Bi-amping With "Y" Splitter: Any Impedance Problem?

[Ron Resnick]

If single ended is noisy, then try the transformer back at the preamp end.

The only thing the evil poltergeists in this room have been unable to attack with success is my noise level. Not to jinx anything, hopefully, but my system employs every noise inducing element possible:

-- different lengths of AC circuits (good for manufacturing ground loops)

-- different components on different AC circuits

-- Jadis amplifiers (prone for making hum problems, apparently)

-- mixing single ended and balanced components

-- mixing single ended interconnects and balanced interconnects with "Y" adapters

-- tube and solid-state amplifiers right next to each other (good for inducing EMI)

 

[DonH50]

I looked briefly at Lundahl; seems like a good company after a very quick look. Been in business a long time, some good technical info on the site, maybe the European version of Jensen? The SE-Differential converters on the pro audio page look reasonable. I did not dig into the datasheets; you might want to ask them (and Jensen) about your application since source and load impedances are on the high side.

One thing to double-check is XLR polarity; some reverse pins 2 (+) and 3 (-).

As for the REI amp, does the company have suggestions for driving from a SE source? The conventional schemes off-the-cuff are:

1. RCA shield to XLR pin 1 (ground/shield), RCA center to XLR pin 2, XLR pin 3 open;

2. RCA shield to XLR pin 1 (ground/shield), RCA center to XLR pin 2, XLR pin 3 to ground/shield;

3. RCA shield to XLR pin 1 (ground/shield), RCA center to XLR pin 2, XLR pin 3 to ground through a resistor equal to the source impedance (1k in your case, this helps maintain common-mode rejection);

4. Some recommend connecting RCA shield to XLR pin 3 so the XLR shield only goes to the chassis, or to the shield of a balanced cable, perhaps through a resistor;

5. RCA to an active (typically op-amp) or passive (transformer) SE to differential converter to the XLR.

The best connection is usually a converter, but many manufacturers have to deal with SE to differential (and/or balanced) conversion. What works best depends upon the amplifier's internal circuit, the input circuit and grounding scheme, so they should hopefully have suggestions. I only saw balanced from preamp to amp in their user manual, however.

 

[Ron Resnick]

Thank you for the brainstorming!

Single-ended into the REI is for my personal experimentation only, so no big deal either way. Right now I am using my in-wall balanced cables, so no solution needed because there is no problem to solve.

In two prior systems and now in my own system I have proven that the REI is a wonderful, synergistic match with Clarisys Audio loudspeakers. But I am a tube guy, so I like to play and experiment.

 

[Holmz]

The only thing the evil poltergeists in this room have been unable to attack with success is my noise level. Not to jinx anything, hopefully, but my system employs every noise inducing element possible:

-- different lengths of AC circuits (good for manufacturing ground loops)

-- different components on different AC circuits

-- Jadis amplifiers (prone for making hum problems, apparently)

-- mixing single ended and balanced components

-- mixing single ended interconnects and balanced interconnects with "Y" adapters

-- tube and solid-state amplifiers right next to each other (good for inducing EMI)

An occasional cob web, does not mean that the house is haunted.

I am a bit more pragmatic…
If there is a problem, only then it should be fixed.
If it is only a potential problem, then “A fix” could be fixing a non existent problem.

Neutrik, and others, have simple XLR to RCA adapters.
It is either the male or female…
https://www.neutrik.com/en/product/na2fpmf
That gets things going, and provides a basis from which to work.
It is @DonH50 version #2.

…
2. RCA shield to XLR pin 1 (ground/shield), RCA center to XLR pin 2, XLR pin 3 to ground/shield;
…

Or jump to the Jenson first.

If it was some traveling show, then having “all the fixes”, means that one does not have to trouble shoot it 10 minutes before the doors open. Which is usually achieved by having balanced connects everywhere.

There are certainly easier amplifiers to use for bi-anping, but I am not sure if there are many tube amps set up for making it easy??

 

[DasguteOhr]

The only thing the evil poltergeists in this room have been unable to attack with success is my noise level. Not to jinx anything, hopefully, but my system employs every noise inducing element possible:

-- different lengths of AC circuits (good for manufacturing ground loops)

-- different components on different AC circuits

-- Jadis amplifiers (prone for making hum problems, apparently)

-- mixing single ended and balanced components

-- mixing single ended interconnects and balanced interconnects with "Y" adapters

-- tube and solid-state amplifiers right next to each other (good for inducing EMI)

To find the source of the noise you have to proceed systematically. First step: get a short circuit plug (RCA) then only connect the power amp to the loudspeaker. Put the short circuit plug on the input of the power amp an switch on. No noise, good if you can still hear noise from the loudspeaker. Usually noisy tubes or a defect in the amp. If it's noise-free, connect the cable to the preamp. Disconnect all signal sources. Choose an input and plug the short circuit plug in there. Then switch it on. Noise-free, then test each signal source individually to find the culprit. Disconnect all unused devices from the main power during the test. Humming is 95% likely to be caused by different manufacturers' grounding and earthing concepts. Only a groundbreaking (RCA) transformer will help here.
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For rca to xlr the neutrik adapters are excellent

NA2M-D0B-TX

Miniatur Transformator Symmetrie Adapter, 3-poliger XLR Stecker - Cinch / Phono Buchse, schwarz kodiert

www.neutrik.de

 

[DaveC]

The Lara currently on audition is SE and balanced.

Jadis JPS2 is single-ended only.

The Jadis amps are single-ended only.


I would be perfectly happy with this scenario, but I have to check with Angus to see if that causes the REI a problem. The REI is true balanced from input to output, so I don't know if it will be happy with Pin 3 unused.


Thank you, but I won't be modifying any REIs.

Why did you choose a Jensen transformer for that purpose rather than a fancier, audiophile-beloved Lundahl?

Components are not single ended and balanced, but if the manufacturer uses separately buffered outputs that can be used at the same time then there you go... SE to Jadis and XLR to REI, each output running one amp only, no splitter.

 

[sparkie]

For our electrical engineer members: Does using a "Y" splitter on an interconnect cable to direct a pre-amp output signal to two different amplifiers for bi-amping cause any impedance problem?

Does having the dual amplifier loads derived from the same interconnect alter the source/load impedance seen by the input of each amplifier?

Thank you!

Yes it can especially if its with two different amp technologies (one tube and another solid state) and interconnect convention (balanced XLR vs unbalanced RCA).

If you are dealing with two unbalanced (RCA) input amps, you have to isolate their inputs by either using a resistor the size of the input impedance in series with the signal input, or signal transformers. If you don't need power isolation, then the isolation resistors could be the size of the preamp's load impedance times 2.

EDIT:
Looking at the Jardis amps online, they look like they are DC coupled so you will have to add the 200K resistor or use a .1uf capacitor when you use a transformer, otherwise the bias of the input stage will be effected.

Since you asked and even though you didn't need it, I decided to give you the solutions. Since the impedance of the Jardis is high, you might be able to use a Y split if you use a capacitor in series with the input of the Jardis.