Repair your Cambridge Audio 840E volume contol issues

Many people with Cambridge Audio 840E (and I think 840A) preamps have reported strange volume behavior where the volume levels will suddenly change. Recall that these are the pre-amps with the relay controlled discrete resistor ladders and the Terrapin modules. There has been a lot of speculation posted on the web as to the root cause for this problem, including bad relays and bad volume knob encoders. Cambridge has since changed the design, removing the relays altogether and replacing them with solid state switches. Some, like myself, believe this is a step backward and would like to find a solution to the original faults with the discrete relays.

I own an early version of the 840E that was sent back to CA for re-work. Their service department added a separate relay board (containing the 28 relay array) with Omron G5V1 relays instead of the Massuse ME-3 relays that originally came from the factory. I was assured by Cambridge Service that the new relays cured the problem, but a few years later my volume control issues returned. I purchased a replacement set of Omron relays and replaced the Omrons supplied by service, and this did the trick for another 4 years or so. When looking into the specs on the G5V1, I found a most unusual disclaimer by the manufacturer:

"• Long-term Continuously ON Contacts

Using the Relay in a circuit where the Relay will be ON
continuously for long periods (without switching) can lead to
unstable contacts, because the heat generated by the coil itself
will affect the insulation, causing a film to develop on the contact
surfaces. Be sure to use a fail-safe circuit design that provides
protection against contact failure or coil burnout."

So what Omron is saying is that these were never designed for continuous use, as one might have in a volume control left at the same volume level for long periods of time. Further, it appears heat and high temperatures are at the root cause of the issue. If you look at the relay array for the volume control, the Cambridge design has these relays mounted as close together (side by side in two rows) as they can fit, and the center relays can get very hot. Due to the design of the volume ladder, not all relays are on at any one volume setting. There are also volume settings where the power generated by the relay array is maximum. From a document sent to me by Cambridge audio, it show that the current drawn by the relay array is a maximum of 271 mA at -32 dB, but drops to 131 mA at -30dB and 178 mA and -38 dB. The -32 dB area is where I see my volume instabilities, so it appears it may be related to power generation (and high temperatures) in the center mounted relays in the array. There are also high current levels at -16 dB and -8 dB (271mA) and -4, -2 dB. Of course, with the volume up above -8 dB, volume jumps to 0 dB are much less noticable when they occur.

So what can be done?

I was told by CA that the Omron replacement was the only one available. Turns out not to be true. I have found that Fujitsu makes a better relay that is plug and play replacement (SY-9W-K) for both the Omron and the Massuse relays. The Fujitsu relay has two contact options as well, one of which is much better for the ladder network. Let me explain. In the Omron spec sheet for the G5V1, there is a MINIMUM current rating of at least 1 mA. That means the circuit must flow a minimum of 1 mA to keep the contact resistance stable. Another condition violated by Cambridge Audio Engineering. The Massuse ME-3 is similar. The Fujitsu, however, has two contact configurations, one at 1 mA minimum and the second at 0.1 mA. The latter is more suitable of low current audio use. I believe the contact material (Pd/Ag under Au) is better as well. Finally, the Fujitsu relays are Japanese made whereas the Omron and Massuse are Chinese made. The Fujitsu relays have no continuous duty disclaimer in the spec sheet like Omron has.

Besides relay replacement, it is wise to do everything you can to keep internal temps down. I have my upper cover mounted on 1/4" stand offs to allow air to circulate inside the pre-amp. Mine is an early version without the vents. I have also mounted small aluminum heat sinks on the relay arrays to re-distribute the heat generated in the center units and lower their temperature.

Hope this post helps some of you who like the 840E and do not want to trash an otherwise fine sounding piece of gear due to the irritating volume control issues.
dhl: Thanks for your reply. I'm not sure why I just saw/viewed it now?

I purchased yet another 840E (I love this thing -and its reasonable price).

The original one-owner had not experienced these volume-control issues, but low and behold, I'm experiencing (loud-ish/sharp/snappy) 'crackling' sounds coming through my R-Channel loudspeaker -loud enough to be concerning to the health of the drive-units !

My 840E (on the other hand) has no ;crackling' sounds but does exhibit the 'runaway' volume problem -in addition to cutting/out (abruptly/sharply -and loud) as the volume control is approaching higher volume attenuation (numerical reading "38" (and lower) on the display.

It's a PIA that remarkably CA refuses to either admit -or offer up a permanent solution/fix. That's the most disappointing aspect. 

If I knew of a better sounding/built preamp anywhere near the 840E's price (new or used), I'd gobble it up. However, in my 40-years of hifi experience, its proven difficult to find not only  a great sounding preamp -but one of reasonable (cash) outlay has proven illusive. (lol)

So, I remain with my wounded peamp -not giving up on her so easily !

Thanks for your help.


Thank you so much for this post, and keeping my 840A out of the skip bin.

3 years on, the Fujitsu's still working correctly?

It is the same omron relay in the 840A v2, that you name.

There are 2 possible causes of volume problems, the relays AND the encoder... If you're as lucky as me it will be both.

If the volume works smoothly when using the remote, the problem is the encoder.
RE: CA 840E Volume Attenuation Circuit (Resistor/Relay)

09-30-2016 6:27pm

dhl: Thank you very much for your most useful/needed explanation
of the volume issue impacting the CAmbridge Audio 840E preamp.

I purchased a second 840E (I love this thing !) that was recently returned
to me from CA Canadian distributor Plurison (Naim-Focal) for this very issue.
( supplied the 28 Fujitsu SY-9W-K relay's as you referenced.
Pluison Repair Depot also replaced the P/S cap's, 'Encoder' -and replaced the
stock faulty/shitty relays with the Japanese Fujitsu's.

Preamp sounds great ! Once again. 

As dhl pointed out, the 840E is worth the effort to 'restore'. I'll go further by saying
it's an exceptional, high-resolution line-stage that easily competes with far greater
priced alternatives.
BUT, this  repair MUST be undertaken; shorting/over-heated stock relays  emit such powerful/loud noises (crackling, "pop's") as to endanger loudspeakers. IT IS, quite 
In Canadian dollars, the 28) Fujitsu (SW-9-W-K) relay's cost $90. CAD.
Labour 'stings'(costing me $240. CAD), a few other pieces/parts, shipping and you're
into $450. (CAD). Plurison used the original (volume) circuit board without issue, I was 
informed !

Was it worth it ? You bet. The 840E is a fantastic, high-resolution, articulate, dynamic
and musical performer; if one can be purchased (used/excellent condition with full/complete factory packaging -you'll need it) between $600-$800, undertaking the demanded repair will
add another few hundred dollars (depending on labor charges) and you will revel in superb SQ. It IS, that good/excellent ! (Oh, and one should/must consider improving top-cover ventilation for the 840E -that inexplicably comes with no top-plate ventilatin holes.
Options would include:
A) Drilling (carefully) holes in the OE top-cover, or
B) Find/buy a top-plate/cover from the newer CA 851 series that offers proper (and desperately required) ventilation; the 851A? Integrated/Amplifier top plate -that has the most extensive ventilation, or the L/R sided 'vent' from the 851N, 851D, 851C etc. 
(Keep in mind the 851 Silver Top-plate is much brighter (different color/tone) than te painted steel top-plate of the 840 series. Perhaps the color black is better here ?
C) Consider using/purchasing a smoked/tinted' plexiglass (3mm/, 1/8" thick) and cut to required size -not forgetting proper ventilation considerations. 

dhl, thanks again for your excellent original post and subsequent replies.

BTW, these Fujitsu relay's are NEAR SILENT in operation -and that's wit the top-cover off / removed - I can barely hear it operating/clicking.      

peter jasz

Dear DHL and everyone else on this forum,

Thank you for this great topic!
A few months ago I purchased a second hand 840A V2 from a private owner. The amp sounds great. Since two weeks the same volume problems appeared on mine. Right channel volume increases or suddenly drops when adjusting the volume at higher levels. I only use the remote control to adjust the volume. But it also happens when I adjust the volume knob manual I discovered.

Do you think in that in my case only the relais ladder causes the problem? So this has probably nothing to do with a bad volume knob encoder?

If so, I was thinking of purchasing the Fujistu SY-9W-K relais, take out the circuit board my self, and bring these all together to a professional print circuit repair company due to the de-soldering issues.

Is the relais board in the 840A V2 also easy to remove? Is it one board or two? I did not open the amp yet, but I saw pictures on the web with only one board with 2x 7 relais. Is the otherone monted below? 

I also tried to find the right sockets for the Fujitsu relais, but I did not find one. Do you have a link or part number of the right sockets?

Thanks in advance and greetings from Belgium,

To answer some of the accumulated questions over the past few years:

My unit has not misbehaved once since I published the mods with the Fujitsu relays, and I use it every day. Note I did not replace the encoder, only the relays. I also have my unit set to turn on and shut off without the relays "clattering" through their volume ranges. I am sure this reduces wear and tear on them.

You can cool the unit better by mounting the top cover plate on .25" stand offs (or spacers) so you have an open slot for the hot air to exit. Just get longer metric screws to allow for the spacers.

If you want the relays in sockets, you have to build you own using "socket strips". The relay itself has odd pin spacing and there are no commercial sockets as far as I know. The socket strips are mounted as to cover an array of relays. As mentioned in the original posts, using these requires the removal of some of the contact positions (or cutting of the leads below these unused positions). Due to the reliability of the Fujitsu relays, I would probably not bother with sockets, and just solder the replacement relays and be done with it.