SN3 Warning Lights And What Actions Required?

The other day I was listening to a record via my Quad all valve phono stage, which is plugged into the CD input on my SN3. The volume was not high by any means when all of a sudden the CD button and the Tuner button started flashing and both channnels cut in and out.
I switched everything off, waited a while, and then switched back on and tried the streamer input and my ND 5XS played ok on both channels I then went back the record and both channels played ok.
I looked in the manual and the only information I can find is that a flasing CD button means Excess temperature and a flashing Tuner button means excess current.
So my questions are:

  1. What is exess current and temperature?
  2. What causes excess current and temperarture?
  3. How do I prevent excess current and temperature in the future?
    Thank you.

Most likely something with the power amp stage. Was the amp hot? What are your speaker cables, how long are they, and hope are they terminated on worker end? Any bi-wiring involved? The speaker impedance should not be a problem I guess, I looked up the LS6 and it says 8 Ohm on the manufacturer page

Edit: didn’t quickly find the 9 though and did not check the subs

Excess temperature = something is too hot
Excess current = to much current being drawn, a typical cause would be speaker impedance dipping into short circuit territory, but unlikely if yours have 8 Ohm nominally, unless something is broken. Unusually weird speaker cable properties could cause it, I guess, hence my question

Sub 3 Specification.
" |Alignment|4th order bandpass|
| — | — |
|Finish|Real wood veneer|
|Dimensions (w/h/d)|30cm by 30cm by 34cm|
|Frequency response|35Hz to 100Hz|
|Nominal impedance|8Ω|
|Sensitivity|84dB SPL (2.83V, 1m)|
|Recommended amplifier power|30 to 80 watts unclipped programme|
|Connections|Gold-plated binding posts|"

Loudspeaker cables are Supra Sword 2M long with 1M jumper from Sub to the LS5/9, not bi-wired and terminated at both ends.
The amp was not hot to the touch.
Cables spec.
" Technical Info

Mechanical specifications

Conductor crossection area 3 / 12 mm2 / AWG
Conductor number 2 pieces
Strand numbers per conductor 12 + 12 pieces
Strand diameter 0.4 mm
Conductor material Enameled oxygen free Copper
Insulation PE
Jacket PVC
External size 9.3 x 18.4 mm
Halogen free / Flame retardant No


Banana/BFA Yes, with CombiCon
Spade (Fork) Yes, with CombiCon and as separate option
Cable connection Airtight high pressure crimp

Electrical performance

Resistance 5.2 Ohm / km
Inductance 0.25 uH / m
Phase dislocation 0.96 cos φ (0.5-100kHz)
Phase error 0 ° (20 Hz - 20 kHz)

Speakers seem fine to my amateur eyes (unless something broke)

The cable inductance seems quite low, but no idea if too low. Yours are short too, though. No capacitance given in the table. From the cable FAQ:

High capacitance &/or very low inductance cables are to be avoided at all costs and may result in damage to your amplifier.

NACA5 specifications are as follows:

Capacitance: 16pF per metre
Resistance: 9 milliohms per metre
Inductance: 1uH per metre

Minimum length: 3.5 metres per channel

@Richard.Dane will be able to tell if yours are a problem or what else it might be

I have found this on the WEB for my speaker cables.
“The test bench for a 5m reference length gave a very low loop resistance of 0.089 Ohm, a negligible 320pF of capacitance with a very low loss factor of 0.05 even at 10 kHz. The loop inductance was also low at 2.83uH, confirming the design objective.”

Found a review for likely your cables, “The test bench for a 5m reference length gave a very low loop resistance of 0.089 Ohm, a negligible 320pF of capacitance”. So that would be 64 pF per meter (edit: if capacitance is divided per meter? Dunno)

Compared to the NACA5 specs this looks more like a cable to be avoided, possibly

Edit: haha, crossover

Does your Quad phono stage have a low frequency filter on it? I suspect perhaps not as low frequency rubbish on LP can cause all sorts of problems for the amp, which has two work really hard trying to reproduce what is in effect just very low frequency noise (and likely inaudible to you, but just watch those bass drivers wobble around). The result of course is that even at relatively modest levels the amp is working way harder than normal. Combine kit with possible other factors such as speaker cable that’s not quite suitable (but otherwise seems to work OK) and you get a thermal trip. This is why many phono stages have LF filters, either switchable, or built in - IIRC IEC EQ standard has it built in, whereas RIAA does not.

p.s. re your speaker cable, capacitance looks a but too high and inductance rather low. The Supernait is much more tolerant of this kind of thing compared to the classic amps, but still likes low capacitance and moderately high inductance cable best.

1 Like

Hello Richard.
I will do some research on the Quad.
Thank you.

Such LF shenanigans can be caused by other things too with vinyl - a compliance mismatch between cartridge and tonearm is a classic example. Easy to check with a test disc with low resonant frequency tests on it.

I have used the same turntable, arm and cartridge for the last 9 years feeding a MF Nu Vista amp without any issues. I have had my SN3 for a month and only played vinyl through it over the weekend.

Quad Spec.
" |Valve Complement|4 x 6111|
| — | — |
|Total Harmonic Distortion|<0.08% (A-weighted)|
|Frequency Response (RIAA/IEC equalisation)|20Hz - 20kHz (+/-0.5dB)|
|Hum and Noise (mm position,input shorted)|Better than 60dB|
|Input Impedance||
|Moving Magnet|47k½|
|Moving Coil|10½|
|Stage Gain||
|High Sensitivity|1.3mV (MM)/130µV (MC)|
|Medium Sensitivity|2.6mV (MM) / 260µV (MC)|
|Low Sensitivity|5.2mV (MM) / 520µV (MC)|
|Nominal Output Level(ref 5.2mV, MM, Low)|1.0V|
|Inputs|Selectable MM/MC cartridge|
|Outputs|1 x Fixed line level, 1 x Variable line level|
|Power Consumption|15VA maximum|"

Roger, I’m trying to investigate what may be the issue. As I say, the speaker cable you’re using is not ideal, but may seem fine under normal circumstances. However, it could just be that vinyl tips it over the edge here. I don’t know for sure, but it could be part of the issue here.

the spec you quote above seems to say it’s both RIAA and IEC art possible either RIAA or IEC - I assume there’s a switch to choose(?), as they are not the same.

Hi Richard.
Thank you for all your help and input. I just assumed a speaker cable is a speaker cable.
Please find herewith a photo of the back of the Quad which shows the switches.

I will change the speaker cables.
Do interconnects create an issue or is just the speaker cables?
Thank you.
Kind Regards.

Internal view

Thanks Roger, unfortunately it leaves me no wiser here. If you play the same piece of vinyl again, can you see whether the woofers in your speakers are moving a great deal, seemingly at random, even at modest levels?

Found a HiFi News review from 2010, it records response 2.6 dB down at 20 Hz and 20 dB down at 5 Hz, so it appears there is a non-switchablevrumble filter in the design.
It does then record what seems a massive 16.0 v maximum output, could it be that there is an overload from the choice of sensitivity setting?

1 Like

It’s either this or, perhaps, the variable line-level output (if this is how @RogerGround is using it?), is wound up too high for the SN3 and the ‘fixed line level’ output would work better, assuming this is true line level ~2v (or lower).

Curious though as to why it worked OK with the MF amp (on the assumption nothing has changed?). If anything like 16v was being pushed in to the SN3, you’d almost have to turn the volume pot negative, noting the issue arose when the sound level was low.

I’ve never used a sub - I also wonder whether the active sub would be better wired up via the optional sub-output on the SN3, with the speakers wired up as normal (as this appears to be how the SN3 manual suggests it can be done?).

Anyone ideas on this?

Hello HappyListener.
I am using the “Fixed Line Level”
The subs are passive and the speaker cable goes from the amp to the sub and then to the two way speaker above, please see photos.

Hello Richard.

I am unable to view the woofers as they are hidden away in the subs, see photo.
I can remove the grill and see the midrange, will this do?