"Tim Wescott" <tim@seemywebsite.really> wrote in message news:4sCdnYHd7pMzDXTPnZ2dnUVZ5qOdnZ2d@giganews.com...> On Wed, 29 Jan 2014 17:44:16 -0500, John Smith wrote: > >> "Lasse Langwadt Christensen" <langwadt@fonz.dk> wrote in message >> news:0e3398dc-c4ba-4202-aa79-bf100371b4c7@googlegroups.com... >>> Den onsdag den 29. januar 2014 22.27.39 UTC+1 skrev John Smith: >>>> "Lasse Langwadt Christensen" <langwadt@fonz.dk> wrote in message >>>> >>>> news:b16e26e5-c5bd-4939-8836-d18278ed8ee2@googlegroups.com... >>>> >>>> Den onsdag den 29. januar 2014 20.53.09 UTC+1 skrev John Smith: >>>> >>>> > "Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message >>>> >>>> >>>> > >>>> > news:lcbgpa$am8$1@news.albasani.net... >>>> >>>> >>>> > >>>> > > On a sunny day (Wed, 29 Jan 2014 13:02:18 -0500) it happened "John >>>> >>>> > > Smith" >>>> >>>> >>>> > >>>> > > <invalid@invalid.invalid> wrote in <lcbfjq$i5p$1@dont-email.me>: >>>> >>>> >>>> > >>>> >>>> > > >>>> >>>> > >>>> >>>> > >>>> >>>> >>>> Thanks for going to that much effort Lasse but I've got started with >>>> drawing >>>> >>>> the schematic myself in LT Spice and will compare it with yours when >>>> I'm >>>> >>>> done figuring out which function key does what. >>>> >>>> How do I change a designator? i.e. change Q3 into Q4? >>>> >>>> >>> right click on the designator >> >> Aha, thanks, I was right clicking the component. >> >> Is there no symbol for a variable resistor? Do I have to make it out of >> two resistors? > > Or one, yes. Your VR2 is really just one resistor that changes when you > turn a knob. Usually in LTSpice (or any SPICE) such user input isn't > modeled -- it's up to you to enter the resistance that would be there.Ok thanks Tim, I figured that the answer would probably be something like that but it would still be nice to have a symbol for a variable resistor which takes two fixed resistance values for the parts above and below the slider. Old Guy> > -- > > Tim Wescott > Wescott Design Services > http://www.wescottdesign.com >
Solderless audio amplifier
Started by ●January 29, 2014
Reply by ●January 29, 20142014-01-29
Reply by ●January 29, 20142014-01-29
Den torsdag den 30. januar 2014 00.37.18 UTC+1 skrev Tim Wescott:> On Wed, 29 Jan 2014 17:44:16 -0500, John Smith wrote: > > > > > "Lasse Langwadt Christensen" <langwadt@fonz.dk> wrote in message > > > news:0e3398dc-c4ba-4202-aa79-bf100371b4c7@googlegroups.com... > > >> Den onsdag den 29. januar 2014 22.27.39 UTC+1 skrev John Smith: > > >>> "Lasse Langwadt Christensen" <langwadt@fonz.dk> wrote in message > > >>> > > >>> news:b16e26e5-c5bd-4939-8836-d18278ed8ee2@googlegroups.com... > > >>> > > >>> Den onsdag den 29. januar 2014 20.53.09 UTC+1 skrev John Smith: > > >>> > > >>> > "Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message > > >>> > > >>> > > >>> > > > >>> > news:lcbgpa$am8$1@news.albasani.net... > > >>> > > >>> > > >>> > > > >>> > > On a sunny day (Wed, 29 Jan 2014 13:02:18 -0500) it happened "John > > >>> > > >>> > > Smith" > > >>> > > >>> > > >>> > > > >>> > > <invalid@invalid.invalid> wrote in <lcbfjq$i5p$1@dont-email.me>: > > >>> > > >>> > > >>> > > > >>> > > >>> > > > > >>> > > >>> > > > >>> > > >>> > > > >>> > > >>> > > >>> Thanks for going to that much effort Lasse but I've got started with > > >>> drawing > > >>> > > >>> the schematic myself in LT Spice and will compare it with yours when > > >>> I'm > > >>> > > >>> done figuring out which function key does what. > > >>> > > >>> How do I change a designator? i.e. change Q3 into Q4? > > >>> > > >>> > > >> right click on the designator > > > > > > Aha, thanks, I was right clicking the component. > > > > > > Is there no symbol for a variable resistor? Do I have to make it out of > > > two resistors? > > > > Or one, yes. Your VR2 is really just one resistor that changes when you > > turn a knob. Usually in LTSpice (or any SPICE) such user input isn't > > modeled -- it's up to you to enter the resistance that would be there. >but you can do something like this: Version 4 SHEET 1 880 680 WIRE 272 80 96 80 WIRE 96 128 96 80 WIRE 528 160 272 160 FLAG 96 208 0 FLAG 272 240 0 FLAG 528 160 out IOPIN 528 160 Out SYMBOL voltage 96 112 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 1 SYMBOL res 256 64 R0 SYMATTR InstName R1 SYMATTR Value {10k*(1-a)} SYMBOL res 256 144 R0 SYMATTR InstName R2 SYMATTR Value {10k*a} TEXT 272 288 Left 2 !.step param a = 0.001 0.999 .1 TEXT 62 308 Left 2 !.tran 1
Reply by ●January 29, 20142014-01-29
Den torsdag den 30. januar 2014 00.43.06 UTC+1 skrev John Smith:> "John Smith" <invalid@invalid.invalid> wrote in message > > news:lcbfjq$i5p$1@dont-email.me... > > > The radio kit hasn't arrived yet (Thread of 18th Jan. Probably due to > > > weather conditions here in Ontario) so I thought I'd try my hand at making > > > my own audio amplifier kit. > > > > Many thanks to Lasse Langwadt Christensen and Tim Wescott for posting LT > > spice files. > > > > I haven't looked at them yet because I wanted to get familiar with drawing a > > schematic in LT spice. I've used schematic capture systems before. I was > > pleasantly surprised with the LT spice schematic capture interface even if > > it does remind me of Windows 3.0 > > > > Here is my first ever LT spice schematic. > > www.pdelectronics.ca/sed/amp2014jan28/amp2014jan28_1.zip > > > > Now I will have a look at Lasse and Tim's files and see if I can run a > > simulation. >just click the little running man in the tool bar and put in a stop time -Lasse
Reply by ●January 29, 20142014-01-29
On Wed, 29 Jan 2014 18:43:06 -0500, John Smith wrote:> "John Smith" <invalid@invalid.invalid> wrote in message > news:lcbfjq$i5p$1@dont-email.me... >> The radio kit hasn't arrived yet (Thread of 18th Jan. Probably due to >> weather conditions here in Ontario) so I thought I'd try my hand at >> making my own audio amplifier kit. > > Many thanks to Lasse Langwadt Christensen and Tim Wescott for posting LT > spice files. > > I haven't looked at them yet because I wanted to get familiar with > drawing a schematic in LT spice. I've used schematic capture systems > before. I was pleasantly surprised with the LT spice schematic capture > interface even if it does remind me of Windows 3.0 > > Here is my first ever LT spice schematic. > www.pdelectronics.ca/sed/amp2014jan28/amp2014jan28_1.zip > > Now I will have a look at Lasse and Tim's files and see if I can run a > simulation. > > Old GuyPut a voltage source at the input, set up as either AC (for AC analysis) or with a sine wave (right-click then push the "advanced" button). If you have crossover distortion the AC analysis will be messed up -- you need to have some standing current in the output transistors for AC analysis to be sensible. Rename one or the other of your 'C3' to 'C7', or 'C42', or whatever. Put a resistor in for the speaker, lest your gain be infinite. Then hit the little running man like Lasse said. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Reply by ●January 29, 20142014-01-29
"Tim Wescott" <tim@seemywebsite.really> wrote in message news:4sCdnYDd7pMeOXTPnZ2dnUVZ5qOdnZ2d@giganews.com...> On Wed, 29 Jan 2014 18:43:06 -0500, John Smith wrote: > >> "John Smith" <invalid@invalid.invalid> wrote in message >> news:lcbfjq$i5p$1@dont-email.me... >>> The radio kit hasn't arrived yet (Thread of 18th Jan. Probably due to >>> weather conditions here in Ontario) so I thought I'd try my hand at >>> making my own audio amplifier kit. >> >> Many thanks to Lasse Langwadt Christensen and Tim Wescott for posting LT >> spice files. >> >> I haven't looked at them yet because I wanted to get familiar with >> drawing a schematic in LT spice. I've used schematic capture systems >> before. I was pleasantly surprised with the LT spice schematic capture >> interface even if it does remind me of Windows 3.0 >> >> Here is my first ever LT spice schematic. >> www.pdelectronics.ca/sed/amp2014jan28/amp2014jan28_1.zip >> >> Now I will have a look at Lasse and Tim's files and see if I can run a >> simulation. >> >> Old Guy > > Put a voltage source at the input, set up as either AC (for AC analysis) > or with a sine wave (right-click then push the "advanced" button). If > you have crossover distortion the AC analysis will be messed up -- you > need to have some standing current in the output transistors for AC > analysis to be sensible. > > Rename one or the other of your 'C3' to 'C7', or 'C42', or whatever. > > Put a resistor in for the speaker, lest your gain be infinite. > > Then hit the little running man like Lasse said.Thanks Tim www.pdelectronics.ca/sed/amp2014jan28/amp2014jan28_2.zip I set the DC operating point for an idle current of 50mA by setting R13 to 22 ohms. It took me a while to figure out how to do an AC plot but it looks like the value of C6 is a bit low for an audio amplifier. Old Guy> > -- > > Tim Wescott > Wescott Design Services > http://www.wescottdesign.com >
Reply by ●January 30, 20142014-01-30
In article <lcbfjq$i5p$1@dont-email.me>, "John Smith" <invalid@invalid.invalid> wrote:> The radio kit hasn't arrived yet (Thread of 18th Jan. Probably due to > weather conditions here in Ontario) so I thought I'd try my hand at making > my own audio amplifier kit. > > The requirements were as follows: > 1. Must use components I already have. I couldn't find any 1N4148 but did > find packets of 1N4001 so that's what I used. Also I could only find one > resistor under 1 ohm so another is made from two in parallel. > 2. Must be simple enough to fit on one piece of breadboard but not be a > trivial design. > 3. Must deliver enough power to make an 8 ohm speaker cone move visibly. > 4. Must run from a single 9V battery. > 5. Must be quick to design with minimal calculation. > 6. Any soldering must be done in advance of taking it into a school and > getting a little guy to build it. > 7. Doesn't need high voltage gain as it will be driven from an ipod so I > designed for a gain of about 10. > 8. Low distortion is not essential as long as there's no obvious issue below > clipping level. > > With those requirements in mind I got a piece of paper out and drew this: > www.pdelectronics.ca/sed/amp2014jan28/schematic.jpg > Then I did the layout: > www.pdelectronics.ca/sed/amp2014jan28/layout.jpg > Then I built and tested it: > www.pdelectronics.ca/sed/amp2014jan28/built.jpg > Actually there was much overlap between those three things. > > I set VR2 to zero resistance and measured an idle current of 60mA, so I > didn't adjust VR2. > I then connected a signal source from a computer, adjusted VR1 and the > requirements seemed to have been met. > > I'm aware that there are people here who can comment on my amplifier design > skills, or lack of them, and maybe some component values can be tweaked for > better performance. > > Are there any free tools available which can run a simulation of this > circuit? > What is the lower and upper 3dB bandwidth? > Is my wild guess at a value for C6 reasonable? > > Old GuyYour power filter of R8 and C3 is definitely not right. The voltage difference between the two circuit halves is going to modulate TR4 via R3. It will thump during power-on and probably motor-boat when the battery is low. The only thing that needs filtering is the voltage divider on your input. Everything else is running in constant current mode and is fine with unregulated voltage. I don't know what current is flowing through TR3, but it should be adjusted so that C6 charges and discharges symmetrically. Sometimes you can put a long wire on the input and adjust the current until you stop hearing AM radio stations :) Unless it's there to be educational, replace whole constant current regulator around TR3 with a simple resistor. You only have +/- 0.4V of input swing to reach full modulation. The current through a resistor should be close enough.
Reply by ●January 30, 20142014-01-30
"Kevin McMurtrie" <mcmurtrie@pixelmemory.us> wrote in message news:mcmurtrie-934B9C.22562129012014@c-61-68-245-199.per.connect.net.au...> In article <lcbfjq$i5p$1@dont-email.me>, > "John Smith" <invalid@invalid.invalid> wrote: > >> The radio kit hasn't arrived yet (Thread of 18th Jan. Probably due to >> weather conditions here in Ontario) so I thought I'd try my hand at >> making >> my own audio amplifier kit. >> >> The requirements were as follows: >> 1. Must use components I already have. I couldn't find any 1N4148 but did >> find packets of 1N4001 so that's what I used. Also I could only find one >> resistor under 1 ohm so another is made from two in parallel. >> 2. Must be simple enough to fit on one piece of breadboard but not be a >> trivial design. >> 3. Must deliver enough power to make an 8 ohm speaker cone move visibly. >> 4. Must run from a single 9V battery. >> 5. Must be quick to design with minimal calculation. >> 6. Any soldering must be done in advance of taking it into a school and >> getting a little guy to build it. >> 7. Doesn't need high voltage gain as it will be driven from an ipod so I >> designed for a gain of about 10. >> 8. Low distortion is not essential as long as there's no obvious issue >> below >> clipping level. >> >> With those requirements in mind I got a piece of paper out and drew this: >> www.pdelectronics.ca/sed/amp2014jan28/schematic.jpg >> Then I did the layout: >> www.pdelectronics.ca/sed/amp2014jan28/layout.jpg >> Then I built and tested it: >> www.pdelectronics.ca/sed/amp2014jan28/built.jpg >> Actually there was much overlap between those three things. >> >> I set VR2 to zero resistance and measured an idle current of 60mA, so I >> didn't adjust VR2. >> I then connected a signal source from a computer, adjusted VR1 and the >> requirements seemed to have been met. >> >> I'm aware that there are people here who can comment on my amplifier >> design >> skills, or lack of them, and maybe some component values can be tweaked >> for >> better performance. >> >> Are there any free tools available which can run a simulation of this >> circuit? >> What is the lower and upper 3dB bandwidth? >> Is my wild guess at a value for C6 reasonable? >> >> Old Guy > > Your power filter of R8 and C3 is definitely not right. The voltage > difference between the two circuit halves is going to modulate TR4 via > R3. It will thump during power-on and probably motor-boat when the > battery is low. The only thing that needs filtering is the voltage > divider on your input. Everything else is running in constant current > mode and is fine with unregulated voltage. > > I don't know what current is flowing through TR3, but it should be > adjusted so that C6 charges and discharges symmetrically. Sometimes you > can put a long wire on the input and adjust the current until you stop > hearing AM radio stations :) > > Unless it's there to be educational, replace whole constant current > regulator around TR3 with a simple resistor. You only have +/- 0.4V of > input swing to reach full modulation. The current through a resistor > should be close enough.Many thanks for your comments. I moved the power filter to the input voltage divider. 330uF is probably overkill. I've also given the battery a 2 ohm internal resistance. TR3 was mostly intended to be educational but for the present circuit I have replaced TR3 with a 4.7k resistor. The LTspice model says that the current in the resistor is 0.82 mA. Can I use the LTspice model to find out whether C6 is charging and discharging symetrically? The current circuit is here: http://www.pdelectronics.ca/sed/amp2014jan28/amp2014jan28_4.zip Quick view here: http://www.pdelectronics.ca/sed/amp2014jan28/amp2014jan28_4.jpg I've also added an equivalent circuit for a loudspeaker which came from here: http://sound.westhost.com/tsp.htm I've no idea how close that is to my real loudspeaker but it may be closer than an 8 ohm resistor. A bode plot of V(input)/V(output) from 5Hz to 3MHz shows the expected 20dB voltage gain. The gain and phase are fairly flat over the audio range but the unity gain frequency appears to be about 2.3 MHz. Is there any advantage in reducing that for an audio amplifier? Apart from reducing the potential for amplification of AM radio signals? Does annyone know whether any of the models on this page can ne used in LTSpice? http://www.onsemi.com/PowerSolutions/supportDoc.do?type=models&rpn=TIP31A Old Guy
Reply by ●January 30, 20142014-01-30
"Lasse Langwadt Christensen" <langwadt@fonz.dk> wrote in message news:b16e26e5-c5bd-4939-8836-d18278ed8ee2@googlegroups.com... Den onsdag den 29. januar 2014 20.53.09 UTC+1 skrev John Smith:> "Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message > > news:lcbgpa$am8$1@news.albasani.net... > > > On a sunny day (Wed, 29 Jan 2014 13:02:18 -0500) it happened "John > > Smith" > > > <invalid@invalid.invalid> wrote in <lcbfjq$i5p$1@dont-email.me>: > > > >Thanks Lasse. I ran your ciruit and found a nice sine wave at the output. Now I want to put some pulses in to see how it handles fast rise and fall times. Old Guy
Reply by ●January 30, 20142014-01-30
"Tim Wescott" <tim@seemywebsite.really> wrote in message news:4sCdnYbd7pMY63TPnZ2dnUVZ5qOdnZ2d@giganews.com...> On Wed, 29 Jan 2014 14:12:04 -0600, Tim Wescott wrote: > >> On Wed, 29 Jan 2014 14:58:07 -0500, John Smith wrote: >> >>> "Tim Wescott" <tim@seemywebsite.really> wrote in message >>> news:4sCdnYrd7pPr2nTPnZ2dnUVZ5qOdnZ2d@giganews.com... >>>> On Wed, 29 Jan 2014 13:02:18 -0500, John Smith wrote: >>>>Thanks Tim. I can see the sinewave at Vout. Old Guy> > Tim Wescott > Wescott Design Services > http://www.wescottdesign.com >
Reply by ●January 30, 20142014-01-30
I haven't put my two cents in yet but here it is : First of all, C4 should be nowhere near 4700 uF. You are not driving a 12" = woofer with it. Look at those good old stereo console pieces of junk, they = got by with as low as like 220 uF. Since it isn't in the feedback loop anyw= ay, forget about phase shift, it means nothing.=20 Next, you are not submitting this thing for evaluation by the IHF (are the = even still around ?) or Hifi magazine (same question) so you can totally el= iminate Q2 and just send the feedback (DC and AC) straight to the emitter o= f Q1. I would suggeast lower values for the voltage divider to yield a lowe= r impedance, off the top of my head use 4.7K for R7 and 470 for R5. Elimina= te C2 of course or the thing won't work.=20 That will set your feedback at about 1/10th of the center voltage at R10 an= d 11. With your voltage divider there, make the voltage at the base of Q1 a= bout that, just add schoch for the drain of Q1. It really doesn't have to b= e all that accurate. Accuracy comes later. Increase R1 and C3 to charge slowly and reduce the turnon transient. Whate= ver the voltage divider feeding the base of Q1, figure the bottom resistor = against the input coupling cap to give the desired lower frequency limit, t= here is no reason to be concerned about anything below 100 Hz unless your s= peakers are going to reproduce it. If they are, that can be done later. (yo= u might want heftier transistors and a realer battery at that point) <tech = jargon there... Now that the thing is designed like a bean counter would, then you and the = kid can go through the refinements. Draw out the scematic and show him the = diff pair, different values for some caps, in fact make it so shitty at fir= st that some minor improvements can make an audible difference. Maybe even = jump out R13 in the beginning to demonstrate crossover distortion.=20 That's what I would do. You know even what was called hifi a long time ago = didn't use differential pairs at the input usually. It worked well enough. = But realize the other thing I am saying is maybe make it so there is room f= or improvement. (of course I was known as the mad modifier back in the day,= nothing was stock) Slide the pennies under the door if I am asleep.
