| tiroth |
About
This is a group buy for a MOX-like adjustable active crossover based on moamps' original project. Jens' Rasmussen has done a layout for this project using DIP8 opamps.
The page for the filter board is here
There will also be a group buy on discrete opamp PCBs, also based on moamps' design. The PCB for the opamps will be finalized in the next 24-48 hours. The final design will be able to replace standard dual opamps in other circuits, although a resistor to ground is needed for DC stability.
The thread for the discrete opamp layout is here.
Features
Each board contains some buffers, low pass and high pass sections, and adjustable gain. Corner frequency and filter Q are independently variable, and 1st or 2nd order filters can be realized with a single board, or higher order with additional boards.
The boards are single ended or balanced inputs and single ended outputs. There is a prototyping area on the boards so that you can easy add EQ, additional filter stages, balanced out, etc. You can use the discrete opamps that are part of this buy, or you can use any FET-input opamp of your choice such as OPA2134.
Boards needed for common configurations, stereo
1st/2nd order 2-way: 2
1st/2nd order 3-way: 4
3rd/4th order 2-way: 4
3rd/4th order 3-way with 2nd order BP: 6
If you need a lot of outputs at high order and want to use less boards, you might buy enough boards to prototype one channel, and then hard-wire some additional filters.
How to order
The cost will be no higher than this:
MOX board: $7
Set of 8 discrete opamp boards: $5
I hope these prices will go down dramatically, but it depends on the level of interest.
Please sign up at the Wiki!
There will be two phases. First, I'd like people who are interested to sign up at the Wiki above. Let me know how many boards you would like--do not send any money yet! Once I know the level of interest, I'll set the price and accept payment.
Please let me know anything I've missed. I will accept PayPal and ship worldwide; shipping is $5 for any number of boards in the U.S., should be similar for Canada, and I will post the cost to other countries as sign-ups come in.
Thanks,
Tyler |
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| tiroth |
Updated opamp PCB. Can be used singly as SIP-6 or two together as dual DIP8 replacement. I'd welcome comments in the opamp thread.
Eight of these are included for $9; I'd like to get this price down to $4-5 but will depend on the number of orders. Please sign up in the wiki! |
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| Tazzy |
| How many board's do I need for 1 lowpass (subwoofer) filter? |
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| tiroth |
Tazzy,
A single board is all you need for 1st-2nd order low pass. Strictly speaking, you would need a pair to get up to 4th order. This would also give you a high pass output for crossing to your mains or satellites, if needed.
Andypairo,
I saw your comment about balanced. The board supports balanced input. There isn't circuitry to support balanced out, but that could easily be added with a single DRV134 in the prototyping area, or a couple of opamps if you want to do it "manually". This is what the prototyping area is for! Does that work for you? |
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| Andypairo |
I hadn't paid too much attention at the veroboard-like area on the PCB image, I think that it will be good for the purpose.
Cheers
Andrea |
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| JoeM |
| Wow! That board is over 1 square meter!:clown: |
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| tiroth |
:confused:
Okay, there is enough interest to move forward. I hope to have the protos by the weekend after next. The following week (week starting 26 April) I will plan on freezing the price. I'll then accept payments and new orders for a week, but the price will not change. I'll accept delivery 4 weeks later (cheapest) and ship out immediately. Please email me if there are any concerns about timing.
Contact me now if you know you can't pay by paypal!
I'm also trusting to fate that there are at least 15 new orders because:
Price drop!
MOX: $7
Opamp set: $6 |
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| rabstg |
Hi-
I am new to this forum, and for some reason I have not been able to figure out how to sign up for this buy on the wiki page.
I would most certainly like to purchase some boards but at this time I have not been succesful in figuring out how.
Pointers for the blind(figuratively)?
Thanks, Troy |
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| tiroth |
No problem. Just go here
http://www.diyaudio.com/wiki/index.php?page=Moxbuy
and scroll all the way to the bottom. You'll see a large link called "Click here now to edit this WikiPage". Click it, and you'll see a textbox with the entire text of the page in it. Scroll to the bottom of that, and you'll see the table laid out like this
||Name||1||2||3||4||USA||Comment||
Just pick a blank line and insert your info where the spaces are.
|| || || || || || || || -> ||rabstg||0||0||0||0||USA|| || |
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| JensRasmussen |
Hello all,
Great work on setting up the group order tiroth :)
I'll start work on a manual and create a BOM for the filtermodule tomorrow.
If there are questions regarding how to get started please contact me, and I'll see if I can help.
\Jens |
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| jhead |
| I just came upon this post and found it interesting in that if I'm to understnd youv'e developed a pin for pin replacement of IC based OPAMPS in other words these can drop into typical 8pin single or dual locations being all things equal I'm curious can these replace for example a OPA627 opamp |
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| tiroth |
jhead,
This IS a generic opamp replacement, with two caveats
1. you need a 4k7 resistor from the output to ground somewhere; that means either connecting the ground pad on boards or adding this resistor to the mainboard.
2. all opamps have different specs, but for the majority of audio applications this discrete should be great.
You might want to read moamps' response in the opamp thread; while he didn't directly compare them, he said that he expects the discrete opamp to be more to his liking than something like OPA627. |
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| jhead |
| Yes I did see his comment thats why it peaked my interest further in that I think that I would like to try these in say the output on a couple of Sony CD players also possibly in a PPA Headphone Amp |
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| tiroth |
| jhead, I suggest you post in the opamp discussion thread. What you ask for is certainly possible, but maybe some changes to resistor values are needed depending on the drive current required. Since MPSA92 can handle 500mA, not a problem. ;) But the biasing may differ depending on the impedance of your headphones. |
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| moamps |
| quote: | Originally posted by tiroth
..on the drive current required. Since MPSA92 can handle 500mA, not a problem.....the biasing may differ depending on the impedance of your headphones. |
Hi,
You are right. This opamp works just fine with output CS set on about 20mA and high impedance headphones like AKG 240.
Regards |
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| tiroth |
A request to those who have different amounts of opamps in the $6 and $5 columns in the wiki: the proportion of MOX boards to opamp sets differs significantly depending on the column. I need to make a decision about how to panelize the order by Monday morning, so I need to have a better idea about how many opamp boards people want given that the price has fallen 33%.
If you signed up when the OPA boards were $9, and would now buy more at $6, please update the wiki
My thanks to anyone who takes the time. I am not ruling out a drop to $5, and in fact having more "confirmed" orders makes this more likely.
I will post pics of the protos when the arrive. Thanks! |
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| JensRasmussen |
Hi Tyler,
Did you get my mail?
\Jens |
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| tiroth |
| Jens, you're got mail. |
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| till |
| how difficult would be balanced in / balanced out? |
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| Peter Daniel |
I still can't see it quite clear, what is required to accomplish a certain filter configuaration.
So, one MOX board contains single channel, both high and low pass filters (up to second order)? If so, how many opamp boards is needed for that setup (small ones)? |
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| tiroth |
till,
Balanced in is already supported. Balanced out could be easily done using the prototyping area. DRV134 would be one option, or you could use a pair of opamp boards to create a differential driver. I will elaborate more on this later.
Peter,
Yes, each board is 1 channel. It can be used high pass, low pass, or bandpass (up to 2nd order). There is an (optional) input buffer, and up to three output buffers.
If you want to use every single filter and buffer on the board, you need four dual opamps (8 single).
But, you don't need this many in most cases. The board is a swiss-army knife; as-is, everything is buffered in and out so you don't have to think about it. But if you know your source impedance is low enough, if you don't need gain adjust, if you aren't driving a cable and have a high Z following stage, you could build this with as few as 2 opamps per board. You'd need to know what you are doing though. ;)
A simpler answer is you need 5 (input buffer, HP filter+buffer, LP filter+buffer) opamps per board, 4 if the board is piggy-backing off of the input or ouput buffer on a another board.
Here is the listing again for the number of boards required for common configurations. Let me know if you'd like me to elaborate on how it would be done.
| quote: | Boards needed for common configurations, stereo
1st/2nd order 2-way: 2
1st/2nd order 3-way: 4
3rd/4th order 2-way: 4
3rd/4th order 3-way with 2nd order BP: 6
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| Peter Daniel |
| Thanks, that explains everything. |
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| till |
sorry, i´m not that bright as Peter, i still don´t really understand. The number of opamp boards needed also depends on the impedances to drive? So what do i need for low impedance source, balanced, 2way 2nd order, balanced out, low impedance power amplifier (SOZ) to drive? 2MOX and how many opamps? my motivation would also rise some higher if balanced out would be implemented on the PCB allready.
Would it be possible to send cash instead of paypal?
What about euopean or german sub-grouporder to simplifiy money and boards transfer? |
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| JensRasmussen |
Till,
If we start splitting up the group order, the price will not be as low as if we all order together.
Regarding the number of opamps it is not depending on the impedance you want to drive. If you use opamps like the OPA2134 I doubt there will be any problems since it can deliver something like 50 mA.
However the question remains if the discrete opamp will drive difficult loads?
A complete filter board needs 4 dual opamps or 8 discrete single ones. However when you use the board, there are several configurations where not all opamps are needed – take a look at the filter page and schematics and consider what setups you need. It all depends on what filter order you need and if it’s a two, three or four way system you plan to make.
I don’t think the board is going to change – if you want balanced out, I suggest you use the prototype area on the PCB for that purpose. The reason being that balanced out can be made I so many different ways that it would be impossible to make everybody happy.
We had enough trouble finding out what configuration to make in the first place :)
\Jens |
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| tiroth |
I'll answer your questions, till, as well as some that keep coming up over and over.
| quote: | | Can the board change? |
No. The proto order is already out, which means any changes will incur a tooling fee. That means changes will be made only if some error is found.
Supports balanced in (and single ended).
Does not support balanced out directly, but can be added with a single DRV134 or use a pair of opamp boards as a differential driver. More on this later. Don't forget that there is an on-board prototyping area for this purpose!
| quote: | | The number of opamp boards needed also depends on the impedances to drive? |
No! But, your understanding of the impedances and kinds of circuits involved may allow you to eliminate some of the opamps to save costs and space.
| quote: | | Would it be possible to send cash instead of paypal? |
I would really like to discourage this for many reasons, but I'm happy to discuss by email. I will work something out for people who truly cannot pay via Paypal.
| quote: | | European or German sub-orders? |
I'm definitely happy to accomadate sub-orders if it will help you save on shipping and transfer fees. (You will need at least a few people involved to actually save anything, I'd think) If you are stepping forward just indicate in the wiki that you would like to coordinate, and/or get in touch with the other people ordering from your country.
| quote: | | However the question remains if the discrete opamp will drive difficult loads? |
Some tests will be shown before going to production and accepting orders. I don't expect any issues though as I am currently driving ~12' balanced lines from FETs with an even higher output impedance in my active XO.
| quote: | | How many opamps do I need? |
You can't go wrong if you start with 4 dual monolithic opamps per board. If you really want the discretes, buy 1 set per board and only build the number you end up needing. I recommend that only experienced builders consider building with <8 opamps per board, because you must have a good understanding of the entire circuit to know which ones can be eliminated. Or be building from someone else's instructions. There are so many scenarios that I am at a loss to explain them all, but I did make some general comments previously.
| quote: | | So what do i need for low impedance source, balanced, 2way 2nd order, balanced out, low impedance power amplifier (SOZ) to drive? 2MOX and how many opamps |
Yes, you need two MOX for stereo, and I would be tempted to use only 8 opamps total. Following my previous advice though, get two sets of discretes if you really want them, and build it with four dual monolithic opamps first. You must understand the circuit to eliminate parts.
You also need 1 DRV134 and be willing to do some extremely simple wiring in the prototyping area. |
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| Peter Daniel |
| And don't forget that opamp board can be used for number of other apllications, besides the crossover;) |
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| tiroth |
Price drop
I've lowered the cost of the opamp sets to 8/$5 and eliminated the extraneous wiki column.
Peter Daniel--you had 10@$6 and 4@$5...I guessed that you meant 4 additional, so I put 14 in the wiki. If this is incorrect, my apologies.
Randytsuch, I got your email and added you to the wiki. |
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| BrianGT |
| quote: | Originally posted by tiroth
Price drop
I've lowered the cost of the opamp sets to 8/$5 and eliminated the extraneous wiki column.
Peter Daniel--you had 10@$6 and 4@$5...I guessed that you meant 4 additional, so I put 14 in the wiki. If this is incorrect, my apologies.
Randytsuch, I got your email and added you to the wiki. |
Will the price change on the MOX board at all? I might increase my order if it does.
--
Brian |
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| tiroth |
| It is possible the MOX price could drop to $6...$5 seems out of reach unless there are a LOT more orders at that price. Do you think it worth adding a column to the wiki? Anyone else feel likewise? |
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| Duck-Twacy |
| Maybe it is usefull to change the price in the first post as well (if thats still possible). Not everybody will read the whole thread. |
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| tiroth |
| I agree, but only a moderator can change it now. Peter, could you do so? I would appreciate it. |
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| BrianGT |
| quote: | Originally posted by tiroth
It is possible the MOX price could drop to $6...$5 seems out of reach unless there are a LOT more orders at that price. Do you think it worth adding a column to the wiki? Anyone else feel likewise? |
I don't think that the additional column is necessary. What is the total number of boards needed for the price breaks?
Also, I wouldn't object to paying a dollar extra per board, and having a donation being made to diyAudio. The server fund could use some cash.
--
Brian |
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| tiroth |
Brian, it is hard to say, because I panelized everything together to save on costs. So, if I suddenly got 150 more mox orders (and no opamp), that might actually increase the cost to me because the ratio of mox to opamps would be severely off.
I guess I can say definitively that if there are 40 more MOX and at least 20 more OPA, I could lower the price to $6. (quite doable) I would need nearly 100 and 90 more, respectively, to lower the price to $5. We're reaching the point where 30 more orders only knocks $0.30 off per board now.
There is definitely enough leeway that DIYaudio will be receiving a donation. Perhaps I should include a "donate $1 to DIY" item in the shopping cart? (additionally, that is--for anyone that would like to) |
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| BrianGT |
| quote: | Originally posted by tiroth
Brian, it is hard to say, because I panelized everything together to save on costs. So, if I suddenly got 150 more mox orders (and no opamp), that might actually increase the cost to me because the ratio of mox to opamps would be severely off.
I guess I can say definitively that if there are 40 more MOX and at least 20 more OPA, I could lower the price to $6. (quite doable) I would need nearly 100 and 90 more, respectively, to lower the price to $5. We're reaching the point where 30 more orders only knocks $0.30 off per board now.
There is definitely enough leeway that DIYaudio will be receiving a donation. Perhaps I should include a "donate $1 to DIY" item in the shopping cart? (additionally, that is--for anyone that would like to) |
I think that a donation would work best if built into the price. I find $1 extra per pcb is quite reasonable for both diyAudio, and the person purchasing the board. For my group order, I have donated $325 so far to the server fund. I will continue to donate more funds from the orders, once I get all the accounting settled.
I did have a "Make an additional donation" button on my order page, and only one person donated a few dollars. This caused a little bit of confusion, as another person accidentally used this button to pay for their order, which caused me confusion, as I had no record of their order.
--
Brian |
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| kestrel200 |
| OK.I'm a little slow, let me make sure I understand this correctly. For a 3rd or 4th order 2 way I would need 4 Mox boards and 16 Opamp boards. I would indicate this on the Wiki by entering 4 under the Mox column and 2 under the OPAMP column. Is this right???? |
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| tiroth |
You are exactly right kestrel200.
I'm including below the first draft of a "shopping list" for MOX. This is a list of all the needed parts available at Mouser (except 2SK389). I have listed both basic parts (e.g. 1% 100ppm metal film/polyester caps) and tried to list at least one alternate (e.g. Dale/Wima) for each item.
The list is split into Input buffer, MOX, output buffer, discrete opamp, and misc. The idea was to make it easier for people to separate out what they don't need.
I stress this: you don't need to fully populate the board unless you want to.
I have undoubtably made a mistake or two, and the proto order is not even in yet, so don't rush out and buy everything on this list. I would encourage feedback, and if someone feels like taking it and adding part numbers for other suppliers, that would be great. I would appreciate it if you would send it back to me though for version control.
P.S. While I welcome debate over whether there is a better part available from the same supplier, this is not intended to be an over-the-top shopping list. Welbourne labs is an excellant source for small film caps, and other specialty suppliers like Michael Percy and Parts Connexion help fill that void. |
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| kestrel200 |
| Thanks!! Just wanted to make sure I've added my order. |
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| tiroth |
kestrel, just double checking, but I took it as a fact that you only needed 16 opamps. This is true if you don't need the input buffer or the extra volume adjust output buffer. (each output is buffered before that stage anyway) If you wanted to totally populate all four boards, you'd need 4 sets of opamps, not two.
1 full MOX = 8 opamps (4 dual)= 1 set of opamps |
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| tiroth |
Just FYI, I got a call from Electronix. I got the last of their 2SK389 stock and their lead time is now unknown. Apparantly their supplier is totally out of stock. Sorry folks.
MCM has stock on hand, but a higher price. |
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| BrianGT |
| quote: | Originally posted by tiroth
Just FYI, I got a call from Electronix. I got the last of their 2SK389 stock and their lead time is now unknown. Apparantly their supplier is totally out of stock. Sorry folks.
MCM has stock on hand, but a higher price. |
You should order 100 (or whatever the demand is) or so from MCM and allow for the option of purchasing them with the boards, as the price is quite a bit lower in quantities over 100.
--
Brian |
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| Vladco |
Could it be used for bass management?
If yes how many boards I should use?
Vlad |
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| tiroth |
| Vladco, could you clarify what you mean by "bass management?" |
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| cowanrg |
| he may be referring to the outlaw IBCM, which is a 5 channel (or could be a two channel) crossover for sending low frequencies to the sub. |
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| Vladco |
It’s my fault what I didn’t clear express myself. What I’m like to have is to direct low frequency in subwoofer. What I meant is to relief main speaker from low frequency – from 40 to 90 Hz region. I think it called hi pass. I didn’t do my homework yet. I’m taking advantage from yours expertise. In my opinion –I could be wrong- majority of decent system will benefit from it.
Is it possible to incorporate variable phase delay in this crossover?
Vlad
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| cowanrg |
you are looking for something like this:
http://www.outlawaudio.com/products/icbm.html
i THINK this should be able to accomplish what you want, but we will see what others think, now that they have a better idea.
hey, you are from denver! small world.
| quote: | Originally posted by Vladco
It’s my fault what I didn’t clear express myself. What I’m like to have is to direct low frequency in subwoofer. What I meant is to relief main speaker from low frequency – from 40 to 90 Hz region. I think it called hi pass. I didn’t do my homework yet. I’m taking advantage from yours expertise. In my opinion –I could be wrong- majority of decent system will benefit from it.
Is it possible to incorporate variable phase delay in this crossover?
Vlad
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| JensRasmussen |
Hello,
This is regarding the question about bass management. The way I understand bass management is a setup where the bass information from multiple channels are LP filtered and the signals are then added to ONE channel for a subwoofer.
So to make a circuit for bass management we need a number of LP filters (Witch we have), and a summoning amplifier with as many inputs as we have channels. Maybe some sort of phase control is a good idea also. Anyway the summoning amplifier and phase compensator circuits can be build relatively easily on the part of the PCB meant for prototyping.
I hope this clears up the questions
\Jens |
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| peranders |
| quote: | Originally posted by JoeM
Wow! That board is over 1 square meter!:clown: |
.... one mil is?*)
Mil in Swedish is 10 km.....
*) Correct 0.001 inch. |
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| JensRasmussen |
HI,
Per you are right 1 MIL = 1/1000 inch.
The only problem is the size of an inch.....there are, as far as I know both UK and US inches....?
1 inch aprox = 2.54 cm
\Jens |
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| tiroth |
Vladco,
Thanks for clarifying. As Jens and cowanrg have said, the MOX boards can handle the filtering side of this task. But, there is no circuitry on-board to do summation or phase adjust. As such, I wouldn't recommend it to you as an out-of-the box solution. If you are able to do some work in the prototyping area, though, it can be used for bass management.
All pass filter
http://sound.westhost.com/dwopa.htm#allpass
General opamp info and summing amplifier
http://en.wikipedia.org/wiki/Operational_amplifier |
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| UrSv |
Jens, there is fortunately only one type of inch when we are talking measures in modern life. For the record also it is not approximately 2.54 cm (or 25.4 mm as some of the Non-Scandinavians would say). It is EXACTLY 2.54 cm BY DEFINITION to save us trouble.
As for weight units. After the first 1023 variations, forget it.... |
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| till |
| quote: | | It is EXACTLY 2.54 cm BY DEFINITION to save us trouble. |
I thought it was 25,4002 mm. |
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| tiroth |
Google sayeth:
1 inches = 2.54 centimeters
Back on subject. |
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| tiroth |
As long as I am able to acquire stock, I will also offer the 2SK389 at cost, 2 for $5. This is 30% less than the best price I have been able to find for small quantities. (I want to ship in pairs so I don't have to break the tubes down too much)
If anyone knows of a cheaper quantity source in the U.S. that actually has these parts in stock, please let me know!
(My cost is 100 for $215, $15 shipping, ~4% fees, about $2.40 each assuming I don't end up with leftovers) |
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| roibm |
tiroth, just need something plain and clear...
the price for opamp boards is a set of 8boards @ $5/set? or $5/board in set?
in wiki we write the number of sets we want to buy? or the number of boards?(I see orders with 20, that would be 160 boards if it is per set).
thanks :) |
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| tiroth |
The price is 8 opamps for $5
1 set in the Wiki = 8 single opamps (4 dual opamps)
EDIT: Fixed the typo. Thanks DT. No need to confuse people further. ;) |
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| Duck-Twacy |
| quote: | Originally posted by tiroth
The price is 8 opamps for $5
1 set in the Wiki = 8 single opamps (5 dual opamps) |
You mean 4 dual I guess ;) |
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| MBK |
| Just downloaded a catalog from a supplier here in Singapore. It's a pdf so who knows if it's up to date and also the minimum quantity assumed is unknown. This being said it claims 900 SK389BL in stock at USD 0.60 a piece. I'll try to call tomorrow to find out what the deal is. |
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| Antonio |
I have just added 2 OP-Amp set boards to the wiki.
Regards,
Antonio |
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| MBK |
OK, false alarm, the Singapore supplier is out of stock on 2SK389 (catalog was from 23 Dec 03, so they seem to be moving fast).
Their pricing seems to be for real though, inquiring about 50 pcs. of 2SK170 , which they do have in stock, I got quoted about 13 cents, which is that catalog price. The 2SK389 in the same catalog was quoted at 60 cents. |
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| tiroth |
| Any idea of lead time? We are, after all, about 4.5 weeks out on receiving the boards. Since that price is less than a third of the best price I've seen, it might be worth pursuing. |
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| MBK |
Tiroth,
I'll inquire on that after the w/e. |
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| tiroth |
| The proto order has shipped. I will post pictures and test results when I recieve it in a few days. I plan to start taking orders at that time. (via a PayPal shopping cart like BrianGT's gainclone order) |
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| BrianGT |
| quote: | Originally posted by tiroth
The proto order has shipped. I will post pictures and test results when I recieve it in a few days. I plan to start taking orders at that time. (via a PayPal shopping cart like BrianGT's gainclone order) |
I can provide you with webspace if you need a place to put your order page. Drop me an e-mail if you need some. I am leaving now to go visit relatives, and will be back tuesday morning.
--
Brian |
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| dqswim |
I looked all over but have yet to find what size range the MOX boards are going to be.
Could someone point me in the right direction.
Thanks |
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| tiroth |
Or for those of us in the states, 6.320x3.940". Opamp boards are 1.45x0.83".
Look for some pictures Tuesday night, I will have assembled boards then. |
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| MBK |
| Hmm, the Singapore dealer has no other info on replacement/backorder/lead time. They in fact claim that Toshiba discontinued the 2SK389 altogether... |
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| tiroth |
| Although it is late, I wanted to post a few pics of the proto boards. |
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| tiroth |
| More of a profile view |
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| tiroth |
| Last one for the night. You can see the discrete opamp does not take up much area on the board. I am afraid I won't have test results to post until tomorrow but everything is looking good. |
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| BDP |
Tiroth,
They are looking good. Waiting to hear about the results. Give us some info on the discrete opamp, how it fits with the DIP socket, output offset voltage, if any. How will a full compliment of the discrete opamps fit on the main board. I'm looking forward to getting started on this project. Great job.
BDP |
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| MBK |
Looks very nice and mighty "technical". Much better to show off than my spaghetti like protoboard dipole EQ and X- ;).
2 questions: What is the total height incl. standoffs and fitted op amp boards? (for enclosure size). And, how is the connection made between op amp boards and main board - right angle pin strips? |
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| dqswim |
Looks great.
Now I have both the dimensions and a picture. :D
-dave |
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| BrianGT |
Looks great! I was initially quite concerned with the board size, since I wanted to do some high order filters for my ribbon tweeter 2-way, but I have decided to just do a seperate chassis for each channel, and see how it works out, along with a stereo amplifier chassis for each channel to power the speaker.
I noticed that the boards look roughly cut apart. Are you production boards going to be cut apart by the manufacturering place?
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Brian |
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| tiroth |
The discrete opamps fit great. If you are using DIP sockets they plug right in with the bypass caps in place so you can switch the discrete in and out with your favorite opamp. If you aren't using sockets, it is probably a good idea lay the bypass caps down on the board. Or just put them on the bottom if your standoffs are as tall as the ones in the pic.
I bought both threaded standoffs and (cheaper) .375" spacers to tie the boards together. While the standoff definitely makes it a bit more mechanically solid, I think the spacers work fine. The combination of the screw thread and the wire power links at the top of the tower make it sturdy enough to plug and unplug many times.
MBK, I'll post the exact dimensions for you tonight, since I'm currently at work. I am indeed using right angle pin strips with 20-mil size pins. Wire links could also be used.
I'll also post the exact footprint of the assembly for those who are interested in replacing opamps in existing designs.
Brian, you're quite right. To save proto costs (to the tune of about $150) I got the protos unscored and dremeled them apart.
:smash: The production boards will be scored by the board shop.
Test results tonight for the MOX and a sanity check to make sure all is well with the discrete opamp. I won't have detailed opamp measurements until Thursday night. |
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| Duck-Twacy |
| quote: | Originally posted by MBK
Hmm, the Singapore dealer has no other info on replacement/backorder/lead time. They in fact claim that Toshiba discontinued the 2SK389 altogether... |
Is their a replacement for it?
The idea to buy a 100 @MCM as part of the PCB buy sounds good to me. |
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| MBK |
I wouldn't be surprised if the 2sk389 was in fact alive and kicking. Whatever they tell me here I take it with a grain of salt. The English is not always the best, and rather than embarrassing themselves in attempting to describe a complicated situation they just cut it short and say "discontinued".
FWIW - what other transistors are a close match to the 2sk389? Maybe I can get an equivalent type locally. It's always nicer to play around with stuff that can be replaced easily in case of crash'n'burn ;) |
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| tiroth |
It works. :D
The MOX board is good to go. I won't have the discrete opamps verified until tomorrow as I...mmm...blew up the only one I built so far. :hot:
Note: the LP filter appears to cut off after 10k, but this is simply crosstalk in my soundcard. |
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| tool49 |
Looks very nice, would you mind giving us a bit more info about the graph? What were the curve chosen, the Q of the filters, the target frequencies, etc...
Also why is the level at -10? What was the gain configured in the buffers?
Thanks!
Sébastien |
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| moamps |
| quote: | Originally posted by tiroth
It works. |
Hi,
very nice work.:) | quote: |
I won't have the discrete opamps verified until tomorrow as I...mmm...blew up the only one I built so far. [/B] |
Problem is maybe wrong BJT's orientation if you are using MPSA42 and 92.
Regards |
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| tiroth |
Dimensions
The completed dual opamps have a footprint that is just about exactly .930x.930", or about 23.6mm square.
They stand 1.45" (37mm) tall, plus another .1" (2.5mm) if you use the headers I used.
The total height of a MOX board populated with opamps is about 2.25" (57mm), less depending on your use of sockets, etc.
Graph
The graph shows the curves for HP and LP @ 2kHz with Q of 0.5, 0.7, 1.4, 1.7 (on the HP).
Don't pay attention to the absolute gain; I needed enough headroom to show the high Q peaking.
Opamp
Moamps, I have the sinking feeling that you are right. I traced my layout against yours, not thinking that your red traces were problably bottom signal for a single layer board. :bawling:
Time to fix. :smash: |
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| tiroth |
| EDIT: The Q values I listed may be wrong. It was rather late last night when I finally got to tracing the curves and I replied from memory. Comprehensive tests are coming tonight. |
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| moamps |
| quote: | Originally posted by tiroth
.....not thinking that your red traces were problably bottom signal for a single layer board. ...[/B] |
Hi,
It's my fault too, sorry. OPAMP PCB is designed at the first time for BC550C and BC560C (diferent pinning). MPSA transistors are later placed on board (mirrored), but I didn't made changes on PCB board picture I published in MOX thread.
Regards |
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| MBK |
| How about leaving it as is and using BC550/560? |
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| roddyama |
| quote: | Originally posted by tiroth
EDIT: The Q values I listed may be wrong. It was rather late last night when I finally got to tracing the curves and I replied from memory. Comprehensive tests are coming tonight. |
| quote: | Originally posted by moamps
Hi,
It's my fault too, sorry. OPAMP PCB is designed at the first time for BC550C and BC560C (diferent pinning). MPSA transistors are later placed on board (mirrored), but I didn't made changes on PCB board picture I published in MOX thread.
Regards |
| quote: | Originally posted by MBK
How about leaving it as is and using BC550/560? |
I hope we can go with the MPSA 42 and 92 since I already have a stock just for this project.
BTW, that was what was shown in Moamp's original schematic. |
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| tiroth |
You could use BC or MPSA parts without modification (you must bend the center lead anyway for the inline package), only the silkscreen is wrong as-is for the MPSA (in proto only). I too have a few hundred MPSA42 and 100 MPSA92 on my desk. ;)
The question is, should the PCB be changed for production? |
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| tiroth |
| quote: | Originally posted by roddyama
I hope we can go with the MPSA 42 and 92 since I already have a stock just for this project.
BTW, that was what was shown in Moamp's original schematic. |
Schematic and board, chotto chigaimashita ne? My problem, will address however people see fit. |
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| BrianGT |
| quote: | Originally posted by roddyama
I hope we can go with the MPSA 42 and 92 since I already have a stock just for this project.
BTW, that was what was shown in Moamp's original schematic. |
Yeah, I already ordered some myself also :)
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Brian |
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| tiroth |
| Supporting MPSA92/42 is a given. But should the board be changed--is it a problem? |
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| roddyama |
| quote: | Originally posted by tiroth
You could use BC or MPSA parts without modification (you must bend the center lead anyway for the inline package), only the silkscreen is wrong as-is for the MPSA (in proto only). I too have a few hundred MPSA42 and 100 MPSA92 on my desk. ;)
The question is, should the PCB be changed for production? |
Crossing the leads of 1 or 2 transistors is no big deal. Much like the FET in the A40 boards from Old Colony (back in the day). But to cross them on many pieces is, statistically speaking, asking for trouble. |
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| tiroth |
| Well, you don't need to cross them, you just flip the whole device around. That is the nice thing about having the base in the center. |
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| roddyama |
| quote: | Originally posted by tiroth
Well, you don't need to cross them, you just flip the whole device around. That is the nice thing about having the base in the center. |
I can live with that easily enough.
BTW, Your doing a great job Tyler, thanks. |
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| moamps |
| quote: | Originally posted by tiroth
[B]You could use BC or MPSA parts without modification (you must bend the center lead anyway for the inline package), only the silkscreen is wrong as-is for the MPSA (in proto only). I too have a few hundred MPSA42 and 100 MPSA92 on my desk. ;)
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Hi,
here is MPSA modification example.
Regards |
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| BrianGT |
I think that crossing the leads might be fine, but if you have a large board order, the extra tooling fee shouldn't be too much extra for getting the layout modified.
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Brian |
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| roddyama |
| quote: | Originally posted by BrianGT
I think that crossing the leads might be fine, but if you have a large board order, the extra tooling fee shouldn't be too much extra for getting the layout modified.
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Brian |
You missed it Brian. I was mistaken, the leads do not need to be crossed. It is only that the center base lead is offset toward the flat ("front") of the device instead of the round ("back"). Look closely at Moamps' picture above. |
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