mr.me

Channel Drift

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I have recently acquired an Eastern Electric Minimax Integrated amplifier running ECL82 valves but find that the central imaging has drifted to the right. Vocals are now located between centre and right speaker. I have replaced the valves for a set of brand new ones, changed the source but to no avail. Does anyone have a solution to this?

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Super Wammer

Daft I know but have you checked that the SCs are plugged into the same Ohm rated taps, as you may be getting a slightly higher output from the right if not, which will make the image drift. 

I had this the following day after a BO where some kit & cable swapping was done. Imaging was way off, and after pulling my hair out for half an hour I discovered someone had knocked one of the sensitivity switches on my monos making one channel louder. 

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Thanks for your suggestion John, but no everything is connecteted correctly. 

I am connected on the 8 ohm taps maybe I should try thre 4ohm to see if the image moves back to centre position. Don't really know whether that would make a difference in this respect.

Edited by mr.me

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Super Wammer

A long shot I know but are you certain the imaging has moved? Could it possibly be down to what you are listening to, I know that when I am listening at home it is rare for things to be exactly centred, vocals especially I find can be placed almost anywhere from slightly left or right of centre to quite close to either speaker.

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A long shot I know but are you certain the imaging has moved? Could it possibly be down to what you are listening to, I know that when I am listening at home it is rare for things to be exactly centred, vocals especially I find can be placed almost anywhere from slightly left or right of centre to quite close to either speaker.

Hi Brook, I am very familiar with the albums I was playing and I know for sure that on my main rig that the vocals are central. I appreciate what you are referring to as I also have recordings where the vocals are either to the right or left of centre.

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Super Wammer

Okay mate I thought that would be the case but no harm in asking.

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Does this amp have auto biasing ? - you say you have changed the valves - it could be that the bias is out on side resulting in a differing output for each channel?  Rabski is your man for advice on valves.

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Thanks uzzy but I changed the valves for the very reason of channel drift as I didn't know how old the original valves were and thought that they might have been the problem. I'm beginning to think that once the amp has been going for a good while that the image appears to move more central, playing the same track each time, though I could be imagining that :/

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Thanks uzzy but I changed the valves for the very reason of channel drift as I didn't know how old the original valves were and thought that they might have been the problem. I'm beginning to think that once the amp has been going for a good while that the image appears to move more central, playing the same track each time, though I could be imagining that :/

If the amp needs manual biasing though you need to get that sorted (wrong bias voltage will shorten the life of your valves too).. send Rabski a message and ask him for advice he is a valve expert.

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Moderator

You rang?

Actually, I can't find anything online so far about the Minimax, but one review I found states it's cathode boiased, which normally means first, that you don't need to adjust anything when changing valves, but second, that you need relatively well-matched valves.

Plus, it's got ECL82s, which are unusual (combined driver valve and power valve in one envelope). I'm a bit lost, because I can't find any serious information or a schematic, plus it's an unusual design and they aren't at all common.

First thing in Sherlock Homes methods is to eliminate the unlikely or seemingly impossible. Therefore, try swapping everything else, one at a time. In other words, turn off, swap speaker connections over from right and left, then turn back on and see if the issue is still in the same direction. Then do the same thing with the source. If no matter which way things are connected, the 'lean' is still to the right, at least you'll have firmly put it down to the amp. Rather than just swapping all the valves, swap them from left to right (and vice versa) and see what occurs. Also, any spare amp you could try? Possibly a wam member close by who could bring something to try?

Lastly, has anything else changed? Not just in the system, but in the room and speaker positioning?

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When my central image drifts to one side it is usually a sign it is time to have my ears syringed again, the right one tends to get blocked up. Just a thought.

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Therefore, try swapping everything else, one at a time. In other words, turn off, swap speaker connections over from right and left, then turn back on and see if the issue is still in the same direction. Then do the same thing with the source. If no matter which way things are connected, the 'lean' is still to the right, at least you'll have firmly put it down to the amp.

I wouldn't normally doubt you @rabski but actually I'd have thought that suggested an issue with a speaker. If it's an amp problem then swapping which channel each speaker is connected to should cause the image to shift in the opposite direction, but if it stays the same, and also does with the source channels switched, it would point to the speakers as they haven't moved. Or an issue with the OP's hearing as someone else has suggested. 

Edited by MartinC

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Nothing wrong with my hearing folks :) I know it's the amp as when i am connected up with my main amps there is no problem. Just wondering what could cause it to be audibly lob sided.

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Nothing wrong with my hearing folks :) I know it's the amp as when i am connected up with my main amps there is no problem. Just wondering what could cause it to be audibly lob sided.

I really doubt it is this but at the trivial level you might just want to give all the connections a clean. 

It's 'lopsided' by the way :)

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