Strange Balance Problem - suggestions?

Apologies for cross posting from PFM, but thius is really bugging me and hope someone will be able to help

I've been noticing recently that the left/right balance when I've been playing vinyl seems to be off to the left and last night decided to get to the bottom of it. Thing is I got some rather strange results. Not trusting my own ears entirely (I am a little deaf in my left ear), I recruited Auntie Ants to confirm what I thought I was hearing, which she did.

Cart is a Denon DL-160 on a Spacedeck/Spacearm. Amplification is a Densen Beat B-100 with Densens DM01 MM phono stage built in. Speaker cables Reson DNM (2x3m runs) into KEF Q55.2. I used the balance test on a Shure ERA III Obstacle Course test record.

1. Everything set up as is, the test record definitely was louder in the left than the right channel. Okay - I assumed at first bias might be the issue, but nope I can mess with that to both extremes - that just results in minor mistracking and wayward cueing and its still louder in the left anyway - So I thought "Is it the amp or phono stage or speakers"? .

2. CD doesn't seem to have this problem so if its the amp it must be in the phono stage. So I swapped the phono inputs round expecting to get either a louder right hand channel if the problem is upstream from the amp or the left channel remaining loudest if its the phon stage in the amp.

Heres the strange bit - The test record showed the left/right balance to now be correct All be it, the wrong way round .

3. Next up I swapped the outputs to the speakers round (so that with both inputs and outputs reversed, the sound would come out the right way round) - the balance remained correct .

4. Finally I put the inputs back the way they should be and left the speaker outputs reversed - now the balance was wrong again - but louder in the right channel

I must say I'm deeply confused. The way I've left it is with both inputs and outputs reversed so that the balance is correct and the stereo image is correct (also reversed the CD inputs - so that it doesn't come out mirrored).

Any ideas? The bit I don't understand is when I switched the inputs - I'd have thought that wherever the issue is it should have either just swapped the balance or left the balance as was - which isn't what is actually happening.

PS. Once I'd reversed all the connections and the correct balance was restored the stereo imagery improved hugely - as I guess you would expect ... Don't you sometimes wish you had a balance control?

Help??

 

I have been told by a friend of mine who has been building hifi for 30-odd years that there is a tendency in many commerical amps (why, I don't know) for the left channel to be a little louder than the right. He has found it to be a 3dB difference in some cases! I know this is certainly true of recordings, and hifi can make it worse, but when you hear it with a test record you know that it is the equipment which is unbalanced. I presume it might just be a lack of tolerances/matching, but who knows. It has been audible, to a varying degree, in most sytems I have ever heard.

I reckon balance controls are essential anyway, because there is no such thing as the perfect recording, and certainly no perfect system to play it on. Perhaps you could mod your Densen?

 

Well maybe ... except it wouldn't explain the fact that on CDs the balance seems fine - unless its just in the phono stage ... but then how come the weird results with the input swapping.

I'm wondering if there is an imbalance coming from the cart ... and an imbalance in the phono stage of the amp ... both approximately equal favouring the left. With everything wired up correctly, they add together and it becomes enough to be noticable. Swap the inputs though and the one cancels the other. Its the only logical explanation I can think of.

Maybe someone who actually understands electronics can offer a better theory. I dunno, with all my inputs swapped round and the outputs ditto it sounds to me like it should now, but I'd love to know what's causing it.

 

Having got balance controls back after a 10 year+ absence I can agree. I can sit off axix now which opens up more options of where speakers anf furniture can go.

 

Well it'd certainly be handy. Mind you I'd quite like to see the return of tone controls as well - but that's a whole different kettle of heresy (to mix my metaphors with abandon).

Mind you tone controls or balance controls would spoil the minimalist chic of the Beat - and that just wouldn't do - I'll never be able to upgrade my amp because the designer in Auntie won't let me.

 

I've had this before .....in my case it was the first signs of an aging cart on the TT

swap the TT phono leads over and see if the problem tracks to the other channel.

check your antiskate bias as well ....as an after thought.

 

Hmm, I see what you are getting at but the carts all of about 3 months old.

Bias is near as dammit right so far as I can tell (even adjustments to the bias didn't have any effect other than as I said in the first post, mistracking and wayward cueing)

Swapping the phono leads over didn't (as I expected) track the problem to the other channel, but seemed to FIX the problem (albeit with a mirrored stereo image). That's what seems so weird.

 

I'd put it down to a vol pot imbalance.....are you listining in the first 25% of the pot ?

 

Yes - any louder than that and the neighbours'll complain.

That said though if it were a problem in the amp (the phono section aside), then I'd have the same problem with my CDP I would of thought ... but I don't.

PS. The view over on the asylum is that a smallish imbalance coming out of the cart and a similar smallish imbalance in the phono stage could combine to make a noticable imbalance overall and that swapping the inputs - they would cancel out. I'll live with that for now, by setting all my ins and outs back to front I have a solution so

 

You could swap the connectors on the cart. Then you would only need to swap the phono inputs to the amp

 

Very true ... if I can be bothered ... but then I'd still need to switch the speaker cables over if I didn't want left to be right and vice versa ... ditto for the CDP in ... er ... nah. I can't be bothered, but thanks

Besides the wires on the Spacearm are very skinny and make me very nervous whenever I mess with them.

 

Ok .....yes know what you mean.....

the thing about vol pots is they can be miss matched at low levels ie one channel will appear to sound louder than the other but as you raise the volume level they match more closely.


Now why only on the phono input ..........?

phono inputs are very sensitive .....to all sorts of things
Not a lot you can do if the problem lies there.

Back to basics is the head shell horizontal ?
whats your VTA like,
is the cantiver straight ?

from in front of the cart slowy raise the arm and watch the cantiliever, does it go off a little to one side ?

spacearm ? a unipivot ?.......check the set up of the arm , you only need the minute ist off centre weight to create odd side effects with a uni.

But I think thats more likely the source of the problem if the cart is newish.

 

Out of phase connections to the cartridge itself on the 4 pin connectors will give you a very similar result.

Dig out your cartridge fitting leaflet and recheck the 4 colour coded wires are going to the correct pins on the cartridge. The amount of times a colour blind twit like me has transposed the red and green wires is too many to mention

 

Hi Guys,

Just finished (well half finished ) an evening of IKEA wardrobe building, but did have half an hour to play.

The cart is level from the front
VTA? well the headshell is flat horizontal
cantilever dead straight
counterweight dead on vertical
alignment spot on according to my protractor
tracking at the recommended 1.6g
and its correctly wired

In fact from what I can make out, its pretty much spot on setup wise - it storms through even the torture tracks on this (my only - maybe I should get a more modern one) test record. No end of side distortion or other nasties either.

So the moneys still on a slight mis balance in both cart and phono stage equals a noticable difference. I'm sticking with the workaround for now ... in fact, I don't think its ever sounded better.

Thanks for the suggestions anyway.

 

VTA is in effect the angle of the stlus in the groove [looking from the side ], this is effected by the height of the pivot, so if the arm is not parallel to the playing surface [assuming cart top plate is square ] if the pivot is high it excentuates the treble ,if the pivot is low the sound is bass heavy. Thats the "Noddy does TT" version it can be more complicated than that.

With unipivots you only need to be a fraction off........


can you check using graph paper ?

take a sheet of G paper and fold it so it will stand on the record surface, with the lines parallel to the record surface. Place this behind and parallel to the arm, with the arm on the playing surface [record not going round!]. Look at the lines and the arm and see if there is any deviation? More difficult place the G paper ahead of the arm and look along its length from behind check the head shell is square.

I've used this method a lot in the past even though I have a box of posh protractors.

By the way the Elite is the best by a country mile.....where you plot the distortion on graph paper for different positions on the playing surface. You then adjust to minimise the distortion plots ...and replot the graph.

Some thing else to have a look at is the arm lead, unplug and reconnect oh and check for shineyness, clean connections are good! and do the same for the cart pins...yes I know a complete pain.......I use some long nosed pliers to ease the pins on and off, gripping them where they clamp the cable.

What else .......................

check the earth post on the amp all wires are making good contact.

Whip the lid off the amp and have a look to see if every things ok nothing odd or out of place no strange smells......

Let us know how you get on

 

I checked with graph paper as suggested and its near as dammit flat level - maybe, just maybe a smidge tail up. Took it down flat level - that made no diff though.

From the front the headshell is flat level.

contacts are shiny clean, earth post good.

I don't actually know how to get into the B-100 - no obvious screws - it looks like the monolith out of 2001 but with knobs on Certainly haven't noticed any odd smells - one thing I have noticed - I think my leccy here must be a bit cleaner than the old house - I used to get a little bit of transfiormer buzz - but now its dead quiet.

Since I did the switcheroo thing, the balance seems just fine - so I'll leave it at that I think. Cheers for all the useful advice though everyone.

 

It's worth trying attenuation if you're only using a bit of the vol pot. It can sometimes improve the overall performance - or it can mess it up! Doesn't really help with your problem though....

 

Hmm. I've heard it generally just messes things up, but what can I do? Also I wonder, are their any catridge loading issues if you do this on a phono input? (I know next to nothing about electronics - so apologies now if this is an ignorant qurestion)

Options that I can see are:

1. Attenuation

2. A less powerful amp? Don't really want to lose the amp and get a weedier one (and anyway Auntie wouldn't let me - she's no hifi buff but she cares about aesthetics - and as far as she's concerned the Beat with silver knobs is prettiest bit of hi fi she ever saw ).

3. Some less efficient speakers (the Kefs are 91db, which I suspect is probably a bit too efficient with 60W available from the Densen and the listening levels I'm comfortable with)? - and anyway I'm a bit skint.

4. Use the Densen as a pre (it has a pre out) and get some less powerful but high quality power amps? - and anyway I'm a bit skint.

5. Live with it - after my input and output switcheroo, balance is restored and I'm happy again (whether I'm only using the first 25% or not). - I'm going with the last option. Do Nothing - its cheaper - and why mess with it if your happy with it. To be honest since I sorted the balance out its never sounded better.

Cheers