Muting will not work in all instances!
Craig,
When I first read about your plan to mute Apox-1 by adding a muting relay to ground from the + phase I thought it was a great idea.
Now I am not so sure. You see, this will not work if (like me) you are using two gain stages with Apox-1 in between and the DC level is not zero.
Please consider an alternative which is to add another element in shunt mode (next to the other 8 with zero resistance). This will do the same as using the relay to ground but will be way more flexiblel and parts count will be the same (1 stereo relay per stereo board)
Finally, the other thing that you could do in software is to set up a software muting algorithm that remembers the latest volume setting and switches back to it. This is nice in that requires zero hardware, but muting to zero rather than extremely low level is typically more fun.
Also, I would just like to re-verify that the relays are set up in fail-safe mode which is normally open (pass elements) and normally closed (shunt elements, including muting element). At boot time, muting element should be closed for a few seconds as well to avoid pops, but should have instant toggle when equipment is hot.
Naturally, the muting element if implemented in hardware doubles as zero volume setting when the knob is twiddled all the way down.
I am still not sure that I have gotten a reply to the pre-scaling question ("same" level for all inputs regardless of how "hot" they are by courtesy of setup in controller which dynamically switches in a "gain" by applying the "wrong volume setting). Is this something that others are interested in?
Petter
Craig,
When I first read about your plan to mute Apox-1 by adding a muting relay to ground from the + phase I thought it was a great idea.
Now I am not so sure. You see, this will not work if (like me) you are using two gain stages with Apox-1 in between and the DC level is not zero.
Please consider an alternative which is to add another element in shunt mode (next to the other 8 with zero resistance). This will do the same as using the relay to ground but will be way more flexiblel and parts count will be the same (1 stereo relay per stereo board)
Finally, the other thing that you could do in software is to set up a software muting algorithm that remembers the latest volume setting and switches back to it. This is nice in that requires zero hardware, but muting to zero rather than extremely low level is typically more fun.
Also, I would just like to re-verify that the relays are set up in fail-safe mode which is normally open (pass elements) and normally closed (shunt elements, including muting element). At boot time, muting element should be closed for a few seconds as well to avoid pops, but should have instant toggle when equipment is hot.
Naturally, the muting element if implemented in hardware doubles as zero volume setting when the knob is twiddled all the way down.
I am still not sure that I have gotten a reply to the pre-scaling question ("same" level for all inputs regardless of how "hot" they are by courtesy of setup in controller which dynamically switches in a "gain" by applying the "wrong volume setting). Is this something that others are interested in?
Petter
Hi Guys,
I'll answer the easy questions first...
Yes, we will post all source code. If people really want to modify the software, they will be more than welcome to change it. The software is written in CCS "C" code. I could probably also post the assembly output.
Brian, I added the jumper for the RS232 connection. I will look at the web page to see if I need to modify the bootloader to properly setup the registers.
Also, the knobs are not included. Right now, the only "chassis" parts that are available are the RCA/XLR connectors. Everyone seems to want different knob styles and those have a dot and don't match the continuous rotation of an encoder.
Petter,
I had planned on having a volume offset for each input channel. For the APOX-2, the offsets are pretty big (2-3dB), so I'm not sure of the usefulness. For the APOX-1, the offsets will represent much smaller values, so should be no problem. The idea would be that the volume display would represent a virtual value and each input channel would add an offset (could be negative) to it. So if channel 1 had an offset of -15 (not dB), it would be added to each volume position. Of course, volumes around zero would be strange.
Other questions:
1) For the APOX-1 and probably the Apox-3, there will be a large number of volume settings. An encoder would be a hard interface to cycle through 200+ settings. Is there an idea on how to give coarse and fine adjustments?
2) I have added the capability to modify the display text for the inputs via the front panel switches/encoder. Should I also do the RS232 version. I know that Grataku does not want an encoder, but everyone else does.
I will probably add functionality to add the offsets to the front panel as well.
Best Regards,
Dale
P.S. Petter, I'll let Craig address your other issues/suggestions.
Brian, I mailed your LCD yesterday. Sorry for the delay. It's been a busy week.
I'll answer the easy questions first...
Yes, we will post all source code. If people really want to modify the software, they will be more than welcome to change it. The software is written in CCS "C" code. I could probably also post the assembly output.
Brian, I added the jumper for the RS232 connection. I will look at the web page to see if I need to modify the bootloader to properly setup the registers.
Also, the knobs are not included. Right now, the only "chassis" parts that are available are the RCA/XLR connectors. Everyone seems to want different knob styles and those have a dot and don't match the continuous rotation of an encoder.
Petter,
I had planned on having a volume offset for each input channel. For the APOX-2, the offsets are pretty big (2-3dB), so I'm not sure of the usefulness. For the APOX-1, the offsets will represent much smaller values, so should be no problem. The idea would be that the volume display would represent a virtual value and each input channel would add an offset (could be negative) to it. So if channel 1 had an offset of -15 (not dB), it would be added to each volume position. Of course, volumes around zero would be strange.
Other questions:
1) For the APOX-1 and probably the Apox-3, there will be a large number of volume settings. An encoder would be a hard interface to cycle through 200+ settings. Is there an idea on how to give coarse and fine adjustments?
2) I have added the capability to modify the display text for the inputs via the front panel switches/encoder. Should I also do the RS232 version. I know that Grataku does not want an encoder, but everyone else does.
I will probably add functionality to add the offsets to the front panel as well.
Best Regards,
Dale
P.S. Petter, I'll let Craig address your other issues/suggestions.
Brian, I mailed your LCD yesterday. Sorry for the delay. It's been a busy week.
Brian,
No currently the knobs are not included. Do you want us to resell them? so you don't have to pay for shipping twice?
Petter,
O.K. I will change from a "+ line shorting relay to gnd"
to a "+line to - line shorting relay".
I agree that is a better idea.
But please no more good ideas. I've finished the layout three times already. 😉 (Just kidding, keep the good ideas coming)
I'd much rather change the board now then after I place the order.
Also the relays I have are "normally open", but so is the input
select board. So as long as Dale's software sets the volume
before selecting an input line, we should be all set.
Also don't forget I also added the shunt resistor with no relay
to help the open circuit condition.
P.S. I'm almost done with the APOX-3 schematic.
-Craig
No currently the knobs are not included. Do you want us to resell them? so you don't have to pay for shipping twice?
Petter,
O.K. I will change from a "+ line shorting relay to gnd"
to a "+line to - line shorting relay".
I agree that is a better idea.
But please no more good ideas. I've finished the layout three times already. 😉 (Just kidding, keep the good ideas coming)
I'd much rather change the board now then after I place the order.
Also the relays I have are "normally open", but so is the input
select board. So as long as Dale's software sets the volume
before selecting an input line, we should be all set.
Also don't forget I also added the shunt resistor with no relay
to help the open circuit condition.
P.S. I'm almost done with the APOX-3 schematic.
-Craig
Prescaling
Dale,
Volumes around zero will probably not be very strange even with pre-scaling. Perhaps I am misunderstanding, but we need a dB add/reduce which is the same as a multiplication. So the pre-scaling could be set up as the volume setting times the pre-scale constant -- which agains sets the output.
As far as the number of settings, it is not really necessary to provide a true "every single value" setting when moving up the volume ladder -- the least significant bits will not make a huge impression at high volume settings and would rattle like mad. It is good enough to have relatively small steps throughout the range. Thus there are (at least) three ways to work this:
1. Set up a log scale using the number of positions of say 1-3 turns and select required positions (ignore the rest)
2. Add velocity gain (dangerous for volume control)
3. Use heavy knobs so that they "keep turning" if you spin them up.
I would say 1 is the best way to go.
I am assuming that you boot at zero volume, or is that something that is configurable as a constant (boot at say -40dB) in the software code (or better still display 🙂). The other alternative is to boot at same value that it was switched off at, but I don't like that as it is dangerous, and because encoders don't offer a visual cue as to level of volume as a reguarl potentiometer unit (I always verify the volume setting on an analog pre-amp when I turn it on).
Petter
Dale,
Volumes around zero will probably not be very strange even with pre-scaling. Perhaps I am misunderstanding, but we need a dB add/reduce which is the same as a multiplication. So the pre-scaling could be set up as the volume setting times the pre-scale constant -- which agains sets the output.
As far as the number of settings, it is not really necessary to provide a true "every single value" setting when moving up the volume ladder -- the least significant bits will not make a huge impression at high volume settings and would rattle like mad. It is good enough to have relatively small steps throughout the range. Thus there are (at least) three ways to work this:
1. Set up a log scale using the number of positions of say 1-3 turns and select required positions (ignore the rest)
2. Add velocity gain (dangerous for volume control)
3. Use heavy knobs so that they "keep turning" if you spin them up.
I would say 1 is the best way to go.
I am assuming that you boot at zero volume, or is that something that is configurable as a constant (boot at say -40dB) in the software code (or better still display 🙂). The other alternative is to boot at same value that it was switched off at, but I don't like that as it is dangerous, and because encoders don't offer a visual cue as to level of volume as a reguarl potentiometer unit (I always verify the volume setting on an analog pre-amp when I turn it on).
Petter
Petter,
You are a genius 😉
Somehow, I never thought of a multiplication factor instead of an offset. Brilliant. I will implement as a %
from 0 to 200%
Would that be OK.
Also, I agree with the log scale and limit to 2-3 rotations.
Dale
You are a genius 😉
Somehow, I never thought of a multiplication factor instead of an offset. Brilliant. I will implement as a %
from 0 to 200%
Would that be OK.
Also, I agree with the log scale and limit to 2-3 rotations.
Dale
Multiplication factor and add/subtract dB is the same ... but I don't think it is necssary to go farther than 33%-->300%. Somehow I feel that 0% might be a little weird 🙂
Petter
Petter
Hello,
I am sending out this email to those who expressed an interest by signing up on the wiki. We have ordered the boards for the APOX kits. All four of the boards have been ordered (IS1, IR1, APOX-1, and APOX-2). They should arrive in ~2 weeks. Now, we will start ordering components. I know that we are asking you to take a leap of faith that these will work as advertised. I had one audiophile engineer come over this weekend to try out my setup. He was very enthused by the audition. If fact, he became the first paying customer. In fact, there are now four pre-payed customers.
Hopefully, Grataku can make it over this weekend to try out the unit.
So, if you are still interested, we would greatly appreciate anyone that is willing to make payment now. If you still have questions, please feel free to email or call me at 978-772-9255 (Evenings)
Thanks,
Dale Herman
Craig Beiferman
DipChip Electronics
www.dipchipelec.com
dale@dipchipelec.com
I am sending out this email to those who expressed an interest by signing up on the wiki. We have ordered the boards for the APOX kits. All four of the boards have been ordered (IS1, IR1, APOX-1, and APOX-2). They should arrive in ~2 weeks. Now, we will start ordering components. I know that we are asking you to take a leap of faith that these will work as advertised. I had one audiophile engineer come over this weekend to try out my setup. He was very enthused by the audition. If fact, he became the first paying customer. In fact, there are now four pre-payed customers.
Hopefully, Grataku can make it over this weekend to try out the unit.
So, if you are still interested, we would greatly appreciate anyone that is willing to make payment now. If you still have questions, please feel free to email or call me at 978-772-9255 (Evenings)
Thanks,
Dale Herman
Craig Beiferman
DipChip Electronics
www.dipchipelec.com
dale@dipchipelec.com
Final layout comments for Apox-1
I am impressed with the layout, but since feedback has been requested, I am providing it with my super-critical glasses on. This feedback is not intended to be negative towards anyone, rather an attempt to add a pair of eyes. Is there still time to make some comments????
General: You can make pads smaller if you are using pro-board with plating. This should make your routing somewhat easier, particularly around relays.
J1 pin 2 is 5 V passing directly at into the board. There could be all kinds of noise there. Is it possible to add a small inductor followed by 27uF + .1uF capacitors to clean up this signal before it is allowed to enter the analog section? Maybe the capacitance should be even bigger ƒº. Also, the line becomes thicker as it snakes around the board counterclockwise. It could become thinner (and perhaps be a bit thicker at the bottom) since less and less current will pass along it¡¦s way.
UC3 pin 17 has a relay control line that is very long and very parallell to the signal line. Can it be routed further away from the signal? If not, can there be a ground wire in between.
IC1 Pin 14 ¡V I don¡¦t like the way this is threated between K8 pin 3. This could have gone south of that pin. The same goes for line IC1 pin 13. IC3 pin 17 could then go due South and traverse directly across West.
IC1 pin 10 ¡V you can cross signals at right angles.
IC2 pin 19 wire is routed strangely. Can it not go West, South directly? Also, if you swap R28 with R29 you might be able to clean up some more at pins 15,16. I would also consider if I were you to make the wires that can be wider a little wider (digital section), particularly those going to input/outputs, power etc. The ones going to the crystal for example would have relatively high inductance which could cause interference. Better with a little wider ¡K. Again, I recommend making pads slightly smaller.
C4, pleas set up dual purpose bypassing to allow for multilayer ceramic SMD device ļ
Blue line R2 to output: You could have gone somewhat right and straight down.
The digital section is very close to the analog section. I would recommend adding another 400 mils or more.
I notice the screw terminals for inputs and output. In my experience, such terminals significantly degrade the sound. Have they been placed there in order to be placeholders for other stuff?
I also started looking for ¡§solder under the component¡¨ issues, but realized that you are doing professional prints with plated holes, so there should be no problem there ƒº
Interfaces: North of R36/R11, I want adapter holes to enable stacking onto gain stages without goint the extra route around the input terminals. My brain is huring a little, but other points to tie into other gain stages such as the same horizontal position close to K1 pin 1. May I also suggest that you publish the measurements between in/out terminals (and the aforementioned ¡§direct¡¨ extra interface points) so that the rest of us can start laying out boards with these as reference points ƒº
Between R16 and R4 there is a signal layer running a square corner. This could at least be made into a two step 45deg corner.
I started looking quite hard at R32/33 in relation to output but in the end I decided it was much better than I originally realized.
Via below K5. Jusu get a T-connection. Consider putting the via at that T-point. Also, if you make the via larger, you sort of round out the sharp T-connection.
X-1 to R36, 10,1, why not use a straight line?
X-1 to K11, straight line?
X-3 to R32, straight line?
Under K11 near pin 1: Something strange going on in red? I see you are trying to cross at right angles which I applaud but you could also choose to use a jumper.
X-2 pin 3 to near R12 (blue). This line could have a lot fewer angles. Also, the via at the top could be placed higher (K11 pin 5 for example)
Ground planes:
I agree with you that ground planes on the right is a good thing. This ground should not be connected to analog ground in any way ¡V well certainly not here anyway. However you might still want to add an option with a jumper/resistor/inductor so people can do it if they want to. As for ground plane at the other side, I am not so sure that it is a good thing to have ground everywhere. Please consider how you plan to do this very carefully. Ground wires etc. are typically great to avoid cross-contamination of signal (between left and right in single ended for exampl. But we are using balanced anyway so we should be OK.
I am impressed with the layout, but since feedback has been requested, I am providing it with my super-critical glasses on. This feedback is not intended to be negative towards anyone, rather an attempt to add a pair of eyes. Is there still time to make some comments????
General: You can make pads smaller if you are using pro-board with plating. This should make your routing somewhat easier, particularly around relays.
J1 pin 2 is 5 V passing directly at into the board. There could be all kinds of noise there. Is it possible to add a small inductor followed by 27uF + .1uF capacitors to clean up this signal before it is allowed to enter the analog section? Maybe the capacitance should be even bigger ƒº. Also, the line becomes thicker as it snakes around the board counterclockwise. It could become thinner (and perhaps be a bit thicker at the bottom) since less and less current will pass along it¡¦s way.
UC3 pin 17 has a relay control line that is very long and very parallell to the signal line. Can it be routed further away from the signal? If not, can there be a ground wire in between.
IC1 Pin 14 ¡V I don¡¦t like the way this is threated between K8 pin 3. This could have gone south of that pin. The same goes for line IC1 pin 13. IC3 pin 17 could then go due South and traverse directly across West.
IC1 pin 10 ¡V you can cross signals at right angles.
IC2 pin 19 wire is routed strangely. Can it not go West, South directly? Also, if you swap R28 with R29 you might be able to clean up some more at pins 15,16. I would also consider if I were you to make the wires that can be wider a little wider (digital section), particularly those going to input/outputs, power etc. The ones going to the crystal for example would have relatively high inductance which could cause interference. Better with a little wider ¡K. Again, I recommend making pads slightly smaller.
C4, pleas set up dual purpose bypassing to allow for multilayer ceramic SMD device ļ
Blue line R2 to output: You could have gone somewhat right and straight down.
The digital section is very close to the analog section. I would recommend adding another 400 mils or more.
I notice the screw terminals for inputs and output. In my experience, such terminals significantly degrade the sound. Have they been placed there in order to be placeholders for other stuff?
I also started looking for ¡§solder under the component¡¨ issues, but realized that you are doing professional prints with plated holes, so there should be no problem there ƒº
Interfaces: North of R36/R11, I want adapter holes to enable stacking onto gain stages without goint the extra route around the input terminals. My brain is huring a little, but other points to tie into other gain stages such as the same horizontal position close to K1 pin 1. May I also suggest that you publish the measurements between in/out terminals (and the aforementioned ¡§direct¡¨ extra interface points) so that the rest of us can start laying out boards with these as reference points ƒº
Between R16 and R4 there is a signal layer running a square corner. This could at least be made into a two step 45deg corner.
I started looking quite hard at R32/33 in relation to output but in the end I decided it was much better than I originally realized.
Via below K5. Jusu get a T-connection. Consider putting the via at that T-point. Also, if you make the via larger, you sort of round out the sharp T-connection.
X-1 to R36, 10,1, why not use a straight line?
X-1 to K11, straight line?
X-3 to R32, straight line?
Under K11 near pin 1: Something strange going on in red? I see you are trying to cross at right angles which I applaud but you could also choose to use a jumper.
X-2 pin 3 to near R12 (blue). This line could have a lot fewer angles. Also, the via at the top could be placed higher (K11 pin 5 for example)
Ground planes:
I agree with you that ground planes on the right is a good thing. This ground should not be connected to analog ground in any way ¡V well certainly not here anyway. However you might still want to add an option with a jumper/resistor/inductor so people can do it if they want to. As for ground plane at the other side, I am not so sure that it is a good thing to have ground everywhere. Please consider how you plan to do this very carefully. Ground wires etc. are typically great to avoid cross-contamination of signal (between left and right in single ended for exampl. But we are using balanced anyway so we should be OK.
What are the part numbers for the Relays?
I will sleep on how many Apox-1 boards I should order.
Petter
I will sleep on how many Apox-1 boards I should order.
Petter
Software suggestion
Since the boards are now stackable, it would be great to enable a gain (multiplier again) between each board. This will greatly increase the practicalness of making small adjustments to digital crossover applications as well as home theater setups.
I realize that I am getting to be a bit of a pain to both of you and that my order(s) are starting to get a bit tall. However, Parts count is of course zero (and since you guys are such wizards with software ....)
Thanks for "not throwing rocks" at me.
Petter
Since the boards are now stackable, it would be great to enable a gain (multiplier again) between each board. This will greatly increase the practicalness of making small adjustments to digital crossover applications as well as home theater setups.
I realize that I am getting to be a bit of a pain to both of you and that my order(s) are starting to get a bit tall. However, Parts count is of course zero (and since you guys are such wizards with software ....)
Thanks for "not throwing rocks" at me.
Petter
layout
Petter,
First let me start by saying, that Dale did already send out the
APOX-1 to a boardhouse. (See the post previous to your own)
Secondly, Thanks for all of your comments.
They are certainly things to chew over. I will certainly take your ideas into account the next time I layout a board.
Please don't throw rocks at me, but due to my own personal time demands, I am not going to recall the board layout.
I also believe the board will not have audio quality problems
for the following reasons
1.) The relatively low frequencies we are dealing with
2.) The excessive audio trace widths (50 mils).
3.) There is no interaction of the +5V supply line other than crosstalk.
4.) The PIC 18F4220 microcontroller has internal oscillator which helps lower EMI.
5.) The microcontroller can be put into sleep mode for super low
power dissipation.
However, with all of the stuff we said, The real proof is in the listening test.
I will certainly build up a prototype, and Dale and I will get an independant review. Anyone is the Boston area will be allowed to come over for a listen.
If people feel that they do not like the sound, then I will certainly redo the boards before shipping them out to paying customers.
However, If anyone has Eagle Layout Software, and wants to lend a helping hand. Please let me know?
-Craig Beiferman
Petter,
First let me start by saying, that Dale did already send out the
APOX-1 to a boardhouse. (See the post previous to your own)
Secondly, Thanks for all of your comments.
They are certainly things to chew over. I will certainly take your ideas into account the next time I layout a board.
Please don't throw rocks at me, but due to my own personal time demands, I am not going to recall the board layout.
I also believe the board will not have audio quality problems
for the following reasons
1.) The relatively low frequencies we are dealing with
2.) The excessive audio trace widths (50 mils).
3.) There is no interaction of the +5V supply line other than crosstalk.
4.) The PIC 18F4220 microcontroller has internal oscillator which helps lower EMI.
5.) The microcontroller can be put into sleep mode for super low
power dissipation.
However, with all of the stuff we said, The real proof is in the listening test.
I will certainly build up a prototype, and Dale and I will get an independant review. Anyone is the Boston area will be allowed to come over for a listen.
If people feel that they do not like the sound, then I will certainly redo the boards before shipping them out to paying customers.
However, If anyone has Eagle Layout Software, and wants to lend a helping hand. Please let me know?
-Craig Beiferman
relays
Oh yeah! The relays are Coto 8L02-05-10
But I think
there are quite a few manufacturers that
fit into this footprint.
-Craig
Oh yeah! The relays are Coto 8L02-05-10
But I think
there are quite a few manufacturers thatfit into this footprint.
-Craig
Hey don't make me feel bad. I was actually composing the post while you were adding posts ... I guess it took me a LONG time to make all those supercritical comments.
I have access to Eagle and can produce double sided prototype boards (but not plated through) if this helps. I was going to ask you what software you were using since the layouts were so nice, now I know.
Petter
I have access to Eagle and can produce double sided prototype boards (but not plated through) if this helps. I was going to ask you what software you were using since the layouts were so nice, now I know.
Petter
Hi Petter,
You are technically correct on the APOX-1 version. We have prototyped the APOX-2 version (same IR1, IS1 boards) and were very happy with the results. Since we used very similar parts, and only changed the configuration, we decided to take a risk and order qty. 20 boards. We are very willing to "eat" the boards if they don't meet external expectations (indepedant evaluation).
If you would like to help layout the next run of boards, we would be happy to send you the board files.
Best Regards,
Dale
P.S. We believe that the Pickering DIL (dry or wetted) relays are a drop in replacement for the COTO DIP relays.
You are technically correct on the APOX-1 version. We have prototyped the APOX-2 version (same IR1, IS1 boards) and were very happy with the results. Since we used very similar parts, and only changed the configuration, we decided to take a risk and order qty. 20 boards. We are very willing to "eat" the boards if they don't meet external expectations (indepedant evaluation).
If you would like to help layout the next run of boards, we would be happy to send you the board files.
Best Regards,
Dale
P.S. We believe that the Pickering DIL (dry or wetted) relays are a drop in replacement for the COTO DIP relays.
I'm on board now! 😀 I ordered my parts tonight. I'm wimping out and buying a APOX-1 board (rather than the newer and more snazzy Apox-2). I like all the levels and only having a pair of resistors and a pair of relay contacts in my signal path.
I'm not building a stand-alone preamp, but rather integrating the boards into my Electrostatic Loudspeaker signal conditioning and active crossover box. It will be a two output linestage preamp and crossover now, and I can eliminate my counterpoint preamp with essentially no loss of functionality. I will have to build a phono-preamp at some point, or sell my turntable.
Sheldon
I'm not building a stand-alone preamp, but rather integrating the boards into my Electrostatic Loudspeaker signal conditioning and active crossover box. It will be a two output linestage preamp and crossover now, and I can eliminate my counterpoint preamp with essentially no loss of functionality. I will have to build a phono-preamp at some point, or sell my turntable.
Sheldon
- Status
- Not open for further replies.