Unbalanced to Balanced: Is it worth it ?

[jnewmark]

I have'nt really thought about this in the past when using a pre/power amp rig, but since I have gone back to that rig, I'm wondering if it would buy me anything to place a DI inbetween the unbalanced, 1/4 out of my preamp to the XLR input of my power amp? My signal is not that noisey going out of the unbalanced 1/4 to the 1/4 input of the power amp, but would there be any gain at all in signal strength? Any other benefit, like not having to drive the preamp as hard ?

[rpsands]

You use a BBE 383, right? It's got a balanced out. Use that. Use the DI on the unbalanced out for sending to the board.

Many power amps automatically reduce gain by 6db or so with an unbalanced input. This depends on the brand and model of course. Not all companies do it.

[jnewmark]

Originally Posted by rpsands

You use a BBE 383, right? It's got a balanced out. Use that. Use the DI on the unbalanced out for sending to the board.

Many power amps automatically reduce gain by 6db or so with an unbalanced input. This depends on the brand and model of course. Not all companies do it.

Not sure I'm understanding this. The BBE 383's 1/4 out is an unbalanced signal. The XLR out is balanced, but it is a pre EQ DI. I have tried this using the XLR to XLR on the power amp, and the signal is way weaker than using the unbalanced out. Are you thinking of the effects send as a balanced out ?

[lokikallas]

For short cables, unbalanced is fine. Patchbays are generally all unbalanced T/S cables. Balancing is really just for noise rejection, and grounding issues for long cable runs. It uses the shield to drain noise to ground, where the unbalanced just relies on the twist ratio to cancel out noise. For interconnects in your rig, you will never notice the difference, unless I suppose you have a super noisy transformer throwing off tons of emi. Oh, by the way 1/4" can be balanced tip/ring/sleeve. Just because it's 1/4" doesn't mean unbalanced always. Check your manual. It will also give specs on the output voltages of the various outputs most likely.

[jnewmark]

Originally Posted by lokikallas

For short cables, unbalanced is fine. Patchbays are generally all unbalanced T/S cables. Balancing is really just for noise rejection, and grounding issues for long cable runs. It uses the shield to drain noise to ground, where the unbalanced just relies on the twist ratio to cancel out noise. For interconnects in your rig, you will never notice the difference, unless I suppose you have a super noisy transformer throwing off tons of emi. Oh, by the way 1/4" can be balanced tip/ring/sleeve. Just because it's 1/4" doesn't mean unbalanced always. Check your manual. It will also give specs on the output voltages of the various outputs most likely.

Thanks. Manual does state the the 1/4 out is unbalanced. It does not state the output voltages, though. Just out of curiosity, is the 1/4 send a balanced out usually ?

[rpsands]

Originally Posted by jnewmark

Not sure I'm understanding this. The BBE 383's 1/4 out is an unbalanced signal. The XLR out is balanced, but it is a pre EQ DI. I have tried this using the XLR to XLR on the power amp, and the signal is way weaker than using the unbalanced out. Are you thinking of the effects send as a balanced out ?

I use the XLR out on my BBE 383. It is definitely post-eq. The manual confirms this. It's more than enough to drive my 1540L to clipping (and beyond).

Note: If it is quieter than your unbalanced main out, it means your power amp probably doesn't care about unbalanced or balanced signals.

[jnewmark]

Originally Posted by rpsands

I use the XLR out on my BBE 383. It is definitely post-eq. The manual confirms this. It's more than enough to drive my 1540L to clipping (and beyond).

Note: If it is quieter than your unbalanced main out, it means your power amp probably doesn't care about unbalanced or balanced signals.

Hmm. Where do you see this in the manual ? I just read the entire thing, and can find nothing that states the XLR out is post EQ, or, that it is'nt. When refering to the unbalanced and balanced outs, it states that it has enough signal to drive any application, but nothing about EQ.

[billfitzmaurice]

Originally Posted by jnewmark

Just out of curiosity, is the 1/4 send a balanced out usually ?

A balanced send has three conductors, positive, negative and ground. A 2 conductor 1/4 send therefore cannot be balanced. A 3 conductor (T/R/S) 1/4 can.

I have tried this using the XLR to XLR on the power amp, and the signal is way weaker than using the unbalanced out.

Balanced sends are usually at microphone level, to feed a microphone level input of a mixer. Unbalanced sends are usually line level, to drive the line level input of a power amp. The manual should say what voltage or dBu level each is.

[rpsands]

Originally Posted by jnewmark

Hmm. Where do you see this in the manual ? I just read the entire thing, and can find nothing that states the XLR out is post EQ, or, that it is'nt. When refering to the unbalanced and balanced outs, it states that it has enough signal to drive any application, but nothing about EQ.

The fact that the master affects the strength of the signal is what makes me assume it's post-eq, since otherwise there'd be a separate level control on back.

Plus, I've used it this way for months and when I turn the eq knobs it changes the tone.

[rpsands]

Originally Posted by billfitzmaurice

Balanced sends are usually at microphone level, to feed a microphone level input of a mixer. Unbalanced sends are usually line level, to drive the line level input of a power amp. The manual should say what voltage or dBu level each is.

In this case the levels are not stated but both of them are line level. They are "Main outs" - one balanced and one unbalanced.

It's kind of unfortunate that unlike some preamps there's not a separate di level control or at toggle for line/not-line. The Yamaha PB-1 has a separate Xlr out level, and the Demeter HBP-1 has a separate TRS jack for driving a balanced power amp input (and a separate di level switch).

Every bass preamp seems to be different, and I've owned a bunch.

[jnewmark]

Originally Posted by rpsands

The fact that the master affects the strength of the signal is what makes me assume it's post-eq, since otherwise there'd be a separate level control on back.

Plus, I've used it this way for months and when I turn the eq knobs it changes the tone.

Ok, thanks. I'll try it again.

[rpsands]

Lemme know. I'll double check when I get down to the studio this week, but I am like 98% positive I always err toward the XLR after some experiences with cables getting pulled out and also a Yamaha power amp that laughed at unbalanced inputs (-6db).

[jnewmark]

Originally Posted by rpsands

Lemme know. I'll double check when I get down to the studio this week, but I am like 98% positive I always err toward the XLR after some experiences with cables getting pulled out and also a Yamaha power amp that laughed at unbalanced inputs (-6db).

Got an answer from BBE today - the XLR out is post EQ, and as far as output voltage he said " it can be as high as +11dBv depending where you have the volume and gain set ". Enough to drive a Crown XLS 1000 ?

[billfitzmaurice]

Originally Posted by jnewmark

it can be as high as +11dBv depending where you have the volume and gain set ". Enough to drive a Crown XLS 1000 ?

The amp data sheet will say what's required to drive it to full output.

[jnewmark]

Originally Posted by billfitzmaurice

The amp data sheet will say what's required to drive it to full output.

" Sensitivity for full rated power at 8 ohms, 1.4 Vrms "

[rpsands]

Plenty of output. Don't hesitate to crank the master, btw...the gain not so much, but the master and the power amp attenuator are fine to crank up as loud as you need to.


btw, generally what that "1.4vrms" figure means us that if you turn the attenuator alllll the way up, it'll take 1.4vrms to reach max output. At least that seems to be what it is from what I can tell.