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A mini PPA v2,my first portable attempt. - Page 4

post #46 of 103
Quote:
Originally Posted by H22 View Post

No on-board DAC.........yet....evil_smiley.gif

I'm not sure I would be able to devote enough time to putting together complete or even partial kits, not that it is out of the question, but that takes a lot of effort to do properly, and i would hate to disappoint anyone.

Most of the components are available at mouser, even the case. I have built a BOM that will help getting the parts from them.

Off the top of my head, the parts that will need to be sourced from other vendors are:

Op-amps(mouser doesn't carry a lot of the poplar ones) and SMD caps
Digikey or Newark

Battery (3 cells and PCB)
All-battery.com



So it shouldn't be too hard to get everything that is needed.

joe

Ah ha!

That sounds good to me. Digikey has lotta parts and ships to canada very fast smily_headphones1.gif Can't wait to see the finalized pcb! Everytime i see the picture, its just awesome. I have never seen an amp that is as packed as this one ^_^
post #47 of 103

Joe, i tried the ebay case already and while they are very good casing, the dimension is just not a good pair with either ipod or other portable players.

 

if it were me, i would stick to the hammond case :D

 

looking good Joe.. keep it going!

post #48 of 103
Thread Starter 

Here is a pic of it with a Pimeta board for scale

 

 

and, speaking of iphones, here are a couple with my old iphone 4.

 

post #49 of 103
Thread Starter 

AppleMark

 

AppleMark

couple more pics, I drilled out one of the plastic caps for a faceplate, not the most elegant but it does have a mad max look to it.

 

I have ordered yet another set of parts from digikey, mouser,newark and all battery. In this round of parts ordering I ordered some board hardware that will hopefully facilitate removable op amp module(s), a few more op amps, 827's and 1611's and a few different batteries to try.

 

I want to assemble my last board set with the opa827's, a few people have suggested those so I would like to give them a try.

I am not sold quite yet on the 1641 chip, there is a lot I like about it, it is a lively sounding op amp, but there are some things i hear with it that stand out a bit too much.

 

I found a new Li-po cell to try and ordered some, these will hopefully fit the current board design and allow ~25% more run time. I also ordered 4 14500 (AA sized) li-po cells to use with the OPA627/37 amp I have already built. These should fit in a 20mm longer Hammond case, allowing 14.8 nominal voltage and hopefully with a little work I can make a stable amp.

 

Once this parts order comes in, I will verify some measurements i will order the new boards. Please PM me if you want a board.

post #50 of 103
Quote:
Originally Posted by H22 View Post

AppleMark

 

AppleMark

couple more pics, I drilled out one of the plastic caps for a faceplate, not the most elegant but it does have a mad max look to it.

 

I have ordered yet another set of parts from digikey, mouser,newark and all battery. In this round of parts ordering I ordered some board hardware that will hopefully facilitate removable op amp module(s), a few more op amps, 827's and 1611's and a few different batteries to try.

 

I want to assemble my last board set with the opa827's, a few people have suggested those so I would like to give them a try.

I am not sold quite yet on the 1641 chip, there is a lot I like about it, it is a lively sounding op amp, but there are some things i hear with it that stand out a bit too much.

 

I found a new Li-po cell to try and ordered some, these will hopefully fit the current board design and allow ~25% more run time. I also ordered 4 14500 (AA sized) li-po cells to use with the OPA627/37 amp I have already built. These should fit in a 20mm longer Hammond case, allowing 14.8 nominal voltage and hopefully with a little work I can make a stable amp.

 

Once this parts order comes in, I will verify some measurements i will order the new boards. Please PM me if you want a board.

PM Sent!

 

Also regarding batteries.

 

I am wondering if it has a lipo cut off circuit? I know when voltage of lipo battery goes under certain value, it will not recover...

 

By the way, it looks great :)

post #51 of 103

PM sent...

post #52 of 103
Thread Starter 
Quote:

Also regarding batteries.

 

I am wondering if it has a lipo cut off circuit? I know when voltage of lipo battery goes under certain value, it will not recover...

 

By the way, it looks great :)

 

Yes, there is a battery management PCB,

 

http://www.all-battery.com/pcb-11-1V-13A-32051.aspx

 

This is one of several that will work.

 

Joe

post #53 of 103
Thread Starter 

I have gotten several requests for a GB (Group Buy) for the PCB's, I think this is awesome darthsmile.gif.

 

However, I want to make it clear to anyone and everyone interested in this, that this project is still early in its development stage. Yes, the PPAv2 is a tried and true amp design, but this implementation of it is a fairly radical departure from the original. There is exactly 1 amp that has been built and is working, the first try (with opa627/37s) is sitting on my desk at work awaiting parts and a new power supply to hopefully cure oscillation issues.

 

All that said, I think it is good enough to send out some boards for others to play with and tweak L3000.gif.

A few people have asked for large quantities of boards (4+), I am willing o do this, but I think it might be a better idea to limit the boards to 1 or 2 per user, this way, hopefully, we can get several people building the boards and Beta testing them, any small issues with the layout or overall board design can be ironed out. Also I am hoping that there will be a lot of feedback on improvements or changes that can be made to the board. All this can be taken into account for the subsequent run of boards.

 

I will probably start a new thread dedicated specifically to the GB and BOM. In that thread I will start a list of all those interested and how many boards they want.

 

Should be soon, hopefully early next week i will have a third amp put together with a different set of op-amps. And if the DIY gods are kind i will have the 627/37 version working triportsad.gif.

 

Once that is done, and I have double and triple checked the new layout and component sizes etc, i will order a new run of PCB's. Takes about a week to get them made.

 

I am not sure on pricing yet, but board sets will probably be around $25 each. As i said, this will depend on how many boards I order and what options I choose for having them made.

post #54 of 103

Let me first just say this is incredible. I never would of thought it would be possible to cram a desktop amp (especially one like a PPAv2) in to a portable enclosure. 

 

As for your power caps, Panasonic FM's (improved version of the FC) are often used as power caps, as they perform well and have very low ESR. Also, as far as capacitors go, power caps makes the least difference in sq, so there may not be any discernable difference between ELNA's the the FM's. Assuming that you are using 16v caps, a 470uf Panasonic FM is the same size as the 100uF ELNA's, and so you could get away with only 4 caps, leaving LOTS of space.

 

Obviously a larger battery is priority, but that kind of space leaves you a lot of freedom, like a gain switch, or if you're feeling really ambitious, you could try to cram in a linkwitz crossfeed circuit atsmile.gif

 

 

But really, this is already outstanding. Props to you!

post #55 of 103
Thread Starter 
Quote:

Let me first just say this is incredible. I never would of thought it would be possible to cram a desktop amp (especially one like a PPAv2) in to a portable enclosure. 

 

As for your power caps, Panasonic FM's (improved version of the FC) are often used as power caps, as they perform well and have very low ESR. Also, as far as capacitors go, power caps makes the least difference in sq, so there may not be any discern-able difference between ELNA's the the FM's. Assuming that you are using 16v caps, a 470uf Panasonic FM is the same size as the 100uF ELNA's, and so you could get away with only 4 caps, leaving LOTS of space.

 

Obviously a larger battery is priority, but that kind of space leaves you a lot of freedom, like a gain switch, or if you're feeling really ambitious, you could try to cram in a linkwitz cross feed circuit atsmile.gif

 

 

But really, this is already outstanding. Props to you!

Thanks for the kind words and advice. I tend to agree about the caps.

 

I have been fighting the flu for the last few days, so i haven't been able to make much progress on this lately.

We also started a new project at work, so that has cut into my "real" work a bit...angry_face.gif.

 

However, I did get my shipment from mouser, so hopefully I will have another amp built this week. As I stated before I want to try the 827 op amps in this one.

I also received some more cells to play with from all-battery, good news and bad news there. I found some sanyo prismatic cells, 1150ma that would be a much better fit with the current board design. They are the same width, 5mm shorter in length and slightly thicker. according to the spec sheet, 3 of them stacked would just fit in the case, and the extra 5mm on the end would leave plenty of room for the battery PCB. As a bonus they are also much cheaper than any of the other cells I am trying. Unfortunately they don't fit, just slightly too tall frown.gif. It may be possible to machine the enclosure to allow them to fit, I will explore that as time permits.

The good news is that the larger 1250ma cell will fit with the new board layout, and if I use the FM caps there should be plenty of space to work with. Board layout with this design is not quite as sexy, as the main power caps are moved away from the output transistors a bit, but i highly doubt that it will adversely effect the amp as there are very generous internal power plains.

 

The Harwin pins and sockets I got from  mouser look like they may do the trick for allowing the op amp board(s) to be removablebiggrin.gif. The sockets are gold plated and very low profile and fit in a 1mm hole , the pins are .5mm,  tin and will need to be bent 90 degrees and trimmed slightly, but should work. They also have pins that are gold plated, but mouser doesn't stock them. The drawbacks to doing this are the cost of the parts, the pins and sockets are not terribly expensive, but there are a lot of them so it adds ~$8 to the BOM. It also requires two different sized holes for the op amp mounting, this would only be an issue if one elected not to use the hardware. Instead of using a standard .025" right angle break away header (as i am using right now), one would probably need to use individual component leads that were snipped off the caps, and solder them in 1 at a time. This doesn't sound like a big deal but I have done it, it can be a pain.

 

As for adding extra circuitry (variable gain and cross feed etc), a Cross feed circuit could be possible, i will explore that. A gain switch would  be very difficult given the op amp boards layout. It might be possible to add two very small switches to it, but that would really be pushing things. The front panel is very tight right now, that is also a problem.

 

I don't want to get any ones hopes up, but i am also in the very early stages of designing a digital POT system that would allow control of not only the volume, but the gain and BB from a single encoder. It would use an AD5206 digital POT (or similar), this is a single chip with 6 addressable 256 position pots. I have a chip to play with and am working on the code to control it, I have also started on a circuit board that should still fit with the current board design scheme and case. But this is still very early. I am excited about it, but there is a long way to go. I may also try to get rid of the other 6 manual pots used to set the op amp and buffer bias as well and use digital POTs there as well, that way bias settings could be set, and measured, without having to open the case, or even require a volt meter.

post #56 of 103
Quote:
Originally Posted by H22 View Post

Thanks for the kind words and advice. I tend to agree about the caps.

 

I have been fighting the flu for the last few days, so i haven't been able to make much progress on this lately.

We also started a new project at work, so that has cut into my "real" work a bit...angry_face.gif.

 

However, I did get my shipment from mouser, so hopefully I will have another amp built this week. As I stated before I want to try the 827 op amps in this one.

I also received some more cells to play with from all-battery, good news and bad news there. I found some sanyo prismatic cells, 1150ma that would be a much better fit with the current board design. They are the same width, 5mm shorter in length and slightly thicker. according to the spec sheet, 3 of them stacked would just fit in the case, and the extra 5mm on the end would leave plenty of room for the battery PCB. As a bonus they are also much cheaper than any of the other cells I am trying. Unfortunately they don't fit, just slightly too tall frown.gif. It may be possible to machine the enclosure to allow them to fit, I will explore that as time permits.

The good news is that the larger 1250ma cell will fit with the new board layout, and if I use the FM caps there should be plenty of space to work with. Board layout with this design is not quite as sexy, as the main power caps are moved away from the output transistors a bit, but i highly doubt that it will adversely effect the amp as there are very generous internal power plains.

 

The Harwin pins and sockets I got from  mouser look like they may do the trick for allowing the op amp board(s) to be removablebiggrin.gif. The sockets are gold plated and very low profile and fit in a 1mm hole , the pins are .5mm,  tin and will need to be bent 90 degrees and trimmed slightly, but should work. They also have pins that are gold plated, but mouser doesn't stock them. The drawbacks to doing this are the cost of the parts, the pins and sockets are not terribly expensive, but there are a lot of them so it adds ~$8 to the BOM. It also requires two different sized holes for the op amp mounting, this would only be an issue if one elected not to use the hardware. Instead of using a standard .025" right angle break away header (as i am using right now), one would probably need to use individual component leads that were snipped off the caps, and solder them in 1 at a time. This doesn't sound like a big deal but I have done it, it can be a pain.

 

As for adding extra circuitry (variable gain and cross feed etc), a Cross feed circuit could be possible, i will explore that. A gain switch would  be very difficult given the op amp boards layout. It might be possible to add two very small switches to it, but that would really be pushing things. The front panel is very tight right now, that is also a problem.

 

I don't want to get any ones hopes up, but i am also in the very early stages of designing a digital POT system that would allow control of not only the volume, but the gain and BB from a single encoder. It would use an AD5206 digital POT (or similar), this is a single chip with 6 addressable 256 position pots. I have a chip to play with and am working on the code to control it, I have also started on a circuit board that should still fit with the current board design scheme and case. But this is still very early. I am excited about it, but there is a long way to go. I may also try to get rid of the other 6 manual pots used to set the op amp and buffer bias as well and use digital POTs there as well, that way bias settings could be set, and measured, without having to open the case, or even require a volt meter.

Wow... Things are getting more awesome...

 

I wish I could somehow help you design... eventhough I am a recent EE grad...I don't have any experience triportsad.gif

 

What I realized is I am learning new stuff in this thread everytime I read.

 

Thank you for that!

post #57 of 103
Thread Starter 

AppleMark

3rd amp is coming together, both daughter boards assebled. darthsmile.gif

post #58 of 103
Nice.

Are those OPA827s?
post #59 of 103
Thread Starter 
Yes, those are 827s, my camera has a macro mode that I am using, but it's hard to really get good detail, the pics I am posting are are about as good as I can seem to get.
post #60 of 103
Thread Starter 

Couple more pics i think are neat. They show how much room the caps actually take. Outside of the output resistors, input/output connectors and POT, all the extra room on this board is reserved for caps.

 

Pretty sure If I build a board designed just for panasonic FM caps, and revise the op-amp power supply section, I could probably shrink the board down another 40% or so.....

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