Well there shouldn't be hum on any of the outputs tbh, but 2 channel stereo is the feed to use for normal audio.
OK - will try this and the 'shorting' method later on to see if any job. I've got a guy lined up to take a look at the amp. If it's a couple of dodgy capacitors, I'm sure he can repair/replace for a smallish outlay.
OK 🙂
The bottom line is that it should be silent with phono leads connected and that also have the ends shorted. We then take that one step further and say it should still be silent if those then shorted ends are connected together. If it passes that then the amp is OK.
The bottom line is that it should be silent with phono leads connected and that also have the ends shorted. We then take that one step further and say it should still be silent if those then shorted ends are connected together. If it passes that then the amp is OK.
Ok, all tests done and silent with direct on/off. Stuffed small bits of foil down each plug, leaving other ends connected to amp obviously. Does this tell me any more!?
And is it silent when the two shorted leads are also connected together as in the lower diagram here ? If so, then the noise is being introduced externally to the amp. That can be either as 'hum voltage' from the player, or induced hum into the lead/s from external magnetic fields (which means from transformers in nearby equipment).
Like this. Both should be silent.
Like this. Both should be silent.
Attachments
Yes, I touched both ('foiled') plugs together and it was silent. There was plenty of foil stuffed down each. Will see if the ground loop isolator has an affect when it turns up.
So, are you saying it cannot be the amp in any way, shape or form? Remember, it did it with the CD player unplugged but leads connected. That said, the TV and BT Vision box is nearby.
Would the Arcam be extra sensitive over cheaper amps? Thanks again for all your help!
So, are you saying it cannot be the amp in any way, shape or form? Remember, it did it with the CD player unplugged but leads connected. That said, the TV and BT Vision box is nearby.
Would the Arcam be extra sensitive over cheaper amps? Thanks again for all your help!
That's the way the evidence is pointing from these tests. The surefire confirmation is to now try and borrow another player (or a tuner or a cassette deck etc) and see if that is OK.
The variable with this test is not knowing how the player is terminated internally.
Its remotely possible that the amp could exhibit hum if the impedance seen across the phono plugs isn't very low. In simple terms, that is the equivalent of the tin foil in each plug being replaced by a resistor rather than a dead short. Any amp should be unaffected by that... those that are affected are usually diy builds that have a poorly thought out grounding scheme.
Ok, my chum is coming down on sat and is going to bring an Arcam CD player so that's the next test. It sounds amazing regardless of the hum with direct off. I just leave it on! Would be good to know what it is as discussed. Would the isolator help?
Guess the TV and BT Vision box could contribute magnetic issue plus the phono leads aren't the best in the world!
Guess the TV and BT Vision box could contribute magnetic issue plus the phono leads aren't the best in the world!
Let me just expand on that bit. If it hadn't hummed in that state then that would prove the amp was OK, unfortunately the fact it does hum doesn't automatically mean the amp is at fault. When unplugged from the mains the players circuitry is 'floating' and depending on how its all configured, it could be prone to pick up hum. Normally in that situation, plugging the player into the mains ties everything down and the hum would stop... but yours doesn't.
That is why we went on test the amp with its input leads shorted, and then shorted and shorted together, left and right. That has to be silent and it was.
That then comes to the bit I mentioned in the post above... the obscure case of an amp that hums when the impedances seen across the inputs are not low enough. No commercial amp should fall into that category as its caused by basic design flaws in the wiring scheme.
The way to prove that. You need cheap phono sockets to plug the open end of the leads into. You then terminate each socket with a resistor (say 10k). The amp should still be silent and still be silent when (this time) the two grounds of those sockets are touched together.
Just seen your latest post... that would be brilliant as a test.
Great, thanks for the info. The nagging thing that bothers me is the buzz/hum only occurs when the direct switch is off in the situation as described. With all the tests as you suggested, it was silent with direct on or off.
Obviously there is just one left lead and one right lead and the tests were completed in order as instructed.
Don't get me wrong though, the buzz/hum is minor but there's definitely a noise when rigged up with direct button off. I guess the design of the amp is pretty good with all the reviews etc. That's why I went for it. It sounds epic when driving the speakers a little harder. Arcam are notoriously good.
We'll see what the CD player at the weekend does snd I'll report back!
Obviously there is just one left lead and one right lead and the tests were completed in order as instructed.
Don't get me wrong though, the buzz/hum is minor but there's definitely a noise when rigged up with direct button off. I guess the design of the amp is pretty good with all the reviews etc. That's why I went for it. It sounds epic when driving the speakers a little harder. Arcam are notoriously good.
We'll see what the CD player at the weekend does snd I'll report back!
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Actually it's quite a Mediocre (Arguably quite Poor) contraption.
Lacking in Depth, Dynamics, Clarity and almost complete lack of soundstaging.
An NAD easily outclasses it... True. Hearing is proof enough.
Nothing, like what the Magazine Shills claim though... is it?
Live 'n learn.
Lacking in Depth, Dynamics, Clarity and almost complete lack of soundstaging.
An NAD easily outclasses it... True. Hearing is proof enough.
Nothing, like what the Magazine Shills claim though... is it?
Live 'n learn.
Bare, pouring steaming piles of dung on the OP's audio gear won't help him to understand his hum problem in any way nor will his experience here leave him with a good impression of our attitude to helping others with something more to do with basics.
The Alpha 8 is what it is and regardless of our personal experience and opinions, it met with good reviews back in 1998. In 17 years old condition, it still is considered good sound quality in the UK market at ~ £150-300. Prices tend to take a nose dive for gear more than a few years old elsewhere but not often with local products in the UK.
FWIW, I think the suggestion to try with a different (and hopefully dedicated) CD player was probably wise. Up-market DVD players can be fine for audio but I have no idea how good the basic Cambridge model here is. Budget DVD players can be atrocious as audio components.
The Alpha 8 is what it is and regardless of our personal experience and opinions, it met with good reviews back in 1998. In 17 years old condition, it still is considered good sound quality in the UK market at ~ £150-300. Prices tend to take a nose dive for gear more than a few years old elsewhere but not often with local products in the UK.
FWIW, I think the suggestion to try with a different (and hopefully dedicated) CD player was probably wise. Up-market DVD players can be fine for audio but I have no idea how good the basic Cambridge model here is. Budget DVD players can be atrocious as audio components.
Ah well, opinions are like ar**holes aren't they? Everyone's got one!
I think it happens to sound fantastic for my requirements. Unfortunately I don't have ££££s to spend on new gear. A friend of mine who worked at O'Brien HiFi in Wimbledon happens to think that the Arcam series of amps are fantastic so I'll go with his opinion - because he isn't an.... (you can guess the rest!)
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I have two Arcam alpha 3's and they both have the 'fault' described here; a hum through the speakers only when the direct is not used! must be a design problem, you can't need to add a ground loop isolator to all arcam amps!?😕
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