I can't troubleshoot for beans but the 808 service manual might give you a different perspective than the Eagle files.

Congrats on finishing by the way!

As far as i can tell, in the original 808, there is a separate audio ground and power ground. In the yocto, there is only one ground.

I get hum when using the trigger outs.

I don't get hum when using unbalanced leads (with no trigger outs used)

I do get hum if i used balanced leads (as you would in a studio / multicore / patch bay)

I believe that the balanced cable issue is caused by the fact that the yocto uses 'unbalanced' sockets - therefore if a balanced cable is used, there is no where for the 'cold' or 'ring' part of the signal to go. Normally, i believe (can an EE chime in here?) that a balanced socket is used on an um-balanced bit of gear - with the ring 'shorted' (connected) to ground. That way, if a balanced lead is plugged in, the ring part is shorted to ground.

These 2 issues really need to be sorted out, as it makes it impossible to record with it (especially when using trigger outs)

I don't think it would take an EE much time to modify the ground layout (relating to the trig out) to get rid of the hum (50/60hz mains hum).

The next batch of kits should also hopefully come with a modified output board / balanced sockets, if this is proven to be an issue.

Can any existing yocto builders test how their yocto behaves and report any hum issues, so that we can establish if it is a design fault or user problem in the build..

Hey thanks for the reply (ies).

What is described above, is pretty much to a T with my experience. At first I thought I must have missed something, some backwards component, or some component gone wrong or a ground short; pulling my hair out, you wouldn't believe how many times I've checked everything, reflowed it all etc. but after even more troubleshooting, the above explanation makes a whole lot of sense. The only way i've been able to get the trigger hum problem to go away is by making a cable with no ground. That is, positive tip only and leaving the ground unconnected at both ends, the hum goes away, and the trigger works as it should. I'm not experiencing the same hum stacking effect that you describe with the multiple outs, but then again i haven't hooked them all up at once to an interface to record yet. it could be there, at least to some extent, but its very subtle if at all.

Again thanks for the info, its been helpful. In a way its reassuring, at least to some extent, to know that i'm not the only one with this issue. If it is in fact something to do with the design of the boards' ground and how it interfaces with other instruments and devices, hopefully its something that can be fixed down the line.


Thanks again.

Hi everybody.
I recently noticed that I have the same problem concerning the hums when trig outs are on. (it's the same when din sync out is plugged i Think) Which makes the machine unusable for live acts ;(
Can somebody tell if there's a way to get rid of these hums?
thank you

Bump..

We need to get these 2 issues resolved - especially for the TRIGGER OUT users..

It would be good if those that have completed their builds could check how their units work when using multiple cables, unbalanced cables, balanced cables and trig out cables..

1 As mentioned previously, I believe that the use of 'unbalanced' sockets in this build is a bad idea because if the unit is connected to a 'balanced' device (ie. most sound cards) using 'balanced' cables (as you would expect to see in any half decent bedroom studio) it leaves the 'ring' or 'cold' floating (ie. nowhere to go) and therefore the unit causes severe hum that multiplies with each connection - this makes a multi out recording impossible.

I believe this is resolved by the use of 'balanced' sockets - with the 'ring' shorted (connected) to 'ground'. This will therefore allow for the use of balanced cables (as the ring will be shorted to ground - therefore no hum)

Vincent, have you found a solution to this? I think it would be a good idea to implement 'balanced' sockets in the next batch - should be pretty simple to do.

2 The original 808 has 2 ground paths - power ground (references to the +/- 15v rails) and audio ground (references to the 5v rail) The yocto appears to have a common ground for both power and audio. I have spoked to a couple of techs here that suggest that this arrangement can sometimes be problematic - i.e.. not ideal.

The Trigger out might require some more filtering to get rid of the hum it induces when its plugged in.
This is outside my area of expertise (i'm not a tech, took me ages to figure out that the unbalanced output sockets cause hum)

Vincent, would you be able to have another look at the grounding arrangement and come up with a mod to get rid of the hum?
the machine you have created is amazing in so many ways (and 808 with a 707/606 sequencer and more) but i'm unable to record with it (using trigger outs or balanced cables) as it hums too much.

If the community here could provide more feedback on their issues, then perhaps we can move towards a solution for everybody.

Best,

Harry

Dear discodisco,

1 As mentioned previously, I believe that the use of 'unbalanced' sockets in this build is a bad idea because if the unit is connected to a 'balanced' device (ie. most sound cards) using 'balanced' cables (as you would expect to see in any half decent bedroom studio) it leaves the 'ring' or 'cold' floating (ie. nowhere to go) and therefore the unit causes severe hum that multiplies with each connection - this makes a multi out recording impossible.

We didn t have any hum on the Yocto output because we are using Unbalanced to balanced cable but you re right it will be better if the IO board has balanced connector with ring connected to the ground.

Vincent, have you found a solution to this? I think it would be a good idea to implement 'balanced' sockets in the next batch - should be pretty simple to do.

I think that will be done

2 The original 808 has 2 ground paths - power ground (references to the +/- 15v rails) and audio ground (references to the 5v rail) The yocto appears to have a common ground for both power and audio. I have spoked to a couple of techs here that suggest that this arrangement can sometimes be problematic - i.e.. not ideal.

In the Yocto there are two separate grounds too who also join in the power connector. Trig out Hum problem comes from that the trig ground is common with digital ground and not with analog ground. But it can be solve with using cable without the ground connected.
We will make a tutoriel how to modify the IO board to solve Trig OUT Hum problem without using non-connected ground cables.

discodisco wrote:the machine you have created is amazing in so many ways (and 808 with a 707/606 sequencer and more) but i'm unable to record with it (using trigger outs or balanced cables) as it hums too much.

Do you still have hum noise when using unbalanced to balanced cable ?

Thank you harry for all the criticism it will allow us to further improve the Yocto

Best regards,
e-licktronic

Thats great news Vincent.

Luckily it should be very easy to change the unbalanced sockets for balanced ones. Do you have a mouser/digikey link to they exact brand/type of socket used? I can only find different ones locally (they don't fit the pcb).

I'll be eager to try your mod to get rid of noise on the Trigger out as well when you post it.

Thanks for looking into these minor issues. I didn't mean to sound critical - i think the machine you have created is amazing - in particular the sequencer. Once we resolve these issues, the unit will be perfect for recording.

Thanks again!

Not using balanced connections myself, but while I'm still building I'd also like to know what I can do to fix this right away.
I am using dinsync a lot, so I hope I don't get any issues

discodisco wrote:Do you have a mouser/digikey link to they exact brand/type of socket used? I can only find different ones locally (they don't fit the pcb).

You can find the TRS jacks here http://eu.mouser.com/ProductDetail/REAN ... 6e1PL0U%3d but the IO board jack footprint doesn't match with TRS jack. You have cut the both ring pins then solder a wire between ground and the ring or you can drill the IO board and solder a wire between both pin but i do not recommend you drill the IO board.

Best regards,
e-licktronic