I don't thin you will get any followers for your view here _ rather, this project has very good reputation as you see.
But by all means - good luck with yours - why not start an own thread?
//
But by all means - good luck with yours - why not start an own thread?
//
Hi pbisiac,
I have to agree with TNT on this. The RTX 6001 has been a great enabler for those of us who were able to grab one. That means it allows DIY efforts to go further and themselves compete with commercial offerings.
Why not try this experiment .. do a survey of all audio performance systems available, their main capabilities and then the cost associated with one configured like the RTX. Once you have done this, pick one out as if you were actually going to use it on your bench. Input range will also be important, and if you're going to attempt to use a sound card, your custom attenuator needs to have a flat frequency response. Your noise floor also have to be in the same ballpark as the RTX.
This isn't a difficult assignment, because I did this very thing when the RTX 6001 group buy was announced. I did put my money where my mouth was. There were three serious solutions to my problem, plus this one. Include the MI integration with the RTX, plus it's cost either full blown, or with just the features you need. Then have a look at the support for MI. That's pretty hard to ignore.
-Chris
I have to agree with TNT on this. The RTX 6001 has been a great enabler for those of us who were able to grab one. That means it allows DIY efforts to go further and themselves compete with commercial offerings.
Why not try this experiment .. do a survey of all audio performance systems available, their main capabilities and then the cost associated with one configured like the RTX. Once you have done this, pick one out as if you were actually going to use it on your bench. Input range will also be important, and if you're going to attempt to use a sound card, your custom attenuator needs to have a flat frequency response. Your noise floor also have to be in the same ballpark as the RTX.
This isn't a difficult assignment, because I did this very thing when the RTX 6001 group buy was announced. I did put my money where my mouth was. There were three serious solutions to my problem, plus this one. Include the MI integration with the RTX, plus it's cost either full blown, or with just the features you need. Then have a look at the support for MI. That's pretty hard to ignore.
-Chris
@pbisiac
You never told us what you were referring to when you told us about this fantastic “mystery product”, which is “a better (and more resalable) unit”.
So with no further details. I assumed that you felt it was better in every way. So it would of course also support the input voltages supported by the RTX6001.
But apparently that is not the case!
“I took a look to the photos...your interface seems more inspired to an AK application note than to a real measurement instrument. For example: did you really use NI "simple switcher" voltage regulators in an instrumentation device ? OMG ...”
Actually I don’t use simple switchers at all. I don’t know where you get that impression. On the other hand, there would be no problem in using them, as long as it is done right. The QA401 uses 4 x SN6501 for the isolated supplies.
In the following I will assume that you are talking about the QA401.
Regarding the cost. You claim that your “mystery product” (QA401) is “VERY similar, (same converters…” to the RTX6001. Please take a look at the pictures below and tell me again that they are “VERY similar”. (The Picture of the RTX6001 is from the prototype version. Minor changes have been made later on, e.g. added shields over the input stages and heat sink bracket for the ADC).
The converters are not the same! The DAC is the same, but the ADC is not. In my initial design I used the AK5397 (as the QA401), but I changed to the AK5394A, because the distortion of the AK5397 was much higher. If you had followed the thread, or even had read the first post, you would have known this.
Yes, the RTX6001 is a more expensive product than the QA401. This is because better (and more expensive) solutions were chosen. That’s a choice really. I could have designed a lower cost product, but decided to aim for a higher performance, knowing very well that it would increase the cost.
The input stages were one focus area. I use 2 x LSK389 per input, to get a very low noise and low distortion (also with high source impedances), even though they cost in the range of USD 5 each. And 0.1% metal film resistors. And a bunch of relays for range switching, AC/DC selection and overvoltage protection.
The input amplifier and the protection circuit allow me to get a typical noise floor around 0.55 uV over 20 kHz bandwidth. The QA401 has a noise level of 1.8 uV by the way. And AP typically state 1 uV.
Apparently you don’t like the thread as a whole and I assume that you therefore gave it a one star rating, since it went from a 6 votes 5.0 average to a 7 votes 4.43 average (and no, I haven’t given any votes to this thread myself).
The transition from describing a DIY hobby project to describing a project, which would be available to other forum members in a group buy, was discussed and agreed with the forum moderators. Technical discussions in this thread and commercial topics in the group buy thread (which is now locked).
And, as I have stated previously, I have no interest in bashing the QA401. It looks like a fine product, given the price point. But I had to set things straight when you come forward with unproven claims that it is “better” than the RTX6001.
I don’t know what your objectives are in relation to this, so I see no interest in continuing this pointless discussion.
Perhaps you could tell me where all of your designs are shared on this forum? Since you have been a member for over 13 years, there must be a lot of material to look at.
You never told us what you were referring to when you told us about this fantastic “mystery product”, which is “a better (and more resalable) unit”.
So with no further details. I assumed that you felt it was better in every way. So it would of course also support the input voltages supported by the RTX6001.
But apparently that is not the case!
“I took a look to the photos...your interface seems more inspired to an AK application note than to a real measurement instrument. For example: did you really use NI "simple switcher" voltage regulators in an instrumentation device ? OMG ...”
Actually I don’t use simple switchers at all. I don’t know where you get that impression. On the other hand, there would be no problem in using them, as long as it is done right. The QA401 uses 4 x SN6501 for the isolated supplies.
In the following I will assume that you are talking about the QA401.
Regarding the cost. You claim that your “mystery product” (QA401) is “VERY similar, (same converters…” to the RTX6001. Please take a look at the pictures below and tell me again that they are “VERY similar”. (The Picture of the RTX6001 is from the prototype version. Minor changes have been made later on, e.g. added shields over the input stages and heat sink bracket for the ADC).
The converters are not the same! The DAC is the same, but the ADC is not. In my initial design I used the AK5397 (as the QA401), but I changed to the AK5394A, because the distortion of the AK5397 was much higher. If you had followed the thread, or even had read the first post, you would have known this.
Yes, the RTX6001 is a more expensive product than the QA401. This is because better (and more expensive) solutions were chosen. That’s a choice really. I could have designed a lower cost product, but decided to aim for a higher performance, knowing very well that it would increase the cost.
The input stages were one focus area. I use 2 x LSK389 per input, to get a very low noise and low distortion (also with high source impedances), even though they cost in the range of USD 5 each. And 0.1% metal film resistors. And a bunch of relays for range switching, AC/DC selection and overvoltage protection.
The input amplifier and the protection circuit allow me to get a typical noise floor around 0.55 uV over 20 kHz bandwidth. The QA401 has a noise level of 1.8 uV by the way. And AP typically state 1 uV.
Apparently you don’t like the thread as a whole and I assume that you therefore gave it a one star rating, since it went from a 6 votes 5.0 average to a 7 votes 4.43 average (and no, I haven’t given any votes to this thread myself).
The transition from describing a DIY hobby project to describing a project, which would be available to other forum members in a group buy, was discussed and agreed with the forum moderators. Technical discussions in this thread and commercial topics in the group buy thread (which is now locked).
And, as I have stated previously, I have no interest in bashing the QA401. It looks like a fine product, given the price point. But I had to set things straight when you come forward with unproven claims that it is “better” than the RTX6001.
I don’t know what your objectives are in relation to this, so I see no interest in continuing this pointless discussion.
Perhaps you could tell me where all of your designs are shared on this forum? Since you have been a member for over 13 years, there must be a lot of material to look at.
Attachments
I think even the continued effort looking into further improving the product is also a plus for this project.
Looking through the recent discussions on the effects of the transformer, I am wondering whether the phase difference between the secondary outputs might be the cause. I have experienced such even in switching power supplies depending on the design. Certainly would wish for an improvement kit. However, I do realize this might mean a new safety certification for the product. I certainly would accept an improvement kit even prior to any certification as long as it improves performance.
Looking through the recent discussions on the effects of the transformer, I am wondering whether the phase difference between the secondary outputs might be the cause. I have experienced such even in switching power supplies depending on the design. Certainly would wish for an improvement kit. However, I do realize this might mean a new safety certification for the product. I certainly would accept an improvement kit even prior to any certification as long as it improves performance.
I have been close to both efforts. i think they are both valid in different ways. for most amateur and many professional applications a QA401 is more than adequate. The RTX6001 is more of a state of the art effort at a digital analyzer. Its more like a digital Shibasoku 725. If you need to explore at or near the lowest distortion and lowest noise electronics its the most accessible you will find at 10% of the cost of an APx555 and you can use it with software that even the AP doesn't support like DiAna.
The QA401 does have good dedicated software and can get someone new to audio testing up and running quickly. The new ASIO does extend it a little. But its distortion floor and max and min input are more limiting.
There are others once you go the commercial route and even then they are not directly comparable. Its not like comparing SOTA DVM's which are all directly comparable.
I have both and use both. The QA401 fits in a briefcase if I need. The RTX can test in ways that otherwise need a shelf of special purpose electronics. They are not interchangeable given the different strengths. If you committed during the group buy you got a very good deal.
If you are looking for a project instead of a tool there are several here on DIYaudio that can burn through many hours to get close to a QA401 in utility.
The QA401 does have good dedicated software and can get someone new to audio testing up and running quickly. The new ASIO does extend it a little. But its distortion floor and max and min input are more limiting.
There are others once you go the commercial route and even then they are not directly comparable. Its not like comparing SOTA DVM's which are all directly comparable.
I have both and use both. The QA401 fits in a briefcase if I need. The RTX can test in ways that otherwise need a shelf of special purpose electronics. They are not interchangeable given the different strengths. If you committed during the group buy you got a very good deal.
If you are looking for a project instead of a tool there are several here on DIYaudio that can burn through many hours to get close to a QA401 in utility.
I don’t know what you have against switching modules. It actually shows your lack of knowledge and experience. A lot of the modules with internal shielded inductors are quite good. If you search you will find a teardown of a 1.3 million dollar Keysight UXR oscilloscope which uses what looks to be at least 12 of them. A skilled designer knows how to make use of them.
Also, the RTX uses a linear supply, so I don’t know where your complaints are coming from. Either way it’s probably best you take your whining somewhere else.
Oh look, 5 more votes, all 5 stars
It seems everyone else appreciates your work, don't waste your time on this.
Best wishes
David
It's unfortunate that a thread of such quality has been subject to this. I will reiterate that this product is of the highest quality and the designer is highly skilled and a thorough gentleman.
He has helped other projects and threads with insightful comments, advice and pointers.
He has helped other projects and threads with insightful comments, advice and pointers.
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indeed.
i missed the group buy, saved my pennies and bought my RTX the "hard" way.
i have no doubt that i got a great deal, very high performance per $ and couldn't be happier!
mlloyd1
i missed the group buy, saved my pennies and bought my RTX the "hard" way.
i have no doubt that i got a great deal, very high performance per $ and couldn't be happier!
mlloyd1
Hi mlloyd1,
That must have hurt and been annoying at the same time.
I just caught the thread just as it was going to group buy and decided to trust a few of our members and dive in. Reading up on it later confirmed that it was a good choice. Later on, the MI software deal came together. Both companies have been wonderful in their support.
Two things that you have that we don't. You got the retail pack that included a certificate for calibration. You also didn't have to do some work on your own unit to fix things that were later done at the factory. I'm not complaining. If I had to pay full pop this would never have happened. Same for the MI software.
What software package are you using with it? MI controls the unit and will run a sequence of steps, automating tasks.
-Best, Chris
That must have hurt and been annoying at the same time.
I just caught the thread just as it was going to group buy and decided to trust a few of our members and dive in. Reading up on it later confirmed that it was a good choice. Later on, the MI software deal came together. Both companies have been wonderful in their support.
Two things that you have that we don't. You got the retail pack that included a certificate for calibration. You also didn't have to do some work on your own unit to fix things that were later done at the factory. I'm not complaining. If I had to pay full pop this would never have happened. Same for the MI software.
What software package are you using with it? MI controls the unit and will run a sequence of steps, automating tasks.
-Best, Chris
I’m with pbisiac. I’ve wasted rather a lot of time looking at this thread, only to find little info that’s useable in a DIY sense.
If PCBs and schematics were available at close to production cost (I’m thinking of what Frex or many others do), then I’d think differently, but the thread sucks people in with the promise of a DIY analyser and it’s only after much reading that you find out it’s a commercial product.
I couldn’t give a fig whether it’s a good commercial product or not. That’s entirely beside the point. It’s still a commercial product, and it’s misrepresenting itself.
If PCBs and schematics were available at close to production cost (I’m thinking of what Frex or many others do), then I’d think differently, but the thread sucks people in with the promise of a DIY analyser and it’s only after much reading that you find out it’s a commercial product.
I couldn’t give a fig whether it’s a good commercial product or not. That’s entirely beside the point. It’s still a commercial product, and it’s misrepresenting itself.
It is all in the very first post of the thread, with a link to the GB (long closed btw) stating that it is a fully assembled product. Not easy to miss really.
I'm sorry you wasted your time, but it could have all been averted by reading from the start rather than skimming.
OK, I won't disturb the users of this thread anymore. I would have liked to be able to carry out this project myself (although building by yourself testing instruments does not give you the certainty that your DUT is measured objectively). This is not possible due to a precise choice of the author.
I think the selling price is too high and I will use a different strategy (I’ll look for a refurbished instrument with a solid reputation).
Anyway, if the fact that no one can build this converter does not violate any forum rule, if the commercial vocation of this project was clear from the beginning (but I recall a post where the author, requested upon availability of documentation answered “maybe later”) and all users willingly accept it then continue calmly without me.
I think the selling price is too high and I will use a different strategy (I’ll look for a refurbished instrument with a solid reputation).
Anyway, if the fact that no one can build this converter does not violate any forum rule, if the commercial vocation of this project was clear from the beginning (but I recall a post where the author, requested upon availability of documentation answered “maybe later”) and all users willingly accept it then continue calmly without me.
Yes, the GB was for a fully assembled product, but that was a different thread.
For those who followed the thread here over the years it is clear that the RTX6001 is not available in a DIY form (be it empty boards, assembled board, gerber files, full kit, whatever). However, this may not be obvious for newcomers to the thread, and I can see how the thread title combined with photos and diagrams in the first post may lead newcomers to think that parts or documents are available to build this as a DIY project. It would not hurt to clarify this point in the first post to avoid confusion of newcomers to this thread.
To return to actual technical discussion...
You use a toroid and take some care to shield it.
Perhaps your experience in very low noise means you can answer a question about stray field emission from toroids that I have had for a while.
If the primary is simply wrapped about the toroidal core then there are two components of the current.
One is the loop around the cross section of the core.
There is a second loop around the "plan" of the core.
(Think of the core cross section reduced to an infinitesimally thin circle and it is clear there is still a loop around the diameter of the toroid)
This second component radiates a field that is not captured by the core permeability.
Are there any steps taken in commercial toroid transformers to cancel this field, do "low stray field" transformers eliminate the problem or just add a shield or strap?
Obviously if any of the other "low noise" experts have information please jump in.
Best wishes
David
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At 1000 dollars it still looks like a good product for what it does and i saw a long buyer list with prestigious names on it. It may be cheaper like any electronic product on the market , but i remember one painter answering : How much do you want for this painting?/ One million dollars, says the artist!/ WOW , that's expensive, says the prospective client, what makes you think that your painting is worth a million dollars?/ I don't know...but a million dollar sounds good to me!
If no schematic or other details are available , this is clearly not a DIY project ...so why are we here on DIY audio reading promises? Answer: that's life!At least we can enjoy beautiful , detailed pictures of a working model.I'd reverse engineer that board.
If no schematic or other details are available , this is clearly not a DIY project ...so why are we here on DIY audio reading promises? Answer: that's life!At least we can enjoy beautiful , detailed pictures of a working model.I'd reverse engineer that board.