Wiring stereo amp from XLR

audiogurujax · « **on:** 18 Oct 2016, 04:53 pm »

Hi an audio engineer told me mto wire my PrimaLunaHP this way comming from a Balanced Preamp/DSP (DEQX HDP4) But I am afraid since it is nothing I have seen befoer I need some help from the experts here.

Preamp -->XLR Cable --> (PrimaLuna HP Power amp in stereo)

connect the xlr cable to the Primaluna this way:

Pin 1 (ground) --> to both RCA outer shield

Pin 2 (positive) --> to right channel RCA center pin

Pin 3 (negative) --> to left channel RCA center pin

Connect the speaker this way:

If the speaker is 8ohm

Connect the speaker positive lead to the right channel 8 ohm positive tab
Connect the speaker negative lead to the left channel 8 ohm positive tab

The amp switch stays in stereo mode

Purpose get more gain?

will this work? or will it blow my amp?

Best,

Eric

Davey · « **Reply #1 on:** 18 Oct 2016, 05:26 pm »

This advice is for a bridging configuration of your amplifier and (might) yield 6db more output......relative to your previous hookup configuration.
But you now have a mono amplifier. You're aware of that, yes?

It will work as expected if the XLR output from your preamp has active signal on both Pin 2 and Pin 3 of the XLR connectors. (Not all balanced outputs have active signal on Pin 3, but I believe the DEQX does.)
Also, the two power amplifier output channels need a common electrical connection between the two black posts.

Dave.

audiogurujax · « **Reply #2 on:** 18 Oct 2016, 05:30 pm »

so it is safe to try even on tube amps like the primalunas I would not damage the transformer by not having nothing connected on the neg posts?

Davey · « **Reply #3 on:** 18 Oct 2016, 05:46 pm »

I'm not familiar with the primalunas but, as I said, it will only work if the black (or ground) posts between your two channels have a common electrical connection. You'd need to check that with an ohmeter.

Dave.

audiogurujax · « **Reply #4 on:** 18 Oct 2016, 06:15 pm »

ok if they do and I use both poisitive 8ohm tab will that actually yield 4ohms or 16omhs

Armaegis · « **Reply #5 on:** 18 Oct 2016, 07:38 pm »

Splitting pins 2 & 3 apart on an xlr is really terrible practice and loses most of the benefit of balanced connection, nevermind compromising the signal. If the dac has transformer coupled outputs, this is especially bad. Why do you need to do that when the DEQX already has rca outputs?

It looks like the Primaluna has transformer coupled outputs as well. As Davey said, unless you know with absolute certainty that the negative posts are shared and that the amp can be bridged (ie: check the manual or ask the manufacturer), this is not something you should be doing. There is no benefit to be gained.

Davey · « **Reply #6 on:** 18 Oct 2016, 11:13 pm »

He's trying to achieve a bridging scheme.....that's why using the DEQX RCA outputs is not applicable. (That should have been clear initially.)
Separating pins 2 and 3 is not terrible practice as long as a user knows why he's doing it......and understands how to do it. Obviously, you no longer have a traditional balanced interface, but that's not the objective of this configuration.

jax, it seems like there's enough unknowns here that I wouldn't recommend attempting this with your current setup.

Dave.

JohnR · « **Reply #7 on:** 19 Oct 2016, 01:07 am »

Plus, each output transformer is now seeing a 4 ohm load.

G Georgopoulos · « **Reply #8 on:** 19 Oct 2016, 04:37 am »

Quote from: JohnR on 19 Oct 2016, 01:07 am

Plus, each output transformer is now seeing a 4 ohm load.

((v = x2 i=1 p=x2) = zspk/2)...

JohnR · « **Reply #9 on:** 19 Oct 2016, 03:34 pm »

Quote from: G Georgopoulos on 19 Oct 2016, 04:37 am

((v = x2 i=1 p=x2) = zspk/2)...

Right.. I think you may have missed the point of my comment, which is that the secondary impedance is reflected back to the primary.

craig sawyers · « **Reply #10 on:** 19 Oct 2016, 07:53 pm »

It looks like the PrimalumaHP is a premium quality 4-grand valved/tubed integrated amp. It has single ended inputs.

And the DEQX HDP4 has both single ended and balanced outputs, can do room correction, and has a DSP crossover, or a full range output.

Since it has single ended outputs, why not just wire the thing to one of the the PrimalunaHP inputs using regular single ended phono cables. Why bother using XLR at all?

Davey · « **Reply #11 on:** 19 Oct 2016, 09:36 pm »

Quote from: craig sawyers on 19 Oct 2016, 07:53 pm

Since it has single ended outputs, why not just wire the thing to one of the the PrimalunaHP inputs using regular single ended phono cables. Why bother using XLR at all?

Gents,

If you don't understand what he's trying to do here, how about withholding your comments?
I've explained his bridging scheme/objective.....twice now.

Dave.

Armaegis · « **Reply #12 on:** 19 Oct 2016, 10:21 pm »

We get it. I think it's more we're alarmed over *why* he's attempting to do so in such a juryrigged manner. If it was a solid state amp with common ground at the negative terminals, yeah sure go ahead. A transformer (autoformer?) coupled tube amp is a different matter.

Davey · « **Reply #13 on:** 20 Oct 2016, 12:27 am »

If you got it, you wouldn't have suggested using the RCA outputs from the DEQX. The whole premise was based on using the XLR outputs so there were a normal and polarity-inverted signal available to create the proper input configuration for bridging.

It's not a jury-rigged setup if the power amplifier supports the proper output configuration. I've seen dozens of different tube amplifiers (utilizing output xformers) with both channels having common secondary ground connections tied together. They're easily bridgeable. I've done it myself numerous times.

Dave.

Armaegis · « **Reply #14 on:** 20 Oct 2016, 02:15 am »

I still stand by my assertion that splitting an XLR is bad practice. It's a great coincidence that most sources which are electronically balanced will also be symmetrically mirrored across ground/0V, but there's no guarantee of that. If you're splitting an XLR who's hot and cold pins both happen to float at a non-zero voltage (perhaps not intentionally, but a differential output doesn't necessarily care), then potential bad mojo ensues. The best bet is a transformer isolator, use a pair of matched resistors and tie the midpoint to ground on the output side and derive your RCA's from that.

All this for a meager 6db of gain and debatably no better performance.

craig sawyers · « **Reply #15 on:** 20 Oct 2016, 03:28 pm »

The question was "will this work? or will it blow my amp". The answer is "we do not know"; there is no information in the user manual on bridging. It might be OK, or it might not. You're going to have to ask Primaluna.

Davey · « **Reply #16 on:** 20 Oct 2016, 04:00 pm »

The DEQX does not float pins 2/3 of the XLR outputs.....they are properly referenced to ground. That's the unit the OP has referenced and the source unit we're talking about here...not some oddball exception.
A transformer scheme is a more complicated setup the OP doesn't have and is probably not interested in implementing.

Obviously we don't know 100% for sure if his audio engineer friend's suggested scheme will work and not blow up his amp. Do we have to qualify EVERYTHING with that disclaimer in audio nowadays? My goodness.

Dave.

craig sawyers · « **Reply #17 on:** 20 Oct 2016, 08:26 pm »

Quote from: Davey on 20 Oct 2016, 04:00 pm

Obviously we don't know 100% for sure if his audio engineer friend's suggested scheme will work and not blow up his amp. Do we have to qualify EVERYTHING with that disclaimer in audio nowadays? My goodness.
Dave.

Hey - the advice you offer is entirely up to you.

My most recent major projects were the Mercury Imaging X-Ray Spectrometer due for launch to that planet early 2018, and the High Resolution Optical Spectrograph on Gemini South in Chile, so forgive me for being cautious in offering advice on connecting two pieces of specific gear in a mode for which there is no precedent other than a guy that the OP knows.

Armaegis · « **Reply #18 on:** 20 Oct 2016, 08:27 pm »

I've worked with people who've managed to set their speakers on fire... twice. At this point, unless someone explicitly knows what/why they're doing something, I tell them don't do it.

Get this and skip all the weird adapter kludging and keep the gain you're looking for: http://www.sweetwater.com/store/detail/DTI

Or if you care about options and Jensen transformers: http://www.sweetwater.com/store/detail/JDIDuplex

Davey · « **Reply #19 on:** 20 Oct 2016, 09:17 pm »

No DIY spirit here at all.

As I mentioned, there certainly IS a precedent for doing this. But obviously a few factors need to be known/understood......which you'll note I identified in my first post. However, I would certainly hold off on launching that X-Ray Spectrometer.....unless you have established precedent and are sure of its success 100%.

His friend is an "audio engineer" and outlined a perfectly workable scheme...IMO. But, unless they know explicitly what they're doing, they shouldn't do it?? It's not clear to me that his audio engineer friend doesn't know EXACTLY what he's doing. Maybe I'm wrong???
Adding external adapters when you already possess a superior (and simpler) setup is kludging....IMO.

This is the "The LAB" Circle BTW.

Dave.