Hi Petter,
That is pretty much how I answered Alex. Since, he is using single ended and has an all tube system, I recommended a single APOX-2 board for him.
Craig and I have been talking about the PGA2310 (APOX-3) board. Here were my suggestions:
1) Completely dual mono, means opto-isolating the digital control signals to avoid a common ground.
2) On board LDO regulators LT1792? for +/-15 +5V (6 total)
3) provide a headphone output (BUF634?) that is switched via a relay.
Does anyone think that we need an additional buffer. The PGA says it will drive a 600 Ohm load?
Dale
That is pretty much how I answered Alex. Since, he is using single ended and has an all tube system, I recommended a single APOX-2 board for him.
Craig and I have been talking about the PGA2310 (APOX-3) board. Here were my suggestions:
1) Completely dual mono, means opto-isolating the digital control signals to avoid a common ground.
2) On board LDO regulators LT1792? for +/-15 +5V (6 total)
3) provide a headphone output (BUF634?) that is switched via a relay.
Does anyone think that we need an additional buffer. The PGA says it will drive a 600 Ohm load?
Dale
Dale,
I'm having trouble finding the datasheet for the PGA2310. Can you post a link or source? Thanks.
I'm having trouble finding the datasheet for the PGA2310. Can you post a link or source? Thanks.
APOX-IS1 troubles!
AHHHHHHHHHHHH!
Well, we found a small problem with the APOX-IS1
(The input select board)
We swapped the sex of the input and output XLR connectors
by accident.
It seems the standard is the inputs should be female, and the outputs should be male.
This was discovered after we already ordered 40 boards!
and cannot stop theorder.
This problem will affect only users with XLR connectors!
So you/we currently have three options.
1.) Use the connectors as they are. (Just make the correct XLR cable)
2.) Mount the correct XLR connectors on the bottom of the board.
3.) Tell us we are idiots, and that you need the boards fixed,
or you are going to need a refund.
I will fix the boards in the next round of sales. And contact
all current customers. But please e-mail us if you choose option 3
-Craig Beiferman
AHHHHHHHHHHHH!
Well, we found a small problem with the APOX-IS1
(The input select board)
We swapped the sex of the input and output XLR connectors
by accident.
It seems the standard is the inputs should be female, and the outputs should be male.
This was discovered after we already ordered 40 boards!
and cannot stop theorder.
This problem will affect only users with XLR connectors!
So you/we currently have three options.
1.) Use the connectors as they are. (Just make the correct XLR cable)
2.) Mount the correct XLR connectors on the bottom of the board.
3.) Tell us we are idiots, and that you need the boards fixed,
or you are going to need a refund.
I will fix the boards in the next round of sales. And contact
all current customers. But please e-mail us if you choose option 3
-Craig Beiferman
If anyone cares about what I think, I went and checked out Dale's setup and I found a very nicely done layout that functioned as advertised whether was operated by remote or by encoder. The display actually looked better than on the picture, the encoders are good quality and give a 'beefy' solid feel when pushed and/or turned (you need to push to access adjustment features like display brigthness etc). The name of the source can be typed in using the encoder. During volume adjustment there are no pops or noises of sort. Input selection works fine too.
Harvardian mentioned the Xtalk, I don't know why since I don't believe it's caused by the Apox setup were everything is not only completely dual mono but also is physically located on separate boards.
Bottom line if you want to be able to operate your hi-end diy system from the couch, impress your friends with a truly professionally looking preamp this is the product for you. Although Dale couldn't wait to tell and spoil the surprise, I was impressed enough by it that I will be getting one myself. 😉
Eye-balling a case for it I would say everything should fit into an 11x11x4 case, that is all the APOX boards plus a BOSOZ gain stage. I plan to use a separate case for the PS.
How was that Dale? 😉
Harvardian mentioned the Xtalk, I don't know why since I don't believe it's caused by the Apox setup were everything is not only completely dual mono but also is physically located on separate boards.
Bottom line if you want to be able to operate your hi-end diy system from the couch, impress your friends with a truly professionally looking preamp this is the product for you. Although Dale couldn't wait to tell and spoil the surprise, I was impressed enough by it that I will be getting one myself. 😉
Eye-balling a case for it I would say everything should fit into an 11x11x4 case, that is all the APOX boards plus a BOSOZ gain stage. I plan to use a separate case for the PS.
How was that Dale? 😉
grataku said:
I was browsing through ML literature yesterday and I will also build it in two separate chassiss. I'll put controller with display and PS in one and boards and active stage in the other. I hope it's possible.
Peter, that's another way to do it.
Since I can't do steel boxes to shield the transformer completely I like to stick the PS box away from the low level signals. By putting the display in the PS you can't really isolate that anymore.
Since I can't do steel boxes to shield the transformer completely I like to stick the PS box away from the low level signals. By putting the display in the PS you can't really isolate that anymore.
Wrong gender XLR connectors
Reversed the gender on the XLR connectors...
Gee, Im glad Ive never done that. The really tough part is after youve used it for a few years, having a friend or colleague find out and...
Well I guess having to confess to the world on this web site may top my own embarrassing experience(s). Its very understandable when doing layouts designs and parts ordering after 1AM.
I thing that Peters suggestion for using jumpers is great, much easier if you havent built the chassis yet.
I'm trying to scrape together the funds to place my order. I just need to work out some house issues and a new timing belt.
Reversed the gender on the XLR connectors...
Gee, Im glad Ive never done that. The really tough part is after youve used it for a few years, having a friend or colleague find out and...
Well I guess having to confess to the world on this web site may top my own embarrassing experience(s). Its very understandable when doing layouts designs and parts ordering after 1AM.
I thing that Peters suggestion for using jumpers is great, much easier if you havent built the chassis yet.
I'm trying to scrape together the funds to place my order. I just need to work out some house issues and a new timing belt.
APOX-2 in 1U sized chassis
All,
I ordered the APOX-2 and IR board (I don't need the input select board, yet) and I'm trying to fit it all in a 1U sized chassis that is 8" deep (I bought it from www.par-metal.com).
I intend to remove the LCD and two control knobs from the IR board to fit on the front panel (I need to do this because the chassis is 1.75" tall), and then mount the IR board in the front of the bottom chassis very close by. The APOX-2 board will fit in the 1U chassis w/o any problem, but it's the IR board that will need some basic tweaking to fit the front panel. I also will need to use a 5V power supply that is more slim than the run-of-the-mill wall-wart supply so it can fit in this chassis.
I don't know if anyone else will be using such a chassis or find themselves in a situation where they need to remove the LCD and controls from the IR board, but when I work with Dale on the build and instructions, I'll take notes and let everyone know my experiences so it will make the job easier for those who are doing something similar to me. 😉
For now, I plan to use the APOX-2 with 10K resistors in Passive preamp mode (replacing my DACT CT2), but I also plan to add my DACT CT101 buffer preamp (www.dact.com) into this chassis.
Maybe Dale and Craig can add SW that will allow me to remotely switch between "active" and "passive" preamp mode? 🙄
Just kidding, for now I'm very happy with all your hard work and I think it will work out very well in my application.
Denon 2800 DVD/CD player --> APOX-2 --> AKSA 55 --> 😎
-Vinnie
All,
I ordered the APOX-2 and IR board (I don't need the input select board, yet) and I'm trying to fit it all in a 1U sized chassis that is 8" deep (I bought it from www.par-metal.com).
I intend to remove the LCD and two control knobs from the IR board to fit on the front panel (I need to do this because the chassis is 1.75" tall), and then mount the IR board in the front of the bottom chassis very close by. The APOX-2 board will fit in the 1U chassis w/o any problem, but it's the IR board that will need some basic tweaking to fit the front panel. I also will need to use a 5V power supply that is more slim than the run-of-the-mill wall-wart supply so it can fit in this chassis.
I don't know if anyone else will be using such a chassis or find themselves in a situation where they need to remove the LCD and controls from the IR board, but when I work with Dale on the build and instructions, I'll take notes and let everyone know my experiences so it will make the job easier for those who are doing something similar to me. 😉
For now, I plan to use the APOX-2 with 10K resistors in Passive preamp mode (replacing my DACT CT2), but I also plan to add my DACT CT101 buffer preamp (www.dact.com) into this chassis.
Maybe Dale and Craig can add SW that will allow me to remotely switch between "active" and "passive" preamp mode? 🙄
Just kidding, for now I'm very happy with all your hard work and I think it will work out very well in my application.
Denon 2800 DVD/CD player --> APOX-2 --> AKSA 55 --> 😎
-Vinnie
That may be the standard, but isn't that backwards? I was taught that a cable with signal on it should have male connectors on the out of the source component, and thus when there is no cable, the source output can't easily be shorted out.
With the cable plugged in, the live end of the bable also has a female connector (no exposed pins). Thus it's also hard to short out the source.
It appears that audio pre-amps don't work that way. But you've got your pre-amp boards set up that way.
Sheldon
With the cable plugged in, the live end of the bable also has a female connector (no exposed pins). Thus it's also hard to short out the source.
It appears that audio pre-amps don't work that way. But you've got your pre-amp boards set up that way.
Sheldon
grataku said:
I picked up one of these displays for myself, and I like it more than any other displays, even my vfd. It is beautiful. The only feature that I like better in the vfds is the ability to use larger fonts, but for 1/5 the price, I can deal with this limitation. I am really suprised how the side lit backlight is so evenly lit.
It does look better then the pictures, and has a nice front panel, unlike other displays, allowing a larger cutout on the front of the case.
--
Brian
stokessd said:
It is true for power cords, but for amps and preamps it's actually better if you can't short or touch the input pins, especially in professional gear, when nobody puts much attention when handling those things and nobody wants a big thump in the speakers😉
XLRs are also made in a way that a ground pin gets in contact first.
Chassis mount versus PCB mount connectors
I don't see this latest issue as a big deal at all. DIY'ers don't mind spending the extra time to wire up the inputs. If one goes into volume production, now that is a different kettle of fish.
The practical upshot of all this is that people don't have to work so hard to get exact lineup of connectors to PCB which will be very hard unless you are Peter Daniel. Furthermore, I believe chassis mount connectors are much stronger anyway and i routinely swap out PCB mount units with chassis mount units on existing equipment.
I say don't worry. If this is the only problem you have had with layout, you are doing REALLY WELL!
Petter
I don't see this latest issue as a big deal at all. DIY'ers don't mind spending the extra time to wire up the inputs. If one goes into volume production, now that is a different kettle of fish.
The practical upshot of all this is that people don't have to work so hard to get exact lineup of connectors to PCB which will be very hard unless you are Peter Daniel. Furthermore, I believe chassis mount connectors are much stronger anyway and i routinely swap out PCB mount units with chassis mount units on existing equipment.
I say don't worry. If this is the only problem you have had with layout, you are doing REALLY WELL!
Petter
APOX-1 C++ program available
Hi guys,
I've been struggling with the choice of the
<h2>APOX-1 resistors </h2>
for a while now. And I think I finally came to a conclusion.
The full 1020 volume settings would really not buy you much, because some settings are extremely close together.
I also found that I could not calculate the dB using the microcontroller because of the limited code space. (only 1.5K)
However, I wrote a C++ program
available here
which does the following:
It calculates every possible attenuation, based on the resistors values.
It then finds the minimum and the maximum attenuation.
I then choose 255 evenly spaced attenuations based on the min and max.
I then do a search through all of the available settings and store the binary relay settings for the pass and the shunt.
I then write these values out to a file, in a C header file format.
I found that the 255 settings looks really nice. because their are fewer settings at the low end of the volume. The linear line gets a little steppy at very high volumes. But I think the step sizes are still small enough that you won't notice it.
I then calculated resistors for a 5K, 10K, 20K and 50K minimum impedance. (I then picked real resistors that I can actually buy)
Then using the C++ program again, I input all of the actual resistor values. I then calculated the lookup table for the 10K
resistor chain. I then used this same lookup table to see how well my other resistor chains would work. They tracked almost perfectly. (see the attached data in the link above.)
See inside the C++ program for the final resistor values.
I'll update the excel spreadsheet tommorow.
Did I just confuse everyone? 😕
-Craig
Hi guys,
I've been struggling with the choice of the
<h2>APOX-1 resistors </h2>
for a while now. And I think I finally came to a conclusion.
The full 1020 volume settings would really not buy you much, because some settings are extremely close together.
I also found that I could not calculate the dB using the microcontroller because of the limited code space. (only 1.5K)
However, I wrote a C++ program
available here
which does the following:
It calculates every possible attenuation, based on the resistors values.
It then finds the minimum and the maximum attenuation.
I then choose 255 evenly spaced attenuations based on the min and max.
I then do a search through all of the available settings and store the binary relay settings for the pass and the shunt.
I then write these values out to a file, in a C header file format.
I found that the 255 settings looks really nice. because their are fewer settings at the low end of the volume. The linear line gets a little steppy at very high volumes. But I think the step sizes are still small enough that you won't notice it.
I then calculated resistors for a 5K, 10K, 20K and 50K minimum impedance. (I then picked real resistors that I can actually buy)
Then using the C++ program again, I input all of the actual resistor values. I then calculated the lookup table for the 10K
resistor chain. I then used this same lookup table to see how well my other resistor chains would work. They tracked almost perfectly. (see the attached data in the link above.)
See inside the C++ program for the final resistor values.
I'll update the excel spreadsheet tommorow.
Did I just confuse everyone? 😕
-Craig
Hi Philo,
That is only 14 resistors per channel!!!!
The beauty of the design (Thanks to Petter and all who greatly contributed) is that there are several series and several shunt resistors that can be switched in.
Nice straight dB curve and pretty even spacing.
That is only 14 resistors per channel!!!!
The beauty of the design (Thanks to Petter and all who greatly contributed) is that there are several series and several shunt resistors that can be switched in.
Nice straight dB curve and pretty even spacing.
Craig, Dale,
This is brilliant work. Paul Kaplan and I went through this, Paul did the maths (I'm almost innumerate!) and we came to the same conclusion; it really had to be done with both series and shunt elements to minimize resistor numbers while maximising tiny, even intervals between settings.
You have taken it the next step, helped along by a the horrendous number crunching of a clever C++ program on a PC, and delivered a wonderful result.
Once again, I'm open-mouthed in admiration. I know how hard this stuff is; it takes a lot of patience, and a very flexible mind.
I doubt anything in the consumer world would match this APOX of yours. How many relays are you using?
Cheers,
Hugh
This is brilliant work. Paul Kaplan and I went through this, Paul did the maths (I'm almost innumerate!) and we came to the same conclusion; it really had to be done with both series and shunt elements to minimize resistor numbers while maximising tiny, even intervals between settings.
You have taken it the next step, helped along by a the horrendous number crunching of a clever C++ program on a PC, and delivered a wonderful result.
Once again, I'm open-mouthed in admiration. I know how hard this stuff is; it takes a lot of patience, and a very flexible mind.
I doubt anything in the consumer world would match this APOX of yours. How many relays are you using?
Cheers,
Hugh
Dale, yeah, I was just clowning around. I have been following this thread pretty closely and checking your web site regularly. I am very psyched about your designs, both the Apox-1 and 3. I am a closet integrated amp fan and I think your boards will be part of my path to a nice Sim Audio or Mark Levinson style integrated here in the future.
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