The attenuator is an integrated part of the analyzer.
The maximum input range is 100V. The minimum range is 316 mV. I did consider implementing a 100 mV range, but decided not to. Even though the input stage has a very low noise, the noise contribution of the input stage will still be higher than the noise contribution from the ADC at the highest gain.
There might be a way to implement a 100 mV range in a fairly simple way though, by increasing the gain of the input stage. So if it is a real need, I could take a look at it. I don't want to make too big changes at this point in time.
On the output I have got a maximum level of 10 Vrms differential, with a differential output resistance of 50 ohm (XLR). And a single ended output at 5Vrms with an output impedance of 25 ohm (BNC).
The maximum input range is 100V. The minimum range is 316 mV. I did consider implementing a 100 mV range, but decided not to. Even though the input stage has a very low noise, the noise contribution of the input stage will still be higher than the noise contribution from the ADC at the highest gain.
There might be a way to implement a 100 mV range in a fairly simple way though, by increasing the gain of the input stage. So if it is a real need, I could take a look at it. I don't want to make too big changes at this point in time.
On the output I have got a maximum level of 10 Vrms differential, with a differential output resistance of 50 ohm (XLR). And a single ended output at 5Vrms with an output impedance of 25 ohm (BNC).
Electroacoustics Toolbox
I have been using this last several years and is very good and stable. I believe the most comprehensive software for Mac. This guy, develops majority of his software for iOS as well.
Just for info, not directly related, for iPad/iPhone there is really nice audio app with formulas and various data calculations and translations - Electronic TB.
http://electronic-toolbox.com/electronic-toolbox/
One thing that makes AP so comfortable is very easy access - switched attenuated inputs with every connector one might think off. BNC, XLR, Dual Bananas, Toslink, AES/EBU... In my mind that is a big part of successful measurement device.
Last edited:
The scheme used in the Shibasoku 725 seems to work very well. They have an input attenuator down to 3V and the input amp has a 10 dB adjustable gain range. The input amp is quite complex to be able to have really really low distortion across the range but I suspect something similar can be done with your input circuit. 10 dB steps would keep an input in the optimum range of the ADC. There are always compromises. the APx525's best performance is at 2V in. it degrades at any other input level to extremely good but not a lot better than competitive products.
If the output amp can drive a 50 Ohm load then its possible to make very low noise attenuators to work with mike and phono inputs.
Hi Demian,
Since my latest post I just modified the design so that a 100mV input range is also available. It was in fact fairly easy to do.
So now the input range goes from 100 mV to 100V in 10 dB steps.
I have not tested the performance with the gain setting needed for the 100 mV input range.
Since my latest post I just modified the design so that a 100mV input range is also available. It was in fact fairly easy to do.
So now the input range goes from 100 mV to 100V in 10 dB steps.
I have not tested the performance with the gain setting needed for the 100 mV input range.
Maybe what we all need is something akin to this: http://www.cieri.net/Documenti/Misu...gy - Stereo Test Panel model 1200A (1978).pdf I have one and have found that is not that well suited to today's audio equipment. A revisit to the core features and adjusting to what is needed in terms of interfacing to a PC or audio analyzer and having the I/O for mobile and digital as well as traditional amps would be really nice. Today it could be much smaller and controled from USB or some simple front panel buttons. the scope interface would be pretty redundant as would the FM generator interface. Not a small project but really useful.
Attachments
I'll think it through over the next few days and try a first pass at a spec. I'll post in a separate thread. I suspect it will be similar to Pete millet's with some additions and setup for external control. I would welcome input from anyone.
I think Jens enhancement to the input circuit will really address the harder parts. its interfacing all the different types of audio devices that is difficult today.
Here is a quick list-
Analog
Mobile
3.5 mm headphone level (100 mV)
3.5 mm line level
3.5 mm microphone level w/ optional power
Traditional
RCA in line level
Speaker in
RCA out Phono
RCA out line level
Digital
SPDIF in (RCA)
Toslink in
AES EBU in
SPDIF out (RCA)
Toslink out
AES EBU out
Let me know all the options i forgot.
I think Jens enhancement to the input circuit will really address the harder parts. its interfacing all the different types of audio devices that is difficult today.
Here is a quick list-
Analog
Mobile
3.5 mm headphone level (100 mV)
3.5 mm line level
3.5 mm microphone level w/ optional power
Traditional
RCA in line level
Speaker in
RCA out Phono
RCA out line level
Digital
SPDIF in (RCA)
Toslink in
AES EBU in
SPDIF out (RCA)
Toslink out
AES EBU out
Let me know all the options i forgot.
Out in the real world, you'll see about 1,000 large XLRs for every mini. Maybe more.
@ jasse
Regarding SW there are many options. There is a discussion here:
http://www.diyaudio.com/forums/soft...gestions-free-spectrum-analyzer-software.html
I use mainly audioTester. I have also tried HP Works and Arta/Steps.
It is preferable if the SW supports ASIO.
Regarding connectors:
In my Audio Analyzer I use XLR and BNC for the outputs. XLR is used for the inputs. If other connectors are needed adapters can be used. If a single ended input is required an adapter like this can be used:
NA2MBNC - Neutrik
Regarding SW there are many options. There is a discussion here:
http://www.diyaudio.com/forums/soft...gestions-free-spectrum-analyzer-software.html
I use mainly audioTester. I have also tried HP Works and Arta/Steps.
It is preferable if the SW supports ASIO.
Regarding connectors:
In my Audio Analyzer I use XLR and BNC for the outputs. XLR is used for the inputs. If other connectors are needed adapters can be used. If a single ended input is required an adapter like this can be used:
NA2MBNC - Neutrik