Indeed. And then you get Self’s method etc etc
Probably best to try to understand the pros and cons of each methodology and mitigate accordingly.
Hi Bonsai,
Does HBR values affect to hum level? It seem you are using relatively high values more than 10R as normal.
I'm thinking anti-parallel diodes that usually connect together with HBR. It only operates when V drop through HBR >= Vf. Is it right?
What condition to happen it? It seem NEVER.
Thanks & Regard,
Does HBR values affect to hum level? It seem you are using relatively high values more than 10R as normal.
I'm thinking anti-parallel diodes that usually connect together with HBR. It only operates when V drop through HBR >= Vf. Is it right?
What condition to happen it? It seem NEVER.
Thanks & Regard,
Walkalone, I've used from 3.3 Ohms through to 33 Ohms.
10-15 Ohms seems to work well for me, although I've gotten good results at 3.3 as well.
The anti-parallel diode trick just ensures that if you get a large signal ground potential between two pieces of equipment, when you plug it in, the HBR is protected. If you try to run it with the diodes conducting, you would have problems (hum/noise etc).
The safe value if you must have a number would be 10 Ohms.
10-15 Ohms seems to work well for me, although I've gotten good results at 3.3 as well.
The anti-parallel diode trick just ensures that if you get a large signal ground potential between two pieces of equipment, when you plug it in, the HBR is protected. If you try to run it with the diodes conducting, you would have problems (hum/noise etc).
The safe value if you must have a number would be 10 Ohms.
I surprised no one has mention this option, which is to design a balanced output.
Then there is no power ground requirement. It has benefits over using a balanced input. You don't get 3dB of noise increase as you would with a balance input. Outputs are truly floating. No rectified current on the ground. Downside is the increased cost. But not so bad if you view it as $/watt. This is a different design approach from simply bridging two amplifiers.
Since the output voltage is doubled, one could save money by using a smaller power transformer. Half the voltage.
Then there is no power ground requirement. It has benefits over using a balanced input. You don't get 3dB of noise increase as you would with a balance input. Outputs are truly floating. No rectified current on the ground. Downside is the increased cost. But not so bad if you view it as $/watt. This is a different design approach from simply bridging two amplifiers.
Since the output voltage is doubled, one could save money by using a smaller power transformer. Half the voltage.
Last edited:
I worked an a Sansui AU-X901, it uses un-balanced inputs, but drives the speakers balanced. Uses a transformer for the headphones.
I got the impression from my short testing, that it controls the bass differently, like it is damped better, hard to describe what I hear vs what is really going on.
I got the impression from my short testing, that it controls the bass differently, like it is damped better, hard to describe what I hear vs what is really going on.
Yes. The Sansui is a good example.
When one thinks about the electronics to do this, it's usually quite bit cheaper than the cost of a power supply. These days the power supply might be half the cost or more of the entire amplifier. And if you add shipping cost for all that copper and possibly iron...
When one thinks about the electronics to do this, it's usually quite bit cheaper than the cost of a power supply. These days the power supply might be half the cost or more of the entire amplifier. And if you add shipping cost for all that copper and possibly iron...
Invalid at the frequencies where the cap becomes inductive.
Not isolated sockets should be prefered.
I think that ground loops should not be the main topic when speaking of how to wire up electronics. EMI immunity first. Then, thinking of the impedances between the different ground points inside the chassis and how to lower them as much as possible.
I am doing the inverse since some years. Large success.Originally Posted by brian92fs
Bonsai (and Poldaaudio) - What are your thoughts on Douglas Self's recommendation is chapter 25 of his "Audio Power Amplifier Design" book? He suggests tying the signal input ground to the audio-chassis ground at the input connector. Self says this causes ground loop currents to flow to the chassis ground and then mains ground and not through the loop in Poldaaudio's diagram presented above (Assuming I'm reading it correctly).
That was a big disaster when I tried that 40 years go. Had to go out a buy some extruded plastic washers to isolate the RCA input connectors.
Weak EMI protection then.
Seems you always have a countervailing view forr. It’s good because it makes for an interesting discussion.
I’ve been successfully using the generally accepted view on how to wire an amp for low or zero hum for some years, and deal with RFI.
I am pleased you have found success with your method. Why don’t you post some pictures/ drawings for discussion?
I’ve been successfully using the generally accepted view on how to wire an amp for low or zero hum for some years, and deal with RFI.
I am pleased you have found success with your method. Why don’t you post some pictures/ drawings for discussion?
At the begining of the century, some guys proposed to consider ground problems with master word equipotentiality in mind.
Think of the way to get equipotentiality.
Wonder if there are good reasons :
- for the generally accepted view on how to wire an amp should to be so different from the way to wire laboratory equipements.
- for the potential reference 0V to be elsewhere than at the input socket.
Searching Herve00fr's DiyAudio posts on the topic may help you.
Hervé is much more competent than me and he presents arguments in a far better way than I can.
You know him.
Major misconception that has been perpetuated through the years. (I also once believed that.) A given output power will require a power supply that can deliver that power. Going to a bridged design only trades voltage for current. If you want 200 watts out, that plus the losses MUST come from the power supply.
Fred I don't see where the misconception is. Given the load is the same, the current requirement won't change if the voltage across the load is the same. You can do this with half the supply voltage plus a bit more to make up for losses.
With a non bridged amplifier you can't utilize all the power of the transformer. only half at a time.
With a non bridged amplifier you can't utilize all the power of the transformer. only half at a time.
Your answer is too as I expected. So you do not ignore that there is an approach on wiring which is different from the generally accepted one. What may attract attention is that experiments show its validity.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.