Is the gain correct?
Are the two 100uF coupling capacitors on the Phono Amplifier PCB correct?
Which side of the adapter board are you using?
Are the two 100uF coupling capacitors on the Phono Amplifier PCB correct?
Which side of the adapter board are you using?
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maybe now's the time for photos of both boards?
with the adapter board annotated wrt insertion direction.
with the adapter board annotated wrt insertion direction.
I'll get some photos as soon as I can. The two 100uF caps are brand new, as are all the other electrolytics on the Phono board, and the Disc Adapter board is in M1 position (with the 47k and 330pF loading for the V15 III) The second phono recording I posted was made with the M2 position.
Not sure. The 10nF are X2 polypropylene, the 29nF is made with 6n8 polypropylene with 22nF polyester underneath. Just what the shop had....
Yes, phono only. Line inputs for CD and DAC via Radio 1 and Tape respectively are fine for bass. Sorry this has been slow, I'm still on the last stage of a pain/infection/A&E/antibiotics/more pain thing. On going over the phono amplifier board and checking it against the rather fuzzy circuit diagram and photo from the Quad service supplement, I also found that the same halfwit as before had installed TR302 and TR303 with emitters and collectors reversed. I corrected this, and it made no difference whatsoever - why would this be? What's the problem with X2 capacitors?
Sorry to have taken so long - health issues kept me from further progress. However, I have now changed the .01uF capacitors on the Disc Adapter board
And, more importantly, I discovered that I had been mistakenly following the illustration in the Quad Service Supplement for the 12019 Issue 4 board which does not correspond to my board at all - despite my board being marked 'Issue 4'. This illustration not only contains a typo with R308 appearing twice, once in place of R318, but also has a different layout of components
Further research of pictures online and identifying values from colour codes showed that this is the correct layout for my board (albeit with one typo - there is no R319, it should be R318)
Having finally got all the components of the correct value in the correct place, everything now works really well, with excellent bass reproduction.
Also, once that was sorted, I followed the Dada recommendation of reducing the gain of the amplifier boards and increasing the gain of the phono stage, with the result that, along with a 6K8 series and 3K3 shunt resistor on Radio 1 and Radio 2 inputs, playback of LP, CD and computer via DAC are all at more or less the same level.
I can only conclude that several components were wrongly placed by me a long time ago and that I was used to the sound. I hadn't used the system much at all with LPs, and the comparison with CD (at a higher level) really showed up the effect.
Many thanks indeed for all your help, advice and guidance - I was on the point of giving up and using a separate phono stage, but I am very pleased with it now!
Also, once that was sorted, I followed the Dada recommendation of reducing the gain of the amplifier boards and increasing the gain of the phono stage, with the result that, along with a 6K8 series and 3K3 shunt resistor on Radio 1 and Radio 2 inputs, playback of LP, CD and computer via DAC are all at more or less the same level.
I can only conclude that several components were wrongly placed by me a long time ago and that I was used to the sound. I hadn't used the system much at all with LPs, and the comparison with CD (at a higher level) really showed up the effect.
Many thanks indeed for all your help, advice and guidance - I was on the point of giving up and using a separate phono stage, but I am very pleased with it now!
