Okay to use RCA adapter on a fully balanced amp?

@blkwrxwgn

Jensen makes a box that’s incredibly handy to have for these scenarios. It takes SE / RCA inputs and converts to balanced / XLR outputs via transformers (you will also need an extra IC). I have this and can confirm its transformers are transparent enough to improve SQ versus just feeding "half your amp" via RCA => XLR adapters. Great to have in your audiophile toolkit!

Ralph Karsten of Atma-Sphere @atmasphere (I’ll try not to get this wrong but I’m no authority here) will probably point out any amp like yours is not really "balanced". A true balanced amp should take any input, even an SE signal on its XLR inputs, and still operate fully differentially. To achieve this, the amp needs a differential input stage. This can be done either with transformers (like the Jensen box), or with special active circuitry. Amps that use an inverting opamp on their RCA inputs are to be avoided - that’s not a proper differential stage!

When high-end headphone’ing was a "new" hobby, the first balanced headphone amps did not have differential inputs. Later on the Kevin Gilmore designs starting using "Super Symmetry" (SuSy or SS for short) input stages that are just wonderful - RCA, XLR, or even SE on XLR: it’s all fully balanced throughout. NO performance penalty for RCA inputs or SE-on-XLR (besides whatever noise & aberrations the signal may be subjected to on the way there via cable). I believe the DIY community even released an SE-to-Balanced conversion box using this circuitry (all discrete, very linear). Most of the electrostatic headphone amps (Stax) also have differential inputs.

Here’s the part that concerns me about this amp possibly not having a "true" differential input, despite earlier verbiage:

If a balanced connection cannot be used, note that the amp cannot be driven to full power from a 2-volt single-ended output, the limit of most receivers. You leave half the power on the table.

Maybe it’s a real differential input and the amp simply has a very low sensitivity that requires more than 2 Volts to hit its full rated power output (i.e. use a single ended preamp with some gain, or a DAC with some extra gain, and you’re golden). Or maybe it actually DOESN’T have a differential input, and half of the amp’s 4 phases will be sitting at 0 whenever you use RCA-to-XLR adapters.

We’re trying to derive precise meaning from their verbiage, which could be either partially erroneous or easily misinterpreted. I’d contact the company for clarification.

OK, so I was totally wrong to doubt the amp’s description - it is indeed truly balanced, albeit with a rather low sensitivity (5 Volts is a lot to ask)! Sorry about that. An RCA-to-XLR adaptor will be a perfect solution, so long as you have enough upstream gain to get where you want in volume.