Digital inputs stopped working on CA 840C

[Strider]

Hi all you tekky guru's!

Today for no apparent reason all the digital inputs on my Cambridge Audio 840C have gone belly up, I've tried both optical and digital inputs on inputs 1 and 2 but nowt. The display shows 'Unlocked' so that means there isn't a signal present, CD replay works fine. I have tried both sources, Freesat box and Coaxial/optical on my Logitech SB3 into my external sound card and both are working fine so it all points to the CA 840C inputs.

Now, I understand cables and equipment as I install AV/audio gear every day but dinky little components are beyond me, I know what each component is but looking at a PCB I might as well be looking at a map of the bottom of the Atlantic....

Anyone got any ideas what may of happened and it it gonna cost/be worth repairing?

Cheers,

Mark.

 

[vacdac]

Hi Mark

On most PVR's/TV's/DVD players etc you need to set them to output 2ch stereo, rather than 5.1 via the digital outputs when fed into most stereo Dacs & you won't get a lock on your Dac if you are outputting 5.1. Most soundcards would handle this fine though. ;-) Also if your Dac input only handles red book ceedee standard it may not handle DTV/Sat etc which is 16bit@48khz.

Is there any chance you are outputting at a higher rez (wordlength/bit* sampling frequency) than the C.A.'S DAC input can handle? Is it possible to disable the digital output on your SB3??......sorry I'm not overly familiar with this incarnation of Squeezy-box, but I have run SBT's.

BR

C.

 

[Strider]

Hi Chris, many thanks for the reply!

The SB3 only outputs 16/44 and the Freesat is set to stereo as well, both sources were working fine on Monday and nothing has been unplugged or changed prior to the fault. The DAC on the 840C automatically recognises the input bit rate..

Here is some guff:

See below for the guff!

Cheers,

Mark

 

[Strider]

Adaptive Time Filtering (ATF) Asynchronous upsampling

technology converting 16-bit 44.1 kHz CD data to 24-bit 384kHz

32-bit Analog Devices “Black Fin’ DSP

Dual differential DAC’s 2 x Analog Devices AD1955 24-bit

DACs running at 384kHz

Fully differential output stage topology

Anti-aliasing filters based on linear phase Bessel filters for

constant group delay and minimum phase shift

DC servo circuitry with no capacitors in the signal path

Digital inputs 2 co-axial, 2 optical allowing upsampling and

playback of other sources

Digital outputs 1 co-axial, 1 optical allows recording

of raw or up-sampled audio (192kHz maximum)

Audio outputs 1 balanced (XLR), 1 unbalanced

Other connections Control bus input/output, 1 IR emitter in,

1 RS232C, 1 IEC type mains inlet

Extruded aluminium side panels and solid aluminium

front panel

Ultra rigid, acoustically dampened chassis

Full function aluminium face azur navigator remote

Available in silver/black

Performance

Frequency response 20Hz to 20kHz (+/-0.1dB)

THD @ 1Khz 0dBFs <0.0005%

@ 1Khz - 10dBFs <0.0004%

@ 20Khz 0dBFs <0.0007%

(19/20kHz) 0dBFs <0.0002%

Linearity @ -90dBFs +/-0.5dB

Stopband rejection (>24kHz) > 120dB

S/N ratio, A weighted > 113dB

Total correlated jitter > 130pS

Crosstalk @ 1kHz > -130dB

@ 20kHz > -114dB

Output impedance > 50 ohms

Digital input word widths supported 16 - 24 bit

Digital output word widths supported 16, 20, 24 bit

Digital input sampling frequencies supported

32kHz, 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz, 192kHz

Digital output sampling frequencies supported

32kHz - 192kHz pass through (including 44.1kHz for CD) 48kHz,

96kHz, 192kHz upsampled

Audio output upsampling Fixed 24 bit, 384kHz

Dimensions hxwxd 115 x 430 x 360mm (4.5 x 16.9 x 14.7")

Weight 8.5kg (18.7lbs)

 

[vacdac]

Cheers Mark.......Yeah not tryin ter teach you to suck eggs or nuffing......it's just that the old stereo/5.1 thing for PVR's etc, seems to come up pretty often.

Does rather point to the external digital input receiver being foooked here dunnit. However the Dac does seem to be working at least as you can still play ceedees. Hopefully it'll be inexpensive to sort if its repairable. I've found C.A.'s transport mechs a little flakey with their stuff I've tried (possibly been unlucky here but I've had ceedee & DVD mechs fail inside a year :dunno: ) but their electronics do seem reliable IME.

16-bit 44.1 kHz CD data to 24-bit 384kHz32-bit Analog Devices

However this bit does make me wonder whether It'll handle 16/48......unless it says so elsewhere in the specs. :dunno:

Edit

Digital input word widths supported 16 - 24 bitDigital output word widths supported 16, 20, 24 bit

Digital input sampling frequencies supported

32kHz, 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz, 192kHz

Digital output sampling frequencies supported

32kHz - 192kHz pass through (including 44.1kHz for CD) 48kHz,

96kHz, 192kHz upsampled

Audio output upsampling Fixed 24 bit, 384kHz

Seems it should handle pretty much anything you'd care to throw at it......soooo digital input receiver or dodgy connections would be my first thoughts

soz fer all the edits bud. :roll:

 

[Strider]

Cheers Mark.......Yeah not tryin ter teach you to suck eggs or nuffing......it's just that the old stereo/5.1 thing for PVR's etc, seems to come up pretty often. Does rather point to the external digital input receiver being foooked here dunnit. However the Dac does seem to be working at least as you can still play ceedees. Hopefully it'll be inexpensive to sort if its repairable. I've found C.A.'s transports mechs a little flakey with their stuff I've tried (possibly been unlucky here:dunno but their electronics do seem reliable IME.

However this bit does make me wonder whether It'll handle 16/48......unless it says so elsewhere in the specs. :dunno:

Edit

Digital input word widths supported 16 - 24 bit

Digital output word widths supported 16, 20, 24 bit

Digital input sampling frequencies supported

32kHz, 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz, 192kHz

Digital output sampling frequencies supported

32kHz - 192kHz pass through (including 44.1kHz for CD) 48kHz,

96kHz, 192kHz upsampled

Audio output upsampling Fixed 24 bit, 384kHz

Seems it should handle pretty much anything you'd care to throw at it......soooo digital input receiver or dodgy connections would be my first thoughts

soz fer all the edits bud. :roll:

No worries mate, thanks for the help:flowers:

I've tried a multitude of cables and all work on my soundcard so like you I think it points to a dodgy input receiver. I know I can give it to Richer Sounds to get repaired but obviously if it exceeds the value of the unit then I might have to invest in a new DAC.

Thanks again,

Mark

 

[Strider]

Well, I've started the ball rolling to get the C840 repaired by returning it to Richer Sounds in Botley Oxford.

The staff were extremely helpful and they've lent me a Dacmagic Plus whilst my 840C is being repaired, thoroughly decent service!

 

[old_school]

I hope you'll follow up when you get the diagnosis. I have an 840C as well, and use it as DAC for my SBT. Hopefully nothing goes wrong, but it's alays good to have some extra ideas if something does. I hope it's a simple fix for you.