April 3, 2022 at 5:56 am #24128
I just finished the second speaker of a pair of DINAS, and I have a problem.
So, if I connect both power supplies to the plates, they both have interference noise. I’m guessing this is some kind of ground loop happening. Even if I do not turn on one of the speakers, just having the PSU connected to the board gives noise to the second.
My setup is currently this:
AIYIMA T6PRO tube pre-amp
2x the recommended DTK 19 V, 4.74 A
The plate amp I use is not the one from Lepai, but from nobsound. Everything is identical, in terms of looks, so I guess its the same as the lepai, but just a copy, probably even made in the same place. The problem is that the lepai board here in europe costs the equivalent of 110$, while the nobsound is what is priced equivalently to the lepai in the US.
Do you think that a digital pre-amp would get rid of this problem? Or getting a single power supply for both speakers? (Found a 180W 19 V PSU, I would need to chop the cable and create two pigtails for each DINAS).
Thanks for the input in advance!
April 3, 2022 at 11:24 am #24139
Just an update to clarify that the noise starts once the T6Pro turns on the audio output. Once the receiver knows there is audio to be played, there is an audible click on the pre-amp and the output starts.
I guess there is a relais-shutter inside that turns output on and off and it is at that moment that noise starts, so only when there is a complete loop between both speakers.
Still, my thoughts are that all cathodes get connected together and probably the power supplies work with absolute grounds while the pre-amp works with floating ground. When a single DINAS is connected, everything is fine because wherever the regulation is being made, it all can follow the ground of a single PSU. But when both are connected the regulation cannot follow both absolute sources and things just fluctuate and maybe this is due to a beating between the switching frequencies of the 2 PSUs. This is just all but a supposition, I am not an expert in electronics.
I am a bit afraid of connecting both amplifier plates to the same PSU, because maybe then there will be a different kind of cross-talk between the amps as music is being played and they display impedance fluctuations that affect each other. But maybe I am just being paranoid and it would be totally fine. After all in a normal amp, and also in this amp, all channels have a common voltage input source…so maybe I am just being paranoid.
April 3, 2022 at 3:41 pm #24151
Sounds like the Aiyima is the problem. If you use a different source (physically swapped out for the Aiyima), does it still do the same thing?
Also, if you have a recording/video of the noise, from before it starts to when It kicks in and turns off, that might help to narrow it down.
April 3, 2022 at 6:34 pm #24174
The problem is that this is my first endeavour into the audio world, I did not own any pre-amp or amp before, so I am very limited in things I can try to debug this.
I can also try to get a jack to RCA and connect the DINAS directly to my phone or computer. This will also connect all grounds together so its also a good test to see if its the amps that make the problem.
The aiyima is definitely the one that in the end closes the loop and connects all cathodes together and can’t follow that. But as I said, as there is no noise from using the aiyima and a single speaker, it means that it has no problems dealing with the power supply of the end amplifier. But in the case of the DINAS, being that each uses its own independent power supply, it seems that this is a problem.
As in its current state it is not possible to use both power supplies simultaneously I will try to pigtail one of them and power both speakers with a single PSU and see if this solves the problem. My idea is that this would solve the problem as it isn’t different from connecting both RCA terminals to a single amplification plate using a single PSU (as in both left and right channels will have a common ground, which is the cathode of the PSU).
If I make tests or solve the problem I will make an update.
April 3, 2022 at 11:51 pm #24179
There was an earlier thread with your same problem. The answer to that one was at least one of the power supplies was bad from the manufacturer. I do believe that OP did what you suggested at the end of your first post.
IF you suspect manufacturer defect, will you be trying to send them back for refund or replacement? If not, you can open one up to see if you can find anything obvious, like a cap that is bulging or leaking, or bad solder joints. Quality these days from online suppliers has been subject to sketchiness.
The rough thing about these is that they are switching supplies, not some beefy linear supply with a massive transformer. As such they run the possibility of, as you’ve already explained, being off frequency or out of sync, which causes a beat frequency when you have a common connection between the two.
If the frequency (for you) is either 50 Hz or 100 Hz, then that points to power line issues and a ground lift may help.
Or, if you can add another larger electrolytic cap and maybe a small ceramic cap near the output of the PS. These will help quell ripple and RF.
April 4, 2022 at 12:55 pm #24199
If I could give more likes I would.
Those all sound like great advice. I am thinking that in my case it really is the operation principle of the tube pre-amp and its underlying electronics coupled with 2 distinct switching PSUs. I wish I had another AC/DC PSU lying around with the right plug and between 15 to 22 V just to test different combos.
I still am not sure that its a faulty PSU, as each PSU works fine with no perceivable noise when just one being used. But it can also of course be, I am not ruling that out.
In the meanwhile I ordered the 180W PSU because it was 60% off and I guess ill give it a try with the 2 pigtails, plus some ferrite beads on the ends.
But I will still look into all that you said.
April 7, 2022 at 2:34 am #24272
So, after receiving the 180W PSU, any combination of the the old PSUs with the new still resulted in noise.
I pigtailed the 180W PSU, so now I have a single power supply for both and there is no noise anymore.
And finally I can hear both simultaneously and I’m really happy!
April 7, 2022 at 8:12 am #24274
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