Autoranger for soundcards

:cop:

Thread edited to keep chronological order of moved posts.

Introductory note from Jan carried forward from old thread.

Since I started my design for an autoranging attenuator/amplifier I have been posting in other threads sometimes hijacking them. So I asked the mods to collect those posts in a new thread here.

Comments invited.

Jan

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Hi hochopeper,
If it's a 100 KHz source you need, an LC circuit could make an effective filter to hang after a crude sine wave source. Any of the HP oscillators like the 3336B or 3325A or B would serve quite well. Digital frequency accuracy, digital level stability. The L-C filter network would really do a number on distortion products.

Any of the XR2206 type circuits could also be used with a drop in stability, but still probably better than you need.

-Chris


Hi anatech,


XR2206 looks like the go, thanks! It's times like this that I regret not buying the -S model when I bought my Rigol scope.

Another milestone in the development of the autoranger!
Finalised and tested the cal procedure.
Especially calibrating the freq response for 0.1dB flatness out to 100kHz is a challenge if you don't have a fully equipped lab :eek:

I now have a procedure that needs only an AC DMM with reasonable performance and a signal generator that can output 10kHz and 100kHz, preferably up to 10V or more but that's not critical.

The procedure directs you to do some measurements and enter values in a small spreadsheet and the spreadsheet then tells you what to adjust (cap trimmer) for which DMM indication.
For -20dB and -40dB settting, in both SE and BAL mode.

It's done faster than described!

Jan

Jan,

In your note above you mention a source that can provide 10kHz, 100kHz at ~ 10V ideally for calibration. The cheapo XR2206 kits seem to be set for 2V sine wave output. The datasheet has mention of changing a resistor and increase supply voltage to 25V to get more voltage out so no worries there. I don't want this thing to cost any more ($$ or time) than it needs to, should I care about the 2.5% distortion for this purpose? Or should I look for something a bit more sophisticated?



Regards,
Chris
 
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The calibration for the autoranger can also be done with, say, 50kHz with probably same results - it's only an octave lower.
Lower level than 10V works also well, if you have a good RMS multimeter that works down to say 20mV.
The procedure is universal, and the measurements are comparatively, not absolute.
Source distortion is no issue.

I wouldn't start buying test equipment for this yet!

Jan
 
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when do you think the kit will be available for purchase and what is the asking price? Any ideas yet?

I have been looking at a kit consisting of:

- Painted and labelled enclosure;

- Complete assembled and tested SilentSwitcher power supply;

- Attenuator/amplifier PCB;

- Control PCB;

- Programmed controller.

and that would probably come close to € 150.

Jan
 
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As far as I can ascertain the board layout and parts list are complete to achieve the design specifications so, imho, it would be unfair to expect Jan to start redesigning anything at this point in time...

Yes that is correct. Just today talked to the outfit that did the enclosure prototype about getting a bunch made. You know, like drop the display window 0.5mm, raise the switch hole 1mm and decrease diameter 0.2mm, that sort of thing :cool:

Now I have to decide if I want to commit a couple of grand to get it going.

If any of you have plans (or make any after reading this ;)) of visiting RMAF this fall, I'll have a fully operational prototype to check out.

Jan
 
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Thank you MarkS for pointing me to the pictures. I know the kit price is €150, I am asking for the costs of the electronic components which will add to the kit costs.

Michael

Probably another $ 120 to $ 150. Depends a bit for instance on the display type you want to use. There are three single (or a dual and a single; there's sockets for both) opamps; I am using NE5534's but you can live it up there.

There are 9 1-form-A reed relays; I have been using both Pickering at $ 5 a pop as well as Coto 9007 series at $ 1 each. Doesn't seem to make a difference. The Pickerings will probably last longer (like 100 million switches versus a mere 5 million or so ;-).

My equipment (dScope series III) cannot measure better than about -118 dB distortion on a good day; and there's basically no difference between the loop back and with the autoranger inserted.

Jan
 
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Yes that is correct. Just today talked to the outfit that did the enclosure prototype about getting a bunch made. You know, like drop the display window 0.5mm, raise the switch hole 1mm and decrease diameter 0.2mm, that sort of thing :cool:

Now I have to decide if I want to commit a couple of grand to get it going.

If any of you have plans (or make any after reading this ;)) of visiting RMAF this fall, I'll have a fully operational prototype to check out.

Jan

Hi Jan,

I'll look forward to seeing the prototype at RMAF.

Cheers,
Bob
 
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Hi anatech,


XR2206 looks like the go, thanks! It's times like this that I regret not buying the -S model when I bought my Rigol scope.



Jan,

In your note above you mention a source that can provide 10kHz, 100kHz at ~ 10V ideally for calibration. The cheapo XR2206 kits seem to be set for 2V sine wave output. The datasheet has mention of changing a resistor and increase supply voltage to 25V to get more voltage out so no worries there. I don't want this thing to cost any more ($$ or time) than it needs to, should I care about the 2.5% distortion for this purpose? Or should I look for something a bit more sophisticated?



Regards,
Chris


I think I have one of those.

Send me a PM with a mailing address and it's yours.
 
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Yes that is correct. Just today talked to the outfit that did the enclosure prototype about getting a bunch made. You know, like drop the display window 0.5mm, raise the switch hole 1mm and decrease diameter 0.2mm, that sort of thing :cool:

Now I have to decide if I want to commit a couple of grand to get it going.

If any of you have plans (or make any after reading this ;)) of visiting RMAF this fall, I'll have a fully operational prototype to check out.

Jan

Just signed an order for 50 enclosures. The plot thickens! :cool:

Jan
 
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There are services in Asia that will build the complete PCB for not much more than the cost of the parts. At 50 pcs. its a good number to pursue. There are shops near me that could handle the PCB assembly as well but I'm a very long way from you.

Typically getting a PCB with the passives SMT mounted and the more modest parts (opamps) costs a small increase over the the basic PCB. Then let us mount expensive chips and connectors. it keeps the up front costs lower but addresses the most tedious part of assembly.
 
QuantAsylum QA400 and QA401

Yes that's a possibility I am pursuing. But most of the SMT Rs are 0.1% 25ppm or so and that's not something they have in the parts bin, so they need to order specially for this project. Which is not something they like!



Jan


Jan, I can provide a source in China that will allow you to deliver your own parts. You can see the LSK389 in these pictures - in fact, I supplied the entire BOM. They even included little QC stickers and stuck them in individual static bags :) The quality was okay - I did the prototype boards using stencils and my boards seemed to come out a bit better.

In the end, I was lazy and needed a bunch of these boards

I would be glad to assist anyway I can - feel free to hit me up via PM

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Jan, I can provide a source in China that will allow you to deliver your own parts.

Good tip, thanks!

I got a few hours in front of an AP 2722 yesterday with the proto autoranger (thanks Guido Tent!) but it was somewhat disappointing - no difference between loop back and with the AR in the loop, except a slightly higher baseline noise. :cool:

Red is loopback.

Jan
 

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