| nobody special |
I was thinking about making a kit for the BPA-200 design. For those who aren't familiar, it uses the National LM3886 power amplifier IC's in a bridged-paralleled configuration to produce 200 watts into 8 ohms. The plan is to make a very high quality double sided PC board, and to include a suitable heatsink and all components with the kit. You would have to supply the power supply and a suitable case and hardware. I will most likely modify the circuit to include balanced or single-ended inputs, and possibly other opamps for the input buffer/s or servos.
At this point, this is only conceptual. I'm just trying to get a feel as to how many people would be interested in such a kit. Please offer any suggestions or criticism, as this will help me decide if it's worth doing, and how to implement it if it is.
Thanks,
Steve |
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| avenger |
| Hi sure, that would be great. Can you share with us your findings if any in regard to this topology since in my oppinion looks like this issue of bridging/paralleling configuration is like black magic....some get it to work great while others seem to get inconsistent results. Will it be with the servos or very basic (which seems to work good for some)? Please let us know. I believe you will get a great response to this project, and me in particular, I will be very interested in the PCB only option. Please keep us posted. |
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| nobody special |
Thanks for the replies...
Yes, I understand that there are other implementations available for this amplifier.
I will be experimenting with different configurations and doing extensive prototyping before designing the pcb for the project. I tend to like the most simple implementation possible, but as you said there are some stability issues with this topology. It will most likely have the servos. The idea is to make the design as easy to build as possible, so that anyone who can solder can assemble it. This will mean complete and detailed instructions, parts lists, suggested power supply, etc. |
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| peranders |
| I think Thomas Madsen has succeeded quite well in in doing a simple 200 W amp. Can it be much simplier? OK, you can remove the DC-servos and the balanced option, but besides that? One thing maybe, using standing LM3886TF. |
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| nobody special |
| quote: | Originally posted by peranders
I think Thomas Madsen has succeeded quite well in in doing a simple 200 W amp. Can it be much simplier? OK, you can remove the DC-servos and the balanced option, but besides that? One thing maybe, using standing LM3886TF. |
Yes, I understand that Thomas has a nice kit available.
My circuit and implementation will be different.
Also, as I am in the US, it will be easier for Canadians and people from the US to buy (no overseas shipping). |
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| punchpeanut |
| I for one would like a PCB. |
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| nobody special |
| I am going to go ahead with this. I hope to have it ready early next year (jan, feb. 2004). Thanks for the replies. |
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| peranders |
If you want, please keep us informed about your progress. I'll guess that you already have seen my Ultra universal Gainclone. Feel free to steal anything from me.
BTW: I'm amazed that Fred hasn't complained yet about your "commercial" movements. |
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| nobody special |
| Thanks for the offer. Sorry if I posted this in the wrong place. Maybe it's not a DIYaudio crime until I actually have something for sale? |
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| saletel |
| id be interested, as most people who make pcbs arent in the states. would this be all parts included? or just pcbs and a part list? |
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| theChris |
IMO, i think you should do lm4870s. they will probalby be better at paralleling as the amplifer are on the same die. this could eliminate the need for servos.
i too am thinking of build some small boards for DIY stuff, i'd likely post the relevent info in the trading section though. |
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| Dxvideo |
I have some questions;
1- What if I remove the servo circuits (op-amps)? In the app notes they say "it reduces offset voltage".. If there are output voltage differences between power op-amps what happens? They get warmer?
2-In the same app notes the power output table; for 4 ohms the BPA200 can drive 450W "Burst Clipping Power". What does is mean? Can we say it is RMS value or PMPO? So we can really get 450Watts / 4ohm?
3-In the reference BPA200 design, they use %0.1 tolerence metal film resistors. I cannot find that resistors. Can I use %1 resistors instead of them? What happens if? And for the serial 0.1ohm resistors I can find only wired resistors and they have %5 tolerence. Can I use they?
Thanx... |
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| nobody special |
| quote: | Originally posted by saletel
id be interested, as most people who make pcbs arent in the states. would this be all parts included? or just pcbs and a part list? |
I am considering offering it 2 ways:
1- PCB with 3886's and heat sink adapter only.
2- PCB with all components supplied.
I don't have the biggest budget to work with, so it will most likely be option 1, with a parts list and possible vendors (for those in the US and Canada) for the other components. If there are any components that are hard to find, they may also be included.
Moderators:
Since everyone seems so concerned that I posted this here, I have no problem with it being moved to the appropriate forum. It wasn't my intention to break the rules.
Thanks.
Steve |
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| tschrama |
I agree ... go for the LM4780.......can be made even smaller (= cheaper PCB)..
Goodluck,
Thijs |
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| peranders |
| quote: | Originally posted by Dxvideo
I have some questions;
1- What if I remove the servo circuits (op-amps)? In the app notes they say "it reduces offset voltage".. If there are output voltage differences between power op-amps what happens? They get warmer?
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Yes.
| quote: | Originally posted by Dxvideo
2-In the same app notes the power output table; for 4 ohms the BPA200 can drive 450W "Burst Clipping Power". What does is mean? Can we say it is RMS value or PMPO? So we can really get 450Watts / 4ohm? |
I have also some trouble to figure out the _real_ max output power but I suspect this means power a few seconds until the chip is hot.
| quote: | Originally posted by Dxvideo
3-In the reference BPA200 design, they use %0.1 tolerence metal film resistors. I cannot find that resistors. Can I use %1 resistors instead of them? What happens if? And for the serial 0.1ohm resistors I can find only wired resistors and they have %5 tolerence. Can I use they? |
You can use 1% which you match. Normal 1% is usually around 0.3% according to my experience.
For the other resistors I think 5% will do. |
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| peranders |
| quote: | Originally posted by nobody special
I don't have the biggest budget to work with, so it will most likely be option 1, with a parts list and possible vendors (for those in the US and Canada) for the other components. If there are any components that are hard to find, they may also be included.
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The only part you can consider (if you want to earn money) is the LM3886 but you have to buy at least 100 if you want to get a good price so you can earn something. Dealing with resistors :whazzat: takes only time, no money involved. |
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| peranders |
| Thomas Madsen, have you tried to squeeze out max power? Anyone else? |
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| nobody special |
Thanks for the direction, everyone. I will look into the LM4780. Is this a new product? The only thing that would bother me about a single die is getting the heat out of it.
I believe that the burst clipping power is just that- a very brief "burst" (mS long) that shows the dynamic power of the amp. I think the difference is that it is power output that is possible before the supply sags from the current draw.
I plan on doing a few nice updates to the circuit. These will probably include better opamps for the buffers, true balanced or unbalanced inputs, and the option of using the board as a stereo unit with 4 devices per output, or as a mono unit with up to 8 output devices. Also to be included is a pre-machined heat sink adapter which will be thick enough to have very good heat transfer to the sink, and the devices will be mounted standing up, not laying down on the board.
I am thinking of using all output devices in the inverting mode only, and burr-brown opamps as input buffers/inverters. Any other suggestions would be great! Let me know what you want! |
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| tlmadsen |
I am rather ”surprised” to see that from some of the replies to this tread it seems like US/Canadian DIY’er prefer to buy “local” PCB’s.
This is almost to imply that only US/Canadian PCB’er are any good. I almost feel offended.........not really
Shipping PCB around the world is very easy, since they can go in an normal envelope are not to heavy and don’t cost much to send. The only problem for US/candians to buy “overseas” could be the payment, but even that is normally easy to solve.
To Dxvideo
1. You MUST take care of the DC-issue when you are paralleling chip amps (or other amplifiers for that matter). Failing to do so will result in huge amount of current flowing between the amps…………..I suspect this is what happens when people try to use the parallel approach and can’t get it to work properly.
Personally I think that use of the DC-servo are the “technically” correct solution. However from a more “esthetical” point of view the DC-servo looks slightly “misplaced” since it almost uses more components than the amplifier it-self. Having a carefull “look” at the gain-resistors and use of a large capacitor in the lower feedback arm will get you a very low DC-offset………………….I am working on a “paralleling basic” that I hope will be usefull for all the “BPA-people”………..I hope.
2. Getting 450 W into 4 ohm is probably to “push it to fare”. However 350W into 4 ohm is possible, but you need more that 2x2 LM3886 or an extreme efficient way off cooling them.
3. One of the reason for using 0.1 % resistors is to get AC-current balance. If your parallel amplifiers don’t have (exact) the same gain, then one will be doing all the work (and get to hot). And we are talking a big difference in distribution here. In teori 1% is not good enough to prevent this. However in my expirence, 1% resistors in real life turn out to be 0.3%-0,5% relatively to each other coming form the same batch. (I have up to now used 1% resistors in my constructions). The 0.1%-issue will also be discussed in my “paralleling basic”. For now, just buy 1% and handpick them to be as close as possible.
About the 0.1% “output” resistor. I was very “suspicious” when I saw this requirement. Up on close inspection/calculation it turns out that using 5% resistors worst-case you will have a 10% “imbalance in AC-current between your amplifiers……..it is up to you if you can live with that….
Again, for now I recommend that you just get the 5%/5W and handpick them to be as close as possible. (they are also normally better that the 5% coming from the same batch).
It is also quite hard to get hold of 0.1 % /5 W resitors. 1% would be fine if you can find them.
Have fun and let us all know how you get one.
Regards
Thomas |
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| tlmadsen |
Peranders
Sorry,didn't se you post before.
I have not tried to get max power in 4 ohm, since the biggest transformer I have used is 500 VA.........and you need something bigger to get max power in 4 ohm.
If this is importent to people I don't mind prallel two 500 VA transformers and give it a go when I have the time.
You need max power for how long ???................it will become a cooling problem after about a minut or so......
Thomas |
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| peranders |
A cool 500 VA toroid can take 200% for a couple of minutes at least. If you can test, please do so and tell us your results.
I can't either see the problem with americans buying not from USA. Things in a regular envelope and PayPal works 100% for me even to America. The only thing I notice (before I used Paypal) is that americans in general have problems with regular bank transfers which seems to be very easy in the rest of the world. It can be something with that americans aren't used to it. I don't know. How do you pay bills, creditcard? |
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| nobody special |
There definitely must be some kind of thing with Americans that is different from the way you Europeans are used to doing it. As far as I'm concerned (being an American) I would rather not buy something from overseas unless it is the absolute last option. I feel about the same for Canada. This has nothing to do with national pride or anything like that... I just haven't ever done it before. Maybe a fear of the unknown? That, and there are options if you get screwed by someone in the US. It's easier to get your money back. Shipping is definitely cheaper, no way around that.
I pay our bills by personal check. Is it different over there? |
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| theChris |
overseas shipping takes longer and costs more. if you'r paying $20 for a small PCB and $10 for shipping that takes a month, well, it kinda sucks.
just design for difference amplifers this will allow for a wider range of options - inverting, non-inverting, or a difference amplifer. |
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| theChris |
| i posted a while back about tieing both inverting inputs and both non-inverting inputs together on the lm4780. any opinions on this? |
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| tschrama |
Hi all,
I glad to see so many responds, so I thought I put in a few more remarks too..:clown:
About the size of the PCB: well why not keep is as small as possible. 3.8 x 2.5 inches PCb cost 51$ c for 3 pcs at ExpressPCB.. If it can be made small .. (about 1.9x1.25inch) , such a size would be enough for 12 amplifiers .. less than 5 $ each.. that would be nice
http://www.expresspcb.com/ExpressPCBHtm/Costs.htm
Further more, how about that super-short-feedback-path??? I do not believe in it.. but why leave that oppertunity...
About DC-servo's: I think you can leave them ... the LMseries have very stable offset, which can be adjusted with the input resistors... If you use a unity-DC-gain topoly, offset can be made 1mV easely .. so two amplifier= 2mV max working in 2 series 0.22 Ohm resistors.. hmmm .. gives 4.5mA DC current hobbing between amplifiers.. no problem here
The AC gain should be close I think.. 1% error gives 2% error max between amplifiers.. 2% of 35V max out = 0.7 Volt.. 0.7 volt over 2 0.22 Ohm series resistors is 1.6A .. Too much.. because this will flow from one V+ to amp1 to amp2 to V- ( is that so?) and would give enormus power dissipation.. 1.6A over 2x35V = 112W.. CAN THAT BE RIGHT???? hmmm
the 0.22Ohm output series resistors can be 5% I think.. I don't care if one amp is taking 45% of the current (so also power) and the onther one 55% .. it shouldn't matter much...
ehhh .. yep that was it ..
Hope it helps.. else just ignore me..
Greetings,
Thijs |
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| theChris |
"Originally posted by Dxvideo
2-In the same app notes the power output table; for 4 ohms the BPA200 can drive 450W "Burst Clipping Power". What does is mean? Can we say it is RMS value or PMPO? So we can really get 450Watts / 4ohm? "
-from my understanding, the test conditions for this very much favor unrealistic numbers. |
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| peranders |
| quote: | Originally posted by nobody special
I pay our bills by personal check. Is it different over there? |
Checks is Sweden is nearly "what did you say?" They are very rare these days. A majority(?) pays bills via internet banks.
I wonder how many (american) people really hesitate to order from Hugh in Australia if they really want his stuff. Is it really easier, really, to get your money back from american companies for americans, if you are screwed?
I have ordered cactus books from USA without any problems.
I think Mr Madsen will be happy to deliver pcb's also to americans but I think also there may be room for your project too. If you start you may see how big the interest is. I have got a huge interest for my implemetation but not enough to trigger anything. A power amp is little bit more expensive (and takes much more time) to develop so I'll stick with small things at the moment.
If a couple of people (>5) want to build it (before I do), send me a message and we can work something out. |
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| theChris |
yeah, next year i was thinking of going into the pcb industry, because i have access to a milling tool. i wasn't looking to make a lot of money off it, but i realised that most people won't pay $5 shipping on a $1 part...
also, generic PCBs are a little harder for GC becasue you have so many different opinions on components and this can change the size consciderably. |
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| Dxvideo |
Thanks for your close interest.. If I am not wrong; its very important to equalisation dc-offset in parallel processing so servo circuits should be there. %1 tolerance resistors are ok, because they have %0.3 - 0.4 tolerance in fact. And finally nobody believes that circuit gives 450W RMS...
Am I right? |
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| peranders |
| quote: | Originally posted by theChris
also, generic PCBs are a little harder for GC becasue you have so many different opinions on components and this can change the size consciderably. |
Have you checked my then? Any features missing?
DeLuxe version:
* Inverting or non-inverting LM3886, can be chosen
* Inverting or non-inverting input buffer, with or without gain, can be chosen
* Feedback network which can satisfy everyone, full gain at DC or gain of 1 using a capacitor in the feedback
* With or without DC-servo for both inverting or non-inverting LM3886, can be chosen
* Output filter, L//R, small handwound inductor plus a resistor.
* Inputfilter, lowpass and also highpass to block incoming DC-signals. You could also skip the filters if you want to. I recommend though to use a high frequency lowpass filter.
* Mute, the LM3886 is "dead" for a short time at power up, can be chosen.
* Bridge connection and the LM3886 can operate in inverting or non-inverting mode, can be chosen.
* Pcb for 2 separate channels, stereo, or one channel in bridge connection. It's possible to change mode easily with help from a jumper.
* Power supply be on the pcb with sufficient amount of smoothing capacitance.
* Stabilized power supply for the buffers. +-12 V is chosen (can easily be changed) so the amazing AD8620 can be used.
The pcb is made but never manufactured and tested. |
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| Upupa Epops |
| Per, I have exactly the same (all function which you describe ), double sided PCB, but with LM 4780, PCB is not also maded. We are thinking parallel :D . |
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| peranders |
| Want to show it? |
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| tschrama |
Hi DXvideo,
| quote: | | Thanks for your close interest.. If I am not wrong; its very important to equalisation dc-offset in parallel processing so servo circuits should be there. %1 tolerance resistors are ok, because they have %0.3 - 0.4 tolerance in fact. And finally nobody believes that circuit gives 450W RMS... |
I really don't think you need a opamp-servo .. just get the voltage offset to 1 or 2 mV and you'll be OK....
450W rms ..| quote: | | Instantaneous Peak Output Power |
.. sure .. I don't believe that is stretching the thruth one bit.. 1 LM3886 can deliver 11.5 A peak.. and has 135W peak power.. read the datasheet.. 450W peak power will be easy occomplished.. for just a ms or so..... RMS.. that easy.. 1 LM3886 can is rated for 68W .. 4 LM3886 should be able to give 272W RMS ... I don't think that numver will be far off... needs a good supply offcourse
Greetings,
Thijs |
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| theChris |
peranders, your board seems very flexible, but will it accept 14/ watt resistors AND SMD resistors? what about 1 watt wire wounds... and for caps can you use 1" long film and foil as well as 5mm electrolytics...
for the buffers and servos, can you use single dual or quad opamps...
i don't think it's possible to satisfy everyone, thoguh i definately like the ideas you present. my GC design is looking like it is very adjustable as well. i'm pretty sure it'll be based on my hi3gc (high input impedance inverting gainclone) with 100k input inpedance. since i'm using active crossovers i figure i can do an inverting configuration without worries. |
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| peranders |
I thought about SMD but the average DIY'er can't handle it. I have chosen not to use big caps. I wanted a small PCB.
You're right, I can't satisfy everyone but rather many I suppose... |
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| Dxvideo |
| quote: | Originally posted by tschrama
I really don't think you need a opamp-servo .. just get the voltage offset to 1 or 2 mV and you'll be OK....
[/B] |
-Without them, can we get 1 - 2 mV offset?
-For one channel, what kind of power supply we need?
-What can you say about BPA200's gain? As I can see its 21... So for 300W/4 ohm what is the input sensivity?
-Can we realise that circuit by 2xLM4780? It would be very compact... Any modification need?
-And finally, two LM3886s or (one) LM4780 in parallel, can that circuit gives 150W/4ohm RMS?
Thanx. |
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| jackinnj |
the BPA Application Note AN1192 at National Semi has been updated as of June 2004.
jack |
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| Jean |
| if there is going to be a pcb run for bpa-200 I am in for a pair ;) |
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| peranders |
| quote: | Originally posted by Jean
if there is going to be a pcb run for bpa-200 I am in for a pair ;) |
Why wait guys? "Das Modul" is there for you. If the price isn't of major concern why don't you buy Thomas Madsen's pcb? |
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| jackinnj |
| quote: | Originally posted by theChris
overseas shipping takes longer and costs more. if you'r paying $20 for a small PCB and $10 for shipping that takes a month, well, it kinda sucks. |
Overseas shipping to most of the world is available through Global Priority Mail -- I assume that the rates would be reciprocal -- i.e. the same in Sweden to the US as US to Sweden (but haven't checked). It costs $5 for "small package" GPM, $9 for "large package" standard envelope.
For countries without GPM (like Italy and Argentina) Registered Air Mail is convenient, but more expensive.
There is a bit of labor involved in preparing the envelope as a Customs Declaration has to be filled out by hand -- only with Global Express Mail can the Customs Declaration be filled out by computer. |
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| nobody special |
I decided not to do the PCB, because of a lack of interest. Why waste my time, when there is "DAS modul" or whatever :xeye: ?
Obviously T. Madsen and Peranders have this covered.
On a side note, I have decided to frequent more American friendly boards, so you won't see me around here anymore. I do check into the passlabs section once in a while, because Nelson is the man!
see ya.
Steve |
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| tlmadsen |
To nobody special
Do you really mean that about "more American friendly boards" ???
Regards
Thomas |
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| jackinnj |
| quote: | Originally posted by tlmadsen
To nobody special
Do you really mean that about "more American friendly boards" ???
Regards
Thomas |
I think it's pretty darn'd friendly -- particularly when you get to know the folks.
Unfriendliness is caused by a lack of communication. |
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| peranders |
| quote: | Originally posted by nobody special
I decided not to do the PCB, because of a lack of interest. Why waste my time, when there is "DAS modul" or whatever :xeye: ?
Obviously T. Madsen and Peranders have this covered.
On a side note, I have decided to frequent more American friendly boards, so you won't see me around here anymore. I do check into the passlabs section once in a while, because Nelson is the man!
see ya.
Steve |
Mr Nobody I think you have got the wrong indea about things. First you start to make a pcb, build it and test it. When everything is ready you can offer it as group buy. If you are lucky there is real interest also.
Das Modul exsist and everyone can buy pcb's to regular prices. If Mr. Madsen or someboby else want to make a group deal, it's up to them. At the momemt Mr. Madsen doesn't want to be in charge of any bigger deal and that's his choice.
A group deal requires enery and somebody got to do the job.
I must say that I didn't get the part "amnerican friendly boards". Do you mean that diyAudio.com is not very american friendly? Is this caused by the low intererst of your non-existing products? |
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| peranders |
| quote: | Originally posted by theChris
overseas shipping takes longer and costs more. if you'r paying $20 for a small PCB and $10 for shipping that takes a month, well, it kinda sucks.
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Maybe it's different from USA rather than to. I can say that from Sweden it takes 2-3 days to Europe, 3-7 days to USA, 5-10 days to Australia, New Zeeland. The charge is 2-5 USD + fee for regisitered mail 8-9 USD. 10 USD in shipping from the other side of the world, is that much?
One month of shipping??? Where do you live and where came the shipment from? |
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| rabstg |
Hi All-
Please remember one individual does not speak for all here.
This board is not American "unfriendly" and people should try NOT to post when they are emotional.
It is more difficult purchasing items from across the globe, but the wonderful thing is we CAN get things from anywhere.
If cost or time makes a long distance purchases impractical that is when you design and manufacture locally. In the case of Das Modual, I am hoping some one will design and sponsor a GB on a similar board here in the US.
Eagerly watching this post:
http://www.diyaudio.com/forums/show...0298#post430298
Thanks,
Troy (who is happy to be able to visit this board) |
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| tlmadsen |
Just to chip in
"Das Modul" came out of a article to a Hi-Fi magazine for for that reason I can't make it into a group-buy. However I someone could give me a short introduction to "a group-buy" I might consider it for a "non-servo"-version of Das Modul.
If you want to get the price down for something like the PCB you need to get up to something like +100 pieces.
How will I know how many people "join" the group-buy ??
Regards
Thomas |
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| peranders |
Money investment *), how much?
1 Gather all wishes and design the pcb. *) One man is in charge, YOU or someone is in charge of the business and one another is in charge of the design. Make it clear from the beginning who runs the show.
2 Build one or more prototypes. Bug hunt, add features maybe. It's very important to have a ready and functional product to offer. DON'T OFFER NON-EXISTANT PRODUCTS. Compare this thread starter and also the Jung Super Regulator deal and how it started. Even if you are a pro and really skilled things can turn up and make the design not so good. Prototype first!
3 Start a wiki page and write down your offer which of course must be attractive. Be clear with what you really are offering.
4 Make people to sign up. State a last date for this.
5 Get an offer from a pcb maker.
6 Create a Paypal account so the money collecting will go easier.
7 Collect the money in advance, my recommendation. Don't risk anything if it is a low profit deal. Note low profit, not non-profit. It's OK to get a small reward for your efforts. State a last date for the payment.
8 Order the pcb's, parts etc.
9 Deliver all by yourself or with help from a couple of people.
10 Make a clear table (like I did) over payments, dates, amounts, delivery times and maybe also aknowledgements from the "customers". We have seen here that status of payment and delivery is very important.
If this "openness" of some reason not is wanted by the organizers, and want to keep it more hidden, make sure that the customers get inforrmed and also which person the shall get in contact with if they ahve questions about payment and delivery.
11 Start a homepage.
12 Create your own support forum like I have done (costs nothing!) or start a thread here. You also may use my forum for a closed group so the beta builder can exchange info in peace and quiet. It can be more peaceful if the development is a bit protected.
*) If you aren't sure if you dare to risk a prototype series, collect a gang of beta builders like I did. 3-10 persons is enough. Ask them to put up some money and return some or all of it AFTER completed task. If you know the builders, trust them and know their building speed it's not necessary with this deposition of money but if you don't know them too well I'll recommend this type of "blackmail" (money talks!). |
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| rabstg |
Hey peranders-
That was a great post on the break down of a GB.
We should have the moderators edit it and set up "Requirements or guidelines" for all group buys based on this type of information and then everyone would have the same expectations.
Thanks,
Troy |
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| sunil |
Peranders,
Excellent guidelines for starting a group order.
Thanx,
sunil |
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| Tsanford |
I have been searching for hours for a design for a BPA-200 board with no luck.:bawling:
I would even etch my own......In the DIY spirit.:D
Guess I could really "Do It Myself" and create the layout too. So, here I go.
Good Luck all. |
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| nobody special |
| quote: | 1 Gather all wishes and design the pcb. *) One man is in charge, YOU or someone is in charge of the business and one another is in charge of the design.
2 Build one or more prototypes. Bug hunt, add features maybe. It's very important to have a ready product to offer. DON'T OFFER NON-EXISTANT PRODUCTS. Compare this thread starter and also the Jung Super Regulator deal and how it started. Even if you are a pro and really skilled things can turn up and make the design not so good. Prototype first!
3 Start a wiki page and write down your offer which of course must be attractive. Be clear with what you really offer.
4 Make people to sign up. State a last date for this.
5 Get an offer from a pcb maker.
6 Create a Paypal account so the money collecting will go easier.
7 Collect the money in advance, my recommendation. Don't risk anything if it is a low profit deal. Note low profit, not non-profit. It's OK to get a small reward for your efforts. State a last date for the payment.
8 Order the pcb's, parts etc.
9 Deliver all by yourself or with help from a couple of people.
10 Make a clear table (like I did) over payments, dates, amounts, delivery times and maybe also aknowledgements from the "customers". We have seen here that status of payment and delivery is very important.
11 Start a homepage, Thomas!
12 Create your own support forum like I have done (costs nothing!) or start a thread here. You also use my forum for a closed group so the beta builder can exchange info in peace and quiet. It can be more peaceful if the development is a bit protected.
*) If you aren't sure if you dare to risk a prototype series, collect a gang of beta builders like I did. 3-10 persons is enough. Ask them to put up some money and return some of it AFTER completed task. If you know the builders, trust them and know thier building speed it's not necessary with this deposition of money but if you don't know them too well I'll recommend this type of "blackmail" (money talks!).
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Good info. I just had an email saying there was a new message, so I decided to check in.
I guess my intent in asking was to see if there was a market for this. I have no doubt I could lay out a pc board for it, and it would be tested and prototyped with good documentation so that anyone can build it.
Things in life change, and I found out I have a son on the way. :) This means that I won't have nearly the free cash I thought I would. Making an investment in a product that no one wants would not be a good thing for me at this point.
I was testing the waters, and it was fairly obvious that this has been covered by others, even if outside the US.
This isn't to say that I won't go ahead and do it, just that it's not likely. Thanks for the perspective in your post... obviously you have done this before.
Steve |
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| peranders |
| quote: | Originally posted by nobody special
Making an investment in a product that no one wants would not be a good thing for me at this point. |
Congratulations to your coming son (do you know this already?)
If you read through my instructions once more you have an item which is about investment. The thing was _not_ to risk money. If you can't create any interest the project is dead if you won't risk anything.
If you can't come up with something really different compared to the Das Modul, you only have the price left. Don't underestimate the work you have to put into the project. |
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| nobody special |
Thank you!
Yes, we had the first ultrasound last week and we found out he is a boy! He's our first- due Christmas day.
I think it would be difficult to improve on "Dad Modul" or the BPA application note. I'm not so sure that a non-buffered version is the right thing to do. Maybe sonically it would be superior, but I think it would be risky putting together a kit around such a design. There is the problem with offset and instability that would not be as fool-proof, in my opinion. |
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| neodyne |
| hello sell you to it kit BPA200 and how much? thank you |
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| nobody special |
I decided this week now that everything has settled down with the baby I will go ahead with the PC board layout. A prototype will then be built, and if it's successful I will be offering the boards for sale, and probably a component kit as well in the future. At that time, I will let you know how much.
Even if there are other designs out there, I want to do this for myself anyway, so I might as well just do it!
Some ideas for the PC board are:
Up to 8 3886's per board (per channel). I will use the servos, because I think it's the best solution. For those that don't want them, I don't think it will be an issue not to populate that part of the board. I will make the board with provisions for using them or not.
The plan is to create a left and a right handed version to optimize layout for stereo amps. Those that only need one can specify either right or left mount at that time. I will provide a drilled and tapped heat sink adapter that will mount the devices and mount to the pc board. It will be up to you to mount the adapter to your heat sink (will not be included).
I plan to put the power supply recitifiers and filter capacitors on the PCB. For maximum versatility, there will be provisions for an off-board supply as well. My thoughts at this point are to include a place for using individual TO-220 type soft/fast recovery rectifiers with stand-up board mounted heatsinks, and radial snap-in filter caps.
There will be balanced or unbalanced inputs.
Boards will be HEAVY, excellent quality.
As I progress with this, I will offer more specifics. These are only my preliminary ideas.
I will begin work on the layout this weekend, with a completion date in the next month planned for the prototype. |
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| los_ren |
i built a BPA-200, sorta. its based on the BPA-200 design, the PCB is a single LM4780 bridged, with a LF411 buffer, part values based on the national schematic. i took two of these bridged PCBs and paralleled them at the outputs. basically its a BPA-200 with two buffers, one for each bridged set.
anyway, its layout is similar to the BrainGT LM3875 amps i built, adding an input buffer and output resistors. it was tested in a 4x7 bass amp cabinet of questionable sanity i built, sounded fine, no hum. if youre interested i could post pics of the boards, bare and populated.
configured this way, theoretically you could parallel additional bridged pairs forever, and run the power into lower and lower impedances.
ill go back and read the rest of the thread now, i only caught the last few posts.
=] |
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| nobody special |
| sounds good. You might want to start another thread to give it the proper attention. I would like to see it. |
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| los_ren |
sry, been busy.
will do soon tho =].
(before i do i wanna see if i can run a board bridged , but not paralleled using two PCBs, into an 8ohm load with a 25v psu). |
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| nobody special |
| sounds cool... better have some good heatsinking! |
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| peranders |
| quote: | Originally posted by nobody special
Some ideas for the PC board are:
Up to 8 3886's per board (per channel). |
Don't overdo things.
1 LM3886 gives you ?? Watts
2 LM3886 gives you ?? Watts
4 LM3886 gives you ?? Watts
6 LM3886 gives you ?? Watts
8 LM3886 gives you ?? Watts
For you to fill in. It seems that 4 LM3886 is optimum. Adding 4 extra LM3886 adds very little costs twice! |
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| tlmadsen |
Dear P-A
I am not sure that 4 x is the "optimum" number of LM3886 to use in a BPA-config. 4 is actually the minimum you need to make a BPA-config.
For a lot of people 2x2(4 pices of LM3886) if fine, but from a more "technical point of view" I think (I have not doen the calcualtions) 2x3 (=6 pices of LM3886) is closer to the point of "deminishing return", if you can call that point "otimum".
To Nobody sepcial.
Remember to take care of the DC-offset if peopel don't use the DC-servos
..........have fun
Thomas |
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| Tweeker |
I woud like to make a sub amp to power an Acendant Avalanche 18 in a very large folded transmission line. I was thinking either 4 LM4780 or 8 LM3886 in bap arrangement would do the job. Cooling would be a concern. This woofer could easily eat 544 watts in such an enclosure. So I would definetly be interested in such a beast.
I have no problems with buying foreign goods, except my goverment is running a massive deficit, and we have a voracious appetite for cheap chinese crud and gasoline, so the trade balance isnt so good either. My dollars dont go quite as far as they used to overseas. |
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| peranders |
| quote: | Originally posted by tlmadsen
[B]I am not sure that 4 x is the "optimum" number of LM3886 to use in a BPA-config. 4 is actually the minimum you need to make a BPA-config.
/B] |
I ment also when you take into account how many extra dB's you will get with these extra two LM3886 but I'll guess this also has to do with the cooling arrangements. More LM's are easier to cool. |
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| nobody special |
| quote: | Originally posted by peranders
I ment also when you take into account how many extra dB's you will get with these extra two LM3886 but I'll guess this also has to do with the cooling arrangements. More LM's are easier to cool. |
Exactly my thoughts for why to use 8. Less current per device for a given wattage into a given impedance, more surface area to heat sink. I know there will be some that will want to push the amp hard into 4 ohms. |
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| nobody special |
| quote: | Originally posted by tlmadsen
To Nobody sepcial.
Remember to take care of the DC-offset if peopel don't use the DC-servos
..........have fun
Thomas [/B] |
Thanks for the pointer, Thomas. I'm still debating whether to even bother with not using the servos. I think the design really does need them, and I don't want to deal with people freaking out about the amp not working when they don't use them.
Developement continues... Building a lot of parts in P-cad currently. I hope to have a prototype amp built very soon.
I also have an interesting plan for the heat sink adapter which will allow direct mounting of the 3886T(non-insulated) devices and more surface area for good heat distribution while still isolating the devices from the heat sink.
How many reading this would prefer a design that would mount the pcb parallel with the heat sink as opposed to perpendicular? My original intent was to provide a board that would mount perpendicular to the heat sink, and offer left and right versions for a stereo amp with side mounted heat sinks. If I find there is more need for it to be parallel-mounted, I will take that into consideration. |
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| tlmadsen |
Steve .
There are ways that it would work fine without the servos, so you might consider it.
Thomas
Go for the parallel mounting of the LM3886 (despite that I, myself did not on Das Modul) |
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