Okay to use RCA adapter on a fully balanced amp?

I test it many times. If pre with RCA output and  power amplifier with XLR input,and you use RCA to XLR cable to connect?

At least in my system, it is not ok on sound quality.

@mulveling please note I was specifically talking about my amps, the original post is about amps from a different company and I cannot speak to those.

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. 

@orchardaudio that will be tricky for a lot of tube preamps. Our preamps can drive that no worries, but our preamps are balanced so its moot...

@atmasphere I agree in this scenario, the input impedance on my amps using an RCA to XLR adapter would be 22k.

@orchardaudio Most preamps can do 5Volts easily as long as the input impedance of the amp isn't an issue! My recommendation is thus to simply try it.

My amps are fully balanced and there is no issue with using them with RCA to XLR adapter. 

The adapter grounds one of the differential inputs to ground and then the amplifier behaves like a single-ended to the differential converter.

The gain of the amplifier does not change and it requires 5V input to get it to full power. This is an issue with standard RCA 2V outputs as 2V will get you less than 1/4 of the amps rated output power.

This is why I recommended to most my customers to get my active RCA to XLR converter that @evank refers to above. With 8dB of gain, it takes 2V up to 5V.  

I have experienced what the OP is talking about. That is why I purchased the active adapter in my previous post

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.

@mulveling According to their website, the amp is fully differential and balanced from input to output. Its a bit hard to imagine, but it is possible that the input stage has a really poor CMRR (Common Mode Rejection Ratio) which would cause it to be more distorted and lower power when run with a single-ended source. But its hard to imagine that they would know to do balanced and get the CMRR thing so bad in that light- although I have seen that sort of thing happen.

At any rate it won't hurt to try! If the CMRR is anywhere near what we've been getting with our amps over the last 45 years it won't be any problem at all.

I just received my Orchard Audio Starkrimson amp today and this is what I purchased with it to convert the balanced to unbalanced and it also supplies an extra 8db of gain

Stereo RCA to XLR Converter (orchardaudio.com)

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.

@blkwrxwgn , you should be able to drive the amp single-ended using an adapter. I would expect that your amplifier would sound the same driven balanced or single ended based on the statement above.

I trust your judgment, It's also not my final amp, there will be upgrading and I'm sure not all will be fully balanced.

true fully balanced differential amplifier from input to output.

@blkwrxwgn , you should be able to drive the amp single-ended using an adapter. I would expect that your amplifier would sound the same driven balanced or single ended based on the statement above.

Another option is to use a Schiit EQ (Lokius or Loki Max). Plug an RCA from the preamp into the EQ input and use the EQ output XLR to go to the amp. It will convert to balanced output voltage. The EQ is probably a lot quieter that an RCA/XLR adapter, plus it has a transparent bypass if you don't want to use the EQ to tweak your system.

@mulveling 

Nicely done.

Use a Jensen Iso-max transformer instead of the adapter; RCA in, XLR out. It's not truly balanced but will eliminate any noise during the conversion.

@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.

Thank you everyone, this has helped a lot.

@soix stated it well. I agree with doing the OPs ask totally wastes the abilities paid (probably dearly) for.

The only way that he is going to find out if it sounds worse to him is by comparing it Most of what is around here is theory.

Sound will suffer.

@soix, is correct!

Mike

A similar discussion came up on a Denafrips DAC forum. Because the Denafrips are R2R ladder DACs and fully balanced there’s four ladders to support the left (signal A and signal -A) and right (signal A and signal -A) channels. By using a single ended connection only the signal A ladders are contributing to the output being sent to the amplifier.

If you use a unbalanced RCA cable with an XLR connector on the amplifier end I would expect that the signal -A pin on each channel would not be connected. Components that are not fully balanced but do have balanced outputs use something to create the signal -A by inverting the signal. If your amplifier doesn’t have unbalanced inputs then it probably doesn’t have any mechanism to create the signal -A which would mean your amplifier would only be using half of it’s internal bits.

In your shoes, I’d absolutely work towards a balanced preamplifier.

OP,

Any difference is likely to be small. In this price range of gear cables tend to be less important than in really pricy stuff.

There are no absolutes in audio, but audio components are like scientific instruments, the better and more resolving they get the more small differences tend to make a big difference. So, for instance, the manufacturer of my amp and preamp recommends using XLR interconnects. So, I tried both. I really couldn’t tell the difference. I did not spend weeks comparing… but I still went ahead with the XLR (this was a $17K preamp and $22K amp). I think the quality of the interconnect typically makes a bigger difference.

I’ve used xlr to rca adapters as a test. I’ve used them on a First Watt J2,and a pair of Monarchy Audio amps. I don’t run a balanced pre,but I wanted to see if there was a noticeable difference. I could not detect any. Now,if I was running a balanced pre, I’m guessing the outcome would have been different with end to end XLR cables.

Thank you @soix that's what I was getting after, didn't know if it made a massive difference or not in audio quality.

@soix You are assuming there is an inherent benefit to balanced cables. Many, if not most, do not agree with that assumption. Having multiple inputs=good. Having ability to accomodate both xlr and rca=good.

@carlsbad No, I’m not assuming that at all, and you’re totally missing the point here. The OP’s amp is constructed in a dual mono and presumably in fully-balanced fashion, and if you feed it with single-ended cables that benefit largely goes away regardless of interconnects being used. It’s not about cables but more of system design. Dual mono and fully balanced is different from single-ended stereo, which you seem to totally disregard. Perhaps @atmasphere can interject here and describe it much more eloquently and completely than I can, but a truly fully-balanced design goes far beyond cable choice, and if you feed a fully-balanced amp with a single-ended preamp the benefit of a the fully-balanced amp is largely lost and negated.  You might’ve well just bought an amp with RCA inputs. Maybe Ralph can explain this better than me, but you’re absolutely wrong in your assertion that it’s just about cables. 

Not really concerned about the noise or if XLR is better, the only thing I'm worried about is the quote again.....I've never heard of this before and don't want to only get partial power from my amp.

"The MEGAschino is a true fully balanced differential amplifier from input to output. It is essentially two  amps for each channel, and one amp per phase. This means it really should be used in a fully balanced system.The manufacturer supplies an XLR to RCA adapter, but these should not be used. 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."

Using an adapter as you stated in your original question technically will create additional noise on the line, I have no idea if you will detect the noise.

On a normal 1 meter cord, you won’t hear the difference, but on longer runs, XLR. 

You likely will experiience no difference. However, instead of an adapter, I would make or have made a quality cable with XLR on one end and RCA on the other.

@soix   You are assuming there is an inherent benefit to balanced cables.  Many, if not most, do not agree with that assumption.  Having multiple inputs=good.  Having ability to accomodate both xlr and rca=good.  Needing another RCA because your component doesn't have xlr out=common problem.

So, with your amp you paid a lot extra because the manufacturer had to create two independent channels instead of just one, which ups the parts count and price considerably and you basically lose that benefit by sending it an unbalanced signal.  Use a fully-balanced preamp would be my suggestion.

you are loosing what the amp is capable of if you are sure your amp is fully balanced.

Same quality more noise. Should not be noticeable.

You WILL notice a volume reduction. Then it only depends on the efficiency of your speakers.