| JensRasmussen |
Please post pictures and other relevant material here
\Jens |
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| tiroth |
PLEASE do not forgot that the 3-pin transistor silkscreen on the opamp boards is correct for BC550/560, and REVERSE for MPSA42/92.
So depending on which you are using:
MPSA42/92: REVERSE of silkscreen
BC550/560: SAME as silkscreen
If you need more info, the relevant posts start here:
http://www.diyaudio.com/forums/show...3422#post383422 |
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| JensRasmussen |
MOX builders thread is about the construction of an adjustable cross over module, partially based on moamps original design – hence the name has been reused.
Thanks to moamps for his efforts in both the descrete opamp and the original filter design found here : http://www.diyaudio.com/forums/show...7651&highlight=
Also many thanks to Tyler who has made it all happen, for managing the group order and for his excellent page here:
http://www.anidian.com/audio/home.shtml
The board is a module that can form the following signalpath:
My prototype board looks like this:
More info can be found here on my homepage
Active filter two - mox
Please post pictures and other relevant material here
\Jens |
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| BDP |
Tiroth,
I have noticed two different resistor values listed for collector resistor R3 on the discrete opamp. One is 392 ohms and the other is 360 ohms. Which value would be more optimum? You had posted your findings on a very low DC output offset, with which resistor value? Was this one of the follower buffers, HP, LP filter or was it with gain?
Putting together my order of parts. It always adds up to more than you think. A couple hundred dollars just to populate six boards. Still deciding on a power supply. What is everyone else going to use?
BDP |
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| Bas Horneman |
| quote: | | Still deciding on a power supply. What is everyone else going to use? |
2*12V(33aH) batteries. 29$ each. (surplus) is what I am planning. Could be bettered I suppose..but not for the money and effort.
Cheers,
Bas |
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| tiroth |
Batteries are great, but 33AH? Pretty stiff supply! ;)
BDP, I used 392. The offset is going to vary slightly depending on the supply voltage. You can trim it to zero by using a pot or a selected resistor in R4. I did not need to trim it for my use--the offset was so small that it did not affect the operating point in the MOX circuit.
I measured the offset both in-circuit with one sample and on the bench (Gain=1 buffer). The results were similar. |
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| JensRasmussen |
Manual here Manual
Parts list
\Jens |
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| marsupialx |
Probably a stupid question...
Can two active xovers be hooked in parallel to one set of output jacks, ie one rolling off at say 200 hz and one going out to 2000?
Will it do what I want, reinforcing the lower bass, or will it screw something up?
A simple equalizer circuit built on the experiment hole portion of the board is probably a better idea. Thanks. I hope I can comprehend the answer. We'll see... |
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| tiroth |
| At minimum, you need some kind of summing circuit, whether that is an opamp or a simple resistive summer; otherwise, they will fight each other. |
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| marsupialx |
Potential compounded stupidity...
Can the output buffer play a role in the afore mentioned summing, feeding both signals thru the one buffer?
I'm way out on a limb, way past my comprehension of electronics on this, sorry. |
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| marsupialx |
| I'm starting to get my head around what is needed to sum two crossovers. It's a mixer, without all the knobs. - Thanks - |
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| JensRasmussen |
Grimberg
Parts list as word file here : Partslist
It's the best I can do. Tyler has an excel file with values.
Tyler could you post it here?
\Jens |
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| JensRasmussen |
Parts list as PDF now ready : here
\Jens |
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| marsupialx |
All of the parts seem relatively easy to find, except the 1uf cap in the 5mm size in polypro. I can find the other three values, but I am only finding PE in the 1uf. Any mfgs or part numbers would be appreciated.
The 15.2K resistor looks like it can be arrived at by a 28K and a 33.2K in parallel. Gets ya' to 15.19K by my calculations. |
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| JensRasmussen |
PE is just fine.
\Jens |
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| cowanrg |
| quote: | Originally posted by marsupialx
All of the parts seem relatively easy to find, except the 1uf cap in the 5mm size in polypro. I can find the other three values, but I am only finding PE in the 1uf. Any mfgs or part numbers would be appreciated.
The 15.2K resistor looks like it can be arrived at by a 28K and a 33.2K in parallel. Gets ya' to 15.19K by my calculations. |
as Jens said, PE is just fine. as for the resistors, i use vishays in my stuff, and mouser has vishays in 15K range, just get a few extra and since they are 1% tolerance, you should be good with 15.2K. i needed a 120ohm resistor before, so i just got a bunch of 121's and tested them out to 120 ohms.
btw, you still need to email me so i can send out some batteries :) |
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| JensRasmussen |
Hi,
I sorry but there is an error in the partslist. All values are correct, but the position is wrong....Please use the list in the manual I'll change til partslist ASAP
Sorry for any trouble this may give you
\Jens |
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| JensRasmussen |
Thanks to Bryan Pederson for bring this error to my attention.
I think the list is ok now, Bryan please report back when you have had time to check - thanks
\Jens |
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| chipco3434 |
Does anybody want to do a group buy for components for this project? If there is a volunteer for the identification and PN's, I'll do the purchase and mailings.
Raise your hands. |
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| diamdiam |
| i'd be interested in a group buy |
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| tiroth |
I think it is probably cheaper to order from Mouser, the 1% 100ppm tempco are..what, 2 or 3 cents each, and you get exactly the needed values. And you can order in quantities as small as 1. Their shipping for small packages is as little as $5.
I will repost my spreadsheet tomorrow (4th of July observed in the U.S.!) which has the correct part numbers. I just want to vet it again for accuracy, although it is in the big group buy thread.
I tried talking Jens out of a component group buy mostly because it would be an absolutely insane amount of work to kit out all the resistors. ;) |
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| grimberg |
Tyler,
Even though I reviewed the original Moamps’ thread, I could not find the schematic that matches the discrete OpAmp board layout. Could you please tell me where I can find it?
Also, I could not find at Digikey or Mouser a 100 nF capacitor that fits the spacing of C3 on the board. Which component did you use as reference for the layout? |
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| JensRasmussen |
I have a lot of these from work (They were thrown out because they are not used anymore)
If you are interested I can send some of them for free – you only have to pay for the shipping.
Tyler how many do you want - maybe I can send 500 or so to you, and you can send them to people from the USA?
\Jens :) |
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| tiroth |
| quote: | | Even though I reviewed the original Moamps’ thread, I could not find the schematic that matches the discrete OpAmp board layout. Could you please tell me where I can find it? |
Here was the original schematic that the boards were built from; some parts are missing now so I should probably draw a new one, but this can be used to see the component designators.
http://www.diyaudio.com/forums/show...9405#post369405
| quote: | | Also, I could not find at Digikey or Mouser a 100 nF capacitor that fits the spacing of C3 on the board. Which component did you use as reference for the layout? |
This is tough to find. Moamps might be able to respond with the cap he used. I ended up using Mouser 75-MKT1826410064 but the leads had to be bent. You could probably use 23PW310 (10nF!) but I have not tested this.
I am attached a slightly changed shoppping list. It has primary and alternate Mouser part numbers for most everything you need; I stuck to 1% parts, so there are a few Q values that don't exist. You can parallel if you really want them or look up a .1% part. |
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| tiroth |
| quote: | Originally posted by JensRasmussen
If you are interested I can send some of them for free – you only have to pay for the shipping.
Tyler how many do you want - maybe I can send 500 or so to you, and you can send them to people from the USA? |
Very generous of you Jens. :) Sure, I'd be happy to distribute. Shoot me an email re shipping cost. |
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| Jamh |
| quote: | Originally posted by tiroth
Very generous of you Jens. :) Sure, I'd be happy to distribute. Shoot me an email re shipping cost. |
I'm interested in the above. Please let me know. I'm also interested in a group buy for the components, if there is one. |
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| tiroth |
If anyone feels it worthwhile, I'm willing to coordinate purchase of the film caps. This is unlikely to make sense unless you know that you need Jens' caps and want to get it all shipped for one cost--the price breaks aren't huge.
For example, the 100nF Wima ($0.79) becomes $0.57 at 100 units. The cheaper 100nF MKT1826 ($0.21) only drops to $0.17.
I'm not willing to kit out all the resistors though. Chipco3434, are you serious about doing this? If so, it would make much more sense to have the caps sent to you.
People who have an interest, please email me to avoid cluttering the thread. Let me know about how many caps you want and if you want the polyester or the Wima in the spreadsheet. If I think there is sufficient interest (I would be surprised, honestly) I'll start a thread. |
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| moamps |
| quote: | Originally posted by tiroth
This is tough to find. Moamps might be able to respond with the cap he used. I ended up using Mouser 75-MKT1826410064 but the leads had to be bent. You could probably use 23PW310 (10nF!) but I have not tested this. |
Hi,
I tested my opamp with 47nF, 100 and 220nF MKT (whichever I happen to have at hand :)), without a problem. This cap's value may range from 10nF to 1uF and the cap type does not really matter much (small elco, for example).
Regards
Milan
Edit: Mouser 140-PM2A333K 33nF with 3.5mm pitch looks good and cheap. |
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| jhead |
| I would be interested in some of the caps from jen's to fill two Mox pcb's also if the group parts buy take's place would have a interest |
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| marsupialx |
| When I go to Mouser and type in the resistor part numbers, it comes up at .12 single and .10 @ 100. How does one obtain the .03 price as listed on the parts list? Thanks. |
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| tiroth |
| I spot checked a few part numbers and they all came up for $0.03. Are you sure you aren't choosing the 50ppm parts? Mouser sometimes "corrects" your part numbers unexpectedly... |
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| marsupialx |
| Yep, mine are coming up .03 now. It's mysterious. Thanks! |
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| marsupialx |
Another possibly stupid thing...
for a bandpass filter, do you simply set a lower high pass and a higher low pass, and connect them together?
for instance, a 500 hz high pass and an 8000 hz low pass |
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| tiroth |
| quote: | | for instance, a 500 hz high pass and an 8000 hz low pass |
Yep. |
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| BDP |
Stuffed and tested my first high and low pass sections with IC opamps and all tested great. Received the rest of the parts for the discrete opamps. They will be the next to be assembled and tested. I plan on building a few variations with bipolar and mosfet outputs along with a Borbely balanced circuit for the outputs.
BDP |
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| JensRasmussen |
marsupialx
I hate to toot my own horn, but maybe you could benefit from reading the manual about my Active filter One project.
It can be found here: Webpage for Active Filter One
\Jens |
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| Andypairo |
Hello,
I have a question about C2 and C3 in the discrete opamp PCB: C2 is 100pF and C3 100nF.. why the former has a pin spacing that is double the latter? It is pretty hard to find 100 nF film caps with 2,5 mm spacing... or a ceramic is just fine?
Cheers
Andrea |
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| tiroth |
| quote: | | I have a question about C2 and C3 in the discrete opamp PCB: C2 is 100pF and C3 100nF.. why the former has a pin spacing that is double the latter? It is pretty hard to find 100 nF film caps with 2,5 mm spacing... or a ceramic is just fine? |
Answer:
| quote: | | Originally posted by moamps:This cap's value may range from 10nF to 1uF and the cap type does not really matter much (small elco, for example). |
Another option would be to use the free "N" pad. The spacing there is just a bit over 5mm. |
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| Andypairo |
Thank you, I somehow had missed this answer....
Cheers
Andrea |
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| marsupialx |
| Thanks, Jens, the manual for the 'crossover one' is very enlightening. That looks like the board to get once the design is squared away using the mox. Nice work. And thank you again for the work you put into the mox. It is awesome. |
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| MBK |
Hi Jens,
would you, by any chance, have a complete circuit schematic available? In the documents you posted, there is a block diagram, and schematics of the individual blocks with part designation. But there is none of the complete circuit of one MOX board.
The reason why I ask is that I assume to build the layout you have one lying around already, and for ppl like me who will assemble several boards for 4th order 3 channel setup with some parts substitutions etc, a full diagram would help. Also, to locate jumper setup with multiple boards. Any form, pdf or gif is enough, I can then print out 4 copies per channel and assemble/draw on paper.
One error correction: in the manual's block diagram, latest edition, there are two "jumper 2" labels. The one on the right should be labeled "jumper 3".
Markus |
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| MBK |
Another thing I may have missed: for dicrete op amp use (it will take me some time to get there but working ahead) - where on the MOX board do you place the 4k7 for DC stability? I gather it's on the underside, but I can't find holes corresponding to it. Or is it supposed to be surface soldered?
Markus |
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| tiroth |
MBK,
| quote: | | would you, by any chance, have a complete circuit schematic available? |
Jens has posted full schematics on his site. It is the first item in the list of downloads:
http://www.delta-audio.com/Active%20filter%20two.htm
| quote: | | where on the MOX board do you place the 4k7 for DC stability? ... Or is it supposed to be surface soldered? |
Correct...there are no pads for it on the MOX mainboards, which was designed for standard opamps. An alternative to surface mounting is to use R10 on the opamp boards and connect to a nearby ground pad. |
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| MBK |
Hi Tiroth,
yes I have that document. It does have all the schematics, but piecemeal. It would be nice to have a larger, complete schematics, so I don't have to cut and paste the different sub-circuits together from the different pages. Of course that can be done too, but I assume to make the MOX board layout Jens already has a file with the complete circuit in one page...
Markus |
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| JensRasmussen |
Hello,
Well in fact I don’t have complete schematics in one page, simply because putting it in one page would make it to small to read.
However you should be able to follow to off page pointers and get the signal path that way.
\Jens |
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| MBK |
OK, fair enough...
Thanks
Markus |
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| JensRasmussen |
Thank you for the information about the name of the jumper. Webpage and manual are now updated.
\Jens |
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| JensRasmussen |
HI,
I don’t know how many boards Tyler have left. If there are any left I’m sure you can bye some from Tyler.
\Jens |
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| tiroth |
Yes, I still have some left and the order form works. The 2SK389 are marked OOS but I actually got ahold of a few more, so shoot me an email if interested. :smash: |
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| jewilson |
tiroth
Yes I am interested; I also have some friends that will be interested too. I have been considering building an active crossover for while but using discrete amps instead. However, like so may other things I don't have the time. But I have the amps.
:) |
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| chipco3434 |
| quote: | | I'm not willing to kit out all the resistors though. Chipco3434, are you serious about doing this? If so, it would make much more sense to have the caps sent to you. |
Sorry to have stepped out of the thread for a while... Sadly, I have been obliged to W*RK. (Moderators...sorry for the four letter word!)
Few people have really bit on this thread. It seems as the most tedius part of this project is typing in the part numbers for ordering!
I would be happy to distribute those surplus caps from Jens ( for the cost of the shipping) to all the audio junkies in North America.
Of course, I would be happy to forward Jens the money for the shipping. (Via Paypal I would assume.)
So, kick it arround. |
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| BDP |
I have assembled and tested the discrete opamp and all have checked out good. When the first opamp was assembled on the circuit board and power and other leads were breadboarded it oscillated. YIKS? Whats going on??. I regrouped shortened my test leads and now it works. The bandwidth of the follower with 68pF cap for C2 is 5MHz. 100pF was about 4MHz.
I have also used a P-channel MOSFET, a Zetex ZVP3310, in place of PNP MPSA 92. I used a 5K fixed resistor parallel with a 10K pot. at R3 and R4 in order to adjust for zero DC offset. The value of the drain resistance worked out to be 1850 ohms , but this value will vary depending on the ZVP 3310 used, that is if you want a low DC offset. Initially the drain resistance R3 used was 1500 ohms and the DC offset was 230 mV. I also added a 100 ohm gate resistor to the mosfet just for good measure to prevent oscillation.
I have no doubts that the circuits will work when installed in the MOX filter boards.
BDP |
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| tiroth |
| quote: | Originally posted by chipco3434
I would be happy to distribute those surplus caps from Jens ( for the cost of the shipping) to all the audio junkies in North America. |
Jens sent them out to me just the other day; as soon as they arrive I'd be happy to send them out to anyone who is interested. |
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| jhead |
| I would be interested in a set for the MOX please let me know thanks |
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| tiroth |
I have the caps. Thanks Jens!
Anyone who wants some, please send me an email and include- your name
- your address
- the number of caps you need
Thanks. |
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| JensRasmussen |
Tyler,
Let me know if/when you need more caps :)
\Jens |
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| tiroth |
| Thanks Jens. :) USA folks, if you need caps, email me. I've only had a couple of requests so far. |
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| Peter Daniel |
| What kind of caps are those (make and value)? |
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| Nisbeth |
1uF/63V Epcos. Blue with 5 mm. pin spacing. Size is virtually identical to a Wima MKS-2 with the same value.
/U. |
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| MBK |
...sounds like moral philosophy ;)
The compensation caps on the feedback resistors could use some different values IMO unless I am missing some design consideration.
The input FR blocker LP filter is the R003/C002 combo of 100R and 100 pF by manual. The cutoff (RF filter) is thus about 15 MHz. Consider using a lower LP value, between 150kHz and 300 kHz, say for instance by changing R003 to 5k, and R004 or 47k or 50k.
The inverse situation is found on the LP and HP actual filter sections, for the compensation cap around the feedback R to prevent out of band amplification. C200 and C500 parallel to R200 and R500 22k resistor gives an out-of-band LP of about 80 kHz. This could be set a tad higher, to prevent the cumulative LP filters from starting to affect the audio band, say by making C200 and C500 68pF or 39 pF (LP at 106 kHz or 186 kHz, respectively).
Markus |
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| BDP |
| quote: | | The inverse situation is found on the LP and HP actual filter sections, for the compensation cap around the feedback R to prevent out of band amplification. C200 and C500 parallel to R200 and R500 22k resistor gives an out-of-band LP of about 80 kHz. This could be set a tad higher, to prevent the cumulative LP filters from starting to affect the audio band, say by making C200 and C500 68pF or 39 pF (LP at 106 kHz or 186 kHz, respectively). |
In MOAMPS original work up the value was 47pF.
BDP |
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| MBK |
... the input filter is dominated by the R004/C002 combo. Pls ignore my comment on the input filter. I should think more before I write.
The feeback C comment stands...
Markus |
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| JensRasmussen |
Markus,
While I was testing the prototype I never used the feedback capacitors. This does not mean that they are not needed, but I have not had time to verify the size needed in different configurations.
If anybody would like to simulate or test in real life and post results it would be great.
\Jens |
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| MBK |
Jens,
I'll report as I go along, but my testing is quite limited. I can't test for much more than audio frequency responses. Usually I use best guesses from what I see published. I still have some parts missing but otherwise my 8 boards are 80 % finished, maybe in a week or two I'll have first results. That was quite a marathon btw in soldering.
For input RF filters and for compensation caps, usually I see 150-250 kHz LP's applied. The reasoning behind that is that it should be about 10 times audio range to ensure that there is no phase shift in the audio band even when several of these filters accumulate in a chain, as they usually do.
As you said these caps may not even be necessary. They're just a safeguard for these RFI infested times. It may make a difference for anybody using high speed op amps in a dirty environment. As for instance, having a cell phone transmitter nearby.
Same range applies to decoupling caps at the op amp pins. I use X7R ceramics at 10 nF to get the maximum HF performance. This is the value recommended for high speed op amps such as OPA2134 (as of data sheet). For NE5532 for example, I see anything from 1 uF to 10 uF electrolytics recommended... and not even necessarily at the pins but every 2 inches or so. So, your 100 nF is a good median value, all else depends largely on what op amps ppl will use. High speed types will be most picky, and to be honest, proper decoupling was the single greatest effect I saw in my contraptions from parts alone over the past 4, 5 years of DIYing. For instance I use garden variety resistors because I don't expect major effects here. But that's just me - I will just assume the risk of using my best guesses and I can't guarantee it works, for me or anyone else ;) As for caps here I use PP for the smaller caps and PE for the large ones, but in the past I have used dipped PE's that sounded just sweet. So we'll see. I *do* hope for an improvement over my veroboard messes...
Another thing that struck me, the standoff holes will connect a metal standoff to the ground plane. For ppl like me who will connect 4 boards per channel, it may be a good idea to use plastic standoffs or else get multiple ground loops through the chassis. It may or may not matter but better be safe than sorry... I'll use plastic clip-in types.
Markus |
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| JensRasmussen |
Hi Marcus,
I added connection to the ground plane because it’s easier to get rid of than to make later. It is, as you say, a question of using plastic stand offs, instead of metal ones. I have just received a bag of both plastic and metal ones, so it should be possible to find the best solution. I think that I’ll use three plastic and one metal Standoff per board.
I added the ground connection because of the “shielding” effect. Many users (my self included) will use the boards without enclosure and this gives a risk of picking up noise. The shielding may help against this.
\Jens |
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| moamps |
| quote: | | For input RF filters and for compensation caps, usually I see 150-250 kHz LP's applied. The reasoning behind that is that it should be about 10 times audio range to ensure that there is no phase shift in the audio band even when several of these filters accumulate in a chain, as they usually do. |
Hi Markus,
You are right.
Also, compensation caps in this design are needed only on input (and eventually output) buffer opamps. IMO
| quote: | | I'll use plastic clip-in types. |
This is very good idea. (strongly recommended)
(or cutting cupper foil around holes)
Regards
Milan |
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| JensRasmussen |
If you want more BW from the input filter, just change C001 to 22 pF.
This reduces the phase shift to less than 1 degree at 20 kHz.
\Jens |
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| marsupialx |
I'm almost done assembling 10 mox boards. I will be configuring a 4th order capable 3 way xover and a subwoofer xover. Fun, fun, fun.
I'm wondering if someone knows what opamps would be the best sounding for all around use, or are there better opamps for bass, midrange and treble?
Has anyone heard of Sound Odyssey? They are making noises suggesting that the AD8066 is the cat's meow. Expensive little guys, and they would have to be adapted to fit. Maybe just for the midrange???...
Thank you guys for everything, for making this project possible. It is way beyond cool. I'm finally going to build the dream speakers, (and procure a six channel amp.) |
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| marsupialx |
If powering the mox via batteries, is there reason for concern if the power is slightly different between V+ and V- ?
Any guesstimates on how long a mox board will operate on 4) NiMH 9v cells, two in series for each + and - ? I'll probably be using opa2134's, at least at first.
Eventually I'll build a power supply
Thanks. Sorry if the second question is nebulous. I'm looking for ranges, 30 min. or 4 hours, that kind of thing. |
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| cowanrg |
jeff,
in the beginning of this thread there is a mention of the current draw for the boards. i think its 0.5AH or so at max. i think nihms are typically like 2800mah, so it could be powered (from 1) around 5 hours i guess... if you did two, 10 hours, etc... |
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| marsupialx |
SubMox.
Both sides identical.
A few parts left to install. |
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| marsupialx |
| Straight on view |
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| Peter Daniel |
| It's not only nice, it's also very inventive. I don't think I saw a better example of fresh thinking and more original approach yet. |
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| TNT |
OK OK - but how does it SOUND ??
please a litter higher resolution on the pics ?!
/ |
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| marsupialx |
| Couldn't tell you how it sounds, still missing pieces, such as opamps. |
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| cowanrg |
jeff,
if you dont mind, i could host the big pictures you send me on my website. i have the space for them, and people could see them in high res :)
looks great though. even though im not 100% sure of why you are doing some of the things you are doing. |
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| marsupialx |
| Hey Robert, that would be groovy if you would post them so people could see them. There are reasons for most decisions, one was visual, but one was easy availability of both boards for configuring, and 9v batteries (4 per side) fit into the outriggers. - Jeff (marsupialx) |
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| cowanrg |
| sounds good. I'll toss them up on my site once i get home from work. |
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| tiroth |
Very impressive Jeff. :)
My apologies to you and everyone else who requested 1uF caps via Jens--I put all of them in the mail today. If you don't have them by the end of the week, shoot me some mail. |
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| marsupialx |
| Another reason decisins were made is the materials were laying around. I didn't go out and buy the aluminum, I just took stock on what I had and designed around that.Eventually I'm going to do another similar unit with 4 boards per side. Then six channels of tube amps and a tube preamp along similar design aestectics. But that is on down the road. - Thanks to everyone involved in making the boards available. Way cool. - Jeff |
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| marsupialx |
| The triangle little unit 'logo thing' is a storage box for jumpers. I just needed to do something frivolous. |
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| bg40403 |
I find an advisory in ADN003 that says an op-amp's slew rate should be greater than "2pi Vout p-p fc". Could someone shed some light on this for me? Is it frequency dependent (different for high or low fc)?
Also, has anyone measured the performance of the discrete op-amp?
I attach a worksheet for a better understanding of op-amp spec's. For an excel copy of the worksheet, send me an e-mail request. |
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| JensRasmussen |
Not sure if this is right, but it seems to me that SR = 2 x pi x f x A where
f = freq
A = amplitude [V]
\Jens |
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| bg40403 |
OK,
I get the part where 2 pi=6.2832.
My remaining question is: What p-p voltage should we expect going through the Mox op-amps?
3 volts p-p entered into the equation tells me the Slew Rate needs to be around 19. However some of the op-amps deemed acceptable, ie. NE5532 have a slew rate of 8.
I'm trying to understand if this indicates a shortcoming of some chips or is the voltage to high?
Mongo can hunt and gather but this is to high on the tree. Can I get a ladder? |
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| JensRasmussen |
| I get 0.19 [V/µsek] at 20 khz 3 V pp (A=1.5V) |
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| bg40403 |
I see.
So op-amps with a slew rate above 2 should be more than adequate.
Thanks, Jens
And also for the caps! |
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| bg40403 |
Thanks Milan,
I had forgotten that post.
OVER 4V/uS. |
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| JensRasmussen |
| quote: | Originally posted by bg40403
I see.
So op-amps with a slew rate above 2 should be more than adequate. |
I suppose it’s a matter of opinion if it’s adequate or not. If you only look at slew rate and limit yourself to small signals below 20 kHz.
If Vpp = 24V and f=100 kHz you need a SR of 7.5 V/µsek.
This is a large signal case, and since the signal levels from a line out are much smaller, it should not be necessary with more than
Vpp = 10V and f=100 kHz you need a SR of 3.2 V/µsek.
\Jens |
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| chipco3434 |
This project has had some small issues...
Note to self: Try to keep those trimmed resistor leads out of wife's foot.
Now the questions:
1. Anybody have a Mouser part number for the 8 pin dip sockets? Being new to this, there are at least 50 variations on this theme. Ordering the correct part the first time will help me keep the price down.
2. It would appear that the dip sockets must be used to get the height of the discreet boards above the height of C801-4 & C901-4, right?
3. I am unable to identify the components associated with C001 and C002, C200 & C500, and C800 & C900. I could use the values and even better, some part numbers.
4. Is the nomenclature of a 4.7k resistor normally expressed as "4k7"? While we are talking about it, where does it go?
Thanks to all in advance! |
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| chipco3434 |
I almost forgot...
parts list calls out a C1 of 100pF on the opamp but I don't see it on the board???
Could use the help.
Thanks |
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| tiroth |
| quote: | Originally posted by chipco3434
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1. Not offhand, but if you order a gold-flashed machined-pin socket you can't go wrong. Often available cheap as surplus.
2. It helps, but if that is the only reason you are using a socket it would be better to hard-wire and just lay the caps on their side, or on the underside.
3. These compensation caps are not needed with the discrete opamp, nor with the IC ones I've tried.
4. Yes. You can place it on the opamp board, or on the underside of the MOX board.
(5) I think you are mistaken--there is no part C1! Don't confuse moamp's designators with mine. I suggest you take a look at the opamp guide, there are some good pictures to help you out.
http://www.anidian.com/audio/construct/opa_1.shtml
Good luck, and don't be afraid to come back with more questions. |
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