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Rega Elex-R channel imbalance

MasterTape

MasterTape

pfm Member
Hi guys,

Thought I'd check to see if anyone has had any luck sorting this kind of thing.

I bought an Elex-R used and thought it sounded great but soon felt something curious with its sound. I later identified this sensation to stem from the L channel being slightly weaker in volume, most noticably in having a weaker treble shifting voices to the R in the mix.

I first worried about the speakers and possibly my left ear but a few days later I pop an old amp in there - same cabling, same everything - and it's bang on center again. I plug the Elex back in, it's shifted to the right. I switch speakers on the amp side and it shifts left. It's the amp, no question about it.

I have no measuring equipment, all I did was check the speaker outputs and gave them a cleaning to no effect.

Does this snippet from Regas description of the amp have any bearing on where the problem might be?

"The Elex-R uses a combined feedback and passive volume control, where the feedback and input levels are varied to set the required volume level. The level and tracking between the two channels is set by the close tolerance parts in the pre-amplifier circuit and less by the actual potentiometer itself, thus keeping the mismatch of channels due to volume control tracking irregularities to a minimum."

Thanks.
 
Will certainly do, I know my nearest Rega repairman and will call him tomorrow.

Just curious about experiences with similar issues from folks, what could have gone wrong etc. No one but the official repairman will touch it in the end but I'd happily learn more about why it would behave in this manner.
 
Last time I had something like this I cleaned my for cable and it was fixed but sounds like rega engineer neede
 
Sent to service. Part of me really dreads the "nothing seems to be wrong with it" call. It doesn't seem all that uncommon with this issue when reading around the web.

Fingers crossed it's just a failed resistor and it comes back a straight shooter in no time.
 
He appears to be a class act and has a great reputation so I'm hoping this will be the case. He had never fixed this particular issue with a Rega fwiw.

It's a shame the previous owner didn't have it fixed during the warranty period. I have a hard time seeing he sold it for any other reason than this. But I have been spared from these issues when buying used for a very long time so not too upset about it.
 
Hmm I had a sneaky feeling from reading of similar experiences and yes, it does measure identical between L/R in the workshop and he cannot find anything wrong with it despite having a very helpful non dismissive attitude in this.

So I can switch speaker cables at the back of the amp and the balance shifts to the other side. I measure placement to the millimeter and the room is symmetrical. I can switch only the amp out and the problem goes away so probably not a cabling or source (dac in this instance) issue.

Very very strange.

But at least I'm happy the amp is healthy, now I can let it go without worrying about it being faulty if it comes to that.
 
Your tech may have simply run a straight L-R level test at the speaker output terminals.

The way you described the symptom as being 'a weaker treble shifting voices to the R in the mix' suggests that the output from the L ch could be the same nominal level as that of the R ch but lower in the upper mid through treble. IOW, a frequency selective imbalance, which will not be apparent with a straight L-R level test.

I'd recommend using one speaker only and simply transfer the speaker cable connection L/R at the amplifier end between tests. Run log and/or linear frequency sweeps on each channel individually using tracks 6 and 7 respectively from the linked to test tracks below. Should an imbalance be apparent as the frequency rises then there are a number of select frequency test tracks that can be employed to home in. Do note that the frequency sweeps are recorded at 0dB to -6dB, with the set frequency test tracks at -1dB, so start with the volume all the way down and bring it up slowly to a reasonable volume level after a chosen test track starts, and then leave it set as such as you run the same on each amp channel. IOW, get the volume right, listen to one channel, let the track finish, change channel, repeat.

Link to Michael "Bink" Knowles' free PA rig test tracks, aka 'The Bink Audio Test CD'. No need to burn to CD, as the tracks can be run from a connected device.

WARNING: Read the instructions carefully, as a number of tracks (50 through 55 in particular) are for amplifier testing only and will damage speakers!
 
Thanks for that, he did indeed measure test tones at the terminals. He quite confidently dismissed any sort of frequency selective imbalance and implied that it's not even a possibility. I just took his word for it since he's been doing this for 40 years.

I am not 100% certain it's a frequency thing, it's just how it sounds to my ear. The image is shifted to the right and the sound coming out of the left speaker is muted and 'odd' in a hard to place way. It makes me physically uncomfortable in a way that ie L/R imbalance due to different speaker distance will not.

I immediately thought it was the speaker or my ear because of this weird sensation but nope, all back to normal when I pop my other amp in.

I might give him a call and ask him to perform this test to be sure, his next return shipment isn't until Tuesday anyway.
 
Whilst a frequency selective imbalance is not impossible it is VERY unlikely. In a typical SS amp the gain is set by the amount of negative feedback and this in turn by a couple of usually 1% tolerance resistors. For this to be frequency dependent would require frequency selective elements to be added to the feedback network....
Channel imbalance from anything other then a badly tracking vol control is quite rare in SS amps and for it to be frequency dependent.... well it's the sort of rare fault I may see once in 10 years when doing repairs professionally...
 
Are you sure you are not connecting the speakers out of phase because that would give rise to a "weird sensation" and "uncomfortable" ?
 
hifi_dave said:
Are you sure you are not connecting the speakers out of phase because that would give rise to a "weird sensation" and "uncomfortable" ?
Click to expand...
I’d wondered whether one of the speaker outputs was wired out of phase, I know it’s unlikely but I’d check that.
 
Arkless Electronics said:
In a typical SS amp the gain is set by the amount of negative feedback and this in turn by a couple of usually 1% tolerance resistors. For this to be frequency dependent would require frequency selective elements to be added to the feedback network....
Channel imbalance from anything other then a badly tracking vol control is quite rare in SS amps and for it to be frequency dependent.... well it's the sort of rare fault I may see once in 10 years when doing repairs professionally...
Click to expand...

Your comment leaves me wondering what the implications might be wrt how a typical SS amps gain is set vs. Rega's description of how their volume control works, as quoted by the OP above...

"The Elex-R uses a combined feedback and passive volume control, where the feedback and input levels are varied to set the required volume level. The level and tracking between the two channels is set by the close tolerance parts in the pre-amplifier circuit and less by the actual potentiometer itself, thus keeping the mismatch of channels due to volume control tracking irregularities to a minimum."
 
hifi_dave said:
Are you sure you are not connecting the speakers out of phase because that would give rise to a "weird sensation" and "uncomfortable" ?
Click to expand...

Yeah it's not that extreme, I've heard out of phase at my dealer once and that was quite something :)

It's much more subtle. Sometimes when trying to come to terms with it I've put a track on, and as I approach the right speaker head on, closely, it sounds all fine, clear and natural.

As I do the same to the left it sounds muted in a subtle way that kind of makes me want to itch my ear or clear my throat. But I suspect this is due to some weird balance of detail. If I listen close the R, I don't hear the L. If I listen close to the L, I get some detail over from the R side and it probably just confuses my brain somehow. But there is a slight physical sense of something being off when mentally or physically zoning in on the left, definitely.

The thought of soloing the left didn't strike me, I guess that would reveal whether it actually sounds weird in isolation or if it's just some balance issue messing with my expectation.
 
Craig B said:
Your comment leaves me wondering what the implications might be wrt how a typical SS amps gain is set vs. Rega's description of how their volume control works, as quoted by the OP above...

"The Elex-R uses a combined feedback and passive volume control, where the feedback and input levels are varied to set the required volume level. The level and tracking between the two channels is set by the close tolerance parts in the pre-amplifier circuit and less by the actual potentiometer itself, thus keeping the mismatch of channels due to volume control tracking irregularities to a minimum."
Click to expand...

I see no implications here. The pot tracking will always be the crucial bit.
 
hifi_dave said:
If you swap left for right speaker cables, it will show if it's amp or speaker.
Click to expand...

As mentioned I did, and the imbalance is reversed, excluding room, speaker or hearing issues.

I'm not sure we'll get to the bottom of this to be honest. I'm left scratching my head and I have no reason to not believe the tech when he says he plugged it in and gave it a listen and found as little wrong with it this way as he did when measuring test tones to be within a tenth of a milivolt at the terminals.

But in my setup it exhibits this behavior, and the three other amps I've had in this exact setup all were fine. If it doesn't at his place I can only assume there is some very mysterious interplay issue with my source and the Elex, weird as that would be given that anything else I've plugged in has worked before and since.

It's not extreme, think of it as a 10-15% shift to the right for the centre image. But enough for me to not be able to ignore it and enjoy the music since the sensation is one of my left ear not working properly.

I have also had two different dacs in the short time I've had the Elex, same issue with both. So that leaves the little Digione streamer but I don't see how it can be at fault when there are no issues with other downstream combinations. Same thing with the cables, I've tried numerous to no avail despite not seeing how they can be at fault when working just fine with other amps.

I frankly don't have any ideas. All I can do is assure you guys I'm not hearing things since the L/R speaker switch and an amp switch demonstrates the issue to be with the Elex's interaction with my setup.
 
i am from holland and was searching the internet for same issue. However by me the right channel sounds weaker. i am wondering if there is any news in the meantime from you folks. Tried everything but cant solve it. I bought the amplifier new.
 
I have a similar problem which I have "bodged" by fitting another pot for the right hand channel. I was able to do this without butchering my Sugden A21SE amp because I only use one input so I was able to set my vinyl source by defect and use the same hole and knob (?) on the facia for the second identical pot. It´s really quite a big difference in volume levels to get a centred image which I attribute to my crappy room decor and/or lousy lugs.
 
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