To me Tom, it seems you're starting to play games
Oh? What games am I playing? The "let's stay on topic" game? All I'm doing here is holding Joseph K to his own standard. I don't think of that as a game. I get held to my own standards on a quite regular basis.
Tom
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I think I did not deviate an inch, from the topic (which is not topic of this 3D, but anyway)
I am trying to get a better understanding of what could have gone wrong.
First approximation is that I can not repeat it, for now.
Please, do not take it for an attack. It is a problem, somewhere, I am trying to collaborate..
I am trying to get a better understanding of what could have gone wrong.
First approximation is that I can not repeat it, for now.
Please, do not take it for an attack. It is a problem, somewhere, I am trying to collaborate..
Tom said
"I have a good handful of amps that are better than the Modulus-86"
I'd be interested in what they are as I've only come across one better amp, from Trinity in Germany, and that is a "little" more expensive.
The owner of the Trinity Reference would agree with me
Reference Line – Trinity l the perfect sound
"I have a good handful of amps that are better than the Modulus-86"
I'd be interested in what they are as I've only come across one better amp, from Trinity in Germany, and that is a "little" more expensive.
The owner of the Trinity Reference would agree with me
Reference Line – Trinity l the perfect sound
I think I have exactly preemptively gave response in #205, to the rhetoric questions in 219?
And I'm sorry but I insist, because it is not at all academic, it is the real difference between these topologies.
So one output stage (Mod86) will continue to show low impedance when global feedback disconnected
(and it is one move to stabilize that stage and you know it well) (even without global feedback)
The MyrefFE stage will show high impedance on it's output. (not very high: ~a dozen ohm)
The MF FET output stage will show an even higher impedance.
If You connect a speaker, it will not be completely blocked, damped like with the Mod86 output stage.
That is a real world difference, not academic, and You know already..
And I'm sorry but I insist, because it is not at all academic, it is the real difference between these topologies.
So one output stage (Mod86) will continue to show low impedance when global feedback disconnected
(and it is one move to stabilize that stage and you know it well) (even without global feedback)
The MyrefFE stage will show high impedance on it's output. (not very high: ~a dozen ohm)
The MF FET output stage will show an even higher impedance.
If You connect a speaker, it will not be completely blocked, damped like with the Mod86 output stage.
That is a real world difference, not academic, and You know already..
The wobble in the output impedance is caused by the output relay.
The blue trace in attached graph is the output impedance as measured at the output of the amplifier (i.e. after the speaker protection relay).
The orange trace is the same measurement performed with the connection to the audio analyzer made on the 'inside' of the relay (i.e. the ground connection on the relay as the speaker protection relay in the MyRef FE switches the ground connection to the speaker).
Tom
The blue trace in attached graph is the output impedance as measured at the output of the amplifier (i.e. after the speaker protection relay).
The orange trace is the same measurement performed with the connection to the audio analyzer made on the 'inside' of the relay (i.e. the ground connection on the relay as the speaker protection relay in the MyRef FE switches the ground connection to the speaker).
Tom
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Tom...
I imagine You could already see this coming..
Looking at Your last test.. It jumps out that the output impedance curve of the FE amp had gone down almost an order of magnitude..
And in fact, it is now directly comparable with that of Mod86. Do I see well that they run almost precisely together? FE still a bit higher.
If yes, that brings a series of humble doubts.. Is it possible that not only the output impedance, but also the last bits in the distorsion spectra could have been affected by this mishap?
You have mentioned and I do agree that the output impedance curve is like a fingerprint: it is composed of output stage impedance and loop gain evolution..
For me the FE (new) impedance curve tells a story of a high, comparable loop gain at disposal. (to the Mod86)
If that is true, it should be also appearing in distortion performance.
Last bit of my reasoning: I am asking about this, because in fact, my measurements of the FE board with LM318 - were closer to your Mod86, Mod186 results, than to the value appearing in your test sheet. (but not equal, mind You)
All the best, George
I imagine You could already see this coming..
Looking at Your last test.. It jumps out that the output impedance curve of the FE amp had gone down almost an order of magnitude..
And in fact, it is now directly comparable with that of Mod86. Do I see well that they run almost precisely together? FE still a bit higher.
If yes, that brings a series of humble doubts.. Is it possible that not only the output impedance, but also the last bits in the distorsion spectra could have been affected by this mishap?
You have mentioned and I do agree that the output impedance curve is like a fingerprint: it is composed of output stage impedance and loop gain evolution..
For me the FE (new) impedance curve tells a story of a high, comparable loop gain at disposal. (to the Mod86)
If that is true, it should be also appearing in distortion performance.
Last bit of my reasoning: I am asking about this, because in fact, my measurements of the FE board with LM318 - were closer to your Mod86, Mod186 results, than to the value appearing in your test sheet. (but not equal, mind You)
All the best, George
Sure. And the measurement of the Modulus-86 tells the same story. They're both composite amps with a large amount of loop gain. No surprises there.
The difference in THD+N between the MyRef FE powered by a lab supply and the MyRef FE powered by a transformer is due to the PCB layout and not the output relay. I've provided a suggestion for how to address this in my review. You can also read here: Taming the LM3886 Chip Amplifier: Grounding – Neurochrome
I have remeasured and attached the harmonic spectra of the MyRef FE providing 1 W into 8 Ω. I bypassed the speaker protection relay by attaching the BNC connector for the connection to the audio analyzer on the 'inside' of the relay.
Looks like you have some homework to do.
Tom
The difference in THD+N between the MyRef FE powered by a lab supply and the MyRef FE powered by a transformer is due to the PCB layout and not the output relay. I've provided a suggestion for how to address this in my review. You can also read here: Taming the LM3886 Chip Amplifier: Grounding – Neurochrome
I have remeasured and attached the harmonic spectra of the MyRef FE providing 1 W into 8 Ω. I bypassed the speaker protection relay by attaching the BNC connector for the connection to the audio analyzer on the 'inside' of the relay.
Looks like you have some homework to do.
Tom
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So. I did some homework.
After many time I have digged out and reassembled my faithful old EMU1616m. Because the old measurements I have been doing with this card. It's heavily modified, not at all performing like original. The feedback control gave 0,000065% at - 10dBFS signal.
But it's not this aspect what I wish to show. Look at the power supply harmonics. I don't see the effect what Tom has seen. If it had been a PS injection effect into ground, it should not be possible to 'clean up' with 'simple' tight signal cabling, ground loop minimization.. (what I had to do carefully, obviously. It's a single ended test, with ironed in ground loops..)
I have only done a test with my everyday, dual 300VA Talema trafo supplied MyrefFE, the amp & test leads is in the photo. OPA828, sorry..
Test signal is 5W (6,4Vrms on 7ohm load), 1KHz.
I am very open to discuss..!
After many time I have digged out and reassembled my faithful old EMU1616m. Because the old measurements I have been doing with this card. It's heavily modified, not at all performing like original. The feedback control gave 0,000065% at - 10dBFS signal.
But it's not this aspect what I wish to show. Look at the power supply harmonics. I don't see the effect what Tom has seen. If it had been a PS injection effect into ground, it should not be possible to 'clean up' with 'simple' tight signal cabling, ground loop minimization.. (what I had to do carefully, obviously. It's a single ended test, with ironed in ground loops..)
I have only done a test with my everyday, dual 300VA Talema trafo supplied MyrefFE, the amp & test leads is in the photo. OPA828, sorry..
Test signal is 5W (6,4Vrms on 7ohm load), 1KHz.
I am very open to discuss..!
Attachments
George,
My advice: stop socalled collaboration with Neurochrome / Tom Christiansen.
You and Tom have different interests: Tom sells his products, he does business to make a living; you and your Fremen Edition friends are into DIY without those commercial interests.
Collaboration will not work: Tom will continue to make a point that his Modulus 86 is a better amp. Check his website for confirmation, and it does not comply at all with your own findings above. I already expressed my reservations, which now has been confirmed.
Not to disqualify Neurochrome at all but, once more, this does not work and is in nobodies interest.
Just my opinion.
My advice: stop socalled collaboration with Neurochrome / Tom Christiansen.
You and Tom have different interests: Tom sells his products, he does business to make a living; you and your Fremen Edition friends are into DIY without those commercial interests.
Collaboration will not work: Tom will continue to make a point that his Modulus 86 is a better amp. Check his website for confirmation, and it does not comply at all with your own findings above. I already expressed my reservations, which now has been confirmed.
Not to disqualify Neurochrome at all but, once more, this does not work and is in nobodies interest.
Just my opinion.
I hope this all is not too much tiring..
I understand and appreciate what You say.. But this time I beleive that Tom has picked up a bit of interest, like, I think, technical interest in this subject.
And I am interested in his interest. He has good points, which I discuss and fight back where I think there are existing more valid sides of the coin..
He is doing his job defending his business, but I hope that sometime also him gets tired of constantly only doing that and picks up some fun discussing this 'strange' hobby..
I understand and appreciate what You say.. But this time I beleive that Tom has picked up a bit of interest, like, I think, technical interest in this subject.
And I am interested in his interest. He has good points, which I discuss and fight back where I think there are existing more valid sides of the coin..
He is doing his job defending his business, but I hope that sometime also him gets tired of constantly only doing that and picks up some fun discussing this 'strange' hobby..
George: Your board is missing several components, including the input capacitor. I've circled some of the missing parts in the attached screen shot. Do you think that could be the root cause of the difference you measure? After all, the input capacitor is a known hum injection point in the MyRef FE (says Dario). What about the other components?
You also mentioned that you're using the OPA828. Is that the case for the measurements/boards you show? Could that make a difference?
On Dario's recommendation, I did try to short out the input cap, but that didn't change anything in my measurements. I did not take it out of the circuit like you have.
I disagree. We both have commercial interests. Group buys are not non-profit. Granted, we're talking beer money vs rent & food and I'm completely at peace with that.
I measured the performance of the MyRef FE (Evo A Mod) built on a Rev. 1.6 PCB as that's what Dario requested. Dario provided the boards for free and I built and assembled one of them at my own expense.
And similarly, George keeps pointing out that if you change A, B, and C, the MyRef design performs better than the MyRef FE Rev. 1.6 that I measured. I have no reason to doubt that what he measures is performing better than what I measured on the MyRef FE Rev. 1.6 on my bench, but I built the board according to the published BOM and instructions while George is measuring a modified version of the design. We're not making an apples-to-apples comparison, so your claims of bias on my part are, so far, unfounded. As I state in my MyRef FE review, the amp is a capable one. It's based on a good topology (it's a composite amp) and I see no reason it could not be brought to perform better.
If I wanted to trash the MyRef by providing garbage measurements, all I would have to do is to leave my wifi access points turned on during the measurement. You'd see a bunch of spurs starting at 30 Hz and harmonics along with a huge increase in 1/f noise. But that would be an obviously biased measurement. So I unplugged my access points so I could get a clean measurement.
I've sunk a full workweek into characterizing the MyRef FE at Dario's request. I could have spent that week on any number of more productive activities, including growing my business, but I figured I would follow through on my promise to measure the amp. And what do I get in return? If my measurements show worse performance that George's they are declared 'biased', but if they show identical or better performance they're somehow 'unbiased'. Great. I'm glad we got that established.
I guess we're back to "Tom's measurements are biased". As we used to say in the military: No good deed ever goes unpunished.
I know this wasn't directed at me, but that is the best piece of advice I've received in a long time.
George, I wish you and Dario the best of luck with your further development of the MyRef FE. Should you wish for another round of third-party measurements, I suggest you send a completed amp to Amir at Audio Science Review. He uses an APx555.
Should anyone here be interested in an assembled MyRef FE Rev. 1.6 and an unassembled PCB, I am putting mine up for sale here: https://www.diyaudio.com/forums/swa...-built-bare-pcb-selling-cost.html#post6514646
Cheers.
Tom
You also mentioned that you're using the OPA828. Is that the case for the measurements/boards you show? Could that make a difference?
On Dario's recommendation, I did try to short out the input cap, but that didn't change anything in my measurements. I did not take it out of the circuit like you have.
I disagree. We both have commercial interests. Group buys are not non-profit. Granted, we're talking beer money vs rent & food and I'm completely at peace with that.
I measured the performance of the MyRef FE (Evo A Mod) built on a Rev. 1.6 PCB as that's what Dario requested. Dario provided the boards for free and I built and assembled one of them at my own expense.
And similarly, George keeps pointing out that if you change A, B, and C, the MyRef design performs better than the MyRef FE Rev. 1.6 that I measured. I have no reason to doubt that what he measures is performing better than what I measured on the MyRef FE Rev. 1.6 on my bench, but I built the board according to the published BOM and instructions while George is measuring a modified version of the design. We're not making an apples-to-apples comparison, so your claims of bias on my part are, so far, unfounded. As I state in my MyRef FE review, the amp is a capable one. It's based on a good topology (it's a composite amp) and I see no reason it could not be brought to perform better.
If I wanted to trash the MyRef by providing garbage measurements, all I would have to do is to leave my wifi access points turned on during the measurement. You'd see a bunch of spurs starting at 30 Hz and harmonics along with a huge increase in 1/f noise. But that would be an obviously biased measurement. So I unplugged my access points so I could get a clean measurement.
I've sunk a full workweek into characterizing the MyRef FE at Dario's request. I could have spent that week on any number of more productive activities, including growing my business, but I figured I would follow through on my promise to measure the amp. And what do I get in return? If my measurements show worse performance that George's they are declared 'biased', but if they show identical or better performance they're somehow 'unbiased'. Great. I'm glad we got that established.
I guess we're back to "Tom's measurements are biased". As we used to say in the military: No good deed ever goes unpunished.
I know this wasn't directed at me, but that is the best piece of advice I've received in a long time.
George, I wish you and Dario the best of luck with your further development of the MyRef FE. Should you wish for another round of third-party measurements, I suggest you send a completed amp to Amir at Audio Science Review. He uses an APx555.
Should anyone here be interested in an assembled MyRef FE Rev. 1.6 and an unassembled PCB, I am putting mine up for sale here: https://www.diyaudio.com/forums/swa...-built-bare-pcb-selling-cost.html#post6514646
Cheers.
Tom
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George: Our posts crossed. I'm glad you see it that way.
Yep. I was going for a technical discussion.
It's unfortunate that others perceive it as "Tom is biased". For that reason I should probably stop here. There is plenty of room in this world (and on this forum) for both of us and our respective amps. However, if our technical discussion makes it appear that I'm only out to undermine your work, we should probably move the discussion to email.
That said, I am out of time here. I've already spent way more time on this than planned; out of technical interest. I was planning to spend one day and ended up spending five...
Anyway. As I told Dario via email: If you'd like my input on layout changes and whatnot, just toss me an email.
Cheers.
Tom
Yep. I was going for a technical discussion.
It's unfortunate that others perceive it as "Tom is biased". For that reason I should probably stop here. There is plenty of room in this world (and on this forum) for both of us and our respective amps. However, if our technical discussion makes it appear that I'm only out to undermine your work, we should probably move the discussion to email.
That said, I am out of time here. I've already spent way more time on this than planned; out of technical interest. I was planning to spend one day and ended up spending five...
Anyway. As I told Dario via email: If you'd like my input on layout changes and whatnot, just toss me an email.
Cheers.
Tom
Tom,
The pickup by the caps: it could be, and could be both.. (I have observed not nice noise pickup with large body electrolytic bypass/ filter caps on more occasions..)
I will try to see.
And thank You again, Tom, for this work, from my part I had appreciated really.
Wish you all the best!
George
The pickup by the caps: it could be, and could be both.. (I have observed not nice noise pickup with large body electrolytic bypass/ filter caps on more occasions..)
I will try to see.
And thank You again, Tom, for this work, from my part I had appreciated really.
Wish you all the best!
George