@redjr,
After reading about your subwoofer hum, I tried using both sets of Yarra outputs with a combination of four different amps and a Martin Logan DEPTHi subwoofer. The two sets of speakers used have efficiency specs of 99dB and 84dB.
First: V4H and IcePower class D
Second: 6L6 tube amp and USSA5
These combinations acted normally, no additional noise when both outputs were used simultaneously and dead silent when idling. The tube amp inherently has a very faint hum that’s audible on the 99dB speakers but not so with the 84dB speakers and that didn’t change.
Then I connected the subwoofer to output#2 and an amplifier to output#1. I tried each amp with the sub and all sounded beautiful. Actually, I haven’t listed with a powered sub in quite some time, it’s a very different listening experience
Since everything went very smooth with this experiment, I’m probably just as confused as you are as to where your getting the “hum” from. Is there a possible ground loop being introduced from the subwoofer? Do all your power cords have the ground pin intact? I’m just throwing some ideas out......
After reading about your subwoofer hum, I tried using both sets of Yarra outputs with a combination of four different amps and a Martin Logan DEPTHi subwoofer. The two sets of speakers used have efficiency specs of 99dB and 84dB.
First: V4H and IcePower class D
Second: 6L6 tube amp and USSA5
These combinations acted normally, no additional noise when both outputs were used simultaneously and dead silent when idling. The tube amp inherently has a very faint hum that’s audible on the 99dB speakers but not so with the 84dB speakers and that didn’t change.
Then I connected the subwoofer to output#2 and an amplifier to output#1. I tried each amp with the sub and all sounded beautiful. Actually, I haven’t listed with a powered sub in quite some time, it’s a very different listening experience
Since everything went very smooth with this experiment, I’m probably just as confused as you are as to where your getting the “hum” from. Is there a possible ground loop being introduced from the subwoofer? Do all your power cords have the ground pin intact? I’m just throwing some ideas out......
Thanks Vunce for verifying at your end all worked properly. Part of my issue is that no music is coming through the sub. (I've tried 2 different ones, and different cables.@redjr,
After reading about your subwoofer hum, I tried using both sets of Yarra outputs with a combination of four different amps and a Martin Logan DEPTHi subwoofer. The two sets of speakers used have efficiency specs of 99dB and 84dB.
First: V4H and IcePower class D
Second: 6L6 tube amp and USSA5
These combinations acted normally, no additional noise when both outputs were used simultaneously and dead silent when idling. The tube amp inherently has a very faint hum that’s audible on the 99dB speakers but not so with the 84dB speakers and that didn’t change.
Then I connected the subwoofer to output#2 and an amplifier to output#1. I tried each amp with the sub and all sounded beautiful. Actually, I haven’t listed with a powered sub in quite some time, it’s a very different listening experience
Since everything went very smooth with this experiment, I’m probably just as confused as you are as to where your getting the “hum” from. Is there a possible ground loop being introduced from the subwoofer? Do all your power cords have the ground pin intact? I’m just throwing some ideas out......
) Both sets of outputs play fine to regular power amps and speakers. I'm going to do more testing tomorrow, but even with the obvious "hum", you'd think the low frequencies would be coming through. They simply are not. It almost seems like there's a completely open circuit going to the sub. All of my power cables use standard IEC plugs, and my 20amp circuit wall sockets are all grounded properly. This is the very first time anything like this has surfaced. Urgh!Edit! I just had a moment of possible enlightenment. All of the subs I've ever owned use 2-prong plugs, with no ground lug. This may be by design to (maybe) avoid a ground loop? I wonder if this fact is contributing to this 'hum' issue? The Yarra is the first pre that doesn't seem to ground the physical chassis. The RCA connectors themselves provide an audio ground to the chassis I believe, but no earth ground? I could be wrong since the pre is in my rack still and not on my bench, so I can't take my DVM and check different ground continuities.
@X Is the audio ground 'floating' with this pre? Is it tied to earth ground anywhere? (I hope that's not a stupid question!) I just thought of another thing in how I mounted my IEC connector to the chassis. I can't verify until the morning. I'll post my findings.
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Yes. This is only connected to the IEC socket on the PSU board. Both the PSU and Yarra MB PCBs are elevated on 5MM nylon standoffs. They are not grounded to the chassis.
Edit: Correction. RCA jacks NOT in contact with chassis. Nylon fittings.
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Both subs I tested with are commercial subs. My theory is it's a grounding issue with the pre. Somethings up there.
Redjr,
I just noticed your edit to the post. The Yarra chassis is most definitely tied to earth ground. You do not need to support the motherboard or the PSU board with nylon or plastic standoffs. None of the support holes on the motherboard have any connection to a ground plane they are isolated. There is a single mounting hole next to the AC inlet power module on the PSU board that has a metal ring, that is your connection for earth ground to chassis. Drilling the support holes for the IEC plug also created another ground path. (I also drilled support holes, but do not have any negative effect)
Your RCA grounds connect to chassis ground through the ground loop breaker on the motherboard. If checked with your DMM, all RCA grounds to chassis should show 5-7ohm resistance.
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If no sound at all comes out of the sub, I doubt it is a ground “loop” issue, but maybe a reverse polarity ground on +ve input issue. That is, the output of the Yarra is going straight to ground when the sub is connected. Does sound still come from the main channels amp connected to the other output?
To check, use DMM and measure ohms conductivity between output at Yarra RCA out and ground (should be 680R or whatever the output bleed resistor is). When connecting the sub, I bet it shows circa 0 ohms. Sometimes, this can be caused by the reverse of the +ve and -ve leads on the sub’s RCA jack.
To check, use DMM and measure ohms conductivity between output at Yarra RCA out and ground (should be 680R or whatever the output bleed resistor is). When connecting the sub, I bet it shows circa 0 ohms. Sometimes, this can be caused by the reverse of the +ve and -ve leads on the sub’s RCA jack.
Yes
I'm getting circa 5ohms between RCAs and ground - regardless of the sub being plugged in or not. However, I've got something more elusive going on with my rack. When I moved the pre and sub back into my shop the sub works correctly. So there's an issue with something on my rack/power. What, I don't know yet. I'll track it down this morning..
Thanks to X and Vunce for their troubleshooting assistance.
My recently built USSA5 with single SLB was giving me a lot of ground looping hum issues, so I decided to switch over to twin SLB powering the USSA5 as a twin monobloc inside one chassis. Hum issues were quickly resolved, so my USSA5 was super quiet, no hums and no hiss at all.
The moment I plugged in my Yarra preamp, my right channel will hum faintly with my ear to the speaker. I know something is not right in my Yarra's build. I remove both Yarra's pcb to change out all brass standoff to plastic ones, with the exception to the one as shown in the pic below.
On the other preamp pcb, the ground was tie to a thick green cable with NO standoff below it, and it was connected to the main IEC socket's ground tab. This was advised by Vunce.
Put everything back in order, and the same hum still exists on the left channel.
Many more days were spent on troubleshooting the hum issue, then I realized where my mistake was.
When I initially build this preamp, I got magic smoke out on my first powering up, it was caused by all the star nuts that I used, they are bigger in diameter and contacted the VIA ground plain around the standoff.
After replacing those star nuts, the preamp starts singing till today. Little that I know, the 4-star nuts were still used to hold the RCA input pcb, so again they touched the ground VIA and thus the grounding loop issue on my right channel.
Since exchanging out the 4-star nuts on the RCA pcb, all the hums were gone, both Yarra and USSA5 are silent at Max volume!
Lastly, I changed out those big output coupling caps for smaller value as it was not intended for headphone usage at all.
I hope the above can help others in some way when they are building their Yarra.
Note: You do not need to use plastic standoffs, just make sure they stay within and not touches VIA ground plain.
The moment I plugged in my Yarra preamp, my right channel will hum faintly with my ear to the speaker. I know something is not right in my Yarra's build. I remove both Yarra's pcb to change out all brass standoff to plastic ones, with the exception to the one as shown in the pic below.
On the other preamp pcb, the ground was tie to a thick green cable with NO standoff below it, and it was connected to the main IEC socket's ground tab. This was advised by Vunce.
Put everything back in order, and the same hum still exists on the left channel.
Many more days were spent on troubleshooting the hum issue, then I realized where my mistake was.
When I initially build this preamp, I got magic smoke out on my first powering up, it was caused by all the star nuts that I used, they are bigger in diameter and contacted the VIA ground plain around the standoff.
After replacing those star nuts, the preamp starts singing till today. Little that I know, the 4-star nuts were still used to hold the RCA input pcb, so again they touched the ground VIA and thus the grounding loop issue on my right channel.
Since exchanging out the 4-star nuts on the RCA pcb, all the hums were gone, both Yarra and USSA5 are silent at Max volume!
Lastly, I changed out those big output coupling caps for smaller value as it was not intended for headphone usage at all.
I hope the above can help others in some way when they are building their Yarra.
Note: You do not need to use plastic standoffs, just make sure they stay within and not touches VIA ground plain.
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How is this situation remedied? Since the pre and sub worked together fine in my shop and not in my listening room, does it point to internal house wiring that may be amiss? I have a lot of other gear connected to the same outlets/circuit, and have been working fine for the past 5 years. I've never had this issue raise it's ugly head before.
Thanks so much for the detailed explanation, Meanie! I will link this post to the first page.
Redjr, that is very puzzling. So I did not realize that they actually worked together fine in the shop. What is different when they are connected together in listening room?
Can you connect just the pre and the sub together and nothing else? Use a phone to RCA as a source to keep the source isolated from any potential wall plug issues. Only Yarra and sub plugged into wall.
If that works, slowly add one component at a time to the system and check to see if sound keeps working.
Process of elimination to find the bad actor.
Redjr, that is very puzzling. So I did not realize that they actually worked together fine in the shop. What is different when they are connected together in listening room?
Can you connect just the pre and the sub together and nothing else? Use a phone to RCA as a source to keep the source isolated from any potential wall plug issues. Only Yarra and sub plugged into wall.
If that works, slowly add one component at a time to the system and check to see if sound keeps working.
Process of elimination to find the bad actor.
Thanks for your suggestions X.
Okay, I found the bad actor, or should I say bad jack! Even without anything plugged into the Yarra, including the power cord, except the cable to the sub, when I plugged in the sub I got the loud hum. So in my mind this eliminates any AC related issues and the sub and the LINE cable to the sub.
I did the above test - in my listening room - using only the LEFT channel RCA jack of pre OUTPUT #2. I then plugged the sub cable into the RIGHT RCA jack of out #2, and did not get the hum. So, there must be either a solder issue with the LEFT jack of out #2, or it is defective in some way. But, I don't know how that is possible since I used the OUTPUT set #2 with an amp and everything played fine with NO hum. Now I'm really confused.
I then plugged the pre into the wall, and into my amp and using an MP3 player had music and the desired bass from the sub. Hurray! But, I'm not out of the woods yet.
I will pull the I/O board and check the suspect jack and see what looks amiss and try to correct it. This is really bizarre. I'm going to need to do more investigating back on the bench and double-check again if when using both jacks of OUTPUT #2 I get no hum.
I'll keep you posted. What fun it is building and trying to get online a new pre!
Spare Yarra I/O PCB ?
Hi X,
I've traced my grounding issue to my rear panel output jacks I installed. Would it be possible to buy just the I/O PCB, or do I need to purchase a complete set of boards? If you happen to have a spare one around your shop that you're not using, I would be happy to pay you for it. I don't want to dismantle the I/O PCB just yet, until I know whether, or not a replacement is available. If one isn't, I'll have to go to plan B.
With my testing today, I've found that 2 of the 4 output jacks are not grounded. If you plug in a stereo set of RCA cables to your amp, there is no hum issue, due to a least one ground return being present. But if you plug a single sub cable into the non-grounded output jack, you'll get the hum. This does not render the pre unusable, as I suspect most people are using either set #1, or #2 of the outputs as a stereo pair. And, I can still use it by plugging the sub into the proper, grounded output jack.
I don't know exactly how this particular situation surfaced. I either installed the jacks incorrectly (although I'm not sure how that happen), or they are defective. So, I'm exploring my options on how best I can fix the problem that meets my high standards of build quality.
Let me know.
Hi X,
I've traced my grounding issue to my rear panel output jacks I installed. Would it be possible to buy just the I/O PCB, or do I need to purchase a complete set of boards? If you happen to have a spare one around your shop that you're not using, I would be happy to pay you for it. I don't want to dismantle the I/O PCB just yet, until I know whether, or not a replacement is available. If one isn't, I'll have to go to plan B.
With my testing today, I've found that 2 of the 4 output jacks are not grounded. If you plug in a stereo set of RCA cables to your amp, there is no hum issue, due to a least one ground return being present. But if you plug a single sub cable into the non-grounded output jack, you'll get the hum. This does not render the pre unusable, as I suspect most people are using either set #1, or #2 of the outputs as a stereo pair. And, I can still use it by plugging the sub into the proper, grounded output jack.
I don't know exactly how this particular situation surfaced. I either installed the jacks incorrectly (although I'm not sure how that happen), or they are defective. So, I'm exploring my options on how best I can fix the problem that meets my high standards of build quality.
Let me know.
For those members following this thread, and in particular my build travails, the RCA jacks I used were these from Audiophonics.
For any users who may have used these as well, when I installed them, they only appeared to go in one way. But I can't recall for sure. In looking at the 2 sets of output jacks today, it appears they installed 180 degrees from the set of input jacks. Did anyone experience any issues with installing these?
For any users who may have used these as well, when I installed them, they only appeared to go in one way. But I can't recall for sure. In looking at the 2 sets of output jacks today, it appears they installed 180 degrees from the set of input jacks. Did anyone experience any issues with installing these?