Hello all
I've not much experience with power amps having used only integrated until pretty recently when I got a NAD 214 that folk on this forum helped me troubleshoot and get working - it's going great guns.
Just last week however, I was given a Chord SPM 900 that a friend has had for years but has never used. It looks great and I can't believe how tightly packed it is inside! It was in lieu of a rental deposit for studio space that I am renting to him and if it works then I got the better end of the deal as far as I am concerned.
This evening I hooked it up to my system but at maximum volume I was still not up to even my normal listening volume. The sound was very nice, no distortion or anything just very quiet. Before I go blaming the amp I want to rule out that I have set it up correctly.
My regular path is NAD C541i (with Lampizator) >> NAD C350 as preamp >> NAD 214 >> KEF 104ab. So I put the Chord in there to replace the NAD214. I got some XLR to rca cables as there is no rca input on Chord power amp.
This is my first experience of anything other than rca so I suspect that I may have bought the wrong type of cable and need some other adapter or need to wire the cable differently? I read there are different things like balanced and unbalanced but both use the same 3-pin jack? Would this be correct?
Or is the output from my NAD C350 not compatible?
I sense this Chord may start another round of upgraditis if I can get it to work as the low volume I heard was really good.
Thanks in advance for your replies.
C
I've not much experience with power amps having used only integrated until pretty recently when I got a NAD 214 that folk on this forum helped me troubleshoot and get working - it's going great guns.
Just last week however, I was given a Chord SPM 900 that a friend has had for years but has never used. It looks great and I can't believe how tightly packed it is inside! It was in lieu of a rental deposit for studio space that I am renting to him and if it works then I got the better end of the deal as far as I am concerned.
This evening I hooked it up to my system but at maximum volume I was still not up to even my normal listening volume. The sound was very nice, no distortion or anything just very quiet. Before I go blaming the amp I want to rule out that I have set it up correctly.
My regular path is NAD C541i (with Lampizator) >> NAD C350 as preamp >> NAD 214 >> KEF 104ab. So I put the Chord in there to replace the NAD214. I got some XLR to rca cables as there is no rca input on Chord power amp.
This is my first experience of anything other than rca so I suspect that I may have bought the wrong type of cable and need some other adapter or need to wire the cable differently? I read there are different things like balanced and unbalanced but both use the same 3-pin jack? Would this be correct?
Or is the output from my NAD C350 not compatible?
I sense this Chord may start another round of upgraditis if I can get it to work as the low volume I heard was really good.
Thanks in advance for your replies.
C
RCA is 2-conductor. XLR is 3 conductor.
The SPM's "balanced" inputs *should* accept the more common ways to adapt 2 to 3 pins. Where did you get the RCA/XLR cord?
Are you confident to get naked RCA and XLR plugs, and clip-leads to try various combinations? (This could get LOUD.) Most likely the shell of the RCA goes to *two* pins of the XLR. There will be many examples in Google, some dubious.
The SPM's "balanced" inputs *should* accept the more common ways to adapt 2 to 3 pins. Where did you get the RCA/XLR cord?
Are you confident to get naked RCA and XLR plugs, and clip-leads to try various combinations? (This could get LOUD.) Most likely the shell of the RCA goes to *two* pins of the XLR. There will be many examples in Google, some dubious.
XLR inputs usually require +4dbm where as RCA is typically around -10dbm. You're RCA to XLR adaptor probably drives pins 2 and 3 of the XLR. This will explain the loss of level. There's no easy fix really. You need an RCA to XLR buffer stage with the required gain.
Thanks for your replies.
I understand that xlr is +ve, -ve and earth 3 pins and RCA is just the signal and its return but I think my problem is more simple than making sure I have that wired correctly.
While I have not been able to find a user manual for this model I have looked at manuals for some of the other Chord SPM models it looks like I may not be using the correct input (phono instead of preamp) and have wired the speakers to the same channel on A & B speakers!!! There are no labels for any of the inputs/outputs on the rear of the machine
I'm going to sort myself out with the male xlr adapter I need to go into what I think is the correct input and from there will look into a xlr/rca buffer stage as suggested above - or just continue to succumb to upgrade-itis and move to the world of balanced outputs. (Having taken advantage of the super offer on a Shiga Black MkII that will be on its way for Christmas I'm going to be seeing some real weak links in my chain soon)
I understand that xlr is +ve, -ve and earth 3 pins and RCA is just the signal and its return but I think my problem is more simple than making sure I have that wired correctly.
While I have not been able to find a user manual for this model I have looked at manuals for some of the other Chord SPM models it looks like I may not be using the correct input (phono instead of preamp) and have wired the speakers to the same channel on A & B speakers!!! There are no labels for any of the inputs/outputs on the rear of the machine
I'm going to sort myself out with the male xlr adapter I need to go into what I think is the correct input and from there will look into a xlr/rca buffer stage as suggested above - or just continue to succumb to upgrade-itis and move to the world of balanced outputs. (Having taken advantage of the super offer on a Shiga Black MkII that will be on its way for Christmas I'm going to be seeing some real weak links in my chain soon)
Hint: Audio connections are not impedance-matched. It's +4 dBu (1.23 V) vs. -10 dBV (300 mV), or about 12 dB of difference. In practice, pro audio power amps actually tend to have plenty of gain, and input levels are not all that different from hi-fi gear. It is not unusual to find ones that can do full power at 0 dBu input with the input level controls cranked up. In any case, even 12 dB would not be enough to account for an extremely low level.
It would be interesting how the adapter cable is wired up. Most of them seem to be all unbalanced, connecting shield to XLR 1+3 and signal to pin 2. Which is a waste of a balanced input but should give plenty of level.
So the problem may be rooted more deeply, and if it's just contact issues in the output relays.
EDIT:
How annoying.
Why would they have a "phono" input on a power amp anyway?
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> XLR inputs usually require +4dbm where as RCA is typically around -10dbm.
That's one convention. More Studio than Hi-Fi.
"RCA" on "power amps" is often ~~1V, even 1.4V. In the area of "+4dBu".
The little I could find suggests this amp has voltage gain near 29dB, a bit more than customary 26dB, so it should not be weak. It should not take over 1V to make 100 Watts out. It should not be "weaker" than the amp it replaced. I suspect mis-wired XLR side.
That's one convention. More Studio than Hi-Fi.
"RCA" on "power amps" is often ~~1V, even 1.4V. In the area of "+4dBu".
The little I could find suggests this amp has voltage gain near 29dB, a bit more than customary 26dB, so it should not be weak. It should not take over 1V to make 100 Watts out. It should not be "weaker" than the amp it replaced. I suspect mis-wired XLR side.
That's what I thought. Had another look at what I was reading that had the label "phono" - they just meant phono socket as in rca
Have contacted Chord to see if they can supply manual.
Opened xlr adapter - yes, pins 1&3 wired together.
There are 2 pairs of xlr inputs at rear of unit. 1 accepts male, the other female. I had female xlr adapter, now waiting on male to try other pair.
In Britain we call them phono sockets. In many other places they are called RCA (jacks?). As Chord Electronics is British it is unsurprising that they call them phono.sthcoaster said:
That confused me for a while, then I realised that you are actually going from phono to XLR. How you do this depends on the details of the XLR input; for example, does it use a transfomer?
That was just about the only other option remaining. Oldschool.
Have you tried these?
Actually that's one input and one output. If your cable is RCA to female XLR, that's the wrong one indeed, you need one terminating in a male plug. Getting signal into an output has generally proven unsuccessful to varying degrees. That it worked at all may indicate an incorrectly wired XLR pin 1 in the amp (i.e. going to local circuit ground rather than chassis). This model predates the time when manufacturers figured that one out.
If you get any ground loop issues, let us know. A simple mod of your new XLR cable should resolve those if needed.
Ha!
No wonder it was not working!
As I wrote early been a bit in the blind 1) lack of experience with pro level equipment, and 2) no stencilled labelling on anything.
Getting close now.
Will report back tomorrow after male xlr has arrived and I have a chance to play again in the evening.
Also going to read up on balanced outputs to understand how -ve differs from earth!
No wonder it was not working!
As I wrote early been a bit in the blind 1) lack of experience with pro level equipment, and 2) no stencilled labelling on anything.
Getting close now.
Will report back tomorrow after male xlr has arrived and I have a chance to play again in the evening.
Also going to read up on balanced outputs to understand how -ve differs from earth!
Here's a good article:
Balanced Interfaces
BTW, your existing XLR --> RCA output cable as supplied should only be used with floating (e.g. transformer-coupled) outputs. Standard electronically balanced outputs using two single-ended opamps to provide "hot" and "cold" may be seriously unhappy about one side being shorted out; for them shield must only be connected to pin 1 and 3 left floating.
Balanced Interfaces
BTW, your existing XLR --> RCA output cable as supplied should only be used with floating (e.g. transformer-coupled) outputs. Standard electronically balanced outputs using two single-ended opamps to provide "hot" and "cold" may be seriously unhappy about one side being shorted out; for them shield must only be connected to pin 1 and 3 left floating.
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THANKS
Listening now. A very happy camper.
A very big thanks to all who offered advice and solutions.
Looks like the NAD214 will now head for retirement once I return the original caps to it and retrieve the 6 Kendeil caps I installed recently.
Looking forward to the Shiga Black MkII kit I have ordered from
Listening now. A very happy camper.
A very big thanks to all who offered advice and solutions.
Looks like the NAD214 will now head for retirement once I return the original caps to it and retrieve the 6 Kendeil caps I installed recently.
Looking forward to the Shiga Black MkII kit I have ordered from
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