@Tom,
These measurements on first sight look nice, but how about a frequency plot out to 10MHz? My boards (R1.01) have a very nasty oscillation at ~1MHz and clip recovery is pretty nasty, this is simply due to the loop not being stable.
Perhaps you fixed this with a later revision?
These measurements on first sight look nice, but how about a frequency plot out to 10MHz? My boards (R1.01) have a very nasty oscillation at ~1MHz and clip recovery is pretty nasty, this is simply due to the loop not being stable.
Perhaps you fixed this with a later revision?
Oscillation near clipping is an issue for the LM3886. I addressed this in Modulus-86 Rev. 2.0. You can make the fix in the Rev. 1.0 as well.
For better stability near clipping in the Modulus-86 Rev. 1.0 and 1.01, make the following additions:
- Connect 180 pF from Pin 9 to Pin 10 on the LM3886.
- Change R14 to 20k 1 %.
- Add 33 pF NP0 across R14.
These changes apply to Rev. 1.0 and Rev. 1.01 only. These changes have been implemented in Rev. 2.0 and beyond.
I looked at the gain margin and phase margin out to 50 MHz and it looked clean to me. I've looked at the performance of MOD86 Rev. 2.0 and 2.1 extensively both in the frequency domain and the time domain (using an oscilloscope). As far as I can tell, it's rock solid even with reactive loads up to 1 uF || 8 Ω.
The phase margin of Modulus-86 Rev. 1.0 with 8 Ω || 10 nF load measured 76.8 degrees. The gain margin being about 24 dB. I've attached the loop gain/phase measurement of Rev. 1.0. The phase margin is marked and you can read the gain margin from the point where the phase wraps around 180 º. The vertical axis starts at -40 dB and is 10 dB/div.
I have personally built 15 or 16 of the MOD86 Rev. 2.0 boards. They've all performed to spec.
If you are having any issues with your MOD86 boards, in particular if you are seeing instability, please email me immediately via the Contact Us page on my website. I will be happy to work with you in solving any issue you may have with any of the circuits I sell.
Thanks,
Tom
For better stability near clipping in the Modulus-86 Rev. 1.0 and 1.01, make the following additions:
- Connect 180 pF from Pin 9 to Pin 10 on the LM3886.
- Change R14 to 20k 1 %.
- Add 33 pF NP0 across R14.
These changes apply to Rev. 1.0 and Rev. 1.01 only. These changes have been implemented in Rev. 2.0 and beyond.
I looked at the gain margin and phase margin out to 50 MHz and it looked clean to me. I've looked at the performance of MOD86 Rev. 2.0 and 2.1 extensively both in the frequency domain and the time domain (using an oscilloscope). As far as I can tell, it's rock solid even with reactive loads up to 1 uF || 8 Ω.
The phase margin of Modulus-86 Rev. 1.0 with 8 Ω || 10 nF load measured 76.8 degrees. The gain margin being about 24 dB. I've attached the loop gain/phase measurement of Rev. 1.0. The phase margin is marked and you can read the gain margin from the point where the phase wraps around 180 º. The vertical axis starts at -40 dB and is 10 dB/div.
I have personally built 15 or 16 of the MOD86 Rev. 2.0 boards. They've all performed to spec.
If you are having any issues with your MOD86 boards, in particular if you are seeing instability, please email me immediately via the Contact Us page on my website. I will be happy to work with you in solving any issue you may have with any of the circuits I sell.
Thanks,
Tom
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The boards are available for purchase on my website: Modulus-86 Rev. 2.1.
I measured their performance using an Audio Precision APx525.
Tom
I measured their performance using an Audio Precision APx525.
Tom
Well if we have no more than incredible distortion figures and some vague open loop plots we have to check ourselves. Hey this is a diy forum 😀
I am living not far away of SSassen (about 1 hour driving I guess) and I am open to look further into his stability problem for a second opinion.
If he wanted to buy a board to test no one would care. He wanted a FREE board to test, hence the raised eyebrows. In most cases Tom has better test equipment than we do anyway.
You'll find the full specs here: Neurochrome Modulus-86 Rev. 2.1.
"No more than..."? Really? You mean you get more measurements from other vendors? You can see the full set of measurements on MOD86 Rev. 2.1 here: Modulus-86 Rev. 2.1: Composite amplifier achieving 0.000067 % THD. In the support section of my website, you can find links to the Rev. 2.0 and 1.0 pages which show the performance of those amps. If you have suggestions for other measurements that you would like to see on those pages which would be meaningful to a prospective customer, I'm certainly open to suggestions.
"Some vague open loop plots"? I posted an open-loop plot of the loop response near the crossover frequency. That's what was asked for. That's also what's relevant for stability. While these plots do require some skill and knowledge to interpret, I would not consider them to be vague at all. Would you care to elaborate?
Yes it is. Specifically, it's the vendor section of the forum.
I'm working with SSassen via email to get this resolved. He has been very responsive and provided me with the data that I need to go and investigate the issue, if there is an issue.
I was able to dig out a Rev. 1.01 of the board (exactly what SSassen has) and I will see if I can reproduce the issue that he is seeing.
If you would like to help with the debugging, you're certainly welcome to. Perhaps the three of us could get some collaboration going. I do suggest that you be more constructive in your communication, however. Also please do realize that I have a business to run and a life to lead in addition to helping you and SSassen address this issue, provided there is an issue.
I would like to point out that MOD86 R1.01 is nearly two years old at this point. I sold my last Rev. 1.01 board well over a year ago. I know of several successful Rev. 1.01 builds that are performing well in service. This is the first time I hear of any stability issues.
Significant improvements to the clipping response were made in Rev. 2.0 and you can get these improvements by adding two 10-cent capacitors to Rev. 1.0x of the circuit. If you also want the slightly lower gain of R2.0, you need to change a resistor as well. I described this a few posts back. I have openly communicated this change both in this thread and the build thread.
Despite the MOD86 being on the market for nearly two years, this is the first time I have heard of any loop instability in the MOD86 circuit. This in spite of many successful builds by people with test equipment who would undoubtedly have looked at the performance the amp. This also in spite of the thorough testing I performed before I sent the product to market.
As I mentioned earlier, I have seen SSassen's results and know his test conditions. I would like to reproduce these conditions in my lab so I can make an informed decision. I hope you will be supportive of my scientific approach.
Tom
My interest in LM3886 is not too big.
Don't have any amplifier distortion, over LM4562. LM4702
But I never think LM 4562 OR LM4702 makes us find the best amplifier.
I abandoned the LM4562, many years ago LM4702.
LM3886 I have many, many, but I never use it.
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It is acknowledged that THD measurements, taken with the usual notch-
type analyser, are of limited use in predicting the subjective impairment
produced by an imperfect audio path. With music, etc. intermodulation
effects are demonstrably more important than harmonics. However, THD
tests have the unique advantage that visual inspection of the distortion
residual gives an experienced observer a great deal of information about
the root cause of the non-linearity. Many other distortion tests exist which,
while yielding very little information to the designer, exercise the whole
audio bandwidth at once and correlate well with properly-conducted tests
for subjective impairment by distortion. The Belcher intermodulation test
(the principle is shown in Figure 1.1) deserves more attention than it has
received, and may become more popular now that DSP chips are cheaper.
------------
THD isn't very important parameter in the music.
It is almost secondary.
Such as the Swiss amplifier.
dar TZeel 8550 THD <1%.
ransient Intermodulation Distortion TIM = 0000?
-------------
Any using depth, negative feedback circuit, all have very low THD.
But this is no practical use.
------------😉
I just want to know the size of the TIM distortion.
In normal circumstances, by increasing the amount of negative feedback, can significantly reduce the THD + N
I have designed in many years ago < 0.006% of the 200 w AMP. But that have what use?
I would have eliminated it.
If the amount of feedback to double again, the THD will be less than 0.003%.
But TIM distortion in inverse proportion to increase. Doesn't sound will be better.
Basically, THD and TIM distortion are opposite.
Borrow DOUGLAS SELF the words in the book.
The least detectable amount of harmonic distortion is not an easy figure
to determine, as there is a multitude of variables involved, and in
particular the continuously varying level of programme means that the
9
Audio Power Amplifier Design Handbook
level of THD introduced is also dynamically changing. With mostly low-
order harmonics present the just-detectable amount is about 1%, though
crossover effects can be picked up at 0.3%, and probably lower. There is
certainly no evidence that an amplifier producing 0.001% THD sounds
any cleaner than one producing 0.005%6.
It is acknowledged that THD measurements, taken with the usual notch-
type analyser, are of limited use in predicting the subjective impairment
produced by an imperfect audio path. With music, etc. intermodulation
effects are demonstrably more important than harmonics. However, THD
tests have the unique advantage that visual inspection of the distortion
residual gives an experienced observer a great deal of information about
the root cause of the non-linearity.
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So why ask for a sample?
Did you even notice the multi-tone result Tom published or are you just being random troll of the week?
In addition. I don't want to get free PCB.
But I think it's too expensive. I don't have so much money.
I think USD $2 1 PCS PCB I can accept that.
But I think it's too expensive. I don't have so much money.
I think USD $2 1 PCS PCB I can accept that.
I've given a lot of people, many of the PCB. More than 500 PCS.
I don't want to use it. I just want to measure its data.
Of course. Perhaps a friend bought can lend me have a try. I will out of the mailing costs.
If I want to copy it, maybe I won't consider the price.
But for me to design a set of LM3886 amplifier can't more than 20 minutes.
I interested in this amplifier is not much.
THD + N is an easy thing to do, especially the OPAMP.
I don't hate low THD.
But if THD is one of the most important, that's ridiculous.
If the data as advertising to promote, Is not worthy of praise
.
Not many in the world use the OP amplifier is HIEND.
If you can. Please make released TIM test pattern.
It saves me the time of testing. Also can let me eat rice money a month.
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Well I understand English is not your first language but 'sample' has a very clear meaning in this context. Means you want it for nothing. You have an AP, but not much money? Or do you just have access to one?
So? You point being?
Tom has a better test rig than you. You will not measure much of use. Just pointing that out.
You really don't understand what this amplifier is about then. It's a composite, and not something you can toss off in 20 minutes. If you don't want the performance fine, I won't argue with that, but why even bother posting?
So please point us at test results for a 'praise worthy amplifier'. Or find another thread.
http://www.cordellaudio.com/papers/multitone_test.pdf
Some light reading on TIM from Bob Cordell, from at least 30 years ago. You will not he points out that THD20 is not a poor correlation with TIM.
Some light reading on TIM from Bob Cordell, from at least 30 years ago. You will not he points out that THD20 is not a poor correlation with TIM.
Well, I just want to know the LM3886 TIM test.
And I want to see this LM3886 test screenshots.
Not print figure.
Such as like this.
Only need to use it
PRINT SCREEN 😉
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