beppe,
Question: have you ever seen a tube preamp drive a ~2K load with low THD and yet plenty of voltage swing? No? Well, I have only seen a rare few examples and those weren't exactly in audio. Hence, due to the low impedance this will not work with tubes, perhaps when you use a transformer in between, but in that case we are back to square one, still think the AD8620 is a 'bad' solution?
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
Question: have you ever seen a tube preamp drive a ~2K load with low THD and yet plenty of voltage swing? No? Well, I have only seen a rare few examples and those weren't exactly in audio. Hence, due to the low impedance this will not work with tubes, perhaps when you use a transformer in between, but in that case we are back to square one, still think the AD8620 is a 'bad' solution?
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
SSassen said:
I just did not know that the input impedance of the modulator is about 2K Sir.
Please excuse me. I thought some 10K.
Evidently I was completely wrong.
Not that 10K is easy for a tube preamp.
Anyway 2K is very very low indeed.
A nice buffer is mandatory then.
Thank for the very valuable information.
Kind regards,
beppe
Hi Beppe,
You should have read the application note that I linked you to the other day. All these things are answered there.
Hi Sander,
Not to worry, Bruno's work always speaks for itself.
I think your mentioned feedback values are just a little off though.
I personally think anyone trying to stick a toob in a class d amp is simply after a niche market where people have alot of money and absolutely no understanding.... shiny things impress.
Best Regards,
Chris
You should have read the application note that I linked you to the other day. All these things are answered there.
Hi Sander,
Not to worry, Bruno's work always speaks for itself.
I think your mentioned feedback values are just a little off though.
I personally think anyone trying to stick a toob in a class d amp is simply after a niche market where people have alot of money and absolutely no understanding.... shiny things impress.
Best Regards,
Chris
Chris?
Uhm, no, those are for the input buffer, 560R/1K normally, but it sounds a whole lot better with 1K8/3K3.
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
Uhm, no, those are for the input buffer, 560R/1K normally, but it sounds a whole lot better with 1K8/3K3.
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
Hi Beppe,
Your plan sounds good. If I was you I would reduce the gain of your line stage to 4 or 5. The front end of the UCD modules are run off +-12V so you really don't want to exceed that swing into the modulator if possible. If you configure your amp to have single ended inputs you will also lose 6 dB of gain.
Please do not be discouraged by some of the remarks on this thread. There are many very good discrete op-amp circuits available that I would consider to have more potential than the AD8620. I encourage you to try different ones.
As for the other gentlemen here; Beppe is looking for encouragment and advice on discrete front ends. Bruno said it sounded good so why not give it a shot. I mean this is DIY right? He has requested politely and deserves to treated politely. As do people who try to help him. Members aspirations should not be ridiculed nor should they have their educational backgrounds called into question.
Graeme
Your plan sounds good. If I was you I would reduce the gain of your line stage to 4 or 5. The front end of the UCD modules are run off +-12V so you really don't want to exceed that swing into the modulator if possible. If you configure your amp to have single ended inputs you will also lose 6 dB of gain.
Please do not be discouraged by some of the remarks on this thread. There are many very good discrete op-amp circuits available that I would consider to have more potential than the AD8620. I encourage you to try different ones.
As for the other gentlemen here; Beppe is looking for encouragment and advice on discrete front ends. Bruno said it sounded good so why not give it a shot. I mean this is DIY right? He has requested politely and deserves to treated politely. As do people who try to help him. Members aspirations should not be ridiculed nor should they have their educational backgrounds called into question.
Graeme
Graeme,
With all due respect, but for someone without any experience as an analog designer to come up with a discrete solution that performs better than a AD8620 is like winning the lottery every time you buy a ticket.
That's not ridiculing, or making fun of someone, but that's a reality check, it might well save you valuable time trying to improve on something that you cannot improve on, not even in a hundred years. For that you'd need expert knowledge, a sound grasp of the underlying math and physics and a selection of expensive and dedicated tools and equipment. Honestly that's a bit out of reach for 99.9% of the audio enthusiasts that frequent these forums, which for the most part includes myself.
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
With all due respect, but for someone without any experience as an analog designer to come up with a discrete solution that performs better than a AD8620 is like winning the lottery every time you buy a ticket.
That's not ridiculing, or making fun of someone, but that's a reality check, it might well save you valuable time trying to improve on something that you cannot improve on, not even in a hundred years. For that you'd need expert knowledge, a sound grasp of the underlying math and physics and a selection of expensive and dedicated tools and equipment. Honestly that's a bit out of reach for 99.9% of the audio enthusiasts that frequent these forums, which for the most part includes myself.
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
gl said:
Sometimes the voice of reason doesn't tell you what you want to hear. Spare us the soap box, it is boring, and no one treated him anything close to impolite, so we don't need the sympathy routine either. Beppe should probably give them a listen to before tearing them apart to glue some download to it.
I trust he's buying a module because he wants something good, and I don't think download and wire will get him there. Have you even tried your own advice?
Fokker,
As outlined below that IS the sole reason why, do we need to keep repeating this?
http://www.hypex.nl/docs/gainappnote.pdf
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
As outlined below that IS the sole reason why, do we need to keep repeating this?
http://www.hypex.nl/docs/gainappnote.pdf
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
I am not sure if I buy off the gain argument: they can certainly increase the gain on the amp itself (8.2k/1.8k in the AN) to avoid the complexity of having a buffer, if gain were the sole consideration or even the main consideration.
anyway, going with an inverting AND differential design is a little weird for such a small power amp.
anyway, going with an inverting AND differential design is a little weird for such a small power amp.
Fokker,
Exactly what part of how an UcD amplifier works don't you understand? Please let us know, so we can educate you on this matter, or at least fill in some of the blanks. In short the gain is part of the equation that governs the self-oscillating nature of the UcD, it is closely tied with the loop-gain, bandwidth and oscillating frequency of the module. But hey, it is all explained in the documentation as provided on the Hypex website, I'd suggest you check it out yourself, there's some real gems to be found there, especially for the novice builder.
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
Exactly what part of how an UcD amplifier works don't you understand? Please let us know, so we can educate you on this matter, or at least fill in some of the blanks. In short the gain is part of the equation that governs the self-oscillating nature of the UcD, it is closely tied with the loop-gain, bandwidth and oscillating frequency of the module. But hey, it is all explained in the documentation as provided on the Hypex website, I'd suggest you check it out yourself, there's some real gems to be found there, especially for the novice builder.
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
fokker said:
If you're not convinced, clearly you haven't read the link you've been giving what, three times just today? r e a d i t! Research what you read... it will come to you. It's very clearly spelled out in there in one very simple sentence from Bruno to you, so you may as well profit from it! You could also look into instrumentation amplifier theory if you still need more.
Excuse me Sirs but I would like to apologize and put a question.
If the modules are exceptionally good as stock why so many posts about modding them ?
Now I know that:
1) the excution of the PS is fundamental. Anyway I understand that practically no one use the standard power supply solutions by hypex.
2) it is better to power the input op-amps with a separated power supply (of course well filtered and so on). Not so easy to do.
3) the output filter should be revised
4) the coupling caps should be removed
This leaves me a bit undecided.
I have to say that all in all they seem very difficult to use rightly.
It is not a matter of just connect them with wires and go.
Taking also in account that I am everything but an experienced DIYer my hesitation comes of consequence.
That said, honestly I have to admit I have said and asked too much.
Better to stop with posting for a moment, at least until I will have some new direct experience with these modules.
Surely I will keep looking to this forum with the greatest interest.
Thank you and kind regards,
beppe
If the modules are exceptionally good as stock why so many posts about modding them ?
Now I know that:
1) the excution of the PS is fundamental. Anyway I understand that practically no one use the standard power supply solutions by hypex.
2) it is better to power the input op-amps with a separated power supply (of course well filtered and so on). Not so easy to do.
3) the output filter should be revised
4) the coupling caps should be removed
This leaves me a bit undecided.
I have to say that all in all they seem very difficult to use rightly.
It is not a matter of just connect them with wires and go.
Taking also in account that I am everything but an experienced DIYer my hesitation comes of consequence.
That said, honestly I have to admit I have said and asked too much.
Better to stop with posting for a moment, at least until I will have some new direct experience with these modules.
Surely I will keep looking to this forum with the greatest interest.
Thank you and kind regards,
beppe
SSassen said:
I am sorry that my questions so upset you, Mr. Highhorse.
first of all, please make sure you understand my simple questions before you get onto your high horse.
2ndly, please let me know which set of equations governs the work of this amp, lay them out here for us so that we poor souls can admire your mastery of such equations.
No need to hide behind "read this", "read that". if you have the ball, I will follow you to the fullest extent of your capabilities, and beyond a little.
Consider that as a challenge to you.
fokker said:
Sadly, it's up to you to read the available material, which has rather pathetically been handed to you on a platter a multitude of times.... equations and all. You obviously drop the ball time and again by ignoring it. You're either defensive or mostly offensive, when you should be receptive. It's all there, everything you've been speculating over in this thread since it began, really, what more can be said, read it!
Guys, please lose the personal stuff and stick to the topic.I have a Benchmark DAC1 connected to my UCD180ad's. Does the instrumentation opamp inputs of the UCD serve a purpose for me?
It seems to me that my DAC1 is providing a DC-blocked balanced source already. I also notice that I have the gain on the DAC1 turned very low even at loud listening levels.
It seems to me that my DAC1 is providing a DC-blocked balanced source already. I also notice that I have the gain on the DAC1 turned very low even at loud listening levels.
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