Preamp issue

dulcificum

dulcificum

dulcificum

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I'm running a Regar Planar 1 going into a Rega Fono Mini A2D pre-amp.

From there I use the RCA output to go into active speakers.

I was running PreSonus Eris E4.5 monitors but have moved them and replaced them with Edifier R1700BT for the dual inputs and bluetooth.

The line level coming out of the preamp was fine before but now is really really quiet. I have to turn the speakers' amp right up to hear records being played then turn it right down again to play from another source (media centre/PC/console/etc,.)

Any idea what the issue is? I get the same problem whether I use the 500 mV or 700 mV RCA input on the R1700BT.
 
Time for a bit of troubleshooting, I think.

Background: The Rega A2D outputs 500mV when driving with a 5mV input signal. Presuming you still have the standard supplied Carbon cartridge fitted in the tone arm, then it outputs around half that value which was plenty to drive the input of the PreSonus speakers.

As you already know, the Edifiers have an input sensitivity of 550mV (the maximum input signal before the input circuit starts to clip) so it's a reasonable match for the phono pre-amp.

One significant difference in the tech specs between the two sets of speakers is their output SPLs. However, since the issue is confined to the analogue inputs on the Edifier, and perhaps even only when driven by the Rega A2D, then I'd rule out the level difference as being a concern.


Troubleshooting: It's possible that something got damaged in the swap between the two sets of speakers; but to be sure then it would be a good idea (if feasible) to restore the system as it was with the PreSonus speakers. After doing this, if the level is still low then look at the connection leads (swap for another pair), and then try the analogue outputs from another source. RCA phono leads can break, though it would usually be just one of the two cables rather than both. The other possibility is that a solder joint on the board in the A2D got weakened. The move to lead-free solder in circuit boards might be better for the environment, but the joints aren't as strong and they're now more prone to going dry joint.

Oh, it's also worth checking that the Ins and Outs are connected correctly on the A2D before you start. The turntable leads go to the sockets marked INPUT. The connection to the speakers is made from the A2D sockets marked OUTPUT.
 
lucid said:
Time for a bit of troubleshooting, I think.

Background: The Rega A2D outputs 500mV when driving with a 5mV input signal. Presuming you still have the standard supplied Carbon cartridge fitted in the tone arm, then it outputs around half that value which was plenty to drive the input of the PreSonus speakers.

As you already know, the Edifiers have an input sensitivity of 550mV (the maximum input signal before the input circuit starts to clip) so it's a reasonable match for the phono pre-amp.

One significant difference in the tech specs between the two sets of speakers is their output SPLs. However, since the issue is confined to the analogue inputs on the Edifier, and perhaps even only when driven by the Rega A2D, then I'd rule out the level difference as being a concern.


Troubleshooting: It's possible that something got damaged in the swap between the two sets of speakers; but to be sure then it would be a good idea (if feasible) to restore the system as it was with the PreSonus speakers. After doing this, if the level is still low then look at the connection leads (swap for another pair), and then try the analogue outputs from another source. RCA phono leads can break, though it would usually be just one of the two cables rather than both. The other possibility is that a solder joint on the board in the A2D got weakened. The move to lead-free solder in circuit boards might be better for the environment, but the joints aren't as strong and they're now more prone to going dry joint.

Oh, it's also worth checking that the Ins and Outs are connected correctly on the A2D before you start. The turntable leads go to the sockets marked INPUT. The connection to the speakers is made from the A2D sockets marked OUTPUT.
Click to expand...

Thanks for the detailed reply.

Actually the input sensitivity is 700 mV on "PC" and 500 mV on "Aux". I get the same result with both, can barely even tell if one's louder.

My first thought was an issue during the swap but I've put the Presonius back and done A/B tests and they are still fine. Only the Edifiers have an issue. I've always swapped out both sets of RCA to double check :/

Wiring on the A2D is all correct too. I can't find sensitivity specs for the Presonius but they seem to be the same loudness as Edifier with line sources such as a laptop. It's only the line from A2D that is different. It's almost as though the Presonius is detecting a lower signal level and boosting automatically and the Edifier can't. V confused!
 
According to the Edifier R1700BT manual it's as follows:

Input sensitivity:
PC: 700 mV ± 50 mV
AUX: 550 mV ± 50 mV

The AUX input could be 500mV, or 550mV or even 600mV, so we're both right, and we're both wrong... :D :D :D

It's moot anyway as it's 'enough' to be driven by the 250mV signal from the Rega pre-amp.
 
If we've ruled out dodgy leads, broken sockets and back-to-front wiring, and unless there's some other bit of relevant info that's mossing, then what's left as a cause is something more esoteric.

Before we go down the route of wondering about the input impedances of the two sets of speakers and whether there's sufficient signal attenuation to cause such a dramatic difference, are you sure you've exhausted all other possibilities on the speakers?
 
Now this is odd. I tested again last night, A/B between these and the Presonius and between line source from laptop and from A2D and it was definitely still behaving like this.

This morning I disconnected and lugged down my Mackie CR4s to have a third data point to check and, before I bothered to connect everything up, I checked and it was working fine!

No idea what the issue is. The speakers' amp wouldn't automatically normalise two sources would it? I don't think it was a power cycle of the pre-amp because I already tried that a couple of times. But overall relieved it works and that I'm not going mad with a set up which should be fine...

Thanks anyway!
 
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