Juno Chorus

[CJ]

sounds pretty dang cool!

 

[dmp]

Finished the box. Somehow on final assembly I fried all three TL082 ICs. Luckily I used sockets
Hung a LED off the depth pot to get a blinking 'rate'. Nice addition. It follows the triangle wave so it is a slow on - slow off

 

[f.aiseur]

Hi there,

Good looking AND sounding little box dmp, bravo!

I am waiting for a batch of 5x pcbs from jlcpcb, so i’ll have two or three to let go
Will post them on black market eventually but thought i’d say it here first

Happy holidays to everyone

 

[TimG]

Have you seen this project? I am hoping to get in on the Juno 500 project as I am interested!
From fb:

500 love​

Mike Burion ·


I am making a small batch off this Juno-60 Chorus 500-module. It uses the original schematic and the original mn3009 and mn3101 BBD chips. It has a mono input and stereo output (unbalanced).
The kit will include the pcb and the frontplate made of printed anodized aluminum. Furthermore the BOM and a little instruction. Total costs with all the parts will be approx 250€, depending where you are located and what pots, caps, etc. you want to use.
PM me if you are interested

 

[dmp]

Looks really cool. Having some time with it, the depth+rate is much better than building it with just I and II switches. So much more range

Not sure how that will interface with the 500 rack I/O with a unbalanced in and stereo unbalanced out. Will be a little strange.

 

[Potato Cakes]

Question about the link for the PCB info. How would one use those files to get some boards made? Do you download the whole thing and make a zip file? I have custom project I'm doing for my studio and I would like to add this to the build.

Thanks!

Paul

 

[dmp]

I bought the pcb here
Looks like the files at github are kicad. If you have that and can export gerbers, you can get them fabed most anywhere (i.e. JLCPCB)
Or another member made some and have a few for sale in the black market.

 

[Potato Cakes]

I will order them from the link you sent. There are some for sale in the Black Market but shipping to US from them will be more.

Thanks!

Paul

 

[Potato Cakes]

It seems the guy does not actually have the PCBs to sell. So I guess I'll have to explore other options. Thanks for sharing your build details. It will be very helpful when I build mine.

Thanks!

Paul

 

[dmp]

Summary of the notes / mods I did to the PCB/BOM for any other builders. These correct differences to the original Juno schematic and modify the bypass switching to work with a standard 3PDT footswitch

- the square is positive for the electrolytic caps
- R19/R24 should be 100k and R24 should have a 220pF cap in parallel (just solder the cap onto the resistor before putting onto the board). You get some robot noises without this.
- R81=10k, R86&R87=1.5k, R61&R62=10k,R9&R10 omit
- R84&R83 are 100k on the original schematic, but this increases the output gain quite a bit, I kept them at 10k, as in the BOM
- bypass switching:
This was my own solution to use a 3PDT standard footpedal switch with a LED indicator. (The designer used a momentary switch I think, but it did not work for me)
R66=100k, R49 omit, C17 change to be connected + side to R52/R56 junction (as C39 in original schematic), R47=10k, then the two sides of sw1 go to the 3PDT for the LED, and the -Va from the C17 round pad and C17 square pad go to the 3PDT (for ON)

 

[JohnRoberts]

Sorry for be a pedant but if it's not the exact same circuit, then it's not really a "clone".

I am more of a pedant than average. True the scientific definition of a "clone" involves an exact copy. Audio product clones are rarely exact copies, mainly because it's often not even possible, with component obsolescence etc.

I am not a mind reader but modern clone sellers appear to be trying to appropriate good will and trade reputation from a popular product. In many cases by not only replicating features and function, but often copying trade dress (how the product looks). There have been multiple successful trade dress IP lawsuits in other markets, only a handful in audio.

Last century I had one small mixer with a unique controls layout copied almost literally by Behringer, (they even copied my product specifications).

JR

 

[dmp]

You and "Bo Deadly" can take that discussion to the brewery. Leave it out of this thread anyway. Thanks

 

[TimG]

Summary of the notes / mods I did to the PCB/BOM for any other builders. These correct differences to the original Juno schematic and modify the bypass switching to work with a standard 3PDT footswitch

- the square is positive for the electrolytic caps
- R19/R24 should be 110k and R24 should have a 200pF cap in parallel (just solder the cap onto the resistor before putting onto the board). You get some robot noises without this.
- R81=10k, R86&R87=1.5k, R61&R62=10k,R9&R10 omit
- R84&R83 are 100k on the original schematic, but this increases the output gain quite a bit, I kept them at 10k, as in the BOM
- bypass switching:
This was my own solution to use a 3PDT standard footpedal switch with a LED indicator. (The designer used a momentary switch I think, but it did not work for me)
R66=100k, R49 omit, C17 change to be connected + side to R52/R56 junction (as C39 in original schematic), R47=10k, then the two sides of sw1 go to the 3PDT for the LED, and the -Va from the C17 round pad and C17 square pad go to the 3PDT (for ON)

I’m happy your project is mature enough to have improvements!

 

[Potato Cakes]

I've just started building a pair of these. If you don't mind I do have a couple of questions for you:

- What does the on board trimmer do and how did you set it? On the schematic it looks like some sort of feedback adjust for the MN3009.

- For the rate LED, did you connect it to the wiper of RV2 and ground?

- Where did you source the 2SK30's, SA1015's, and MN3101's?

- Did you use a log pot for the input and linear for rate and depth? These are not specified on my schematic.

Thanks!

Paul

 

[dmp]

- What does the on board trimmer do and how did you set it? On the schematic it looks like some sort of feedback adjust for the MN3009.

Adjust for symmetric clipping - have you found the Juno service manual? Has the original schematic and info on calibration I think. I think there were some instructions with this board somewhere too. I used these trimmers from mouser PT10LV10-103A2020-PM-S.

- For the rate LED, did you connect it to the wiper of RV2 and ground?

I connected it to the pot pin1 of the depth pot, so the LED is the same intensity regardless of the setting

- Where did you source the 2SK30's, SA1015's, and MN3101's?

banzai music

- Did you use a log pot for the input and linear for rate and depth? These are not specified on my schematic.

Yes, log for audio, linear for the other two

 

[dmp]

Found the info - it was in German and I translated with google translate
>>>>>>>>>>>>>>>>>>>>>>>>>>>>
The trimmers adjust the offset at the input of the bucket chain so that it clips symmetrically, i.e. the level is in the middle of the bucket chain’s level control range.
This can also be measured with the sound card by tapping the audio signal at the drain of Q16 or Q17. The (anti-aliasing) filtered and DC voltage-free output signals of the two bucket brigades are available there alone. You can listen to this signal to check it.

Slowly turn up the input signal (synthesizer with a not too high sine wave, 200 ... 400Hz), if the trimmers are not completely twisted, then you will get an output signal. This is soon eaten up (flattened) on one side with increasing volume, the ear hears clanking.
Set the trimmer so that the maximum signal height is possible or the flattened areas appear evenly on both sides.
Since that adjusts the straight harmonics to zero, you can hear it quite well - if it sounds like "clarinet" it's right.

The comparison is not particularly critical - it drifts a bit anyway. Don't "run over" too much, that must be correct for slight oversteer.

 

[Potato Cakes]

Awesome! This is very helpful. I do not have the service manual but I'm sure I can find it.

I'm building a dual mono spring reverb/chorus unit for studio use. Two independent spring reverbs feed two independent Juno boards where I'm using the opposite outputs from each board. The signal flow is selectable as either chorus -> reverb or reverb-> chorus. The spring reverb will have external tanks that has three selectable spring lengths per channel. I'll post here when it's done.

Thanks!

Paul

 

[f.aiseur]

Hi there!
After letting this project on a shelve for a while, i came back to it last night and found out its working somehow!
I have a few issues tho :
- i made the 220pf// to R24 mod but still have an annoying noise that fluctuates with modulation rate (i guess thats what dmp called robot noise?)

- it has high pitched noises increasing when i engage the depth knob - or when this one is fully off…
Could this be due to the fact that, for now, i housed it in a plastic box with metal faceplate?

- and lastly, i’d like the rate LED but can’t figure it out…
EDIT : for future reference, this connection worked for me :


Thanks very much!!

 

[dmp]

- i made the 220pf// to R24 mod but still have an annoying noise that fluctuates with modulation rate (i guess thats what dmp called robot noise?)

Did you change the resistors to 100k? The 'robot noise' is the BBD clock leaking through. The RC needs to LPF to cut it. I don't think the housing would matter if it is the BBD clock noise.

 

[f.aiseur]

Hi, thanks for your reply!
i just checked and no, i used all values from gligli's BOM
Will change everything as you did and come back here with some news