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Thread: It's a mystery

  1. #1
    Join Date: Jan 2009

    Location: Essex

    Posts: 23,786
    I'm openingabottleofwine.

    Default It's a mystery

    It’s a mystery


    Yesterday, having just returned home from a charity shop ‘run’ with half a dozen LPs and the same number of CDs, I was keen to listen to them. Imagine my horror, when upon switching my system on, I found the left-hand channel was dead, silence, zilch, nada.

    As someone who cannot be without music, I pride myself in having put together a very reliable system: and to cope with the unlikelihood of component failure, have a substantial number of components held in ‘reserve’ for substitution should the occasion arise.

    Despite it being a bit of a cliché, I switched the system off and then back on again, thinking that the problem might be a ‘sticky’ relay, but to no avail. The left-hand channel was dead regardless of source selected: phono, tuner, CD player. (I didn’t check tape replay as I rarely use tape as a source). Logic would dictate that the problem must be with either the preamp, buffer-amp, or power amps, or perhaps the connecting cables.

    The first thing I did was to swap over the cables between the buffer amp and the monoblock power amplifiers. No joy, the left channel was still dead. I swapper over the cables between the preamplifier and the buffer amp, and also removed the buffer amplifier (as it is not essential component) – left channel still silent.

    So I pulled out the preamplifier and replaced it with a second; not without difficulty as the two use different off-board power supplies, as well as having different connection convention (i.e. some are balanced on one preamp, whereas on the second they are unbalanced; so some swapping around with source interconnects was necessary). Again, there was no change.

    The next thing to do was to physically swap over the monoblock power amplifiers (a pair of Quad 510s with balanced inputs) – no difference. So I replaced them with a pair of heavily modified Quad 405s (‘monoblocked’ by Duncan (‘Tubehunter’), of this parish, with the circuit board modified to Keith Snook Level 3, and with some components upgraded to those of higher quality and precision. The power supplies are also heavily upgraded.). No change, regardless of changing over the 405 monoblocks. I even tried a third set of power monoblocks: a pair of Mark Levinson ML2s; heavy buggers at over 30Kg apiece, but to no avail. I would have tried a set of Quad 50E monoblock amplifiers, but these amplifiers use special connectors, making connection difficult.

    I even interchanged the loudspeakers (Quad 57s), physically swapping left for right – and yes, you guessed it, no change.

    By now I was starting to tear my hair out, and the listening/living room was starting to look like a bomb had hit an audio dealer’s showroom, with items of equipment laying around and a pile of interconnects on the carpet.

    As a last resort I thought I would try another modified Quad 405 (NET modified with dual channel power supplies). Mirabile dictu, we were now firing on all cylinders, with all sources. Just as well; otherwise I would have had to dig out a second or third modified Quad 405, before falling back on a couple of Quad 303s I have. (Did I say I have a lot of components held in reserve?)

    Now we come to the puzzling bit - I slowly restored the system back to the status quo: starting with the preamplifier (and the phono stage), then the buffer amplifier and finally the power monoblocks. And everything continued to work, as it should – phew!

    The only possible explanation was a loose connector either between the preamplifier and the buffer amplifier, or between the buffer amp and the power amps. But with the exception of components used for vinyl replay (these using RCA ‘phono’ plugs), the rest of the system is connected using latching connectors (either XLR or CAMAC), designed not to become loose once mated.



    My partner, having seen me becoming more and more stressed in trying to solve the problem, but not being either able to help, or understand – when I did manage to get the system firing on both cylinders, simply asked how old the system was. Some items have been in near constant use for forty-five years – to which she replied “Well they were tired and were just letting you know they need a rest”!
    Barry

  2. #2
    Join Date: Aug 2009

    Location: Staffordshire, England

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    I'm Martin.

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    Well it worked on swapping in the last power amp so logically the problem must have been in a connector/cable going to the power amp or out of it.

    Anyone might reasonably think cables or connectors will not fail just sitting there plugged in. I don't really see how it happens but it does.
    Current Lash Up:

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  3. #3
    Join Date: Apr 2012

    Location: Southall, West London

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    I'm Geoff.

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    I had a similar problem the other day when I was ''piggybacking' testing a couple of passive pre-amps (I do this with previously untried items, just to make sure there is at least one working volume control before the power amp). With a bit of messing about, I found that one pair of phono plugs didn't want to work with the pre-amp sockets and the centre pin was making intermittent contact.
    The word is 'valves' in this country, not tubes. Tubes are what Smarties come in!

  4. #4
    Join Date: Nov 2010

    Location: Yorkshire

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    I'm AnDreW.

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    I've just had a very annoying ground loop hum that I could not trace for love nor money. So, just like yourself, Barry, I completely stripped down my valve system slowly introducing everything and hey-ho it bloody works, silent as a newly minted corpse! This hobby is very frustrating some tmes.
    SS

    CD Teac VRDS25X(Audiotuned) DAC Caiman SEG+15V PSU+Dorado DECK 1210 Mat Crystal Audio Mods MN Base/Bearing/Platter+Ebony armboard Feet Isonoe/Ebony PSU Paul Hynes SR7EHD-27XL/DCSXL Ag DC lead/3 Stage Regs/Recap PCB+No Pitch/Strobe/Light ARM SME V(Kondo Ag Rewire&Tags) MC Cadenza Black FGS CABLES Arm Yannis SPD-4 IC Yannis 222 Litz+Ag bullets Power WAR PRE ATC SCA2 SPEAKERS ATC 50ASL STANDS Atacama PHONO Sugden Masterclass PA4 SUT Ortofon ST80SE POWER PSAudio P10

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  5. #5
    Join Date: Jan 2009

    Location: Essex

    Posts: 23,786
    I'm openingabottleofwine.

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    Quote Originally Posted by walpurgis View Post
    I had a similar problem the other day when I was ''piggybacking' testing a couple of passive pre-amps (I do this with previously untried items, just to make sure there is at least one working volume control before the power amp). With a bit of messing about, I found that one pair of phono plugs didn't want to work with the pre-amp sockets and the centre pin was making intermittent contact.
    Agree, the dimensional tolerances for the RCA phono plug are poor (I'm not sure they are even specified: the design goes back to the 1940s where it was designed by RCA to simply be a cheap connection between a phonogram and the amplifier in a radio set. Hence the name 'RCA phono' plug.) However, I have found the dimension of the outer part of the plug can be a problem: either it fits snugly or has such a tight fit that one has almost to 'screw the plug on, and in doing so cause the socket to rotate and possibly damage the internal connection.

    IMO phono plugs are horrible little things, and again IMO, the much lauded 'bullet' plug variant does nothing to improve matters. Sadly, thanks to its universal adoption by the Japanese, phono connectors have become an industry standard for domestic audio gear. And no matter how much, gold, silver or rhodium is used in their construction, cannot convert a "sow's ear into a silk purse".


    But I still don't understand why all the cables I either swapped in and out, or transposed, were ultimately the cause of the problem as they were all fitted with XLR latching connectors, which make a satisfying 'click' when fully mated. They are designed to make a reliable contact despite rough handling in the field (either in live performances or in the studio).

    I guess I will never know what actually happened, but at least I was able to test some of my spare gear even if it did not aclually solve the problem.
    Barry

  6. #6
    Join Date: Jan 2009

    Location: Essex

    Posts: 23,786
    I'm openingabottleofwine.

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    Quote Originally Posted by REXTON View Post
    I've just had a very annoying ground loop hum that I could not trace for love nor money. So, just like yourself, Barry, I completely stripped down my valve system slowly introducing everything and hey-ho it bloody works, silent as a newly minted corpse! This hobby is very frustrating some tmes.
    Yes - hum problems can be a bugger to track down and eliminate: there are just so many possible causes.
    Barry

  7. #7
    Join Date: Mar 2017

    Location: Seaford UK

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    I'm Dennis.

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    It is easy to forget just how many connections and components are involved in a chain, all of which are prone to natures entropy.

    I listen all the time and in my case am dependant psychologically on it, being a loner, and also a keen radio follower, so when it suddenly goes wrong it is rather disconcerting, and reveals the comfort zone achieved with a system, now removed.

    Just ten minutes ago, with my new (to me), tuner, 35 years old R4 started to go intermittent and a bit phasey, also on R1. Immediate thought, 'Oh no, it is old and does not like being on 24/7, even though it is only 12W, and is failing'.

    But, using the multi-path switch showed that some odd atmospherics are going on, due to the weather pattern I assume, and we are in the 11 year sunspot cycle.

  8. #8
    Join Date: Jan 2009

    Location: Essex

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    I'm openingabottleofwine.

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    Quote Originally Posted by Pharos View Post
    It is easy to forget just how many connections and components are involved in a chain, all of which are prone to natures entropy.

    I listen all the time and in my case am dependant psychologically on it, being a loner, and also a keen radio follower, so when it suddenly goes wrong it is rather disconcerting, and reveals the comfort zone achieved with a system, now removed.

    Just ten minutes ago, with my new (to me), tuner, 35 years old R4 started to go intermittent and a bit phasey, also on R1. Immediate thought, 'Oh no, it is old and does not like being on 24/7, even though it is only 12W, and is failing'.

    But, using the multi-path switch showed that some odd atmospherics are going on, due to the weather pattern I assume, and we are in the 11 year sunspot cycle.
    Nicely put Dennis - and exactly my feelings.
    Barry

  9. #9
    Join Date: Feb 2008

    Location: Middlesex, UK

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    I'm Alex.

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    I seem to remember way back, buying a brand new Quad 44 when they first came out. After a few days I think one channel was intermittent, some switch cleaner/ lubricant in a relay fixed this, never faulted since.
    Spendorman

  10. #10
    Join Date: Nov 2011

    Location: Seaton, Devon, UK

    Posts: 6,874
    I'm Adrian.

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    Hi Barry,

    I had a similar but intermittent problem with a channel on a Meridian 557 amp some years ago. It was very odd sometimes no issue and then suddenly would cut out, I went through the cable swapping from one channel to another and all would be good and then back and all would be good and then after a week or so the same channel would cut out. I talked with a very well known Meridian engineer and he said it could be that a relay or component on the 557 was on its way out, so I was all ready to send it to him the next week. Then by complete chance a new phono stage arrived that meant I need to get to the rear of the gear and swap the unit. At this point I had the hifi on an old glass TV unit that was on castors. So I pulled it out and did the phono swap and then move it all back, yes you guessed it left channel was then gone. So I thought well the is odd, pulled it out put old phono stage back still no left channel, so started wriggling each cable cable back down the chain, from phono to passive to 557 and when I got to the RCA on the left input of the 557 suddenly it came to life and as soon as I let go off it went.

    So I powered it all down and took the rather expensive Ecosse cable to the left channel out and inspected inside the RCA's at both ends, all visually looked good. Then I thought well something is up so I dug out my cheap meter and tested it from RCA to RCA for continuity, and on the +ve it was dropping in and out, a slight movement of the cable and continuity would come and go. then i tested from end of wire to end of wire and continuity remained constant. I then realised what was going on, I had a dry solder joint at one end, why and how this had occurred after having the cables for over 5 years I have no idea, presumably it was never a good solder joint in the first place.

    As they had a lifetime guarantee I sent them back and they were repaired and returned in 48 hours.

    So I know you have XLR's but it might just be that you have a similar issue, and after moving it all about and putting then back have overcome a dry joint, just a thought.

    Cheers

    Adrian
    Listening is the act of aural discrimination and dissemination of sound, and accepting you get it wrong sometimes.

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