View Full Version : Advice wanted for quad 33/405 interconnects
I am currently having my Quad 33/405 updated by Lee at Redhill and I want to improve the interconnects as well, using 2 core screened Neotech 3004 cable which I know performs well with my son's Naim XS .
I want to make up a 5 pin din to rca to connect the preamp to Chord 2qute dac. The din plug is straightforward, with L and R channels and screen connected to the ground pin. I am unsure how to make the connections to the rca plugs. I have connected the signal cables to the centre pins of the rca plugs, but connected the screen to only one plug ( R channel). The interconnect works but only if the Chord is grounded from the screw terminal on the back of the case. (Incidently, should the 2qute be grounded to the 33 preamp which also has a ground terminal on the back?) Advice would be much appreciated.:rolleyes:
How are you grounding the Chord DAC? Is it directly to the mains earth?
Have you tried splitting the shielding of the Neotech cable and connecting it to the outer part of both RCA plugs?
If it were me, I would buy a ready made 5-pin DIN to RCA phono lead from Flashback sales. They are very well made, can be made to any length, use good quality Neutrik connectors and are not expensive.
https://www.flashbacksales.co.uk/acatalog/5-pin-din-phono-rca-cables.html
Hi, thanks for the reply. The first lead I made up had the screen braid split and connected to both rca plugs. This did not work, no sound. I then disconnected the screen from the L channel plug. When I tried it initially I got severe feedback which was stopped by grounding the Chord to the mains.
I’ve trawled through past posts on the forum and a number of people have mentioned the Rane note 110 on interconnects which, having read it, made me realise that a little knowledge (in my case) can be a dangerous thing which is why I posted the enquiry to see if anyone else had come across a similar problem and found a solution! I am guessing that the Quad 33/405 because of the use of din plugs and sockets is a balanced set up and the Chord is unbalanced because it takes its power from a 12v transformer and isn’t directly earthed.
I take your point about the ready made leads but I would like to use the mono crystal Neotech cable If I can because it does make a significant difference to the sound quality, certainly on my son’s Naim system.
How have you wired the DIN plug?
24047
Connections looking from the back of the plug: screen to pin 2 / R channel pin 5 / L channel pin 3
Worth checking before you go any further whether the power lead to the 33 is actually earthed or not.
I have bought a couple in the past where the previous owner in one case had used a two core lead and in another had disconnected the earth at the mains socket end. Not saying this will cure the problem but it does seem odd that the hum disappears when you earth the DAC.
Obviously if there is no mains earth connection to the 33 then adding a wire between the Chord and the 33 earth terminal on the rear will do nothing.
Incidentally, I don't believe the use of Din sockets on the 33 means they are balanced inputs or outputs - just a different connector than RCA.
Also wondered which input you are using on the 33 to connect the DAC?
The Radio inputs are likely to be too sensitive for the Chord but If you use the Tape input you can make adjustments via the pull-out Tape board ;)
Hi
The 33 is earthed to the mains, I recently had to solder a new Bulgin plug. I am using the tape socket with the card on the 1v setting.
Hi Mike,
A question for you, it looks as though you know your way round the 33. What power amp and speakers do you use? I have had my 33/405 since 1976 (the typical 70’s system Thorens/Quad/Spendor) and really I am only just finding out what it is capable of and I’m exploring ways of making improvements.
Hi
The 33 is earthed to the mains, I recently had to solder a new Bulgin plug. I am using the tape socket with the card on the 1v setting.
Weird then that the Chord is acting up :scratch: - the wiring diagram you posted is correct. Have you any other sources with RCA outputs you could try?
24047
Connections looking from the back of the plug: screen to pin 2 / R channel pin 5 / L channel pin 3
I can't see any problems there.
Using the Tape input on the "H" setting should be OK (1V sensitivity to give 0.5V output, with 10V maximum headroom). You have also wired the mains cable for the 33 correctly, and I'm assuming you use a two-wire mains lead from the 33 to your 405.
I'm at a loss to understand why when you connected the screen (from pin 2 of the DIN plug) to the outer of both RCA phonos, you got no signal at all. Unless of course the plugs were not pushed fully home - but then you would have checked that. Neither does it explain why when disconnecting the shield from the L plug there was "feedback". Can you describe what the feedback sounded like? Was it a loud hum?
Hi Mike,
A question for you, it looks as though you know your way round the 33. What power amp and speakers do you use? I have had my 33/405 since 1976 (the typical 70’s system Thorens/Quad/Spendor) and really I am only just finding out what it is capable of and I’m exploring ways of making improvements.
Up until a year ago when I moved to an integrated DAC/amp (Quad Vena), I was using either a Quad 33 or 34 into a 405-2 (before that a 303) - first with a pair of ageing B&W DM10s and then some Q Acoustics 2020i. I had an audiolab Q-DAC connected to the Tape with no problems.
I gave the 33 a thorough overhaul about 5 years ago using a DADA update kit and this changed the game substantially - I would definitely recommend it. I also converted the connectors form DIN to RCA at the same time and removed the power supply to a separate box. I still use the 33 phone stage for vinyl - I have a classic Braun PS500 with it's original Shure 75-6s cartridge :)
Unfortunately not anymore. I originally used a Chord mojo connected by din to 3.5 jack, no problems.
More than loud , it had me diving for the off switch.
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