BH550 into a 250w 4ohm cab?

[Old Garage-Bander]

I just checked combo manual and it says this:
IMPEDANCES: SEND: 1kΩ / RETURN: 20kΩ (balanced)

OK good. And the connectors need to be correct.
Normally if there are 1/4" jacks/plugs used with balanced signals they are TRS (3 conductor). TS (2 conductor) plugs plugged into a TRS balanced Jack will short out one side of the balanced signal, cutting the available signal in half.

 

[frenfrins]

So, if I understood right, the problem could be that the cable I'm using may not be balanced?
I should buy a new one and make sure it is balanced signal and TRS.
Thank you very much

 

[Old Garage-Bander]

So, if I understood right, the problem could be that the cable I'm using may not be balanced?
I should buy a new one and make sure it is balanced signal and TRS.
Thank you very much

A balanced audio cable has three parts to it. The signal is carried between two conductors, but neither one is ground/shield. On a 1/4" TRS (Tip, Ring Sleeve) the audio plus and minus will be carried on the tip and ring of the connector, with the sleeve being connected to ground.

The balanced input only see the difference voltage across the audio plus and minus connections. The two wires are twisted and this helps to reject noise. Outside noise does not get amplified, or in practice is very well attenuated because the noise is the same on both audio lines and the next piece of equipment only cares about the difference on the two lines.

The cable shield does not carry any signal. It does act as a shield though to further reduce incoming noise from outside of the cable. Often, only one end of the cable shield will be connected to ground. They can be connected at both ends, but if you get some ground loop hum you can disconnect on end of the shield. The other end is still connected and still shields the entire cable.

If you look at a TS cable vs a TRS you can see how the ring will be shirted to ground. Thus causing the loss of 1/2 the signal level.

 

[frenfrins]

A balanced audio cable has three parts to it. The signal is carried between two conductors, but neither one is ground/shield. On a 1/4" TRS (Tip, Ring Sleeve) the audio plus and minus will be carried on the tip and ring of the connector, with the sleeve being connected to ground.

The balanced input only see the difference voltage across the audio plus and minus connections. The two wires are twisted and this helps to reject noise. Outside noise does not get amplified, or in practice is very well attenuated because the noise is the same on both audio lines and the next piece of equipment only cares about the difference on the two lines.

The cable shield does not carry any signal. It does act as a shield though to further reduce incoming noise from outside of the cable. Often, only one end of the cable shield will be connected to ground. They can be connected at both ends, but if you get some ground loop hum you can disconnect on end of the shield. The other end is still connected and still shields the entire cable.

If you look at a TS cable vs a TRS you can see how the ring will be shirted to ground. Thus causing the loss of 1/2 the signal level.

Do you mean this? It seems that my lead is TRS, the rings are like in the first one.

 

[Old Garage-Bander]

View attachment 1035193

Do you mean this? It seems that my lead is TRS, the rings are like in the first one.

Exactly.

You can see how if you have a TS and put it into a TRS jack that is carrying audio on the ring that it will short out the audio carried on the ring.
Since it's balance shorting either the + or - to ground takes away half your signal, you have created an unbalanced audio line that carries all of the pitfalls that come with unbalanced audio.

This is the same connector used for stereo like with headphones for instance.
In that case you have two unbalanced audio signals L Ch. on the tip (normally) and R Ch on the ring.
The sleeve/shield now act as part of the audio circuit and is the common signal return for both channels.
If you put a TS plug into a stereo TRS jack, you'd be shorting out the right channel.

 

[frenfrins]

Thank you, I just don't understand why it is not working properly, all the connections are balanced, what else do I need?

 

[Old Garage-Bander]

At this point it's hard to say without eyes on. And there may a problem with one of the amps.
Do you know anyone locally who can help by actually looking at your setup.

Are you still using the XLR D.I. output to go to the other amp?
If so, and the D.I. out is too low.
Zooberex first mentioned this possibility in post #13.
He suggested that the balanced out might be mic level rather than line level.
If that were the case your audio would be very low.

Do you have, or do you know someone who has a mixer that will accept both mic and line level audio?
You could use that by plugging in to it and see what it requires to get normal levels on the mixer's meters.

Otherwise I would suggest that you review for us the way your setup is connected. After all this time it is becoming hard to visualize. In doing this you will need to include the type of connectors on each end of each cable.
Example:
Bass > TS--TS > amp input. Amp1 D.I. > XLR--TRS > Amp2 effects in (or Amp2 return)...
The > shows the path. The -- is the cable with connectors on each end.

 

[frenfrins]

Bass > TS--TS > amp input. Amp1 D.I. > XLR--TRS > Amp2 effects in (or Amp2 return)...
The > shows the path. The -- is the cable with connectors on each end.

That's exactly the way I did it.
I've tried with with another different amp instead the BH550 and it works perfect, enough volume. It could be what you said, balanced output in the TC must be mic level.
What if I use the headphone output instead? is it safe?
Thanks again

 

[Old Garage-Bander]

That's exactly the way I did it.
I've tried with with another different amp instead the BH550 and it works perfect, enough volume. It could be what you said, balanced output in the TC must be mic level.
What if I use the headphone output instead? is it safe?
Thanks again

It's unbalanced, usually stereo, actually just two channel with the same audio on both sides.
It might work going to an unbalanced effects return (effects in). It might also take a special, possibly custom made cable. Headphone out however might be pretty hot level wise. Without details of all the ins and outs it is hard to say for sure from my easy chair.

 

[frenfrins]

OK, I understand, one last question, could I connect the headphone output into aux input on the second amp or would you just use the "use your ears system" and forget about experiments?
Thank you once again, your help is so much appreciated

 

[Old Garage-Bander]

OK, I understand, one last question, could I connect the headphone output into aux input on the second amp or would you just use the "use your ears system" and forget about experiments?
Thank you once again, your help is so much appreciated

An experiment is something carried out to confirm the expected results of a theory.

Experiments differ from just blindly trying things in that the knowledge and precaution is lacking with just trying things blindly.
But even in those cases you may learn something, though it may be a hard lesson.

How well your experiment works will depend on headphone level output of amp 1 and aux level input range of amp 2.

Often an amp with a headphone jack will disable the speaker when you insert a plug into the Jack.
Also aux inputs on many amps do not have input level controls.

The usual cautions and caveats apply here as well.

 

[frenfrins]

Good advice. Thanks again for your time