Hello,
I have posted a proposed board based on the National LM4702 chip here that I will be ordering several prototypes of in the near future. If anyone is interested, I will be more than happy to get some extras with my order. Since this amp is still in the "new design" category, I have tried to make the board as flexable as possible to allow for a variety of components. I am sure this will not be the ultimate LM4702 circuit, but since I will be ordering parts anyway, I figured if anybody wanted to come along I would be happy to facilitate it!
I am not sure where I will be ordering from, but I know I can get boards from Olimex for ~$10 per board. Obviously Olimex doesn't put out the greatest parts in the world, but the price is definitely right for small quantities. If we get enough parts, I would love to go with Advanced Circuits or another higher quality manufacturer, but my first priority is obviously to get the boards made!
If you are interested, drop me an e-mail at dfdye at netscape dot net or click on the button at the end of this post! (or just post here and I will put you on the list)
Attached is the proposed board design, but if you are interested and would like to see something else, let me know and I will see what I can do!
Thanks!
David
I have posted a proposed board based on the National LM4702 chip here that I will be ordering several prototypes of in the near future. If anyone is interested, I will be more than happy to get some extras with my order. Since this amp is still in the "new design" category, I have tried to make the board as flexable as possible to allow for a variety of components. I am sure this will not be the ultimate LM4702 circuit, but since I will be ordering parts anyway, I figured if anybody wanted to come along I would be happy to facilitate it!
I am not sure where I will be ordering from, but I know I can get boards from Olimex for ~$10 per board. Obviously Olimex doesn't put out the greatest parts in the world, but the price is definitely right for small quantities. If we get enough parts, I would love to go with Advanced Circuits or another higher quality manufacturer, but my first priority is obviously to get the boards made!
If you are interested, drop me an e-mail at dfdye at netscape dot net or click on the button at the end of this post! (or just post here and I will put you on the list)
Attached is the proposed board design, but if you are interested and would like to see something else, let me know and I will see what I can do!
Thanks!
David
Attachments
There are about 5 different output stages that people are using. The simplest is the version Russ White is using based on SAP-16's. I am playing around with some non-thermally compensated darlingstons as per the app sheet as well as some non-darlington descrete transistor options.
Though I have not finished my output stage, I have, gotten to the point where I wanted some different input stage options than what I was working with, so I figured I would make this available if anyone wanted in. Since I know a bunch of people are interested in this relatively new chip I figured I would see if anyone wanted a flexable test board for working on new designs.
I am sure as more people start tinkering with this design, there will be more output stage options available, but as of now I have not implemented a board, rather just p2p options. If you have a specific output stage implementation that you would want a board for, let me know and I will be happy to see what I can do.
As for the schematic, I am working off of the typical application circuit on page 2 of the datasheet. The modifications are the addition of additional bypass caps, addition of a parallel film cap option for the electrolytic coupling caps, and a separation of the power supply ground from signal grounds via "RG." All other part names should be the same as the data sheet to simplify things.
Though I have not finished my output stage, I have, gotten to the point where I wanted some different input stage options than what I was working with, so I figured I would make this available if anyone wanted in. Since I know a bunch of people are interested in this relatively new chip I figured I would see if anyone wanted a flexable test board for working on new designs.
I am sure as more people start tinkering with this design, there will be more output stage options available, but as of now I have not implemented a board, rather just p2p options. If you have a specific output stage implementation that you would want a board for, let me know and I will be happy to see what I can do.
As for the schematic, I am working off of the typical application circuit on page 2 of the datasheet. The modifications are the addition of additional bypass caps, addition of a parallel film cap option for the electrolytic coupling caps, and a separation of the power supply ground from signal grounds via "RG." All other part names should be the same as the data sheet to simplify things.
No problem! If you aren't comfortable with playing around, then I would definitely suggest you wait a while to let a good output stage emerge. I am sure that there will be a round of boards with output stages ordered in the future when some people get output circuits they are happy with.PierreG said:
PS I have your boards down, Vinnie.
Boards
I am in the same situation as pierre G in that i don't have the experience to play around with outputs. Not to mention the exchange rate. I would really like to give this a go, but maybe i should wait until you deside to go with a final board...It's so good to see this project moving ahead, Ive been watching this from the begining and have finally got the 702s from national.
But if you need some more boards sold to get this underway then i would definately buy 2.
Brett
I am in the same situation as pierre G in that i don't have the experience to play around with outputs. Not to mention the exchange rate. I would really like to give this a go, but maybe i should wait until you deside to go with a final board...It's so good to see this project moving ahead, Ive been watching this from the begining and have finally got the 702s from national.
But if you need some more boards sold to get this underway then i would definately buy 2.
Brett
I'll put you down for a tentative 2.
Also, I checked Advanced Circuits online quote calculator, and their demo boards should be on par with Olimex if we can get ~20 boards (and yes, they are full spec). So far we are pretty close, so I am betting we will be able to get there and go with the nicer boards.
David
PS When the output stage is ready, I am pretty sure one of the final options will involve a point to point strategy with TO-3 transistors. I will definitely post what I end up doing, so if you want to get the boards now and implement a final output stage absent a BCB, it will be quite easy!
Also, I checked Advanced Circuits online quote calculator, and their demo boards should be on par with Olimex if we can get ~20 boards (and yes, they are full spec). So far we are pretty close, so I am betting we will be able to get there and go with the nicer boards.
David
PS When the output stage is ready, I am pretty sure one of the final options will involve a point to point strategy with TO-3 transistors. I will definitely post what I end up doing, so if you want to get the boards now and implement a final output stage absent a BCB, it will be quite easy!
As of now, we have interest in ~20 boards. Though I would have liked to have had more interest to get the prices lower, we still should be able to have a reasonable price on an order. I will start getting quotes together tomorrow, so if any last minute interest is out there, let me know soon or it may be too late!
As soon as I know prices, I will send out confirmation e-mails with payment details, but it should be soon!
David
As soon as I know prices, I will send out confirmation e-mails with payment details, but it should be soon!
David
Not anything firm yet, but I will post it when I find out. The preliminary numbers I have from Advanced Circuits is (approx.) $11 per board for 20 (which is where we are now), $8 per for 30, and $5 per for 50.
I was trying to get to ~$10 per board for a small run, and with what we have now we can just about do that. If they have a special this month, we could get lucky and get it a little cheaper, but these are the preliminary prices.
Hope this helps!
David
I was trying to get to ~$10 per board for a small run, and with what we have now we can just about do that. If they have a special this month, we could get lucky and get it a little cheaper, but these are the preliminary prices.
Hope this helps!
David
Quotes are coming in now. I will have a final price sometime tonight or tomorrow! Getting close.
David
Edit: That was fast! I just got a quote in from Advanced Circuits, and the current price is $8/board. If we wrangle up 10 more boards before I submit the order, the price will drop to $6.50/board. I will send out confirmation e-mails shortly, and when I get shipping information back from you, I will send along a final price (I will drop the price on the final invoice if I get enough additional interest.)
Also, I am planning on ordering several extras above what I additionally wanted in order to drop the price to $8, so if there is some interest after the buy, I will probably still have a few boards if someone is interested.
David
Edit: That was fast! I just got a quote in from Advanced Circuits, and the current price is $8/board. If we wrangle up 10 more boards before I submit the order, the price will drop to $6.50/board. I will send out confirmation e-mails shortly, and when I get shipping information back from you, I will send along a final price (I will drop the price on the final invoice if I get enough additional interest.)
Also, I am planning on ordering several extras above what I additionally wanted in order to drop the price to $8, so if there is some interest after the buy, I will probably still have a few boards if someone is interested.
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