Russ that looks great.
What would be perfect is a complete solution for preamp control.
Volume relay control and input mute relay control.
LCD or simple led display all controlled with one PIC Microcontroller.
A universal solution would be the best so you could use it with any kind of preamp.
What would be perfect is a complete solution for preamp control.
Volume relay control and input mute relay control.
LCD or simple led display all controlled with one PIC Microcontroller.
A universal solution would be the best so you could use it with any kind of preamp.
Thanks Man,
The idea is to make the project accessible to those with varying goals. Certainly our desire is to create a community driven project with features that meet our collective needs. That means it will be modular and I hope will have some appeal to those who want a simple basic knob based attenuator solution as well as to those of us who might like a more full featured remote and LCD type controller interface. I intend to make make this a key focus even in relation to our source selector project. The two will indeed meld together very well. All will be open to the public in terms of design and technology. Implimentation is left up to the user, but I will provide a lot to get people started including a nice functional controller. Nothting I have done here is new, I have not invented anything at all, and I intend to give full attribution to those I have learned from as they have done as well.
I just finished my attenuator caculator today it is much more than a simple spreadsheet, but it couldn't be much simpler to use. You just iput your desired resolution in db and the number of steps along with your desisred output impedance and the application spits out correct E96 (1%) resistror values for you, which if you run through SPICE will get you a true logaritmic (not anti-log) curve.
You do not need to supply the resistor values at all, you are given them
Use whatever resistors you like, but we will likely supply Dales(RN60s) with our kits, but it is early in design yet and that has yet to be determined. I am not going to get into the "which resistor sounds better than what" debate as that is just nuts.
The PCBs are still a work in progress but coming along nicely. I have a basic prototype, but a more "final" version will lkely be done by the end of the week (real job schedule permitting) and based on that Brian and I will see what we can do.
Anyway, I think this type of attenuation fills a niche quite nicely, works like the best mechanical stepped attenuators (actually in many ways better) but with more resolution. I know it is exactly what I was looking for with my XBOSOZ. I think it is an ideal match. You could easily use it on input or on output as some like to do. Constant output impedance is much more critical than imput impedance, which is why this solution is much better than an ordinary pot. Output impedance can be as low as 1K while still maintaining high enough input impedance for most any source, and certainly input impedance can easily be adjusted.
Anway it is an extremely exciting project and I think the most significant addition to my audio chain yet.
Cheers!
Russ
The idea is to make the project accessible to those with varying goals. Certainly our desire is to create a community driven project with features that meet our collective needs. That means it will be modular and I hope will have some appeal to those who want a simple basic knob based attenuator solution as well as to those of us who might like a more full featured remote and LCD type controller interface. I intend to make make this a key focus even in relation to our source selector project. The two will indeed meld together very well. All will be open to the public in terms of design and technology. Implimentation is left up to the user, but I will provide a lot to get people started including a nice functional controller. Nothting I have done here is new, I have not invented anything at all, and I intend to give full attribution to those I have learned from as they have done as well.
I just finished my attenuator caculator today it is much more than a simple spreadsheet, but it couldn't be much simpler to use. You just iput your desired resolution in db and the number of steps along with your desisred output impedance and the application spits out correct E96 (1%) resistror values for you, which if you run through SPICE will get you a true logaritmic (not anti-log) curve.
You do not need to supply the resistor values at all, you are given them Use whatever resistors you like, but we will likely supply Dales(RN60s) with our kits, but it is early in design yet and that has yet to be determined. I am not going to get into the "which resistor sounds better than what" debate as that is just nuts.
The PCBs are still a work in progress but coming along nicely. I have a basic prototype, but a more "final" version will lkely be done by the end of the week (real job schedule permitting) and based on that Brian and I will see what we can do.
Anyway, I think this type of attenuation fills a niche quite nicely, works like the best mechanical stepped attenuators (actually in many ways better) but with more resolution. I know it is exactly what I was looking for with my XBOSOZ. I think it is an ideal match. You could easily use it on input or on output as some like to do. Constant output impedance is much more critical than imput impedance, which is why this solution is much better than an ordinary pot. Output impedance can be as low as 1K while still maintaining high enough input impedance for most any source, and certainly input impedance can easily be adjusted.
Anway it is an extremely exciting project and I think the most significant addition to my audio chain yet.
Cheers!
Russ
Banned
Joined 2002
steenoe said:What the heck, take a look at my friends
totally crazy volume control
http://www.briangt.com/gallery/magura-40stepattenuator/pict0001 Can you spot the lighter in there
Steen
http://www.briangt.com/gallery/magura-40stepattenuator
This shows the project from a more informative angle
Magura
Banned
Joined 2002
DaveM said:
analogair said:
You are patly wrong Dave. The cost of the materials turned out pretty hefty as well. Just add the price of half a kilogram of silver, a couple of full ceramic bearings, etc.
Materials alone are at least 500 USD, most likely a lot more, I try not to do the math
Magura
I didn't consider that there was a half kilo of silver in them. That would certianly change things a bit. Very nice work by the way.
I now have access to both an NC lathe and mill. Working for a small company is a wonderfull thing. I believe that my X-BOSOZ will have a face plate machined out of bronze plate. There is a huge sheet left over from a job done about 5 years ago. Hehehehe. Nothing better than free parts.
DaveM
I now have access to both an NC lathe and mill. Working for a small company is a wonderfull thing. I believe that my X-BOSOZ will have a face plate machined out of bronze plate. There is a huge sheet left over from a job done about 5 years ago. Hehehehe. Nothing better than free parts.
DaveM
Awaiting all marvelous project which will arrive in due time I found a real nice solution:
Alps RK27114 which is an unmotorized alps bleu, 4 channel 10k log .
for........
€26.25 !!!!
I just ordered one, if it's the real thing I will directly post it, ohh yeah for those interested:
http://www.albs.de/ecom/stock_fr_de.htm
Be warned, site is little archaic and in german. And don't you dare order all on stock because there are only 182 available!
Ralph
Alps RK27114 which is an unmotorized alps bleu, 4 channel 10k log .
for........
€26.25 !!!!
I just ordered one, if it's the real thing I will directly post it, ohh yeah for those interested:
http://www.albs.de/ecom/stock_fr_de.htm
Be warned, site is little archaic and in german. And don't you dare order all on stock because there are only 182 available!
Ralph
Banned
Joined 2002
I have some questions about this pot Russ is working on.
Russ,
How many turns will it take to turn the volume up all the way. ?
Can or does it act like a normal pot ?
The reason i ask is because with my digi01 pot it takes so long to turn up the pot and takes so long to turn it back down. I think it is the encoder because you have to spin it lots to get any thing out of it but then again it might not be.. Any ideas ?
I Love this pot but i hate the fact it takes to long to turn down the pot but on the plus site it is pretty smooth and each step is small it is nice to only turn it up a little. big pain to get up and turn down wish i had a remote.
Jason
Russ,
How many turns will it take to turn the volume up all the way. ?
Can or does it act like a normal pot ?
The reason i ask is because with my digi01 pot it takes so long to turn up the pot and takes so long to turn it back down. I think it is the encoder because you have to spin it lots to get any thing out of it but then again it might not be.. Any ideas ?
I Love this pot but i hate the fact it takes to long to turn down the pot but on the plus site it is pretty smooth and each step is small it is nice to only turn it up a little. big pain to get up and turn down wish i had a remote.
Jason
It is working
The attenuator can be controlled any way you like, butwith the controller I am using here in the photo it behaves exactly like a true one turn log pot when controlled by a 5K linear pot to the PIC's ADC.
So far it is working pricisely as designed with no nasty surprises. The software worked on the first try, but it is super simple.
I expect this thing to be in full swing here very soon.
Remember the picture is of a prototype, the real thing will be much more polished.
Cheers!
Russ
The attenuator can be controlled any way you like, butwith the controller I am using here in the photo it behaves exactly like a true one turn log pot when controlled by a 5K linear pot to the PIC's ADC.
So far it is working pricisely as designed with no nasty surprises.
The software worked on the first try, but it is super simple.I expect this thing to be in full swing here very soon.
Remember the picture is of a prototype, the real thing will be much more polished.
Cheers!
Russ
Attachments
Re: It is working
Hi Russ,
I'm a little bit curious as to how you managed to get the logaritmic distribution in 128 steps and resolution of 0.5dB using only 7 bits linear 2R-R AD-DA topology?
If your resistors aren't 2R-R weighted are you positive that your resolution is indeed 0.5dB across the whole range?
Regards,
Milan
Russ White said:So far it is working pricisely as designed with no nasty surprises.
Hi Russ,
I'm a little bit curious as to how you managed to get the logaritmic distribution in 128 steps and resolution of 0.5dB using only 7 bits linear 2R-R AD-DA topology?
If your resistors aren't 2R-R weighted are you positive that your resolution is indeed 0.5dB across the whole range?
Regards,
Milan
Re: Re: It is working
It is not a clasic R-2R at all. If it were it would be linear. Yes I am absolutely positive of the resolution as I have it here in front of me to test, and I have.
Here is how it works. Each section is calculated for a given attenuation independantly based on the output impedance of the previous stage. All of the stages have the same output and input impedances, except the first which is calcuated for an ideal source, this can be adjusted to whatever input impedance you actually have, but in practice it usually is not really necessary.
So the LSB stage is .5db (thus we have a .5 db resolution in this case) the MSB stage is 32 db. So when all stages are attenuating you have 63.5db of attenuation. When all stages are off you get 0db.
All relays are always conducting (DPDT) and input impedance varies within reasonable range while the critical output impedance always remains fixed no matter the attenuator setting. This is a very nice plus.
Hope that helps.
Cheers!
Russ
moamps said:
It is not a clasic R-2R at all.
If it were it would be linear. Yes I am absolutely positive of the resolution as I have it here in front of me to test, and I have. Here is how it works. Each section is calculated for a given attenuation independantly based on the output impedance of the previous stage. All of the stages have the same output and input impedances, except the first which is calcuated for an ideal source, this can be adjusted to whatever input impedance you actually have, but in practice it usually is not really necessary.
So the LSB stage is .5db (thus we have a .5 db resolution in this case) the MSB stage is 32 db. So when all stages are attenuating you have 63.5db of attenuation. When all stages are off you get 0db.
All relays are always conducting (DPDT) and input impedance varies within reasonable range while the critical output impedance always remains fixed no matter the attenuator setting. This is a very nice plus.
Hope that helps.
Cheers!
Russ
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