpg/ > > ** Than schem looks horribly familiar, maybe from the same idiot OP befor=e.> > It's the sort of thing you find repeated on many hobby sites that cannot > possibly work. > > As drawn, it only works if the output transistors are biased for class A > operation =A0PLUS it cannot possibly drive an 8 ohm load. 50 ohms might b=e> about the limit. > > The twin rail splitters are an abortion. > > Bias and load driving ability depend on the + DC rail voltage, which is n=ot> shown. > > ... =A0PhilYeah why not push-pull? Or if you want to do class A, use one pass element. George H.
