Good amp.
One more test - put four speakers in parallel on each channel. Crank up volume till lights start dimming to beat. If sound don't turn to garbage, and amp don't go poof... then good amp.
I have built a simple LED Oscillation Detector that has detected nasty HF oscillation before I connect my speakers....
http://www.diyaudio.com/forums/solid-state/112453-nap-140-clone-amp-kit-ebay-27.html#post1625589
For the few parts it has, I was impressed - slapped mine together in about 15 minutes...thanks to unclejed613 on it conception
http://www.diyaudio.com/forums/solid-state/112453-nap-140-clone-amp-kit-ebay-27.html#post1625589
For the few parts it has, I was impressed - slapped mine together in about 15 minutes...thanks to unclejed613 on it conception
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For testing transparency:
Amplifier Test Method
The above is ofcourse irrelevant if U want to design a " sound ".
Amplifier Test Method
The above is ofcourse irrelevant if U want to design a " sound ".
Having designed and built many amps since the sixties, it took me a long time to realise that an amp that measured good ( using basic lab equipment within the range available to the average DIYer), did not necessarily sound good, and more extensive testing was required. Bad measurements did mean bad sound, but striving for very low distortion, extended frequency response etc did not necessarily be worth while.
Graham Maynard has some interesting theories. But certainly the interaction of the amp with speakers is an interesting area. Good and bad amps can be determined by listening, even if the reason cannot be isolated. And its not just a result of personal preference, although this may result in one good amp/speaker being chosen over another.
Graham Maynard has some interesting theories. But certainly the interaction of the amp with speakers is an interesting area. Good and bad amps can be determined by listening, even if the reason cannot be isolated. And its not just a result of personal preference, although this may result in one good amp/speaker being chosen over another.
The ultimate test is after you have auditioned other equipment, price no object, is can you honestly say that the musical experience you get is the equal of anything you have heard.
In other words have you heard better
Would you if offered swap your amp for another.All the tests in the world don't ultimately tell you how it will sound.
A reference product is something you have heard that you aspire too.
If you can honestly say that you haven't heard better than your DIY amp then you have nothing to worry over... if you have and you can identify the type of sound you want... or are aware of any shortcomings in your design, be it performance, noise, hum, operationally, looks etc then you have something to work to and develop for the next one.
If there's no smoke after several days of enjoying the sound then I take a break. Come back to it later and then if I still like the sound, it's good to go.
I have zero interest in measurements, having already done all the measurements in Spice
so Spice will tell you among others
----- that your zobel inducror is proper
----- your gtound rooting is correct
----- your pcb is perfect
----- your wirining was also perfect
----- and the thermal behaviour of your amp is also perfect
that was the faniest thing i listen for a very long time now
thank you ...you made my day perfect !!!
some times and after that i begin to belive in miracles ....
The ultimate test is after you have auditioned other equipment, price no object, is can you honestly say that the musical experience you get is the equal of anything you have heard.
In other words have you heard better
All the tests in the world don't ultimately tell you how it will sound.
A reference product is something you have heard that you aspire too.
If you can honestly say that you haven't heard better than your DIY amp then you have nothing to worry over... if you have and you can identify the type of sound you want... or are aware of any shortcomings in your design, be it performance, noise, hum, operationally, looks etc then you have something to work to and develop for the next one.
That would require more honesty, than anyone here can offer
The amp that cost you a month salary, your social life, and almost cost your marriage, will always sound pretty darn good to you.
Magura
A listening test may perhaps pick up gross problems, like huge distortion, hum, other noise, but if it sounds "OK" you will never know what "OK" is supposed to be. So you may listen to a music track on 3 different systems, and they all could be "OK" but at the same time all different. Which one is closer to the original sound? And how do we define "original sound". There are so many variables it is impossible to quantify.
I have been building a guitar pre-amp for about 6 months (on version 3 now). First version worked, with slight bugs that were fixed on the PCB but overall design could be heavily improved so am re-designing it.
Here's what I do for pre-amps and low wattage ( < 1 W ) amps:
I do not use op-amps.
I do not use feedback.
I do not use class AB or long tail paired transistors (except final stage of power amp which is AB).
Use a twenty-times rule for biasing circuits (to help with temperature changes, tolerances and soldering changes).
I do not use more than one active device on the signal path at any stage (eg no current mirrors, cascade etc).
I *may* just use a transistor to regulate the supply rail but I am not too keen on that idea either.
I use an Excel spreadsheet to calculate bias points and then I build a bread board to do some measurements with oscilloscope and function generator and bench power supply. The problems here are: (a) the breadboard has stray capacitances and resistances which will have you scratching your head and waste hours chasing shadows (b) the bench power supply is perfect and in no way simulates a basic PSU that you would build yourself, so then you get hit with hum when you do not expect it and (c) it takes a very long time to make slight adjustments and retest.
So now I use a SPICE simulator (Multisim 10) to set out the parameters across the circuit. It takes a very long time on Multisim, it would take 10x time on breadboard.
I aim for low distortion (less than 0.1% typically 0.020%-0.050%) and also eye inspection of the curves on simulated oscilloscope to make sure they look OK (eg symmetrical).
Clip every stage on purpose to make sure it clips symmetrically (as much as possible).
Try to keep currents as low as possible to minimise noise, and at the same time over a threshold to maintain a linear beta. Beta and low Ic threshold measured experimentally (not depending on SPICE models).
I hope the end result will sound better than version 1, which does not sound bad at all anyway. It is already the better amp between the Fender and the Vox.
I have been building a guitar pre-amp for about 6 months (on version 3 now). First version worked, with slight bugs that were fixed on the PCB but overall design could be heavily improved so am re-designing it.
Here's what I do for pre-amps and low wattage ( < 1 W ) amps:
I do not use op-amps.
I do not use feedback.
I do not use class AB or long tail paired transistors (except final stage of power amp which is AB).
Use a twenty-times rule for biasing circuits (to help with temperature changes, tolerances and soldering changes).
I do not use more than one active device on the signal path at any stage (eg no current mirrors, cascade etc).
I *may* just use a transistor to regulate the supply rail but I am not too keen on that idea either.
I use an Excel spreadsheet to calculate bias points and then I build a bread board to do some measurements with oscilloscope and function generator and bench power supply. The problems here are: (a) the breadboard has stray capacitances and resistances which will have you scratching your head and waste hours chasing shadows (b) the bench power supply is perfect and in no way simulates a basic PSU that you would build yourself, so then you get hit with hum when you do not expect it and (c) it takes a very long time to make slight adjustments and retest.
So now I use a SPICE simulator (Multisim 10) to set out the parameters across the circuit. It takes a very long time on Multisim, it would take 10x time on breadboard.
I aim for low distortion (less than 0.1% typically 0.020%-0.050%) and also eye inspection of the curves on simulated oscilloscope to make sure they look OK (eg symmetrical).
Clip every stage on purpose to make sure it clips symmetrically (as much as possible).
Try to keep currents as low as possible to minimise noise, and at the same time over a threshold to maintain a linear beta. Beta and low Ic threshold measured experimentally (not depending on SPICE models).
I hope the end result will sound better than version 1, which does not sound bad at all anyway. It is already the better amp between the Fender and the Vox.
The ultimate test is after you have auditioned other equipment, price no object, is can you honestly say that the musical experience you get is the equal of anything you have heard.
In other words have you heard better
So, if my $1,000 DIY amp sounds better than the $5,000 Krell but worse than their $50,000 product (aka I would gladly swap my amp for that), then my project is considered a failure.
Interesting theory.
I guess it does make sense in one case: setting out to make the best amplifier on the planet for just $1,000...
Thank you for all the responses. So much to learn, but I'm trying not to go too deep, as professional audio design is not my vocation and now is not the time to change trade.
I'm just tinkering at the moment, but the software test solutions seem perfect. If I've still got the bug after my project is finished, I'll consider investing in some more test equipment, for now, a multimeter and Pc is as far as I'm going. Besides all I've got to do is put everything together with a few blobs of solder and tie the all electrical string together, what could possibly go wrong.........?............
.....................
I'm just tinkering at the moment, but the software test solutions seem perfect. If I've still got the bug after my project is finished, I'll consider investing in some more test equipment, for now, a multimeter and Pc is as far as I'm going. Besides all I've got to do is put everything together with a few blobs of solder and tie the all electrical string together, what could possibly go wrong.........?
.................................I like this testing.Turn up amp with no signal input. No hissy, no buzzy? - good.
Turn down very low. Listen to speech only, at barely audible volume, with head near speaker. Still good? Turn up loud with favourite of piece of music. Still good?
Good amp.
Post3 also makes sense.
A Scope is an essential tool from one end of the amp to the other, you can see things you may not hear from distortion to oscillations. a good scope can be had on fleabay for 100 to 200 dollars . I have bought several on ebay with good results. caveat emptor, there are some who would geek you.
Seasons Geekings, Elwood
Seasons Geekings, Elwood
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