OUTPUT LEVEL knob not working as expected when SUB OUT ports enabled

Started by szszoke, August 19, 2021, 05:19:23 PM

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szszoke

Hello!

I discovered another potential bug/idiosyncrasy with my BOSS GT-1000CORE.

This unit doesn't have dedicated SUB OUT ports. Instead, the SEND1 and SEND2 ports can be configured to act as the physical ports for SUB OUT.

When I configure my unit this way, the OUTPUT LEVEL knob stops affecting the volume of the signals coming from the main and sub output ports.

The output signals are at full volume regardless of the position of the OUTPUT LEVEL knob.

I'd expect that the behavior of the OUTPUT LEVEL knob never changes, or if it does then that is documented in the manual.

I already sent a message to customer service but in the meantime I'm curious if others can reproduce the same behavior.

It's an easy check:

1. Connect any speakers to the main output
2. Turn down the volume on the speakers
3. Turn on the device
4. Go to Menu > Hardware settings > Other
5. Change SEND1 and SEND2 SETTING to SUB OUT
6. Turn the OUTPUT LEVEL knob all the way down
7. Connect a guitar and play something
8. Turn up the volume on the speakers a little bit

I would expect silence but at least with my unit, even though the OUTPUT LEVEL knob is all the way down, there is sound coming from the speakers.

Edit: it looks like the original subject got messed up somehow. I made the post on my phone and at some point things started to scroll off-screen.

PAH

When you configure the sends as Sub out, the sub out signal is fed back into the returns and on to the main outputs... unless you insert a dummy plug into the return jacks.  I believe this is documented in either the Parameter guide or the user guide.

If you insert dummy plugs into the return jacks, it should work the way you'd expect.

szszoke

Quote from: PAH on August 20, 2021, 10:12:17 AM
When you configure the sends as Sub out, the sub out signal is fed back into the returns and on to the main outputs... unless you insert a dummy plug into the return jacks.  I believe this is documented in either the Parameter guide or the user guide.

If you insert dummy plugs into the return jacks, it should work the way you'd expect.

You are indeed correct!

I plugged in two dummy plugs into the two return ports and the output level knob started working as expected.

I think I found the part that you referred to from the parameter guide:
QuoteBe aware that if a plug is not plugged into
the RETURN jack, the signal sent to SUB OUT
is also output to OUTPUT.

If this is the section that you meant then I think it is a really cryptic way of saying that "if you do this and don't plug anything into the return ports then the output level knob stops working and the outputs will be at full volume".

I wonder why it is working this way though.. what do the return plugs have to do with the sub output?

admin

Quote from: szszoke on August 20, 2021, 10:54:39 AM
You are indeed correct!

I plugged in two dummy plugs into the two return ports and the output level knob started working as expected.

I think I found the part that you referred to from the parameter guide:
If this is the section that you meant then I think it is a really cryptic way of saying that "if you do this and don't plug anything into the return ports then the output level knob stops working and the outputs will be at full volume".

I wonder why it is working this way though.. what do the return plugs have to do with the sub output?

The FX Returns are switching jacks. Inserting dummy plugs breaks the "normalled" signal flow from the FX  Send Jacks.

Its common in Boss Gear, for the PARAMETER Guide to contain important information described nowhere else

Read it
https://www.boss.info/us/support/by_product/gt-1000core/owners_manuals/ac5f65be-2c06-4447-93fd-42430b57cf10/

SUB OUT
The SEND jack is used as a SUB OUT jack.
You can send a signal separate from the
OUTPUT jack to a PA system or other
equipment.
In this case, the RETURN jack works as an AUX
IN jack. The input signal is output from the
OUTPUT jack along with the sound going
through the GT-1000CORE effects.
* Be aware that if a plug is not plugged into
the RETURN jack, the signal sent to SUB OUT
is also output to OUTPUT.


This is related to your GT1000core  Feedback issue

PAH

Quote from: szszoke on August 20, 2021, 10:54:39 AM
You are indeed correct!

I plugged in two dummy plugs into the two return ports and the output level knob started working as expected.

I think I found the part that you referred to from the parameter guide:
If this is the section that you meant then I think it is a really cryptic way of saying that "if you do this and don't plug anything into the return ports then the output level knob stops working and the outputs will be at full volume".

I wonder why it is working this way though.. what do the return plugs have to do with the sub output?

I don't know about other manufacturers, but Boss generally uses switched jacks for returns.  If nothing is plugged in to the returns, then the send signal is automatically returned via return.  This is so if you turn on the effects loop with nothing connected, you don't break your signal path and get nothing.

I suspect that the master volume is still controlling the level of the main path, but the sub signal is coming back via return after the master volume and then going out main.

szszoke

Quote from: PAH on August 20, 2021, 04:44:05 PM
I don't know about other manufacturers, but Boss generally uses switched jacks for returns.  If nothing is plugged in to the returns, then the send signal is automatically returned via return.  This is so if you turn on the effects loop with nothing connected, you don't break your signal path and get nothing.

I suspect that the master volume is still controlling the level of the main path, but the sub signal is coming back via return after the master volume and then going out main.

I wrote a long comment but you were quicker with your reply so I didn't post it.

I came to the same conclusion as you wrote but a question still remained.

Why mix the signal in after the master volume potentiometer?

szszoke

Quote from: admin on August 20, 2021, 12:55:49 PM
The FX Returns are switching jacks. Inserting dummy plugs breaks the "normalled" signal flow from the FX  Send Jacks.

Its common in Boss Gear, for the PARAMETER Guide to contain important information described nowhere else

Read it
https://www.boss.info/us/support/by_product/gt-1000core/owners_manuals/ac5f65be-2c06-4447-93fd-42430b57cf10/

SUB OUT
The SEND jack is used as a SUB OUT jack.
You can send a signal separate from the
OUTPUT jack to a PA system or other
equipment.
In this case, the RETURN jack works as an AUX
IN jack. The input signal is output from the
OUTPUT jack along with the sound going
through the GT-1000CORE effects.
* Be aware that if a plug is not plugged into
the RETURN jack, the signal sent to SUB OUT
is also output to OUTPUT.


This is related to your GT1000core  Feedback issue

Thanks! I quoted from the same place in my earlier comment as you did. It just wasn't obvious that the signal from the SUB OUT ports will literally appear on the main output ports, bypassing the output level potentiometer.

Now that I think more about it, and after reading what PAH wrote, I think I have a better understanding.

There are two ways to enable the SUB output, one with the return ports working as AUX IN and another where AUX IN is muted.

I checked with a multimeter and the two tip connectors of the send and return jacks are indeed connected when nothing is plugged in to the ports. (I made sure that I'm not measuring ground)

This confirms what PAH wrote.

When the SEND ports are configured as SUB OUT with AUX IN, then the signal from the SUB OUT ports will be fed back to the RETURN ports which are acting as AUX IN.

It seems that the AUX IN signal bypasses the output level knob and goes directly to the main output.

I suppose this is what you were trying to say.

Back to the feedback bug that I found, the unit is probably still sampling the RETURN ports when the FX loop block is enabled, and when the SEND ports are configured bas SUB OUT, and due to the hardware link between the SEND and an uempty RETURN port, a signal from the end of the chain is fed back to wherever the FX loop block happens to be, which is then output again... causing a feedback loop.

I checked both the manual and the parameter guide but I couldn't find a reference to the send and return ports being physically connected when nothing is plugged in to the return ports.

I did find a mention to the FX loop block not working if the SEND SETTING is anything else than SEND but the bug is that this behavior is not always true.

Something goes wrong when the FX loop block is turned on, or if the active patch is changed to one where the FX loop block is already on.

Thanks for all of your help. It makes more sense now.