Inside High End Equipment

[Milt99]

On 1/26/2018 at 6:11 PM, elcorso said:

 

Then guess this one:

 

 

Roch

Well, not a cd player or power amp although it does have a lot of caps but the transformer is kinda little.

I'm gonna guess pre-amp.

[gmgraves]

12 hours ago, Sam Lord said:

Sure, but you aren't accounting for parts quality.  If the Parasound had bulk-foil resistors and polystyrene caps, it would have been a bargain.  But as you said, it really isn't: I don't expect the Parasound to have better devices than the Schiit.

 

 

Neither do I

[Ralf11]

12 hours ago, Sam Lord said:

 

Geez, why not just pour a big slurry onto the inner walls and call it good?  So much bling machining here; I'd rather have the mass and inelasticity of concrete with a good filler.  

 

 

if it is Al, which some speakers are now using, then it should be a lot lighter and easier to move around

[sandyk]

4 hours ago, Speedskater said:

There is nothing high impedance about  a LM317 regulator circuit.

 

 You are missing the point. Although the 0 volts from the PSU itself may not be earthed, the metalwork that the heatsink is bolted to may very well be earthed. This results in some capacitive coupling from  0volts to mains earth, as well as between  regulators that may be sharing a large heatsink, even if isolating washers are used.

[Speedskater]

In most hi-fi components, the:

• DC supply common @ 0V
• the audio circuit common
• the Safety Ground/Protective Earth
• the chassis

All have continuity from one to another. Nothing high impedance about that.

[sandyk]

31 minutes ago, Speedskater said:

In most hi-fi components, the:

• DC supply common @ 0V
• the audio circuit common
• the Safety Ground/Protective Earth
• the chassis

All have continuity from one to another. Nothing high impedance about that.

Not so.

 The transformer may be bolted to a metal chassis which is earthed for protective purposes, however many linear PSU powered devices do not have the  0 volts connected to the Safety ground. This includes many Preamplifiers, DACs etc. that may have their 0 volts side connected via their Interconnects to the Input of a Power Amplifier which may be earthed and provides the earth reference for them.

 

For example :

[STC]

Counterpoint Hybrid Amp.

 

 

[sandyk]

6 minutes ago, STC said:

Counterpoint Hybrid Amp.

 

 It might work well, but it looks like a rat's nest ! 

[STC]

You haven't seen inside a Surpratek yet! That's a snake pit.:)  My preamp's picture must be somewhere. Will post it soon. 

[elcorso]

19 hours ago, Milt99 said:

Well, not a cd player or power amp although it does have a lot of caps but the transformer is kinda little.

I'm gonna guess pre-amp.

 

I posted after this, it's a pre-amp.  A 100 watts one for a 30 watts power consumption.

 

Roch

[Speedskater]

19 hours ago, sandyk said:

Not so.

 The transformer may be bolted to a metal chassis which is earthed for protective purposes, however many linear PSU powered devices do not have the  0 volts connected to the Safety ground. This includes many Preamplifiers, DACs etc. that may have their 0 volts side connected via their Interconnects to the Input of a Power Amplifier which may be earthed and provides the earth reference for them.

You are mixing several different functions.

* * * * * * * *

Wha do you mean by this provides the earth reference for them part?

[sandyk]

18 minutes ago, Speedskater said:

You are mixing several different functions.

* * * * * * * *

Wha do you mean by this provides the earth reference for them part?

 No.

 I was referring here to the  0 volts reference ("earth" side)  of the signal connections.

 In many cases the Class A/AB Power Amplifier is earthed at it's PSU's  0 volts.  In quite a few designs the Power amplifier's  inputs use earth lift resistors (10 ohms etc.) to help prevent ground loops.

 This 10 ohms "earth" reference then goes back via the Interconnects shield, in the case of a coax type Interconnect to the 0 volts of the previous component. In my own system this 10 ohms  earth/ 0 volts  reference is extended back through the Preamp to the DAC. Neither the DAC (as previously shown in the PSU schematic that I posted) or the Preamp are connected to mains earth via their PSUs, although the DAC's case is earthed via it's 3 pin IEC mains lead. .

[Speedskater]

So let's clarify some of this:

• Safety Ground. The Safety Ground is connected to the chassis near where the AC cord enters the chassis.  Exceptions being double insulated chassis (square with-in a square safety symbol) and wall-warts. The Safety Ground then makes its way back to the main breaker panel where it is connected to the Neutral.
• Ground Rod. The ground rod is also connected to the Neutral at the main breaker panel (some locations have other methods).  But because the ground rod has no impact on day-to-day AC power quality, it is of little further interest to us.
• DC Supply Common. The DC common is connected to the chassis of the unit it is powering at a single point. This is the same point as the audio circuit common.
• Audio Circuit Common.  The audio circuit common is connected to the chassis at a single point near the signal input jacks. (the same point as the DC common). Sometimes there is a low value resistor network between the commons and the chassis.

Note that there is continuity between all these things, but each has it's own function.

[sandyk]

29 minutes ago, Speedskater said:

DC Supply Common. The DC common is connected to the chassis of the unit it is powering at a single point. This is the same point as the audio circuit common.

 

Not necessarily. This was clearly shown in the schematic of the DAC PSU that I previously posted.

[Speedskater]

But Sandy, that's exactly what I wrote:

DC Supply Common. The DC common is connected to the chassis of the unit it is powering at a single point. This is the same point as the audio circuit common.

The DC is not connected to the DC supply chassis. It's attached to the chassis of the audio component.

[sandyk]

1 hour ago, Speedskater said:

But Sandy, that's exactly what I wrote:

DC Supply Common. The DC common is connected to the chassis of the unit it is powering at a single point. This is the same point as the audio circuit common.

The DC is not connected to the DC supply chassis. It's attached to the chassis of the audio component.

 

 I give up !

 Are we even speaking the same language ?

Are you able to read electronic schematics ?

The use of the word "chassis" appears to be a problem here. Perhaps you are talking about a sub-chassis (which isn't usually needed)  inside the main chassis with it's transformers etc, but electrically isolated from the main chassis ?

 

[gmgraves]

On 1/30/2018 at 4:12 PM, sandyk said:

Not so.

 The transformer may be bolted to a metal chassis which is earthed for protective purposes, however many linear PSU powered devices do not have the  0 volts connected to the Safety ground. This includes many Preamplifiers, DACs etc. that may have their 0 volts side connected via their Interconnects to the Input of a Power Amplifier which may be earthed and provides the earth reference for them.

 

For example :

Tell Me Alex, is their some reason why this design has the chassis ground (earth), the ±15 volt supply return and the 5 volt ground all isolated from one another? I would think that this arrangement would be an invitation to ground loops.  I would tie all the grounds together starting with the center tap of the power transformer secondary

[Speedskater]

2 hours ago, sandyk said:

Are we even speaking the same language ?

I try to write in American engineering English (with a few British words added).

 

2 hours ago, sandyk said:

Are you able to read electronic schematics ?

With over a half century experience in broadcast engineering, recording engineering and industrial R & D electrical / electronic engineering I think that yes I can read schematics.

 

3 hours ago, sandyk said:

The use of the word "chassis" appears to be a problem here.

I think that it's the word 'ground' that is the problem. I try to use specific technical meaning for words.

"chassis" refers to the metal enclosure or base of whatever unit we are talking about at that moment.

[Speedskater]

1 minute ago, gmgraves said:

Tell Me Alex, is their some reason why this design has the chassis ground (earth), the ±15 volt supply return and the 5 volt ground all isolated from one another?

The power supply drawing is completely correct. The DC grounding is taken care of at the audio circuit end.

Don't know if this supply is in the same enclosure as the audio circuit or not?

* * * * * * *

does 'sandyk' = Alex?

 

 

[sandyk]

51 minutes ago, Speedskater said:

The power supply drawing is completely correct. The DC grounding is taken care of at the audio circuit end.

Don't know if this supply is in the same enclosure as the audio circuit or not?

 

Attached is a partial photo of the original Silicon Chip magazine DAC.

 My heavily modified version is DC coupled using 2 transformers , and connected to my Class A Preamp with both active and  0volts of the DAC's L and R outputs switched through the Preamp. The Preamp's output is also DC coupled , and connects to the Input of my 15W Class A Amplifier, which is also direct coupled, with no capacitors in the signal or Feedback paths.

Both the Preamp and 15W Class A have their separate toroidal transformers in a 2U rack case below the  Power Amplifier.

The Preamplifier is supplied 2 x 18-0-18VAC from it's 2 transformers, and the 15W Class A has 2 separate regulated +20 and -20V PSU PCBs in this 2U rack case also.

 

To answer George about earth loops.

 I have to use a low noise 10 x preamp ahead of my CRO at maximum sensitivity to see little more than a thickened trace from the Preamp's output at it's maximum gain of 3.2, which appears to be VERY low level SMPS rubbish from the nearby TV.

[STC]

 NAD C372 Integrated Amp

 

 

[Superdad]

4 hours ago, Speedskater said:

does 'sandyk' = Alex?

 

Yes, “sandyk” is Alex K.

 

Not to be confused with me, Alex C.

[gmgraves]

14 hours ago, sandyk said:

To answer George about earth loops.

 I have to use a low noise 10 x preamp ahead of my CRO at maximum sensitivity to see little more than a thickened trace from the Preamp's output at it's maximum gain of 3.2, which appears to be VERY low level SMPS rubbish from the nearby TV.

 after I queried you about the ground (or earth, if you prefer) loop issue, I thought about it further, and I realized that the 5 volts is for the digital circuitry in the DAC and the ±15v is for the analog circuitry, and I can see the need to keep those two supplies isolated one from the other as much as is practical. But surely, the 5v earth and the chassis earth are common to one another. How could it be otherwise?  

[sandyk]

2 hours ago, gmgraves said:

 after I queried you about the ground (or earth, if you prefer) loop issue, I thought about it further, and I realized that the 5 volts is for the digital circuitry in the DAC and the ±15v is for the analog circuitry, and I can see the need to keep those two supplies isolated one from the other as much as is practical. But surely, the 5v earth and the chassis earth are common to one another. How could it be otherwise?  

 

 No George, there is NO connection in the DAC between +5V " earth" side ( 0 volts) and chassis !

I actually use 2 PSU PCBs and 2 transformers for powering this DAC instead of the original single PSU PCB and transformer, for improved isolation between Analogue and Digital areas of my DAC.

The PW5 resistors (different values) are used to balance the currents drawn by both +Ve and -Ve sides of the PSU PCBs better,

to help avoid switch off " plops" .(similar voltage decays on both supply rails at shut down)

[Shadders]

On 31/01/2018 at 8:48 PM, sandyk said:

 

Not necessarily. This was clearly shown in the schematic of the DAC PSU that I previously posted.

Hi Alex,

I think what you are saying as per the schematic, is that the incoming power earth connection is connected to the metal case of the DAC

 

The 0volts on the secondary side of the transformer, is NOT connected to the metal case of the DAC - even though it has an earth symbol on the 0volts line.

 

As such, the 0volts of the DAC circuit power supply is floating when compared to the incoming power IEC earth connection.

 

Is the above correct ?

Regards,

Shadders.