Thursday, September 20, 2018
MXR Micro Chorus
The originals used a now nearly unobtainable SAD512D chip, but the wizards on FSB converted it to work with an MN3007. Now that those are also hard to get a hold of, I've laid this out for an MN 3207–which is almost the same as the 3007, just with a slightly different pinout for power and ground. But if you want to use a 3007, I've included a daughter board that will let you use it (it will also work to use a 3207 in place of a 3007). This will best fit in a 125B and the schematic can be found here.
I'll try to verify it as soon as I can. I have a few 3207 lying around and absolutely love the micro chorus. Thanks for the layouts!
ReplyDeleteLooks interesting? Any ideas on a depth mod?
ReplyDeletehttps://goo.gl/images/mupTSj
DeleteI assume that I can put a Pot between C17 and R28 y R34 ass a voltage divider. Maybe it's wrong, I don't know.
Someone tried this?
DeleteJusto venía a preguntar lo mismo. (I just came to ask the same)
ReplyDeleteHello, thank you very much for your work.
ReplyDeleteWhere Rate 1 should go connected ???
Thank you very much!!
As I understand it, Rate 1 is not connected. You could connect it to Rate 2. It is just the resistance between Rate 2 & 3 that matters.
DeleteUnfortunately, I didn't manage to get my circuit working properly. I only get clean signal out of the circuit. I'm still looking for my wiring mistakes. The thing that bothers me though is the voltage divider around pin4 of the MN unit. The datasheet says that typical voltage for that pin is ~14/15 of supply voltage and as it is, it is much lower than that. I checked the schematic and it gives the values used here, but shouldn't they be reversed?
ReplyDeleteBTW I decided to do so, but I'll be able to chceck the results tomorrow in the morning as it's 11pm at my place :)
DeleteThere could be an error on the schematic, or it could have to do with swapping the 3007 for the 3207. Might be worth swapping those 2 resistors.
DeleteI tried swapping them and I also checked several MN units, but I did not manage to get chorus sound, only the clean sound of my guitar... I'm still looking for some mistakes in my wiring. I'll let you know if I get it working properly :)
DeleteCzcibor Hejwowski
DeleteI have not done this yet, but it seems to me that there is a mistake. In the case of MN3207 pin 7 and 8, the 47 K resistor should go on ground and not on power
There are two 47K resistors in the schematic and layout, one is connected to the ground and the other one to VCC. Isn't that supposed to be a voltage divider/biasing for the circuit?
DeleteThere is hope to see here Catalinbread Topanga(FV-1)? thank you for your work!!!!!!
ReplyDeleteIf you are using the 3207 chip you may need to swap the resistors going to pin 4 of the 3207 around. As is the Vgg (pin 4) voltage seems to suit the MN3007.
ReplyDeleteI compared several schemes with MN3007 and MN3207, and I found the same situation as Slowpoke101, pin4 VGG needs to be fed with less 1volt than the VCC(pin1 MN3007-pin5 MN3207) as the power of the 3007 is negative we need to add + 1V to get more positive. in the 3207 we have to subtract, so we have to swap the resistors of the voltage divider R37 / R38.
ReplyDeleteThe ideal voltage for the 3207, which recommend on several blogs will be between 7 and 8v, some use a voltage regulator, others speak in a 8.2V zener, because 9V seems excessive and can cause distortion. This last situation do not know how applies.😢
Verified! Crystal clear chorus, the rate button produces a very analogous oscillation.
ReplyDeleteSince I had soldered all the components I made a small adapter plate to apply the corrections, it is necessary to swap the resistors, and I ended up also trying out other values R37 1.2K and R38 15K, the capacitor C21 in the circuits that is applied the MN3207 has the value of 4.7uF.
My power supply for the pedals has 10V, and the MN is not advisable to reach more than 8V, so I applied a 8.2V zener with a capacitor to stabilize. I also advise to use a more precise Multi Turn Pot for the Vbias setting because the chorus range is smaller in the MN3207 than in the 3007, I found in 2 different IC's the effect within the 5.40V and 6V (PIN3) .
The ideal would be to use a voltage regulator like the 78L08, with an individual track for the MN, and the rest of the circuit at 9V.
I send a link with the adapter plate, so if you want to try it.
https://imgur.com/Jh5ayhx
Would it be possible to apply these changes in this circuit?
hi, this little adapter you made and shared, is it usable every where for using 3207 instead of 3007? what about some adaptors which don't have caps? and an adaptor in the post?
Deletehi
Deletegreetings from austria!
o hope i understand you right: i populate the board as shown in the layout above, and then i install your adapter board in case of the lm3207? is that correct?
or do i have to replace some parts?
thanks for your work !
bluesanderl
I have not done this yet, but it seems to me that there is a mistake. In the case of MN3207 pin 7 and 8, the 47 K resistor should go on ground and not on power
ReplyDeleteI really expect that someone will solve the problem and everything will be clear with these microchips
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteMy circuit, I had already worked with the changes I made before, but I went to test the "nupel53" change, because I found in the schematic "Thomeeque's EM3207" that 47k resistor (R39) connected on pins 7e8 and then ground instead of VCC. I did not notice big difference the effect continued to work, perhaps the oscillator has become a little more stable.
ReplyDeleteWhat I have been testing are several voltages in Pin5, with 5V we have effect but with very little intensity, the best voltage I found was the 8v, we have effect turning the bias trimer half, which will give the Pin3 within 5.9V.
I tested these changes with an adapter plate in effects that I had already done with the IC MN3007, like "Heladito-2 of Tonepad" and "Touchstone of Madbeanpedals" and with some adjustments in the Bias soon gave effect of chorus.
Has anybody got it working? I'm really missing a nice little chorus in my DIY collection...
ReplyDeleteI already have this circuit working for some time, I was waiting for 10uf and 330nf tantalum, to make one more pcb like the original one.
ReplyDeleteThe changes are not many, I send here, the layout and the pcb for those who want to do. The pcb was half a inch wider and no longer fit in a 1590B we have to use the 125B.
The chorus effect is very good, but I would like to implement a switch or pot to change the Depth, does anyone know how?
https://www.dropbox.com/s/c5orxvypzapubzp/MXR%20MICRO%20CHORUS%20MN3207.pdf?dl=0
Sorry, the link had an error, here is one that works!
ReplyDeletehttps://www.dropbox.com/s/3w16vrdui5ai8m8/MXR%20MICRO%20CHORUS%20MN3207.pdf?dl=0
Hello friend, Is it 100% verified and working?
DeleteThank you
I made this circuit with your pcb with 8v regulator but it has some problems. the chorus effect stops working.strum the guitar and after 3 or 4 seconds chorus works and after a stops again and comes the clean sound .it is not stable. by the way layout is so very small
DeleteI have a problem, the sound on the output is clean. I tried to swap resistors 7.5k and 100k. Nothing changed.
ReplyDeletehow should the 220k potentiometer be set ??
ReplyDeleteDid anyone add a depth pot already?
ReplyDeletehi everybody
ReplyDeletei,d like to build this one, but the list of changes is huge!
has anyone build this succesfully?
and is it possible to update the layout above? ( or is this the final working version?)
greetings from austria
bluesanderl
I've been working on it, but like you alluded to, the change list has been a little confusing to wade through.
DeleteBrother any updates on this. ? I just made today its not working
Deletethank you for your kind answer!
ReplyDeleteso i,ll wait a little and do some other cool projects of your page!
bluesanderl
waiting for the final layout!
ReplyDeleteHello, i done this pcb with the MN 3007 ; it didn't work (only clean sound); after i see the additionnal little pcb to convert but i don't understand how to connect it to main pcb.
ReplyDeleteSorry for my english !
Looks like I'm having the same issue, only clean coming through using a 3207. Any word as to why? I see a bunch of suggestions but no progress on an actual layout fix
ReplyDeleteI just swapped the 7.5K and 100K by the 3207 and it works :)
DeleteShoutout to Methode for figuring this out for me, with that little change this layout works with the 3207.
DeleteSorry, I don't understand what the change is. What should I do with the resistors. I built this circuit a long time ago and I have it waiting for a solution. Thank you very much!!!
DeleteThis comment has been removed by the author.
DeleteThis comment has been removed by the author.
Delete@rjflyinghokie change 7.5k and 100k to what? Can you make it clear?
Deleteel esquema no es el definitivo verdad?? lo pregunto antes de comenzar su construcción,.
ReplyDeletePodrían decirme que elemento es el cuadrado de 220k, no lo habia visto hasta ahora soy novato.
Gracias!
I really love the original pedale. Is there a possibility to verify this build?
ReplyDeleteBoa noite. Essa modificação é para usar usar o MN3207 no lugar do MN3007?
ReplyDeleteComprei um lote de 05 unidades do 3007 na China, 04 vieram com defeito. Comprei outro lote com 10 unidades do MN3101, 06 vieram com defeito.
Alguém pode me ajudar?
Grato.
João esse layout é problemático, as pessoas que conseguiram faze-lo funcionar (ou apenas dizem isso, e acho que estão mentindo na verdade), simplesmente dizem que trocaram um resistor ou outro e na hora de explicar o que exatamente fizeram, pelo que trocaram, simplesmente somem, meu conselho? Monte o Ce-2, queria muito esse pedal, mas já fiz de tudo e não funciona
DeleteHello, where can I find the board for the MN3207 / mn3007.
ReplyDeletePadahal efek chorus ini sangat bagus, tetapi setelah saya mencoba merakit efek ini, ternyata tidak berhasil. Hanya suara jernih yang keluar dari efek ini. Memutar potensiometer juga tidak mengubah suara yang dihasilkan. Apakah ada yang berhasil mengubah rangkaian ini agar dapat berfungsi dengan baik ?
ReplyDeleteSalam hangat dari indonesia
Swapped 100k and 7.5k from pin 4 of 3207 and worked. Really good sound. Thank you very much for sharing.
ReplyDelete
DeleteThat was the only modification you made to make it work?
I don't understand what the change is. What should I do with the resistors ? Please help.
Deleteliar spotted.
Delete@ryohei jpn Is that the only change u made from this layout?
DeleteThis comment has been removed by the author.
ReplyDeleteI swapped the two resistors and the chorus effects is working, but... get a ticking sound coming through too. Any idea how to fix?
ReplyDeleteDisregard... Was able to adjust the trim pot down until the ticking stopped. All is well with it
Deletecan you share the solution with a photo or video?
Delete@ImpostorXXX - I've already given the pedal to a friend. This is a great sounding circuit, but... It does have it's issues. The ticking I mentioned earlier continues to come back, even after adjusting the bias on it. He has to continuously adjust the bias on it to get the ticking to stop. I'm thinking of making another, try to get a bias pot with a tall adjustment, mounting it on the solder side and bringing it up through the enclosure for easy adjustment. But, this is a lot of work and I just don't know if it's worth it.
DeleteYou think the ticking sound is the pot's fault?
DeleteAnalog pedals
DeleteWhat resistor did u change with 7.5k and 100k?
What did u keep in place of them?
After building this circuit numerous times with the V3207 and getting that ticking noise out of every one of them... I finally got my hands on a real MN3207 and built this again... No ticking, just a nice, lush chorus. So, the V3207 is the culprit for the ticking. If you can get your hands on real MN3207's, you will have yourself a nice chorus.
DeleteDo someone know where I can find a working MXR Micro Chorus Schematics/PCB?
ReplyDeleteBuilt this one last year and its awesome chorus! Nice sounding and tnx for this layout anyways more power!Regards fr Philippines. Jun.
ReplyDeleteCan u share the solutiom with photo, video or schematic ?
DeleteSir , below is what i did on my mxr mic chorus i hope this can help. Jun fr Philippines.
DeleteMn 3207 bias voltage on pin 4 guys should be approx 8.36v.remove the 7.5k and 100k resistor and replace it with a 100k trimmer and thats it!with the 220k trimmer the bias voltage on tlo62 should be around 4.7v or just turn the trimm until you get a nice sound output. Dont frget to replace that two 100k resistor connecting the trimm with 560k on the positive side and 270k on the neg side.
ReplyDeleteI hope this would help in any way to let the chorus roll. Regargs fr Philippines.Jun.
The above schem is verified with just a little adjustment..
ReplyDeleteSo if you remove the 7k5 and 100k resistores where does the trimmer go?
ReplyDeleteI have the same question
DeleteSir Massatony,connect the neg side to lug 1 and pos side to lug3 of the trimmer.center lug on pin4 of ic mn3207.
DeleteRahul is right remove the 47k res next 20k res.
DeleteVerified its working
ReplyDeleteI did few things
1. Swapped 7.5k and 100k with each other( both are connected to pin 4 of mn3207.
2.removed 47k resistor which is situated in middle of 20k and mn3207.
Thats its
https://drive.google.com/file/d/1ZH51OzTmgdoPrwXS1H1OMMFxilt6Pryb/view?usp=sharing
Deleteis this correct
Got it working with these modifications too.
ReplyDeleteAlso, I checked several mn3207 and bl3207 and I prefer how the bl sounds.
I'm trying with trimmers for 7'5k and 100k for the next build as I find it has too much regeneration compared with my original.
Had all sorts of trouble with this one. Anyway I put together a circuit provided by Monje...
ReplyDeletehttps://www.dropbox.com/s/3w16vrdui5ai8m8/MXR%20MICRO%20CHORUS%20MN3207.pdf?dl=0
And it's probably the best chorus pedal i've ever made. :)
https://drive.google.com/file/d/1ZH51OzTmgdoPrwXS1H1OMMFxilt6Pryb/view?usp=sharing
ReplyDeleteanyone tried this method?
I can confirm it's working and sounds ok. I used the trimmer instead of the bias resistors of the bbd chip as someone suggested. Does anyone know the right voltage for the tl062 trimmer if there is one?
ReplyDeleteI can verify this as well, with the corrections people have suggested above. Here's what I did for mine:
ReplyDelete1. Swap the 100K resistor at K8 and the 7K5 resistor at L9
2. Omit the 47K resistor at H12
With a BL3208A, this gave me a chorus sound, and adjusting the trimpot allowed me to dial it in by ear. Sounds great!