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”!