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Old 21st November 2013, 06:27 PM   #1751
pidesd is offline pidesd  Canada
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Default or this maybe?

à la f4...
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Old 21st November 2013, 08:56 PM   #1752
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oops, there is an error in post 1748:

the mosfet gate should be attached to the jfet drain instead of being attached to the cap.
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Old 23rd December 2013, 12:45 PM   #1753
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Originally Posted by pidesd View Post
bbp,

ah yes you are right...forgot about that. what about a voltage divider that would tie the jfets gate to 1.65v?

i m also not sure if there is idle current also...but maybe a simple ccs would do it?

in fact i wanted to build a pcm1794 I/V and wanted to share ideas, good or bad.

BIAS voltage for every DAC is very very important, the noise in BIAS will be delivered by the output stage directly.

I am working on a ultra-pure ultra fast response voltage regulator, which will be used in my new DAC.
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Old 23rd December 2013, 01:14 PM   #1754
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Smile My project

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Originally Posted by opc View Post
Hi bbp,

I wouldn't put much weight on that measurement. It's really only to show the general trend. It's a single unit measure (one number to describe all THD+N) plotted over output level, which tends not to show the whole picture.

The AP has a tendency to need a lot of settling time when taking sweeps like the one shown, and it was only set to default, so that's more than likely why you're seeing the peaks in that measurement. I can repeat it on Monday with a longer settling time and it would probably be more linear.

The FFT measurements are the ones I really wanted to relay. They are far more accurate and detailed accounts of what is actually going on.

Take a look at these for example, which show the effects of jitter in the analog domain

Cheers,
Owen

Hi OPC,

Thanks so much about your work and your guide line for us.

My project prototype work is done now, I am gonna share my measurement with you here.

It is a circuit based on a common gate structure like yours. but also, it features in other special points. For example, A pure voltage reference is added, target to get lower noise on the gate of mosfet.

Below is my measurement, it seems that this is the best DAC in non-lope feedback design. It is hard to keep non-feedback design in ultra-low THD+N below -120dB, but I believe my work does. It presents lower THD than a AP signal source. I think I have to use AP 2722 to test the 2nd prototype board.



Thanks again.


Regards
Paul Lu
Attached Images
File Type: jpg DIY AUDIO LINEARITY.jpg (155.6 KB, 506 views)
File Type: jpg DIY AUDIO JITTER.jpg (107.2 KB, 480 views)
File Type: jpg DIY AUDIO 50HZ FFT.jpg (195.3 KB, 467 views)
File Type: jpg DIY AUDIO 1K FFT.jpg (252.2 KB, 451 views)
File Type: jpg DIY AUDIO 7K FFT.jpg (255.3 KB, 61 views)
File Type: jpg DIY AUDIO 15K FFT.jpg (238.5 KB, 46 views)
File Type: jpg DIY AUDIO 19K+20K IMD.jpg (280.2 KB, 37 views)
File Type: jpg DIY AUDIO 50+7K IMD.jpg (294.3 KB, 41 views)
File Type: jpg DIY AUDIO 1K FFT VS AP.jpg (218.3 KB, 56 views)
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Last edited by bbp; 23rd December 2013 at 01:15 PM. Reason: add more information
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Old 24th December 2013, 10:24 AM   #1755
chendiy is offline chendiy  China
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bbp can you share your circuitry?I want to know how you improve. Thank you!
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Old 24th December 2013, 04:48 PM   #1756
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bbp can you share your circuitry?I want to know how you improve. Thank you!
Sorry, Chen. I am trying to write a PAT. on it.
I think it is possible to do this.
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Old 26th December 2013, 10:59 PM   #1757
savvas is offline savvas  Greece
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I was wondering if we can substitude zener diodes (MMSZ4683) with similar like BZT52C3V0.

Owen, correct me if I'm wrong, but for now your TPS7A3301 board are for up to 32V DC, right ?
IIRC, you had a plan modding them so we can get the 45VDC required for D1.
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Old 27th December 2013, 12:38 AM   #1758
bbp is offline bbp  China
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Originally Posted by savvas View Post
I was wondering if we can substitude zener diodes (MMSZ4683) with similar like BZT52C3V0.

Owen, correct me if I'm wrong, but for now your TPS7A3301 board are for up to 32V DC, right ?
IIRC, you had a plan modding them so we can get the 45VDC required for D1.
In my measurement, the negative kick from Source point will be < -10V sometime when I power the original NTD1 off. I think no Zener can protect ES9018 from such a high kick.
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Old 29th December 2013, 12:59 AM   #1759
opc is offline opc  Canada
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bbp:

It's a little hard to get a read on the intentions of your posts, but I'm not getting a very warm and fuzzy feeling from the last few things you wrote.

There are a few basic etiquette items you're not respecting:

1. You've hijacked a thread to show results from your "modified" circuit, claiming it's a large improvement, and then not sharing the actual circuit. What was your reason for doing this? How is this information relevant to anyone in this thread if you don't share the underlying circuit?

2. You've made a claim that your circuit is achieving better performance, when it's actually a little bit worse. The noise floor looks to be higher, and the distortion is also higher than a standard NTD1.

3. You're claiming that the NTD1 is going to damage an ES9018 when this is not the case. The NTD1 is a thoroughly tested and widely used circuit. Mine has been in constant service for several years and is still performing perfectly. I have posted measurements way back in the thread of the voltage swing on the output of the DAC (source of the fets) during startup and shutdown, and there is no risk of damage with a properly built and adjusted NTD1, with or without the zener diodes. Please don't make completely false and unsupported claims that the NTD1 will harm the DAC.

As for the patent, I think you might be getting a little ambitious. It's essentially impossible for an individual to foot the bill for a patent application and the subsequent legal muscle required to protect it. This of course is in addition to the fact that I strongly doubt there is any new art to be had in this area. A better voltage source on the gate is hardly groundbreaking and not really a deviation from the existing circuit. Add to this the fact that performance is worse, and you're not looking at much of a patent application.

Forgive me if I've misunderstood the intentions of your posts, and I don't mean to be overly harsh, but this forum is all about the sharing of information for the betterment of everyone's knowledge and personal listening experience. After all, it's how you found this circuit in the first place isn't it? Tis the season for more giving and less taking!

Regards,
Owen
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Old 29th December 2013, 03:52 AM   #1760
bbp is offline bbp  China
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Quote:
Originally Posted by opc View Post
bbp:

It's a little hard to get a read on the intentions of your posts, but I'm not getting a very warm and fuzzy feeling from the last few things you wrote.

There are a few basic etiquette items you're not respecting:

1. You've hijacked a thread to show results from your "modified" circuit, claiming it's a large improvement, and then not sharing the actual circuit. What was your reason for doing this? How is this information relevant to anyone in this thread if you don't share the underlying circuit?

2. You've made a claim that your circuit is achieving better performance, when it's actually a little bit worse. The noise floor looks to be higher, and the distortion is also higher than a standard NTD1.

3. You're claiming that the NTD1 is going to damage an ES9018 when this is not the case. The NTD1 is a thoroughly tested and widely used circuit. Mine has been in constant service for several years and is still performing perfectly. I have posted measurements way back in the thread of the voltage swing on the output of the DAC (source of the fets) during startup and shutdown, and there is no risk of damage with a properly built and adjusted NTD1, with or without the zener diodes. Please don't make completely false and unsupported claims that the NTD1 will harm the DAC.

As for the patent, I think you might be getting a little ambitious. It's essentially impossible for an individual to foot the bill for a patent application and the subsequent legal muscle required to protect it. This of course is in addition to the fact that I strongly doubt there is any new art to be had in this area. A better voltage source on the gate is hardly groundbreaking and not really a deviation from the existing circuit. Add to this the fact that performance is worse, and you're not looking at much of a patent application.

Forgive me if I've misunderstood the intentions of your posts, and I don't mean to be overly harsh, but this forum is all about the sharing of information for the betterment of everyone's knowledge and personal listening experience. After all, it's how you found this circuit in the first place isn't it? Tis the season for more giving and less taking!

Regards,
Owen
Hi Owen,

I am sorry about showing the measurement in your thread. I will delete the measurement post later to avoid misunderstood.

The fist time I post measurement here is intend to share the result together with the circuits. But as my work goes on, I made a miracle circuit based on common gate structure which is also used in NTD1. The new circuit presents miracle -140dB THD and my AP system can not measure the real distortion! The output voltage as high as 30Vrms with 120v VDD. That's why I have no post my circuit and share with you guys at last.

The original NTD1 is great, we're no doubt about that. No other simple circuit can presents such a low THD for IV use in the world except NTD1. That's why I give my thanks to you many times, for you share such a great circuit with us. Thanks again ^_^

But the output voltage is limit for a standard balance output DAC, only ~2Vrms for 100kohm load. That's I have to modify it. Simply increasing the 200R is not the best option, because large R means large voltage swing on Vds of MOSFET, which will cause larger non-linear for the output signal. The original design by you is nearly the best! Because you pay lots of time to work out NTD1.

For the damage, I can see no out of function damage for my ES9018 with NTD1, but I think the several voltage negative kick do have degraded its original performance.
In my simulation based on NTD1 which generous post by you, the negative kick during power-on/power-off is real. In my bench test, the kick is also real. I will give my appologize to you in case you can post the real non-negative kick measurement waveform with us later.

Have a nice weekend.

regards
Paul
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