First picture: Actual connection: LM317/337/LF353 board, +/-14V output, without any hum or buzzing ...
Second: "genuinne" connection with C.T 24V toroidal and rectifier bridge, with hum problem ...
There was a post that the signal ground should be separated from the power 0V ground, but I really don´t know, how to change wirings on these "slowdyier" PCB´s ...
Normally I'd be concerned about an hum in an uncased build like that, but since there is only noise when you switch power supplies we can isolate the problem to toroidal transformer, diode, and related wiring. Or, the S-reg regulation circuit on the Emerald boards. If the on board regulation wasn't functioning properly, the circuit would still work with the regulated power supply. Assuming your V+ 12 V and your V++ is 16 V or more, it should be OK. If your regulated supply is only 14 V, depending on how the S-reg is set up it might not actually be working under that condition. Not that that matters since you have already regulated the power supply in that case, I'm just pointing it out.
(The output V+ should be 3-4 V lower than the input V++. The S-regs have very high dropout voltages.)
With 24 V C.T. the center tap connects to COM.
Test noise with the inputs to the Emerald shorted.
(The output V+ should be 3-4 V lower than the input V++. The S-regs have very high dropout voltages.)
With 24 V C.T. the center tap connects to COM.
Test noise with the inputs to the Emerald shorted.
Hello
Looking for some advice here. Still experiencing hum/buzz when connecting the Emerald. It’s still not connected to my turntable, so only output to amp. While it’s powered on and I touch either the outer case or the inner psu case the noise decreases but not completely.
The mains ground and the transformer ground is at the inner psu case. The Emerald grounds are at the outer plate.
Here’s a couple of pictures. Maybe you can spot an obvious reason or tell me what I can do to test it and narrow down the options. Sorry for the not so great wiring but it’s only mounted on this plate temporarily.
Looking for some advice here. Still experiencing hum/buzz when connecting the Emerald. It’s still not connected to my turntable, so only output to amp. While it’s powered on and I touch either the outer case or the inner psu case the noise decreases but not completely.
The mains ground and the transformer ground is at the inner psu case. The Emerald grounds are at the outer plate.
Here’s a couple of pictures. Maybe you can spot an obvious reason or tell me what I can do to test it and narrow down the options. Sorry for the not so great wiring but it’s only mounted on this plate temporarily.
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I've only built the Emerald with an external power supply. Putting the toroid and diodes right up next to the boards like that may not be the greatest idea, even with your shield box, since the magnetic flux won't care about that aluminum metal.
You want to short the inputs before thinking about evaluating noise levels.
Also worth checking if it's still noisy with the MM gain option selected.
Try removing the earth connection. i.e. leave the box/circuit disconnected from safety ground. If that solves it, you can then implement a safe, permanent fix.
What I'd suggest if you have tired of troubleshooting is to convert your build to have the diodes and transformer in an external box. The power supply is earthed, the EMerald box is not.
Else you have to rig up a "humbuster" to separate the circuit common from the earthed case.
You want to short the inputs before thinking about evaluating noise levels.
Also worth checking if it's still noisy with the MM gain option selected.
Try removing the earth connection. i.e. leave the box/circuit disconnected from safety ground. If that solves it, you can then implement a safe, permanent fix.
What I'd suggest if you have tired of troubleshooting is to convert your build to have the diodes and transformer in an external box. The power supply is earthed, the EMerald box is not.
Else you have to rig up a "humbuster" to separate the circuit common from the earthed case.
I would suggest the opposite.
Keep the circuit connected to the case through the GND terminals.
Disconnect the case from the earth terminal on the IEC socket. Essentially, use a two wire AC connection, no earth.
(I know what people are going to say, but if this solves the issue - and it likely will, then we go back and fix it in later to be a safe.)
Richard, effectively that does the same thing, splits the signal gnd from mains earth. Though one needs to be done under class II to be safe and the other doesn't...
The iec socket should always be earthed to chassis in any device isn't double insulated.
Alternatively the gent could put a DDRC in between chassis and the central earth point on the pcb.
All that said, when wired without the loop, the Emerald is the quietest opamp phonostage I've built or heard
The iec socket should always be earthed to chassis in any device isn't double insulated.
Alternatively the gent could put a DDRC in between chassis and the central earth point on the pcb.
All that said, when wired without the loop, the Emerald is the quietest opamp phonostage I've built or heard
Thank you both for the input. But I decided to go for the standard two box setup instead with an umbilical.
Disconnected everything and cut my plate in two. I’ll be getting the xlr connectors tomorrow, already have the cord. Then…
PSU
1. IEC ground goes to chassi.
2. Transformer ground goes together with IEC ground?
3. DBRB Coms goes to xlr ground?
Emerald
4. Pcb middle ground together to chassi.
A quiet phono
atleast this is where I’ll start and see how things goes. Probably get back here along the way.
Disconnected everything and cut my plate in two. I’ll be getting the xlr connectors tomorrow, already have the cord. Then…
PSU
1. IEC ground goes to chassi.
2. Transformer ground goes together with IEC ground?
3. DBRB Coms goes to xlr ground?
Emerald
4. Pcb middle ground together to chassi.
A quiet phono
atleast this is where I’ll start and see how things goes. Probably get back here along the way.
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The advantage of the two box solution is it allows you to disconnect the phono preamp case from the mains earth while satisfying relevant safety codes. The phono preamp case is connected to the circuit common for good shielding, it's not connected to earth and doesn't need to be.
"Richard, effectively that does the same thing, splits the signal gnd from mains earth. Though one needs to be done under class II to be safe and the other doesn't..."
Not quite. For best shielding, the chassis should be connected to the circuit common at a single point. No currents should flow through your chassis. Connecting the chassis to both the earth and the circuit common creates ground loops if the audio common is connected to the earth elsewhere (like in the amplifier). If you connect the chassis to the earth but not the common, then there's a potential difference between the chassis and the input circuitry which introduces capacitive coupling aka noise.
"Richard, effectively that does the same thing, splits the signal gnd from mains earth. Though one needs to be done under class II to be safe and the other doesn't..."
Not quite. For best shielding, the chassis should be connected to the circuit common at a single point. No currents should flow through your chassis. Connecting the chassis to both the earth and the circuit common creates ground loops if the audio common is connected to the earth elsewhere (like in the amplifier). If you connect the chassis to the earth but not the common, then there's a potential difference between the chassis and the input circuitry which introduces capacitive coupling aka noise.
I connected my board grounds to the thumb nut binding post that my turntable ground connects to.
My Emerald it literally dead quiet.
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dwinstonwood's is the "rulebook" connection scheme for the standard 2 chassis build.
Note that the chassis pictured has no earth connection, avoiding the possibility of a ground loop.
Not all turntables have or need a separate connection to the phono stage common. The lug (thumb nut) on the chassis is there for those that do.
Note that the chassis pictured has no earth connection, avoiding the possibility of a ground loop.
Not all turntables have or need a separate connection to the phono stage common. The lug (thumb nut) on the chassis is there for those that do.