Cable conundrum: Parasound A21 with RCA AND XLR

Ok, hope someone can give me a lesson. I recently aquired a Sonic Frontiers Line 2 preamp with both unbalanced and balanced outputs. First I hooked up my Audio Metallurgy GA-0 XLR's to my A21 amp, and I was not pleased with the sound. No depth, soundstage was choked. (gain was adjusted) I then connected my Synergistic Res RCA's to the outputs after disconnecting the XLR's. still not that pleased with what I thought was an upgrade.

In an accidental discovery, I reconnected the XLR's to the preamp WITHOUT ever disconnecting the RCA's. BLAMMO!! What sound I got! almost 5.1-like wide soundstage, reach-in depth, and the detail...let's just say i heard things from my CD's I never heard before. can this be? Both outputs from the preamp go to both inputs at the amp (balanced and unbalanced). Parasound tells me this is not a detriment to the amp. But I thought you could only use one or the other. Not both at the same time.
Any explanation?
In what position was the switch on the A21 that selects between the balanced and unbalanced inputs, when you had both sets of cables connected? And in what position was the ground lift/normal switch?

-- Al
Having got this amp over the weekend, I am more than eager to know what Evergrey found out and which was better (RCA or XLR)? Some people claim that RCA is more musical than XLR. To them XLR seems more clinical.
The positioning of the switch is on 'balanced'. But, this does not make a difference in sound level/quality if i were to put it on 'unbalanced' as long as both connection types are in.
The ground switch is currently on 'lift'. I have not tried to change that. What about phasing?
At this point, i would have definitely said good quality RCA's are the way to go in my system if i could only run one type. The XLR's just did not have the the same sonic vibrancy/detail/depth. The initial increase in gain, actually seemed to deteriorate the sound, so i lowered the gains on the amp.

I can't formulate a precise explanation for your findings, but I suspect that if you put the ground lift switch to "normal" you may very well obtain results with only one set of cables connected that are similar to what you have obtained with both connected.

The ground lift switch isolates the ground sleeves of the rca connectors (and possibly also the ground wire on pin 1 of the xlr's) from the amp's chassis. I would only use that position if it is necessary to prevent ground loop hum or buzz. That isolation could conceivably account, in subtle ways related to the grounds, leakage paths, stray capacitances, etc. within the amp, for the sonic effects you observed when only one set of cables was connected.

Having both cable sets connected, while the ground switch is in the lift position, could conceivably alter the paths and impedances through which signal return currents flow, between the input circuits of the amp and the preamp. That in turn could conceivably alter or undo the sonic effects of having the cable grounds isolated from chassis.

That's all conjectural, but I definitely think it is worth reassessing your findings with the ground lift switch set to normal.

Re your question about phasing, I don't see any relevance, because neither the relative phase nor the absolute phase (polarity) of whatever inputs are selected (balanced or unbalanced) would be affected by the presence of the other set of cables.

-- Al
I have a Parasound C2 preamp processor normally connected to a Parasound A23 amp using balanced cables. My ground switch was and is in the normal position and the cable switch set for balanced cables. I decided to try adding a set of unbalanced cables between the C2 and A23 based on Evergrey's post. The sound seemed fuller and more detailed through my Salk SongTower Speakers with both balanced and unbalanced cables connected whether the amp was switched to the balanced or unbalanced cable position. The unbalanced position sounded slightly better to me when the sound level was matched.
I do not believe the position of the ground switch is the explanation since mine is set to normal (not lifted). I have noted that even when the switch on the amp is in the wrong position for the type of cables used (that is unbalanced if only balanced cables are used or balanced if only unbalanced cables are used) there is some sound output albeit at a lower level. It may be that the amp is being input by both sets of cables although one at a much lower level that for reasons unknown to me gives a richer sound at the same volume. Then again this may be a placebo effect. In any case it was worth trying as I had the spare cables available. YMMV.
Well, this investigation has taken a turn for the worse. I decided to remove the Synergistic RCA's from te amp and turn the ground switch to 'normal'. After i turned my equipment back on from the cable change, i lost sound out of the left chennel. I've tried every scenario to see if it wasn't my source, preamp, speakers or different cables. I've deduced that my amp blew a channel. The 4 buss fuses inside, although taped uo to hide the filament, seemed to still work because the 2 blue lights on te front panel were lit up, the 'Hi Temp' light was off, and te right channel worked.
This is a total bummer and now i have contacted Parasound to see what my options are.
Thanks to everyone for all your input.
Mlenn, are you going to leave both IC's sets connected? didn't know that it would have a similar result for others or not.
Evergrey, sorry to hear about the problem with your amp. I do not know why this problem would be related to your cable change if the system was off when the change occurred as you indicated. Thanks for the warning and please keep us updated on what you hear from Parasound.

Yes, I plan to leave both sets of cables connected to my A23 for the present, but will continue to avoid any changes in switches or cables unless the equipment is off. I blew the external fuse on my A21 (used in separate HT system) once when thoughtlessly switching from ground to lift with the system on. Fortunately, a simple replacement of the fuse fixed my problem. Lesson learned.

My C2 will sometimes switch into a silent protection mode if I touch the unit or connected equipment and get a static spark. Switching to another source or turning mute on and off returns the unit to normal operation. I appreciate this is likely unrelated to your A21 problem.

Hope you get your amp problem resolved soon.
Mglenn, thanks for the support. I'd like to open the discussion back to this cable discovery. I wonder why this is not discussed more frequently amongst users, in utilizing both XLR and RCA at the same time, if results like this can be achieved. I suspect that the approach of good quality cables in both categories can help achieve some terrific results.
EG, sorry to hear of the left channel problem, which I can't shed any light on.

Re your and MGlenn's observations of improved sound with both sets of cables connected, I suspect that the reason it is not discussed more frequently is that it is specific to your equipment.

I think that MGlenn's observation that significant sound comes through even when unconnected inputs are selected is key. That indicates crosstalk between inputs within the A21, and is most likely an unintended (and non-ideal) characteristic of the design. For whatever reason, though, it apparently happens to be synergistic with the A21's overall sonic characteristics and/or the characteristics of the rest of your systems.

Best regards,
-- Al
Was your issue resolved? What reply did you get from Parasound?

I believe that the A21 is not a "true" balanced design and so you are able to listen to some music when the switch (balanced/unbalanced) is in wrong position. But some manufacturers are of the opinion that RCA is more musical than Balanced.

In my home theater system, I use a Parasound C2 controller (yes, I have 2 of these) with Parasound A21 and A51 amps connected with balanced cables. In my opinion this sounds very musical driving three Von Schweikert VR4JR speakers and four TS150 speakers whether used as a 7.1 system or where only the left and right speakers are driven. For some reason, the C2 and A23 combination driving my Salk SongTowers sounded somewhat thin and veiled in my 2 channel system when connected with balanced cables alone.
I shipped my amp out to Parasound since it is still under warranty. They are standing behind they product and will resolve this for me.
As for your assessment, this cable arrangement worked with each CD i tried. Perhaps Mgleen is correct in stating that there is crosstalk between the RCA/XLR connections. But to make such an impact doesn't seem to be accidental to me. Again, i wonder if this configuration would work with different amplifiers. The sonic quality improvements in the combined configuration mode of having both RCA and XLR inputs hooked up to my preamplifier from my A21 cannot be downplayed.
Hope you have got the amp back by now. How do you like the sound now?
Hey Milpai, I have been enjoying the amp now for a few months. Parasound took care of the problem and actually brought it up to current standards. I am very pleased with the sound and the current setup. The combination of the Sonic Frontiers preamp with the Parasound A21 amp works very well. I am considering some tube rolling in the near future.
Good to know that Parasound provided you a great service. I am simply stunned by this amp every time I listen to my music. Which tube pre-amps are you considering?
Well tell us, are you still running both XLR and RCA?

If so how does it sound now?
Sorry for the delayed response. Milpai, i share the same thoughts as you do about this amp. Running through my Sonic Frontiers tube preamp, I feel like i have a great combination of both detail and warmth. The soundstage is very plentiful as well. I gotta say that this combination of BOTH xlr and rca connections really makes that combination wake up. Insofar as tube rolling goes, i was referring to the stock sovtek 6922 tubes that came with the preamp. I'd like to change (roll) these 6 to the recommended Amperex or Phillips equivalent.
My speakers are the next thing to be upgraded, but i really am not sure what to go for. Considering my appetite for prog rock, jazz and tech metal, I am keeping my eye on B&W 803's, Tyler Acoustics, Von Schweikert VR4jrs, Dali Ikon/Euphonia's.....but i am not sure if these are the right combination. I have no ability to audition these locally. What is the speaker choices that other A21 users enjoy?
Re-opening an older thread. I have ordered a pair of XLR cables to go between my preamp and the A21. Of course, they are Signal Cable Silver Resolutions.
Very keen on knowing what others have experienced when they switched from RCA to XLR on the A21.
A shot in the dark -- any chance you dropped your effective input impedance to the A21 in half by using 2 parallel sets of interconnects? This shouldn't tell the tale, since the SF output impedance is pretty low (~ 150 ohms) and the A21 input impedance is suitably high (33 kOhm & 66 kOhm, depending on which inputs you use), but you never know. Is the amp seeing the preamp "halved"?
My path of discovery with Xlr's vs. Rca's to my A21 was the XLR's where a more refined and taller image and increased separation between instruments, plus a lower noise floor. Last year I added a HFT Silver Star fuse for the main ac line. The cables used for the comparisons at the time where AQ's Columbia XLR & RCA I then switched those out for Morrow Audio's MA3 XLR's which where a better synergistic match in my setup to reveal the A21's musical prowess!

Yes, I have read the same about XLR on A21. I am hoping to get the cables this weekend. Thank You for the info.
ALRIGHT - received the XLRs, installed in the system and finally got the answer I was looking for. Without keeping you guy waiting, here it is - JUST GO for XLR.

Did not take more than 15-20 seconds to realize this with 2 CDs I used - Famous Blue Raincoat and Hobo (Sara K).

FBR is well recorded and I have used it on multiple occasions to test various components. Listening to "Bird On A Wire" it was immediately apparent that the stage depth and height had increased. Hobo is also very well recorded. But my constant complaint was that the recording sounded thin. With the XLRs in place this is no more an issue.

Here are the changes that I noted with XLR compared to RCA:
1. Superb dynamics (big, bold, lifelike presentation)
2. Excellent depth
3. Subtleties became so apparent
4. Increased stage height
5. Pinpoint imaging (separation of individual sound?)
6. Center vocals do not move to sides if you move your head
7. More muscle to music
8. Increased gain

That last point above is what I don't understand. I had to go down 2 notches on the volume control. Why did this happen? My CDP remains the same. Only the connection from preamp to amp changed. If someone could care to explain, it will be very helpful. Thanks in advance.

I can say this confidently - if you are not utilizing the XLRs on the A21, then you are only listening to $1000 amp. Use the XLRs on the A21 and now you are listening to the $2300 amp that you really paid. You really don't know what you are missing on the A21, unless you listen to it using XLRs. I am not going back to RCA on the A21 for sure.

For people who are using passive preamps or TVCs - XLRs is THE way to go if your amp is A21. You will be surprised by the "gain" that you gain (no pun intended). I am pretty happy with the positive change in my system, that the XLRs have bought. Though the CDP is the weakest link in the chain now, I am in no hurry to replace it - since all my old CDs are NEW again and I need to listen to them again - at least once!!
There is typically a 6 dB gain difference between balanced and unbalanced connections. In a balanced connection, the signal is differential -- e.g., when the positive leg increases by 1 volt, the negative leg decreases by 1 volt, and there is a net 2 volt differential signal. In an unbalanced connection, we only see one leg, or 1 volt of signal.

Twice the signal = 6 dB of added gain.
That last point above is what I don't understand. I had to go down 2 notches on the volume control. Why did this happen? My CDP remains the same. Only the connection from preamp to amp changed. If someone could care to explain, it will be very helpful. Thanks in advance.
Pretty simple answer - Balanced output is in general twice the output in voltage (typically 4V vs 2V but that also depends on the manufacturer). Balanced was designed for professional setups where 50+ feet are needed. Also balanced has better noise rejection.

That being said I did a shootout about a year ago with Nordost Frey's and found the soundstage to be wider which I really liked but found the gain to be too much which I really hated. I went with the Rca's. My cd is a meridian G08 and my integrated is an Octave V70SE which both have a true balanced output and input. Just upgraded to the Tyr2 w/rca's.
Thank You for explaining. Please note that my current CDP only has RCA and that is how it is connected to the TVC.
I was under the impression that for TVC, there is no real gain, as it does not have electricity input. I think a TVC only attenuates. I was aware that if I changed my CDP and the new one had 4.0V out instead of the current one's 2.2V, then I would stand to have a "gain" in my system.
Xti16 - for me the increased gain is a welcome change.
Finally got a simplistic answer I was looking for, on the gain that I gained in my system using XLR connection:

The A21 gain is 6dB higher when the balanced connection is used. The output of your Promentheus is also 2x, or 6dB higher than unbalanced. Each "leg" or "phase" of the XLR is the same voltage as the RCA and two legs is 2x more which = 6dB. The same thing occurs at the XLR inputs of the A 21.