read D.Joffe for explanation and solution for multichannel sources into multichannel receivers (Power Amplifiers) that have a ground loop between the interconnects.
Just recently someone posted a sch showing this for a pre-amp input, where it's use is just as valid.
This was the first time I had seen the solution applied to a pre.
I actually never build this sch myself, so never mind about the correctness of that sch. But the problem with RCA interconnect cable is real. It does not matter how perfect your ground loop is, there remain 5% of problem remains as shared here #25 Humming sound in stereo amplifier | Page 2 | All About Circuits
Where I am talking about is exactly this remaining 5%. If 1 ohm ground lift resistor is omitted, you can hear 100/120 hz and spike along with 50/60 hums, that makes it more objectionable, ever the level is only slightly higher. First your amp must be quite sensitive to be able to hear. My OTL amp overall gain is over 100, it is dead quiet as gain is slightly reduced. So I guess ST70 sensitivity is also very good so hum buzz can be heard, I got < 30mV 50 hz hum in output now with 1 ohm resistor lift, , but no additional 100 hz and spike and buzz, the reason is due the high gain of front-end. If all these hums are below your amp sensitivities it's probably does not matter but can not say there isn't any problem? So appreciate review your options please see if you can identify it yourself?
Last edited:
if i were in front of your actual setup, i would be able to fix that in half of half an hour....
i am confronted with issues in my builds, but i usually get over them in no time.....
i have said all i can, the rest is up to you....
if i were in front of your actual setup, i would be able to fix that in half of half an hour....
i am confronted with issues in my builds, but i usually get over them in no time.....
i have said all i can, the rest is up to you....
HBRL and HBRR as the link to Dannel's article is interested I wish I could also sim the problem myself, I believe there is a difference in HBRL and HBRR and mine I already suspected ground lift the screen on both cable is not quite enough.. thanks for all the infoes.
Koo, you are not alone in not recognising the need for HBRR/HBRL.
You are also not alone in putting the added resistor in the wrong location.
Bonzai has it wrong in his amplifier wiring guide. He also has it wrong in the NX pdf build guide.
Yet whoever designed the layout of the NX PCB actually put the HBRR in the correct location even though this is different from the published schematics.
You are also not alone in putting the added resistor in the wrong location.
Bonzai has it wrong in his amplifier wiring guide. He also has it wrong in the NX pdf build guide.
Yet whoever designed the layout of the NX PCB actually put the HBRR in the correct location even though this is different from the published schematics.
I have added added resistor in wrong place? Ya in the begin I repeat others mistake, but my later mod will catch up because I have real thing in-front of me, I believed mine have fixed both HBRR/HBRL and RCA ground loop in one go (1 ohm), and the OTL amp hum fixed, take me many months to find a reasonable solution for RCA interconnect. It's not HBRR/HBRL problem to begin with it was when I put in both RCA cable. Again your're able to differential them, good, but pay attention to the actual issue applied and don't comment beyond the core issue of RCA interconnect say from DAC player (Although HBRR/HBRL is off the issue, I still thank for the comment and help!), or do you mean they're the same problem?
I think you do, you just raised more questions than answer: I asked again if you can't answer don't bother though.
question or statement?
no question here so show what you are referring to
no question. I don't understand.
again no question and I don't understand.
who do you want to pay attention?
you don't want comment about HUM and BUZZ. They are the topic !
I did not comment on a DAC schematic, did you post information to allow comment to be posted?
is this a request for comment/help?
That is a question- What is the same problem?
As I stated I don't understand what you are writing.
yes, but i do read it, nothing about D.Joffe, but do you think there is a lot more info I need to fix the problem? You could provide a link or summary what it's all about, please "don't raise more info than fix"
Chopchip managed to read it and thanked me.
You are doing nothing to help yourself !
Last edited:
How do know mine is not fixed? You can credit to yourself for a simple thank, if that is enough for you then why discredit me??
Edit: I thought he mentioned 1 (1.5) ohm resistor did you mention it?
Last edited:
It is not that simple. The single resistor solution is just not good. Take the example from post 14. It does very little to prevent ground loop currents, plus the input and output interconnects are parallel to the resistor. The audio signal will return via the interconnects (and PE) instead of the resistor.
You should not just insert resistors and believe all is good just because the hum is reduced. You need to know at what cost.
You should not just insert resistors and believe all is good just because the hum is reduced. You need to know at what cost.
Attachments
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.