Actually, in experimenting with the SSM2402, it does not shunt the entire singal to GND, only partially, so therefore the idea is MUTE [noparse]:)[/noparse]
For balanced in and out, the SSM2141 receiver and SSM2142 line drivers are fantastic.
Are you currently working on an audio project yourself? You are more than welcome to share ideas and plans…We seem to have lost one other person that was following these threads so additional interest is always welcome.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Chris Savage Parallax Tech Support
Thanks Chris, I have a lot of interest in audio stuff, I am a producer, engineer, writer, studio owner by trade, although I get sidetracked occasionally with my electronics addiction that usually borders OCD behavior. Currently I am designed a remote control mic positioining system that is controlled via OSX or PC. The project is a 6' high by 12' wide boom system using 4 steppers that move a mic to any speaker in the row of cabinets with rotation on the mic as well. The software moves the mic by keyboard nav, or by recalling presets for each speaker setting including position and amp/cab routing. The system routes a guitar to any of up to 16 amps, then routes those amps to any of up to 16 speaker cabs, all stored in the preset for easy recall. I am using all relays at the moment, but have plans to do a hi-fi tube pre/buffer section with a tube amp guru that has a pretty famous boutique amp company on the market.
Right now I am designing the metal fab for the rack boxes and front/rear panels, that will be grained and anodized after I machine and engrave the parts. Trying to get a design that looks good is the trick. I'll post some completed pics soon with vid. Here is a terribly out of focus web cam pic of the router guts. All the relay boards are on an i2c bus. There is a circuit that detects if speaker is present prior to connecting an amp in the path.
Chris Savage said...
Glad you got your parts. You’ll probably have it wired up and tested before me. I still need to get a dual supply up and running for this. Take care.
I'm not so sure about that Chris. I'm renovating our house which really puts a damper on all things that rhyme with tinkering with electrical stuff
Anyway, My power supply will be a plus, minus + zero (gnd) supply regulated with a 7805 and a 7905. I've got a Heath ET3400 that has a suitable power supply for prototyping it and hopefully I can start this weekend. I've got to pick up some bits and pieces from the local parts place first but I should be able to get started anyway.
Oh ya and "Originator" definitely the more ideas passed around the better. I've been out of audio for a few years but I'm getting back into it again (time permitting).
Chris, After many hours of muting tests, I have come up with my favorite scheme of all time. The circuit uses relays to do all routing, and an optofet driven by the Prop DAC to ramp the control signal up and down. The FET is configured as a shunt to GND as I described early. To get a shunt to work in this case you need to place a resistor prior to the shunt, otherwise there is no change. I used a 33k, and there is minimal feedthrough of the signal while muted and minimal signal loss when on. A larger value will get you down to zero signal, but in my case I just need the mute to act as a mask for the relays, so complete zero isn't required. The larger the value, the greater the loss howeer, so a unity gain op amp could be implemented whereas a 50k for example on the input, and a 50k feedback resistor would keep the levels in tact, while the shunt was tied to the input of the op amp pin, not prior to the resistor. The circuit also serves just as well for volume control, the DAC ramping has a nice "Mercedez Benz" tactile feel to it. The noise contribution is not perceivable. Due to having to insert the resistor in series, any preamp before the circuit is not seeing a dead short, and the resistances I am describing will not harm any gear. These FEts are expensive at $6 each.
Anyways just some info to consider. The SSM2402 are great used in the same citcuit, but you are liminted to either on or of with theme, no ramping as they already have their own ramping feature.
That's a pretty slick system. My only concern, and this is a friendly critique, nothing more, is that that the FETs will be putting a somewhat asymmetric load on the output when it's active. Though they're isolated by the 33k resistor, the body diode on the FET will still short the negative half cycle of the signal to ground once it exceeds the threshold of the body diode forward current times the series resistor 33k here). It won't be a big difference, with the 33k in there, but it might be enough to tweak your THD out of whack, or mess up a servo circuit as it crosses zero.
Something to think about, from a guy who's spent most of the last 2 weeks working on a nanovolt sensor project instead of audio, and may be a little over the top when it comes to tweaky things like this
-dave
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This is not a sig. This is a duck. Quack.
Comments
For balanced in and out, the SSM2141 receiver and SSM2142 line drivers are fantastic.
www.analog.com/UploadedFiles/Data_Sheets/SSM2141.pdf
www.analog.com/UploadedFiles/Data_Sheets/SSM2142.pdf
For transformers, there is a guy in LA that build nice ones.
cinemag.biz
Are you currently working on an audio project yourself? You are more than welcome to share ideas and plans…We seem to have lost one other person that was following these threads so additional interest is always welcome.
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Chris Savage
Parallax Tech Support
Right now I am designing the metal fab for the rack boxes and front/rear panels, that will be grained and anodized after I machine and engrave the parts. Trying to get a design that looks good is the trick. I'll post some completed pics soon with vid. Here is a terribly out of focus web cam pic of the router guts. All the relay boards are on an i2c bus. There is a circuit that detects if speaker is present prior to connecting an amp in the path.
I'm not so sure about that Chris. I'm renovating our house which really puts a damper on all things that rhyme with tinkering with electrical stuff
Anyway, My power supply will be a plus, minus + zero (gnd) supply regulated with a 7805 and a 7905. I've got a Heath ET3400 that has a suitable power supply for prototyping it and hopefully I can start this weekend. I've got to pick up some bits and pieces from the local parts place first but I should be able to get started anyway.
Oh ya and "Originator" definitely the more ideas passed around the better. I've been out of audio for a few years but I'm getting back into it again (time permitting).
Andrew
Anyways just some info to consider. The SSM2402 are great used in the same citcuit, but you are liminted to either on or of with theme, no ramping as they already have their own ramping feature.
www.nteinc.com/specs/3000to3099/pdf/nte3085.pdf
Below is the routing circuit, you can see the mute citcuit in one instance only to get the idea.
That's a pretty slick system. My only concern, and this is a friendly critique, nothing more, is that that the FETs will be putting a somewhat asymmetric load on the output when it's active. Though they're isolated by the 33k resistor, the body diode on the FET will still short the negative half cycle of the signal to ground once it exceeds the threshold of the body diode forward current times the series resistor 33k here). It won't be a big difference, with the 33k in there, but it might be enough to tweak your THD out of whack, or mess up a servo circuit as it crosses zero.
Something to think about, from a guy who's spent most of the last 2 weeks working on a nanovolt sensor project instead of audio, and may be a little over the top when it comes to tweaky things like this
-dave
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
This is not a sig. This is a duck. Quack.