I haven't added a series capacitor.
I tried connecting it to the pre out sockets of a Yamaha AX-550 (which only has a 2 pin ac cord) and it behaved in the same way as with the 33.
I'd like to earth both the Quad IIs properly anyway, so maybe my next move should be to separate signal and power grounds - maybe as per Patrick Turner's suggestion.
I tried connecting it to the pre out sockets of a Yamaha AX-550 (which only has a 2 pin ac cord) and it behaved in the same way as with the 33.
I'd like to earth both the Quad IIs properly anyway, so maybe my next move should be to separate signal and power grounds - maybe as per Patrick Turner's suggestion.
A strange thought, but does it behave any differently if you rotate the Quad II mains plug 180 degrees, and so swap the live and neutral? Does it buzz if you connect a source like a phone or iPod?
I generally avoid anything suggested on the Patrick Turner site. He clearly wanted the Quads to be something different from what they were.
I generally avoid anything suggested on the Patrick Turner site. He clearly wanted the Quads to be something different from what they were.
I have a three-pin mains cord running into my Quads, with the earth tied to the chassis at the screw next to the mains. No other modifications are done. I have absolutely no hum or buzz to speak of.
I’ve also marked which side of the plug is live and which is neutral, and checked this on the inside to ensure they’re always the same.
I’ve also marked which side of the plug is live and which is neutral, and checked this on the inside to ensure they’re always the same.
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I think that is a bit unfair. The basic modifications he recommends are no different to the ones Keith Snook recommends on his site.
He pointed out that the Quad II was a remarkable design, and well executed, but that the implementation is 70 years old, with limitations that were necessary to build a product that was affordable to a post-war world. He explores that notion, and extrapolates where Peter Walker could have taken the topology.
This was my solution to the power supply and earthing problem. I discovered a laptop-style IEC C5 connector just fitted inside the fuse socket on the input voltage selector side of the amp. The input voltage selector is superfluous nowadays anyway, and I set my tube gear to run on 245V, so that hole became free, and I found that a small illuminated rocker switch and 32mm fuse holder fitted snugly in that.
I did not want to hack the metal work, but I drilled two 3.2mm holes for the plate that holds the socket for the C5 connector, and another on the side as a dedicated earth connection, next to the power socket. The old bits are in a plastic bag, should someone want to use them in the future.
That means all the power supply is at one end of the amp, the speakers are in the far corner, and the input is on the opposite side to that, keeping everything as far apart as possible.
The amps when I got them did not have rectifier sockets (that had come from Sverige Radio where they were all converted to silicon rectifiers), or tubes. Since I like NOS tubes, I made up some loktal adaptors for 5B/255M tubes, and I have been very pleased witht he outcome. One of the amps has the very early OPT with lettering ABCDEFGHIJ for the terminals, but I cannot hear the difference when I use them.
(NB: The amp was not on when I took the picture of the side with the speaker connections, with nothing attached!)
I did not want to hack the metal work, but I drilled two 3.2mm holes for the plate that holds the socket for the C5 connector, and another on the side as a dedicated earth connection, next to the power socket. The old bits are in a plastic bag, should someone want to use them in the future.
That means all the power supply is at one end of the amp, the speakers are in the far corner, and the input is on the opposite side to that, keeping everything as far apart as possible.
The amps when I got them did not have rectifier sockets (that had come from Sverige Radio where they were all converted to silicon rectifiers), or tubes. Since I like NOS tubes, I made up some loktal adaptors for 5B/255M tubes, and I have been very pleased witht he outcome. One of the amps has the very early OPT with lettering ABCDEFGHIJ for the terminals, but I cannot hear the difference when I use them.
(NB: The amp was not on when I took the picture of the side with the speaker connections, with nothing attached!)
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Since both amps work very well with no noise at all using an old iPod as source it seemed that the fault could be to do with earthing, which is why I am looking at that (as well as basic safety - I'm not thinking of any major modification)
I'll try the polarity thing, also the earth from the chassis, and I like the idea of keeping the mains together at one end. I'm never going to use the Jones socket or voltage selector, nor will I ever sell the amps - but I would like to be able to use them with a source other than an iPod.
Thank you for the suggestions and photos - it's always good to see what has worked successfully for others!
I'll try the polarity thing, also the earth from the chassis, and I like the idea of keeping the mains together at one end. I'm never going to use the Jones socket or voltage selector, nor will I ever sell the amps - but I would like to be able to use them with a source other than an iPod.
Thank you for the suggestions and photos - it's always good to see what has worked successfully for others!
I did exactly this, and........ no more noise!
Huge thanks to everyone for helping - it has been an interesting and heart-warming experience, and now that they are both working properly I might even tackle the visual aesthetics (one in particular is rather rusty although not much older - 13273 against 13330....)
