Problem with my Cambridge amp / Bi-wire

[rob88wells]

Hi guys, I have a Cambridge 840a stereo amp that I bought from Richer Sounds to power a pair of bi-wireable speakers.

I asked the Richer Sounds fellow if I could use the A/B terminals together to bi-wire the speakers, and he said yes.

So I got home, wired the left/right HF to the A terminals, and the left/right HF to the B terminals, set the amp to output to A & B and it worked a treat. Sounded sublime. Had it cranked up to ear splitting volumes and it still sounded fantastic.

Then a week or so ago I bought a Sony DA2400ES (receiver) and used the front pre-outs to connect it to the Cambridge on a fixed volume input.

But the Cambridge began flashing 'Overload' and then switched off.

The sound wasn't very loud, and I checked all connections and everything was fine.

So my question is: Does this have something to do with me bi-wiring my speakers to the A & B terminals, or is it a problem with the preouts? Or has the Cambridge died?

I also noticed that the Sony was throwing out a huge amount of hiss. I don't know if that has anything to do with it.

Sorry if this has already arisen, but I could't find anything in the search bar.

Any help would be appreciated.

I hope the Cambridge isn't buggered it cost me a whole months wages

 

[rob88wells]

bump

 

[ChrisAV]

Hi

I'm not sure I quite follow what you have done here, so could you just clarify a few points below:

Hi guys, I have a Cambridge 840a stereo amp that I bought from Richer Sounds to power a pair of bi-wireable speakers.

I asked the Richer Sounds fellow if I could use the A/B terminals together to bi-wire the speakers, and he said yes.

So I got home, wired the left/right HF to the A terminals, and the left/right HF to the B terminals, set the amp to output to A & B and it worked a treat. Sounded sublime. Had it cranked up to ear splitting volumes and it still sounded fantastic.

- Does 'left/right HF' mean the high frequencies speaker terminals (the upper set)? If I have read this correctly it sounds as though you have connected each speaker to both the A and B sets via the high frequencies speaker terminals? Can you confirm or correct my interpretation?

- If my interpretation is correct then I'm surprised the speakers were working as nothing is wired to the low frequency (woofer) speaker terminals, unless you have left the metal plate in place that connects the upper and lower terminals - Can you whether or not this was removed?

I'm not sure what you were trying to achieve with this set up, but bi-wiring should just use one set of speaker connections, connected to each speakers with two cables to both sets of terminals, with the connecting plate removed.

Using two sets of speaker terminals is normally used for bi-amping, sending high frequencies from one speaker set and low from the other, but the amp must have a 'bi-amp' mode for this which I don't believe the Cambridge has.



Then a week or so ago I bought a Sony DA2400ES (receiver) and used the front pre-outs to connect it to the Cambridge on a fixed volume input.

- Did you set 'Input Switch 1' to the 'balanced setting'?

But the Cambridge began flashing 'Overload' and then switched off.

The sound wasn't very loud, and I checked all connections and everything was fine.

So my question is: Does this have something to do with me bi-wiring my speakers to the A & B terminals, or is it a problem with the preouts? Or has the Cambridge died?

The first thing I would do (after checking the input switch, so actually the second thing) is to wire your speakers normally (single cable), replacing the metal connecting plate if you have removed it, to remove 'bi-wiring' from the equation and see if the problem persists.

I also noticed that the Sony was throwing out a huge amount of hiss. I don't know if that has anything to do with it.

Sorry if this has already arisen, but I could't find anything in the search bar.

Any help would be appreciated.

I hope the Cambridge isn't buggered it cost me a whole months wages

Chris

 

[rob88wells]

Hi Chris, thanks for replying.

Sorry, I made a typing mistake, what I meant to say was:

left/right HF to the A terminals, and the left/right LF to the B terminals.

Did you set 'Input Switch 1' to the 'balanced setting'

Do you mean on the Cambridge? If so then yes.

I have attached a picture of how I have the speakers connected to the amp. This worked brilliantly, until as you know I added the fixed input from the receiver.



I will try what you said, and remove bi-wire from the equation, and see if the problem persists.

cheers

 

[ChrisAV]

Hi Chris, thanks for replying.

Sorry, I made a typing mistake, what I meant to say was:

left/right HF to the A terminals, and the left/right LF to the B terminals.



Do you mean on the Cambridge? If so then yes.

I have attached a picture of how I have the speakers connected to the amp. This worked brilliantly, until as you know I added the fixed input from the receiver.

View attachment 106005

I will try what you said, and remove bi-wire from the equation, and see if the problem persists.

cheers

Ok, I see what you are doing now. Normally when bi-wiring just one set of teminals is used (so Amp -ve wired to HF -ve and LF -ve, Amp +ve to HF +ve and LF +ve for each channel respectively), but effectively you have split this at the amp end so I can see how it would work, assuming you are driving both sets of speaker terminals.

Unfortunately my physics lets me down here, I can't say with any confidence whether or not this would adversely affect the amp. Still try just using the single cable to see how it goes. Also, disconnect the Sony and confirm the amp still sounds fine when just your normal inputs.

By the way, can you confirm whether or not the metal plate across the termainals was in place ? Also, what Ohm are your speakers?

 

[rob88wells]

The speakers are Mission m34i's and are 8 Ohms, and yes I removed the metal plate.

I guess by using both the A & B terminals together will double the load on the amp, but it seemed to deal with the extra load just fine when I was playing music.

I can't have a fiddle until tomorrow now, but I will try all that you've suggested.

thanks again

 

[William YZF-R1]

Having followed this thread with interest (and the knowledgeable replies) I took the time to read the Cambridge manual online.

It seems plausible that the "biwiring" using A + B is the culprit but I keep wondering why it worked OK until the 2400 was introduced.

It would seem the connections were OK and presumably only 2 phono leads were needed for the 2400.

Its only conjecture as I have never even seen a Cambridge amp but after all this reading about fixed level inputs and the Cambridge acting as a dedicated power amp for that input, for two speakers I was wondering if its conceiveable that A+B speaker selection would be inoperable for a fixed level input and that tipped the Cambridge over the edge.

Anyway its just a thought and lets hope conventional wiring (which also removes A+B from the equation) restores normality.

 

[ChrisAV]

The speakers are Mission m34i's and are 8 Ohms, and yes I removed the metal plate.

I guess by using both the A & B terminals together will double the load on the amp, but it seemed to deal with the extra load just fine when I was playing music.

I can't have a fiddle until tomorrow now, but I will try all that you've suggested.

thanks again

That was my initial thought, and would (I think) be true with two sets of speakers connected. However, I would have thought with both powering a single set then you would only need half the volume at the amp to drive the speakers at the same level (volume). But as I said my physics isn't that great.

I was slightly concerenced about shorting out the amp across the teminals, but now you confimed the plate was removed I don't think this is an issue. Anyway, try it wired normally (and don't forget to put the plates back)!

Chris

 

[rob88wells]

Having followed this thread with interest (and the knowledgeable replies) I took the time to read the Cambridge manual online.

It seems plausible that the "biwiring" using A + B is the culprit but I keep wondering why it worked OK until the 2400 was introduced.

It would seem the connections were OK and presumably only 2 phono leads were needed for the 2400.

Its only conjecture as I have never even seen a Cambridge amp but after all this reading about fixed level inputs and the Cambridge acting as a dedicated power amp for that input, for two speakers I was wondering if its conceiveable that A+B speaker selection would be inoperable for a fixed level input and that tipped the Cambridge over the edge.

Anyway its just a thought and lets hope conventional wiring (which also removes A+B from the equation) restores normality.

That's pretty much what I've narrowed it down to, I think...!

That was my initial thought, and would (I think) be true with two sets of speakers connected. However, I would have thought with both powering a single set then you would only need half the volume at the amp to drive the speakers at the same level (volume). But as I said my physics isn't that great.

I was slightly concerenced about shorting out the amp across the teminals, but now you confimed the plate was removed I don't think this is an issue. Anyway, try it wired normally (and don't forget to put the plates back)!

Chris

I replaced the original plates and ran just one length of wire from the Amps A terminals to the speakers.

Sounded great, worked fine.

I did a couple of tests:

CD > AMP > SPEAKERS
CD > RECEIVER > AMP > SPEAKERS
PS3 > RECEIVER (via hdmi) > AMP > SPEAKERS

All worked fine, so I decided to remove the bi-wire from the equation.
Obviously I then had two spare lengths of cable at hand so I decided to make some jumpers, here they are:





Everything seems to work okay now, which is a relief.

I leapt at the thought of bi-wiring without actually knowing what it meant. But never mind, gotta learn the hard way sometimes!

Cheers for all the help, I owe you one.

 

[ChrisAV]

Nice one - glad you got it sorted and that the Cambrridge is in tact (but probably not half as glad as you are ).


Cheers

Chris

 

[William YZF-R1]

Nice one - glad you got it sorted and that the Cambrridge is in tact (but probably not half as glad as you are ).


Cheers

Chris

+1 On that