There is a wealth of info on the topic of wiring an amp on this forum. Most of it contradictory and spread all over the place. There aren't many full complete examples too. In the hope of making things clearer, I'm going to post a few schemes that have been suggested... and see what you all think of them.
Here's a first round. First one is very simple, with a focus on keeping signal and return close. Second one is based on what is suggested by the ESP website, with a ground loop breaker and the speaker returns going back to the PS. The third one is another classic, with 10r resistors inserted between signal and power ground on the amp pcb.
What's closest to your favourite ? Why ?
edit: I deliberately decided to make it about a stereo amp as it is a bit more difficult to get right than monoblock.
Here's a first round. First one is very simple, with a focus on keeping signal and return close. Second one is based on what is suggested by the ESP website, with a ground loop breaker and the speaker returns going back to the PS. The third one is another classic, with 10r resistors inserted between signal and power ground on the amp pcb.
What's closest to your favourite ? Why ?
edit: I deliberately decided to make it about a stereo amp as it is a bit more difficult to get right than monoblock.
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hifisonix site gives detailed information too along with info on how to do it practically.
http://hifisonix.com/wordpress/wp-content/uploads/2018/06/How-to-wire-up-an-amplifier_2.pdf
http://hifisonix.com/wordpress/wp-content/uploads/2018/06/How-to-wire-up-an-amplifier_2.pdf
No one from given.
🙂
Try to draw fully-differential power amplifier and, i have no doubt, you will come straight to the answer.
None of the examples are really correct. The third example will protect itself from ground loops but the supply should never be directly chassis grounded. The loop breaker in the second example is better. The capacitor to ground on the input is wrong, this should be part of the input filter of the amplifier itself. Opposing direction parallel diodes can be placed there instead though. The return from the speaker should connect directly to the power supply, not to the amplifier as in example 2.
Thx for the answers and getting the ball rolling. 🙂
@prasi: it's on my to-do-list to translate it to the same format for easy comparaison.
@BesPav: yes, fully-differential (or even bridged) amps have great advantages, I won't deny that. But I'm sticking to the most common kind of amp encountered.
@jwilhelm:
- the cap from shield to chassis doesn't serve the same purpose as the rf input filter on the pcb would (I'm not suggesting to omit that one btw) . As David Davenport mentions here: "4.5 – Input Jacks: The RCA jack of a single-ended connection is usually isolated from the chassis and the shield is connected to the star ground. It may be beneficial to connect a 10nF ceramic capacitor from the shell of the RCA connector (shield) to the chassis. This provides a direct path for RF noise from the shield to the chassis right where the shield enters the chassis."
- Any reason why the speaker return should go to the PS rather than amp PCB ? Doesn't that prevent the feedback resistor to optimally sense the output gnd, as it now connects to it through the PS gnd wire between amp and PS, with all the currents generated by the zobel, bypass caps, etc ?
@FdW: it's an interesting option but once again, I'd rather stay in the realm of the good old dumb stereo amp with no additional circuitry (think blameless, lm3886, symasym, etc).
@prasi: it's on my to-do-list to translate it to the same format for easy comparaison.
@BesPav: yes, fully-differential (or even bridged) amps have great advantages, I won't deny that. But I'm sticking to the most common kind of amp encountered.
@jwilhelm:
- the cap from shield to chassis doesn't serve the same purpose as the rf input filter on the pcb would (I'm not suggesting to omit that one btw) . As David Davenport mentions here: "4.5 – Input Jacks: The RCA jack of a single-ended connection is usually isolated from the chassis and the shield is connected to the star ground. It may be beneficial to connect a 10nF ceramic capacitor from the shell of the RCA connector (shield) to the chassis. This provides a direct path for RF noise from the shield to the chassis right where the shield enters the chassis."
- Any reason why the speaker return should go to the PS rather than amp PCB ? Doesn't that prevent the feedback resistor to optimally sense the output gnd, as it now connects to it through the PS gnd wire between amp and PS, with all the currents generated by the zobel, bypass caps, etc ?
@FdW: it's an interesting option but once again, I'd rather stay in the realm of the good old dumb stereo amp with no additional circuitry (think blameless, lm3886, symasym, etc).
One ohm for the hum breaking resistors plus back to back diodes. For the ground loop breaker 10 - 100 ohm resistor plus high current diodes.
DDRC = Diode||Diode||Resistor||Capacitor
Diode: Depends on place, high current between Chassis and Mains-Ground otherwise a pair of 1N4004's will do.
Resistor: Depends on place, 1 ohm 3 watt wire wound between Chassis and Mains-Ground otherwise 10 ohms low power.
Capacitor: 100nF will do in all cases (I think).
Diode: Depends on place, high current between Chassis and Mains-Ground otherwise a pair of 1N4004's will do.
Resistor: Depends on place, 1 ohm 3 watt wire wound between Chassis and Mains-Ground otherwise 10 ohms low power.
Capacitor: 100nF will do in all cases (I think).
You are susceptible to ground loops and will hear every electrical noise in the building.
Yup. There are so much, that i’m really doesn’t understand SE amps designers.
Oh, why you jailing yourself by somebodys fallacies?
See img#3 for example:
http://www.diyaudio.com/archive/blo...d1460406090-bruno-putzeys-micropre-g-word.pdf
Star ground is normally at the power and output ground. Creating a star ground at the input is not an option.
Mark, I know what is normally done, I'm playing devil's advocate to a degree, did you read the beginning of a discussion on grounding on the john curl thread recently, billsherv is supposed to be starting one on the subject
You still have to be practical. Try moving the star ground to the inputs in the schematics already posted.
Ok, leave the star at the power supply but connect mains earth (PE) and the RCA barrel to the chassis at the same point? a la Doug Self Grounding System In Power Amplifiers - DIY AUDIO BLOG, AUDIO WORKSHOP
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