Balanced vs RCA between amp/preamp

As promised, I have downloaded and examined schematics for the OP’s preamp and amp, which as I had mentioned in my previous post can be obtained at hifiengine.com if one is registered there.

The amp is not fully balanced. However, while the circuit configurations used to receive balanced and unbalanced inputs are of course somewhat different, both inputs are processed through circuitry described as follows:

HDAM SA3

Marantz developed its own discrete circuit boards to replace standard IC's. These HDAM's consists of discrete surface mount components with short mirror image L/R signal paths. Those devices are doing exactly the same thing as the Op-Amps, but outperform the regular IC Op-amps dramatically in terms of the Slew Rate and reduced noise level, resulting in a much more dynamic, accurate and detailed sound. Over the years Marantz developed different types of the HDAM to improve quality and to fit to the special requirements of a product category like CD or amplifier.

Two HDAM SA3's are in the path through which each balanced input is processed; one of those two is in the path through which each unbalanced input is processed.

The preamp is also not fully balanced. However, a good deal of the circuitry which precedes its balanced outputs is symmetrical and is therefore balanced, although not differentially (i.e., it does not utilize differential stages). That circuitry also utilizes the HDAM SA3, followed by a number of stages utilizing discrete transistors.

Given all of that, my guess in this specific case is that it is more likely than not that a balanced interconnection will be preferable to an unbalanced one.

Luisma31 8-4-2019

Reading the initial post again I missed something, the input source is single ended, this is a question for the others answering in this thread as I'm not sure of the answer. When the source is single ended shouldn't be the output single ended as well even when using the XLR output?

While I suppose there may be a few exceptions, usually a preamp which provides balanced outputs when it is provided with balanced inputs will also provide balanced outputs when it is provided with unbalanced inputs. And examination of the schematic for the OP’s preamp confirms that is the case here.

Best regards,

--Al

 

I like my balanced connects, no loose or cold welded RCA plugs, always an easy and solid connection.  Using “Worlds Best Cables” with  2534 wire that cost $30 a set.  Couldn’t be happier, but my equipment is fully balanced differential from the dac to amp.   

for anyone interested, HDAM module schematics are available here https://muzgdiy.files.wordpress.com/2015/05/all_versions_2.png

These HDAM's consists of discrete surface mount components with short mirror image L/R signal paths.

IMO, this is marketing malarkey. It is not possible to 'mirror image' active circuitry as devices have functions on specific pins. Marantz literature always shows a pair of identical HDAM modules and never a mirrored L/R pair which, if they existed, would be featured front and center. Additionally the Service Manual has only one HDAM-SA3 schematic for a bipolar amplifier circuit.

Discrete circuity 'suffers' from increased parasitic L & C, component tolerance and reduced supply immunity, all of which contribute to the 'sound'. Some opine that discrete circuitry takes the edge off the literally 1000's of integrated circuits through which the signal passed before the final storage medium.

Somewhat troubling is the -ve phase is derived from the post Wolfson WM8816 volume control unbalanced +ve output through an additional 2 HDAM and 2 gain stages. These then feed a pair of balanced tone control circuits. Strange.

Use caution if driving an unbalanced amplifier. Best results will probably result from using Pin 3 & Gnd ONLY.

A largely ignored electronics property is power supply linearity. The impedance and phase linearity of the ubiquitous LM3x7 / 7xM  et al. regulators vary drastically between manufacturers and implementation. Some are positively abysmal suffering 180° phase and a couple of orders of magnitude Z change in a few Hz.

Marantz makes a fair bit of 'noise' about their power supply design and examination of the schematic shows that the audio supply is discrete and well designed.

A negative in the pre-amp [and any versatile control center] is the large number of relays in the circuitry. ALL switching is audible and cumulative.

Bottom line, if you like the sound, don't worry about the innards.

PS I have a Marantz CD-6006. I like the sound & features. I don't worry about the innards.

Use caution if driving an unbalanced amplifier. Best results will probably result from using Pin 3 & Gnd ONLY.

Hi Ian,

Not sure where you are quoting this from, or if you are quoting it, but to be clear I assume this statement is intended to apply to the unusual situation in which XLR cables are used to connect the balanced outputs of a preamp to an amp which receives the signals provided to its XLR inputs in a single-ended manner, and would short one of those signals to ground if the signals on pins 2 and 3 were both routed to the amp by the cable. In most cases, of course, at least when it comes to consumer-oriented gear, unbalanced amplifier inputs would be driven by the preamp’s unbalanced outputs via RCA cables, and the statement would not apply.

And in most cases involving consumer-oriented amplifiers which provide XLR inputs but are not "fully balanced" I would nevertheless expect signals provided to their XLR inputs to be received differentially, not single-ended. As is the case with the OP’s amp.

In any event, thanks for providing the additional insight in your post.

Regards,
-- Al

I had a low level buzzing in RCA when i went to balanced it went away plus the system got quieter and more dynamic.