X-Can V1 Hum

[ade]

Hi

I have an original X-Cans amp which has been suffering from hum for some time now, and I've been lurking around the forums and trying a few teaks to try and solve it but it still exists.

The hum is most noticeable during quite music / no music at all, and seems to pass from the left side to the right as the volume is increased. (i did see some older posts mentioning the same sort of thing)

So far i have tried (each with no effect)

A Russ Andrews Silencer

A ferrite clamp to the power feed

Disconnected the Led on the X-Can (Read somewhere it was a possible source of interference)

and finally replaced the original tubes with a pair of 6H23p-EB's.

One thing i have recently noticed is that if i listen to the transformer it is making the same sort of hum, not noticeable from any distance away only when up close.

Does anyone have any ideas where my problems lie? Have my cans has their day? Or maybe the transformer is at fault? Is there something else i should try? I'm happy to go down the building / buying a new PSU route or fitting a Cap kit of it will help.

Any hints appreciated .

Cheers

Ade

[rickcr42]

How do you feed the signal to your X-Cans ?

Headphone only system ? Mixed speaker amp/headphone amp system ? If yes is there hum on both or just the one ? Signal path description ?

Having hum in an amp not known to have this problem means the solution likely is not amp centric but system related and usually indicates some type of mismatch or a ground loop somewhere that once identified is easily corrected

[Sol]

ade said:

Any hints appreciated .

Try reading through www.m5abv.com/10.html quite interestingly I was reading it moments before seeing your post.

I bought the filter on the website, (and started another thread on it) ... this page is aimed at a potential buyerof his filter, and he refernces what the filter will not solve - I notice he discusses "hums" at length in this article.

[sometrolls2]

That filter guy used to sell on Ebay and had very good feedback

The original poster should think about a PSU upgrade, this can certainly cure a buzz from the MF supplied transformer, would do no harm, and is a worthwhile upgrade anyway

[PinkFloyd]

The hum is most noticeable during quite music / no music at all, and seems to pass from the left side to the right as the volume is increased. (i did see some older posts mentioning the same sort of thing)

Phew, it could be one of many things and may not actually be anything to do with the amp itself. Please tell me if the hum goes away if you place your hand on the amp.

[ade]

Hi, thanks for the quick replies. :-)

My current setup is cd player connected straight into the X-Cans, in the past I've had the X-Cans connected to the Tape loop on my Amp, but nothing else is connected at the moment.

Both the CD and the X-Cans are plugged into the same 4 way extension block.

The hum on Cans is still audible when no source is attached, I've tried it in various plug sockets around the house and gone as far a taking it to friends house (in case it was mains noise related), but it hummed the same wherever it was.

The hum is also not affected by touching the chassis, only as the volume is turned up does it seem to bias from the left to right side of the headphones.

So I'm thinking the problem lies with the amp or the PSU.

[PinkFloyd]

Have you ever changed the valves and, if so, did you remember to connect the ground tag to the chassis when you put it back together? Another possibility (I have experienced this 3 times now) is the quad Phono socket ground not making contact with the PCB, sometimes they come loose (or snap off) with the constant in and out of interconnects, this results in the same kind of hum you're describing. May be worthwhile removing the boards, easy, and just double check all the connections for mechanical integrity. Check the quad phono sockets with a multimeter don't assume all's well just because it looks ok it's amazing how the legs can just snap off where they enter the PCB and you'd never know it just from looking at it.

[ade]

Hi thanks,

yes, i recently replaced the valves and made sure the earth wire was reconnected, but i'll have a look at the phono socket.

Cheers

[ade]

Hi,

I have tested the connections with a multimeter and the connections seem solid enough.

Without a plug connected the left and right pair of the 4 each create a circuit.

I pulled the cable from my headphones and used this to do an end to end test. The left and right (ground?) connect to front pin of the phono and the end of the 4, and the second pin of the left and right to each of the back two pins of the phono. There doesn't seem to be any continuity between the other 3 pins at this point.

Does that make sense? sound right?

There were a couple of things i noticed while i was in there, the tops of c7 and c8 seemed of bulged to the point of splitting slightly, and while testing I also noticed that if i touch the volume control (without the cap) a slightly different hum is introduced, but this does not happen when i touch the chassis.

I also cleaned and double checked the ground wire to the chassis to make sure.

Does any of this help?

Cheers

Ade

[ade]

Doh!

Just realised i checked the wrong socket, still its nice to know the headphone socket is ok :-)

Yep your right, there is a break one of the phonos, I'll see if i can patch it up with a bit of solder if it works order a replacement.

I would still be interested if you have any opinions on the state of c7 and c8 though.

Cheers

[ade]

Hi,
I have patched up the dodgy phono sockets, but the same buzz / hum is still there. Is there someting else thats could be suspect? I was thinking about picking up a cheap reaplacement PSU from maplins or somewhere over the weekend if that is likely to prove anyting... or do you think is it still more likely to be an internal problem?

Cheers

Ade

[PinkFloyd]

ade said:

Hi,
I have patched up the dodgy phono sockets, but the same buzz / hum is still there. Is there someting else thats could be suspect? I was thinking about picking up a cheap reaplacement PSU from maplins or somewhere over the weekend if that is likely to prove anyting... or do you think is it still more likely to be an internal problem?

Cheers

Ade

Bulging caps are not a good sign and you should replace these immediately. The best wallwart you can get for the V2 costs £5.10 from www.rapidonline.com part number: 85-2923 she's 1000mA so much better than the 500mA MF wart, also comes with the 2.1mm socket attached so it's 100% plug and play.

Try the PSU and replace the bulging caps, may work.

Mike.

[rickcr42]

Hi,
I have patched up the dodgy phono sockets, but the same buzz / hum is still there. Is there someting else thats could be suspect? I was thinking about picking up a cheap reaplacement PSU from maplins or somewhere over the weekend if that is likely to prove anyting... or do you think is it still more likely to be an internal problem?

Cheers

Ade

Short of a bad power supply filter capacitor not much can go wrong with a power supply that will cause hum in a previously working unit so it still could be connection related.

Try swapping the cables from the left and right connections to see if the hum stays the same,moves or otherwise changes and if yes look to a cable replacement or if not the culprit new RCA jacks.

A simple CDP to heaphone amp lashup would seem to preclude a ground loop there being not much for one to enter but on the possibility that one is present- a good read :

www.jensen-transformers.com/an/generic%20seminar.pdf

www.jensen-transformers.com/an/ts_guide.pdf

www.jensen-transformers.com/an/an004.pdf

[ade]

Nice one, thanks.

I'll give it a go, once i get it working again i'll take a look at getting some upgrades :-)

Cheers

[PinkFloyd]

Yup, what Rick says, The fact you found the quad phono "was" broken, as I previously suggested, is kind of pointing the finger in it's general direction... once they get to that stage then replace them, also totally desolder the fixing pads and inspect them to see the pads are actually attached to the track (continuity check with your multimeter) if you find they're broken then simply bridge from pad to track using an offcut from a resistor leg or something.
The phono leg is broken so this means there has been movement in that area over a prolonged period of time so essential it's totally removed in order you can check pad / track integrity.
Mike.

[PinkFloyd]

ade said:

while testing I also noticed that if i touch the volume control (without the cap) a slightly different hum is introduced

Perfectly normal in most cases with the amp out of the enclosure.

[rickcr42]

I am no fan of pcb mounted connections for the very reason that they WILL flex the board when plugged/unplugged no matter what the quality or construction method and when they go it is never a "go/no go" which would make it easy to decipher a problem but more sometines hum/sometimes not,sometimes crackling/sometimes not,sometimes transients sound "dirty" and sometimes not.

Intermittant problems rather than "works great" or " makes no sound" which even when measuring can hide

while trying to do a repair it is a crap shoot also when it can go anywhere from "hell yes ! Fixed and sounding great" to

DAMMIT ! I MELTED THE FKN PLASTIC STRUCTURE OF THE FRIKKIN ' JACK HOLDER ! KNOW WHAT !

or

The damn pcb trace melted ! Yes actually friggin' vaporised right before my damn eyes ! How do i make this right ?

any RCA jack not chassis panel mounted AND not cranked down to the limits of your personal strength level WILL at some point flex the pcb connection and especially so if you follow good audio practice and

A-always plug/unplug in a twisting motion so you clean the mating surfaces as you insert (not close to descriptive when the motion is twist and push)

B-periodically disconnect the interconnects and reconnect to re-establish a good contact which the RCA connector NOT being a gas free connection OR self wiping means any airborne contaminates (smoking,cleaning materials,air fresheners,burning candles,etc) can and will get in making the connection what ?

Intermittant ;D

[Sol]

mrarroyo said:

I know that the people who believe in the cables as the cure for all will start the FIRES NOW.

I blind tested a mate on 4 cables between CD player and Amp (Cyrus CD6 and Cyrus 8Vs with Proac Responce 1SC speakers) ...

We used

• a cheapo computer black and red
  
• Van den hul (forget which one - 100 quids worth),
  
• ebay special (that I really like)
  
• Nordost Blue heaven
  

I'd love to tell you how much difference there was in everything ... the only slight thing we noticed was that the VdH cables seemed somehow different with slight difference to the bass on one particular bass heavy track.

What we found quite alarming was having two cables connected at a time and flicking between channels (CD had two outputs) during playing woud yeild no obvious immedaiate change in sound between a 50p cheap computer thang and a Nordost!!

We did however find once he'd had the system for a while, on repating the exercise and set the thing up properly to get a decent sound stage we did notice slight changes in perceived depth and width, spacing etc. I guess if we'd spent much longer we could have found some minor differences on specific CDs!

Either way it taught us that the very act of swopping out cables was either helping, or the time it takes to do the swop, helps your mind play tricks.

[PinkFloyd]

I am no fan of pcb mounted connections for the very reason that they WILL flex the board when plugged/unplugged

These guys are supplemented by a centre tapped screw which fixes to the rear plate but, even with that, there will be a degree of movement especially if the screw loosens over time. Not a HUGE problem on X-CAN amps but I've come across three, to date, with phono socket problems. Another relatively weak part is the headphone socket, again it's board mounted but not attached to the front panel (It just pokes its nose through a hole on the front panel) .... all it relies on for mechanical integrity are the three solder joints that hold it to the PCB, fair enough if you keep your 'phones connected all the time but if you're in and out like a yoyo this part can fail. V3 is much better, in this respect, as the head socket is actually fixed to the fascia with a securing nut. Actually, come to think of it, the pot is only held in place by six small solder connections on the PCB (V2) and it too pokes its nose out of a hole on the fascia with no supplementary fastening to the fascia.... you're not subjecting this part to a lot of ups and downs and heavy knocks so it stays relatively trouble free but I have seen one that lifted clean off the board (god knows what the guy was doing with it, possibly hitting it with a hammer instead of turning gently with his finger )

[rickcr42]

These guys are supplemented by a centre tapped screw which fixes to the rear plate but, even with that, there will be a degree of movement especially if the screw loosens over time. Not a HUGE problem on X-CAN amps but I've come across three, to date, with phono socket problems

point being there is a potential for problems in any connection that relies on a non flexable material (jack metal) mated to a flexable substance (pcb substrate) bonded with another substance that has no "give" (solder).Well something DOES have to give and that something usually the weak point which is the solder to pcb connection making it invisible to inspection by eye so often missed.

[ade]

Hi,

Good news, the parts arrived from rapid this morning and the hum is gone! :-)

The PSU didn't seem to make a difference to it, but replacing c7 and c8 (and the previous phono bodge) seem to have cured it.

Thanks everyone for you help.

Mike, can you still supply the capacitor upgrade kit and a set of phonos for a V1? If so let me know and I'll sort out sending you some cash.

Thanks again

Ade

[PinkFloyd]

ade said:

Mike, can you still supply the capacitor upgrade kit and a set of phonos for a V1? If so let me know and I'll sort out sending you some cash.

Glad you managed to get rid of the hum ade, nice one I can supply cap kits for the V1, no problems I have everything in stock just check www.rock-grotto.co.uk/v1upgradekit.html to see what's included.

All the best.

Mike.

[ade]

Hi Mike,

The cap kit and replacement bits arrived this morning and i have just fitted them. Nice one i'm really impressed, easy to fit and the amp is better than ever, I can't wait to hear how it sounds after its burned in. :-)

Thanks again for all your help.

cheers

Ade

[PinkFloyd]

ade said:

Hi Mike,

The cap kit and replacement bits arrived this morning and i have just fitted them. Nice one i'm really impressed, easy to fit and the amp is better than ever, I can't wait to hear how it sounds after its burned in. :-)

Thanks again for all your help.

cheers

Ade

Nice one Ade How are you finding the purple LED, just the right brightness or maybe tone it down a bit? If you haven't fitted it yet then the best way to remove the old one is to place the front panel, face down, on a firm surface (like a chopping board) and bear down on the rear of the panel with your weight.... it should pop out no problems. If it doesn't then don't be afraid to give the rear of the fascia a good whack with your hand (it won't damage the front panel as the LED will be sitting proud and will take the blow) When fitting the new LED be sure to run a thin film of superglue around the back edges of the LED, this will ensure it stays in place...... hold the led in position for 30 seconds and that's that.

Give her about 48 hours to stabilise and you should hear noticeable improvements from then on in.

All the best.

Mike.

[ade]

Hi,
Yeah, I fitted the LED at the same time, looks cool i like it :-)