Thanks much!
Traveling this week, so will pick this back up next weekend (ie, sending very basic questions to this thread).
Traveling this week, so will pick this back up next weekend (ie, sending very basic questions to this thread).
Hum-we-don't-need news...
I've now disconnected the internal PSU and connected the original boards, which I placed outside the chassis – no change, even when I closed the chassis and moved the external PSUs 40-50 cm away. A very slight hum, more like a shhhh on the left, a slight brrrr plus shhhh on the right... My suspicion (already yesterday) was that it was a ground loop, which can often cause a significant hum, and a quiet one in any case. So I separated the ground wire between the IEC socket and the chassis. The PSU chassis ground goes directly to the ground wire in the IEC socket and to the turntable chassis ground screw, but not to the Pearl TT hroznd pins. And lo and behold – the slight hum (brrrr) has disappeared, but the very slight background noise (shhhh) remains, audible up to about 20 cm in front of the speaker. So I have a grounding problem. Do the TT chassis ground connections on the Pearl board need to be separated from the chassis ground or not even connected, when the mains ground goes directly to the chassis ground? Currently, my grounding looks like this – do you see a problem? Will the TT chassis ground cause a ground loop if it is not isolated from the amp chassis? Many thanks in advance.
I've now disconnected the internal PSU and connected the original boards, which I placed outside the chassis – no change, even when I closed the chassis and moved the external PSUs 40-50 cm away. A very slight hum, more like a shhhh on the left, a slight brrrr plus shhhh on the right... My suspicion (already yesterday) was that it was a ground loop, which can often cause a significant hum, and a quiet one in any case. So I separated the ground wire between the IEC socket and the chassis. The PSU chassis ground goes directly to the ground wire in the IEC socket and to the turntable chassis ground screw, but not to the Pearl TT hroznd pins. And lo and behold – the slight hum (brrrr) has disappeared, but the very slight background noise (shhhh) remains, audible up to about 20 cm in front of the speaker. So I have a grounding problem. Do the TT chassis ground connections on the Pearl board need to be separated from the chassis ground or not even connected, when the mains ground goes directly to the chassis ground? Currently, my grounding looks like this – do you see a problem? Will the TT chassis ground cause a ground loop if it is not isolated from the amp chassis? Many thanks in advance.
Try keeping your signal grounds floating, and mains earth should always be connected to the amplifier chassis.
Usually the turntable's arm cable ground wire isn't connected to mains earth, and should go to signal ground.
Otherwise a small or large resistance between mains and signal ground may help.
All IME.
Usually the turntable's arm cable ground wire isn't connected to mains earth, and should go to signal ground.
Otherwise a small or large resistance between mains and signal ground may help.
All IME.
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Thanks! Yes, there is a resistance of 1.43 Mohms between chassis ground and signal/psu ground, realized with a bridge rectifier, so the signal ground is floating. However, on my Rega amp there is no resistance between TT ground screw, signal groznd and chassis ground.
JFYI.......
The way I did it:
PSU.
From IEC earth to bridge rectifier, then 10 ohm to chassis in psu enclosure.
Both enclosures connected via umbilical.
P-3
Ground terminal for TT ground isolated from P-3 chassis.
10 ohm from ground terminal to P-3 chassis.
10 ohm from left P-3 ground point to ground terminal.
10 ohm from right P-3 ground point to ground terminal.
This gives me NO hum at all 😉
The way I did it:
PSU.
From IEC earth to bridge rectifier, then 10 ohm to chassis in psu enclosure.
Both enclosures connected via umbilical.
P-3
Ground terminal for TT ground isolated from P-3 chassis.
10 ohm from ground terminal to P-3 chassis.
10 ohm from left P-3 ground point to ground terminal.
10 ohm from right P-3 ground point to ground terminal.
This gives me NO hum at all 😉
so:
enclosures connected via umbilical... shield or a separate wire?
Pearl signal boards grounded to... where?
enclosures connected via umbilical... shield or a separate wire?
Pearl signal boards grounded to... where?
Hi All,
Instruction suggests to use 15VA toroidal transformer, but - sadly - digikey is out of stock of both 15VA transformer options (TE2253-ND and 1295-1028-ND). I found 10VA version (1295-1043-ND or here's the link: https://www.digikey.pl/en/products/detail/talema-group-llc/70043K/3881436) and the question is if 10VA is good enough?
If yes, does this 10VA transformer fit the PSU board from DIYaudio store? It has the same PC pin termination style as TE2253-ND and 1295-1028-ND, but not sure if it works with PCB.
Regards,
Nick
Instruction suggests to use 15VA toroidal transformer, but - sadly - digikey is out of stock of both 15VA transformer options (TE2253-ND and 1295-1028-ND). I found 10VA version (1295-1043-ND or here's the link: https://www.digikey.pl/en/products/detail/talema-group-llc/70043K/3881436) and the question is if 10VA is good enough?
If yes, does this 10VA transformer fit the PSU board from DIYaudio store? It has the same PC pin termination style as TE2253-ND and 1295-1028-ND, but not sure if it works with PCB.
Regards,
Nick
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Nick, I just ordered the TE2253-ND from Digikey. It's on back order, but I called them and they expect them to be in stock by June 30.
John
John
Thanks for the hints!
The only problem is - we all use different and/or not fully clear terminology 😀
Is it with the original psu boards and do you mean the psu boards's "to chassis ground" connection (which is already a floating ground due to the rectifier bridge)? So IEC ground to this point and with 10 ohms to the chassis?
Do you connect psu chassis ground and and P3 chassis ground with the umbilical?
So, it is only connected to the P3's TT ground point, not to the amp chassis.
Which ground terminal do you mean?
Ground point: do you mean ground point of the P3's psu connector? To which "ground terminal"?
Many thanks in advance.
The only problem is - we all use different and/or not fully clear terminology 😀
Is it with the original psu boards and do you mean the psu boards's "to chassis ground" connection (which is already a floating ground due to the rectifier bridge)? So IEC ground to this point and with 10 ohms to the chassis?
Do you connect psu chassis ground and and P3 chassis ground with the umbilical?
So, it is only connected to the P3's TT ground point, not to the amp chassis.
Which ground terminal do you mean?
Ground point: do you mean ground point of the P3's psu connector? To which "ground terminal"?
Many thanks in advance.
There is one (??) thing I don't understand. The psu ground is a floating ground because of the rectifier bridge to the chassis ground and so is the TT ground a floating ground too. The wiring diagram of the two-chassis solution shows however, that the TT grounding post should be connected to the chassis ground. The wire between psu and P3 has +, -, 0 and gnd - and gnd should or shouldn't be connected to the P3's chassis, depending on "what sounds better". But if I connect it to the chassis ground (where the TT ground is connected to the chassis ground), then I just short the floating ground to the ground and it makes it unfunctional. Where is the knot? 🤔
Sorry for the shady artwork.
Try and see, if this answers your questions 😉
And of course....... All RCA´s "cold" isolated from chassis as well.
Does it matter???
Anyway..... did it with a 4-lead wire....... No shield.
Many commercial phone pre's has a "ground lift option". In my P3 build I installed a permanent ground lift. Signal Gnd on P3 boards goes via their own "ground lift resistor to chassis gnd. I my case I used 2 x NTC to chassis gnd. I have no hum.
I used MJ's PSU in own chassis and the yellow/green wire is part of the PSU cable so both my chassis have direct connect to safety gnd.
The TT-gnd goes directly to P3 chassis.
I used MJ's PSU in own chassis and the yellow/green wire is part of the PSU cable so both my chassis have direct connect to safety gnd.
The TT-gnd goes directly to P3 chassis.
Thanks for the artwork 😀
So you are using a further, separate rectifier bridge between IEC ground and chassis, via 10R.
The PSU floating ground is connected via umbilical to the P3's onboard ground connector.
You connect the PSU chassis ground via umbilical to the P3 chassis ground.
You have isolated TT ground post, grounded via 10R to the P3 chassis ground and via 10R to the P3 board TT ground point.
Are your PSU boards grounded to the chassis somehow?
Regarding rca isolated from chassis.. when i installed my neutriks, the ones in housing, i thought all was well, but i decided to test it with multimeter, and i did show from 70 to 100k ohm depending on how tight the nut was pulled, so i used extra fibre washers, and ohm reading went into mega Ohms.. dont trust...test..
I used differential mode chokes in my pearl psu.. dc resistance 2-3 ohm..
Sits in series with each power rail (like +15 V and -15 V).
– Blocks high-frequency noise between +15 V and -15 V—like power supply ripple, switching spikes, or digital hash.
– DC power passes through easily because DC current doesn’t mind a bit of inductance.
– Acts like a filter for differential noise: only the steady DC “calm” survives, the HF “storm” gets throttled.
Perfect for sensitive analog circuits where you don’t want your ±15 V lines to be a secret highway for squealing digital noise.
Sits in series with each power rail (like +15 V and -15 V).
– Blocks high-frequency noise between +15 V and -15 V—like power supply ripple, switching spikes, or digital hash.
– DC power passes through easily because DC current doesn’t mind a bit of inductance.
– Acts like a filter for differential noise: only the steady DC “calm” survives, the HF “storm” gets throttled.
Perfect for sensitive analog circuits where you don’t want your ±15 V lines to be a secret highway for squealing digital noise.