Grounding question for

[ppdl3]

Hey there. Still a relative newbie here and have a question about grounding In a relatively complex system. Thanks in advance for sharing your wisdom.

So, my setup is running two phono preamps and two amplifiers and switching between them all. It's really quite fun.

Currently, I run RCA out of a '70s Sony Ps4300 TT into a Rolls ss412 RCA switcher. Out of there, I switch between a Pro-Ject Tube Box and Parks Audio Waxwing. The waxwing runs to my DAC and the Tube box to Schiit Freya preamp. The preamp then feeds a Marantz 2230 and everyone's favorite Chinese monoblocks. Switching between amps and speakers is then handled by the Neohippo.

The fun is being able enjoy different ends of the spectrum. Vintage and modern, while also limiting the wear and tear on the family heirloom, the 2230. I do want to stress this: everything sounds great! And I notice no sound degradation with the switching.

But I am wondering... What would be the most proper way of grounding everything? Do I need to just ground to the phono preamps? Or should I then also make a run from each phono preamp to the preamp? What about the amplifiers?

Open to any and all, even creative ideas. Relatively handy with a soldering iron.

Thanks!

 

[SIY]

Are you having a hum/buzz issue?

 

[ppdl3]

Are you having a hum/buzz issue?

Yes. Not terrible, but present. I "split" the ground wire coming from the TT to each of the preamp terminals, but nothing else.

 

[ppdl3]

Not that there seems to be much interest in this topic, but I solved the issue with quite a bit of trial and error and many permutations of connections. I daisy chained all grounds, from TT, to Preamps, and even the amplifiers, but the main kicker was grounding the RCA switcher. Just connected to a screw holding case together.

 

[HaveMeterWillTravel]

Not that there seems to be much interest in this topic, but I solved the issue with quite a bit of trial and error and many permutations of connections. I daisy chained all grounds, from TT, to Preamps, and even the amplifiers, but the main kicker was grounding the RCA switcher. Just connected to a screw holding case together.

I would suspect that internal to the Rolls there is poor continuity on the RCA's "ground" path. Similar but no where near as bad as barely inserting an RCA so just the center pin is connected. By tying the chassis of it to the components, you've provided an alternative electrical path for the currents on the shield.

 

[Canyoncruz]

Hello, I need some clarification on a phono preamp with separate power supplies. The preamp chassis uses a 10:1 transformer and the it also utilized and output transformer. This is where I am getting stumped. Whist this config, how do I ground the signal and regulated power. Do I need ground loop breakers. Aslo, I am using Pete Millet's amp sequencer board the turn things on, What do I do with its ground. Please see block diagram. And suggestions more then welcome

 

[AnalogSteph]

My, that's a lily-gilding exercise if I've ever seen one. Dual mono everything in a phonopre, really? Why? The quest for an outboard power supply is still understandable if you've got vacuum bulbs in there, but then I don't see a heater supply? And a 16-conductor power cable? Good luck finding something suitable. (And why do you even think you need a power sequencer?) What exactly is your plan for this monstrosity?

At least you've already spec'd output transformers, which are going to come in handy for the RCA outputs on the IEC Class I device. (Keep at 90° angles relative to each other.) You'll need RF bypass caps (about 10 nF typ) between RCA ground and chassis ground everywhere. I would also consider going transformer-coupled on the XLR outputs but you might have difficulty spacing / orienting all these transformers adequately.

Give your phono arm ground about a 1k || 100 nF in series, that's plenty low enough impedance for a bit of electrostatic shielding.

The 10:1 is an MC step-up, I assume? Are you sure you can do better with that than with an active preamp circuit? One of these things would buy a whole bunch of low rbb' transistors...

I would put my star ground in the amplifier enclosure and connect to chassis ground there (if nothing else, that would simplify the power cable situation a fair bit). I would prefer to keep my power and signal ground returns separate if the audio PCB allows, but that's down to the specifics of the PCB design.

 

[Canyoncruz]

My, that's a lily-gilding exercise if I've ever seen one. Dual mono everything in a phonopre, really? Why? The quest for an outboard power supply is still understandable if you've got vacuum bulbs in there, but then I don't see a heater supply? And a 16-conductor power cable? Good luck finding something suitable. (And why do you even think you need a power sequencer?) What exactly is your plan for this monstrosity?

At least you've already spec'd output transformers, which are going to come in handy for the RCA outputs on the IEC Class I device. (Keep at 90° angles relative to each other.) You'll need RF bypass caps (about 10 nF typ) between RCA ground and chassis ground everywhere. I would also consider going transformer-coupled on the XLR outputs but you might have difficulty spacing / orienting all these transformers adequately.

Give your phono arm ground about a 1k || 100 nF in series, that's plenty low enough impedance for a bit of electrostatic shielding.

The 10:1 is an MC step-up, I assume? Are you sure you can do better with that than with an active preamp circuit? One of these things would buy a whole bunch of low rbb' transistors...

I would put my star ground in the amplifier enclosure and connect to chassis ground there (if nothing else, that would simplify the power cable situation a fair bit). I would prefer to keep my power and signal ground returns separate if the audio PCB allows, but that's down to the specifics of the PCB design.

Hello AnalogSteph. Thank you for replying. This circuit is Sys' HMN phono pre which utilizes a pentode and a triode. Hence the two different HY values. The LV is the heater voltage powering both tubes and raised with a bias voltage at the "0" point. At the RCA and XLR I have a PCB with each switched thus providing their own termination ( see below - excuse my schematic skills). In and Out share their respective transformers.

Question, I am planning on using the umbilical shield for the chassis to chassis ground, should I raise the Q of this as you illustrate for the tonearm also?

As for the amplifier ground, Since I am using the in/out transformers, is a signal ground needed if the Power is tied to the chassis?

 

[SIY]

Hello AnalogSteph. Thank you for replying. This circuit is Sys' HMN phono pre which utilizes a pentode and a triode. Hence the two different HY values. The LV is the heater voltage powering both tubes and raised with a bias voltage at the "0" point. At the RCA and XLR I have a PCB with each switched thus providing their own termination ( see below - excuse my schematic skills). In and Out share their respective transformers.

Question, I am planning on using the umbilical shield for the chassis to chassis ground, should I raise the Q of this as you illustrate for the tonearm also?

As for the amplifier ground, Since I am using the in/out transformers, is a signal ground needed if the Power is tied to the chassis?

If you follow the grounding guidelines in the article, the preamp will be extremely quiet and hum-free. I used a single raw supply, a single heater supply, then just separate B+ regulators.

 

[Canyoncruz]

If you follow the grounding guidelines in the article, the preamp will be extremely quiet and hum-free. I used a single raw supply, a single heater supply, then just separate B+ regulators.

Thank you Sy. I posted a couple of questions on your site but never heard back. Figured you were off enjoying retirement. Ha! BTW. The board are all built and working but not as a complete components. I am designing the chassis (I am an optical mechanical guy) and don't want to pull the plug units i know the complete layout.

 

[SIY]

Thank you Sy. I posted a couple of questions on your site but never heard back. Figured you were off enjoying retirement. Ha! BTW. The board are all built and working but not as a complete components. I am designing the chassis (I am an optical mechanical guy) and don't want to pull the plug units i know the complete layout.

"Retirement" lol. I'm working three jobs.

In all seriousness, I didn't see your questions, but I was so inundated with spam, I turned the comments off. Love to see what you have in mind for the chassis layout. Mechanical design has never been a skill of mine. In any case, the ONLY thing which should be directly connected to the chassis is safety ground. The audio and power supply grounds are connected together, but held off the chassis ground by either a parallel RC or a pair of paralleled diodes connected head-to-tail. In my hardwired version, the order of grounds was done the way I indicated in the schematics- this was basically incorporated into the PCB version (Jack Walton designed them).

 

[Canyoncruz]

"Retirement" lol. I'm working three jobs.

In all seriousness, I didn't see your questions, but I was so inundated with spam, I turned the comments off. Love to see what you have in mind for the chassis layout. Mechanical design has never been a skill of mine. In any case, the ONLY thing which should be directly connected to the chassis is safety ground. The audio and power supply grounds are connected together, but held off the chassis ground by either a parallel RC or a pair of paralleled diodes connected head-to-tail. In my hardwired version, the order of grounds was done the way I indicated in the schematics- this was basically incorporated into the PCB version (Jack Walton designed them).

Here are my initial layouts. There amp contains regulators for HV and also for +/- LV for heaters.. The layout is pening the grounding scheme. I am probably going to switch sides with the audio boards and the umbilical connector. The HMN board I also bought from Jack. I will be able to switch from RCA to XLR in and out. I also added a pot for adjustable load resistance from 40 yo 5400 Ohms. One of my questions on your site was why you chose the value you did as I am using the same Denon cartridge. Denon says use 40 Ohm with a step up trans and the common value is 100 Ohm.

For the power supply I added a transistor and resistor to bleed the capacitors on turn-off in the HV section The turn- on sequencer is from Pete Millet. It also has indicator lamp drivers. I added a PCB ( Not yet fabricated) for DC Blocking, Ground loop breaking and to power a mains on indicator lamp or LED.

On your site I mentioned: I found this newer 1.5 Vf, IR emitter, it has the same I-V curve (slope resistance?) as the HLMP-6000. The other queation was about the encapsulation compound your colleue used on the DL103. Was it off the shelf or a mad scientist formulation?

For the ME stuff, I use Solidworks and have serveral of the Italian Company HiFi2000's chassis 3D modeled. If anyony wants a model. Hit me me up. Sy, if you ever need hepl with your chassis, hit me up. I would be more then happy to aid or knock somthing out

 

[SIY]

One of my questions on your site was why you chose the value you did

I used a square wave with the same source impedance as the Denon (I think it was 14R?) and adjusted the load resistor to get the best response. Note that this value is specific to the Sowter stepup I used. For other transformers, I described the method in the article.

The other queation was about the encapsulation compound your colleue used on the DL103. Was it off the shelf or a mad scientist formulation?

Long enough ago that I remember nothing about that.

Hit me me up. Sy, if you ever need hepl with your chassis, hit me up. I would be more then happy to aid or knock somthing out

Thanks so much! I've pretty much given up on phono, but I have a high performance tube power amp in mind...