Unexpected results from small Behringer mixer testing

[[email protected]]

I'm more of a software guy than hardware, so I haven't used mixers much. I was surprised at what I was finding w/ a small used Behringer Eurorack UB-1202 I grabbed on eBay. I was running a single channel from my player into each input to test with a 1/4" TS plug. Everything was working fine until I got to the paired (L&R) line inputs #9-#16. When I plugged the cable into each of the left-side inputs, all was good. But when I plugged into each of the right-side inputs I could barely hear a signal. I double-checked the pan settings and they were all centered. I tried jiggling the plug, although the odds of all four having a bad jack was infinitesimal. The markings on the mixer show "mono" for the Ls and "BAL OR UNBAL" for the Rs. I might have a misunderstanding of the inner workings, and I was not able to find documentation to give me a definitive answer. But I was expecting a TS plug would work the same in both the L and R inputs. My two theories of why that isn't true are:

1) A TRS plug is needed for either a balanced or unbalanced signal because the R side inputs connect to the RING not the TIP. (If this is true, then is it true for all inputs that can be both BAL or UNBAL - they always need a TRS plug?)

OR

2) There's some auto-switching between the channel inputs of the same line whereby if you plug something into the R channel, you have to have something plugged into the corresponding L channel.

Appreciate any augmentation to my knowledge on this topic.

Thanks,
- DK

[geoff]

On 23/04/2018 12:28 PM, wrote:
> I'm more of a software guy than hardware, so I haven't used mixers much. I was surprised at what I was finding w/ a small used Behringer Eurorack UB-1202 I grabbed on eBay. I was running a single channel from my player into each input to test with a 1/4" TS plug. Everything was working fine until I got to the paired (L&R) line inputs #9-#16. When I plugged the cable into each of the left-side inputs, all was good. But when I plugged into each of the right-side inputs I could barely hear a signal. I double-checked the pan settings and they were all centered. I tried jiggling the plug, although the odds of all four having a bad jack was infinitesimal. The markings on the mixer show "mono" for the Ls and "BAL OR UNBAL" for the Rs. I might have a misunderstanding of the inner workings, and I was not able to find documentation to give me a definitive answer. But I was expecting a TS plug would work the same in both the L and R inputs. My two theories of why that isn't true are:
>
> 1) A TRS plug is needed for either a balanced or unbalanced signal because the R side inputs connect to the RING not the TIP. (If this is true, then is it true for all inputs that can be both BAL or UNBAL - they always need a TRS plug?)


They are unbalanced mono inputs. A 'ring' will go nowhere (or maybe even
shorted to ground).

>
> OR
>
> 2) There's some auto-switching between the channel inputs of the same line whereby if you plug something into the R channel, you have to have something plugged into the corresponding L channel.

The point is that a single unbal mono jack plugged into the L input will
also be routed to the R side of the stereo channel.

Pretty much the same scenario on all small semi-pro ( and upward) mixers.

Hope that clarifies.

geoff

[Mike Rivers[_2_]]

On 4/22/2018 8:28 PM, wrote:
> I was surprised at what I was finding w/ a small used Behringer Eurorack UB-1202 I grabbed on eBay. I was running a single channel from my player into each input to test with a 1/4" TS plug. Everything was working fine until I got to the paired (L&R) line inputs #9-#16. When I plugged the cable into each of the left-side inputs, all was good. But when I plugged into each of the right-side inputs I could barely hear a signal.

The way the stereo inputs on mixers like this are usually configured is
like this: When you plug into the left and right inputs, the L input
signal goes to the left mix bus, and the R input signal goes to the
right mix bus. The Pan control on the stereo channels works like the
Balance control on a stereo Hi-Fi receiver - panning full left turns off
the signal to the right bus, and vice versa. When you plug into the L
input only (leaving the R input open) internal switching routes that
signal to the pan pot, which, when centered, routes the single input
equally to both mix buses, and when off center, reduces the level to the
bus opposite of how the knob is turned.

When you plug something into the R input and leave the L input open, the
input signal goes only to the right mix bus, but it also goes through
the pan pot. If the pan is set fully left, that will turn the right
input signal completely off in the right channel, the same as if you had
left and right inputs and panned the stereo channel fully left. But with
the pan pot centered, you should get some signal in the right channel.

> I double-checked the pan settings and they were all centered. I tried jiggling the plug, although the odds of all four having a bad jack was infinitesimal. The markings on the mixer show "mono" for the Ls and "BAL OR UNBAL" for the Rs.

Actually, the BAL or UNBAL label applies to both jacks of the pair, and
"Mono" applies to the Left jack.

I might have a misunderstanding of the inner workings, and I was not
able to find documentation to give me a definitive answer. But I was
expecting a TS plug would work the same in both the L and R inputs.

Only if the pan pot is centered.


> My two theories of why that isn't true are:

> 1) A TRS plug is needed for either a balanced or unbalanced signal because the R side inputs connect to the RING not the TIP.

That's not correct. The input is balanced (correctly, it's
"differential."). When you insert a TS plug, the low (ring) terminal of
the jack is connected to the sleeve, so you still have a signal between
tip and ring of the jack, which is what the input is expecting.

> OR

> 2) There's some auto-switching between the channel inputs of the same line whereby if you plug something into the R channel, you have to have something plugged into the corresponding L channel.

Half correct - see above. Try it again, and, after assuring that the pan
pot is centered, or anywhere clockwise of center, watch the Right meter
or listen to the Right output of the mixer. There's some switching in
the jacks, but it only serves to connect the right and left channel
outputs together when nothing is plugged into the Right input of the
stereo input pair. If those jack switch contacts were not making good
contact, what you'd see when plugged into only the L input jack is
output only to the left channel of the mixer, not both channels (as
panned).



--

For a good time, call http://mikeriversaudio.wordpress.com

[[email protected]]

>
> 2) There's some auto-switching between the channel inputs of the same line whereby if you plug something into the R channel, you have to have something plugged into the corresponding L channel.
>
> Appreciate any augmentation to my knowledge on this topic.
>
> Thanks,
> - DK

yes there is switching.

if you have a mono source, plug it onto L in and it will feed both L and R.
if you have a stereo source plug L to L and R to R.

plugging only one input into the R is not defined.

mark

[Mike Rivers[_2_]]

On 4/23/2018 9:24 AM, wrote:
> plugging only one input into the R is not defined.

Of course it's defined. It goes to through the pan pot to the right
output bus. Admittedly, it's not every day that you pan a signal hard to
the right channel, but there's an output from a right-only-plugged
source if you know where to look for it.

If it's really not there, then something's broken.

--

For a good time, call http://mikeriversaudio.wordpress.com

[Peter Larsen[_4_]]

On 23-04-2018 14:24, wrote:

>> 2) There's some auto-switching between the channel inputs of the same line whereby if you plug something into the R channel, you have to have something plugged into the corresponding L channel.
>>
>> Appreciate any augmentation to my knowledge on this topic.
>>
>> Thanks,
>> - DK
>
> yes there is switching.
>
> if you have a mono source, plug it onto L in and it will feed both L and R.
> if you have a stereo source plug L to L and R to R.
>
> plugging only one input into the R is not defined.

Or there is a problem with the switch in left channel. I do not see it
mentioned whether it worked as intended: as a stereo input.

> mark

Kind regards

Peter Larsen

[geoff]

On 25/04/2018 3:56 PM, Peter Larsen wrote:
> On 23-04-2018 14:24, wrote:
>
>>> 2) There's some auto-switching between the channel inputs of the same
>>> line whereby if you plug something into the R channel, you have to
>>> have something plugged into the corresponding L channel.
>>>
>>> Appreciate any augmentation to my knowledge on this topic.
>>>
>>> Thanks,
>>> - DK
>>
>> yes there is switching.
>>
>> if you have a mono source, plug it onto L in and it will feed both L
>> and R.
>> if you have a stereo source plug L to L and R to R.
>>
>> plugging only one input into the R is not defined.
>
> Or there is a problem with the switch in left channel. I do not see it
> mentioned whether it worked as intended: as a stereo input.

I read as OP was wanting to plus a 1/4" TRS in with L on tip and R on
sleeve, rather than a mono jack tip (bal or unbal) going to L and R
master bus channels.

geoff

[[email protected]]

On Sunday, April 22, 2018 at 8:28:34 PM UTC-4, wrote:
> I'm more of a software guy than hardware, so I haven't used mixers much. I was surprised at what I was finding w/ a small used Behringer Eurorack UB-1202 I grabbed on eBay. I was running a single channel from my player into each input to test with a 1/4" TS plug. Everything was working fine until I got to the paired (L&R) line inputs #9-#16. When I plugged the cable into each of the left-side inputs, all was good. But when I plugged into each of the right-side inputs I could barely hear a signal. I double-checked the pan settings and they were all centered. I tried jiggling the plug, although the odds of all four having a bad jack was infinitesimal. The markings on the mixer show "mono" for the Ls and "BAL OR UNBAL" for the Rs. I might have a misunderstanding of the inner workings, and I was not able to find documentation to give me a definitive answer. But I was expecting a TS plug would work the same in both the L and R inputs. My two theories of why that isn't true are:
>
> 1) A TRS plug is needed for either a balanced or unbalanced signal because the R side inputs connect to the RING not the TIP. (If this is true, then is it true for all inputs that can be both BAL or UNBAL - they always need a TRS plug?)
>
> OR
>
> 2) There's some auto-switching between the channel inputs of the same line whereby if you plug something into the R channel, you have to have something plugged into the corresponding L channel.
>
> Appreciate any augmentation to my knowledge on this topic.
>
> Thanks,
> - DK

Thank you all for your responses. I filled in some gaps in my knowledge with yours, thanks. After more experimenting the answer became more obvious - the mixer is defective. Wiggling and inserting with more/less effort would cause the right inputs to work for a brief time and then they would drop out again. Sometimes pushing the level way up would have the same temporary effect. Regardless, the unit is unusable as is, and I don't have the time to try to fix it. #$%@*(!

- DK