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Jensen ISO-Max CI-1RR Review (Isolation Transformer)

DualTriode

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-10dB/decade noise floor slope is interesting. What is the reason?

In this time frame I was sorting through a bunch of different type tubes looking for low distortion and mostly low noise was the focus.

0.1 Volts output was about enough to get an idea of what the harmonic signature looked like.

Mostly I was interested in what level of noise to expect from the tubes under test. Given a chance power supply hum and buzz frequencies are the worst tube amplifier offenders.

The sloping noise floor in the FFT plot is, I think, due to 1/f noise. Shot noise starts to increase well above above 20 KhZ audio band.

Thanks DT
 

IVX

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I did measure CMRR of my $10 ISO trafo, [email protected], [email protected] 0db is 2Vrms.
2021-06-12_15-42-00.jpg
 

pma

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I measured this CMR on a DIY signal trafo made by a colleague. Looks similar like Jensen result posted by @SIY . I bought it at about $80.

linetrafo_CMR.png
 

BlackH20

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Jensen, believe I had some 6 x 9 speakers in the rear deck of my Ford Granada.
 

Rottmannash

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I found this one I once used in my car system.
 

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ChuckL

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AES Articles on Ground Loops:
Suggest looking deep into this collection of presentations and papers, way down the list concerning "Articles on Studio Wiring".
Lots of professional solutions on removal of ground loops and dealing with Common Mode noise. If you are not an AES member then look here - free data:
JH Brandt Resources
This brings up a question: When ASR tests equipment with balanced inputs, does his analyzer check for CMRR? (IEC CMRR Test Edition 3 2000, or later?)

I just ran across these articles here the other day, though I have read some of these before obtained from other channels.:)
 

sczm

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This unit solved my long-standing issue of noise coming out of my Lyd 8 active speakers. I have an Nvidia 3090 with HDMI out to my LG CX and eARC audio from the TV to a Denon X3700H. I connect the speakers to the pre-outs on the receiver. When the GPU was under load, my speakers would produce some pretty ugly noises. There's no noticeable noise if the GPU has low utilization. The noise also seems to occur at very high frame rates and the pitch varies with the frame rate. The speakers do have tweeter hiss and it is unrelated to the noise I am describing. I plan to test a Marantz pre-amp with balanced XLR outs in the future to see if that also eliminates noise.
 

milosz

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Computers have switching supplies that often put out lots of powerline and radiated hash especially under load. Some brands of computer power supplies are better than others in this regard. I don't know for sure, but I would guess that a top brand like Seasonic would introduce much less noise than bargain brands.

You can do a rough check for noise that your PC is putting out by placing an a portable AM radio, tuned between stations, near the PC's power cord. You will hear some of what the power supply is putting out onto the power line. This could be part of your problem.
 

sczm

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Computers have switching supplies that often put out lots of powerline and radiated hash especially under load. Some brands of computer power supplies are better than others in this regard. I don't know for sure, but I would guess that a top brand like Seasonic would introduce much less noise than bargain brands.

You can do a rough check for noise that your PC is putting out by placing an a portable AM radio, tuned between stations, near the PC's power cord. You will hear some of what the power supply is putting out onto the power line. This could be part of your problem.

The power supply I am using is a Corsair AX1600i which is one of, if not the, best PSUs available. I did previously have a Seasonic SSR-1000TR and I had the same problem. I might try your suggestion with a radio.
 

milosz

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Corsair should be OK, yeah.


If the noise is coming over the power line, you might try plugging the computer into an isolation transformer - this one is good for 450 watts, check to see what your PC is drawing off the line when it is running, this unit may be large enough or you may need a bigger one https://www.amazon.com/dp/B00R5CDG8O/ref=cm_sw_em_r_mt_dp_E438D0NPNSZC7A3PH6G9

If you are hearing noises when the GPU is under load, this tells me that noise from the GPU drawing bursts of power off the 12 volt power bus in the PC as it is doing it's thing is generating noise that is getting into your speaker's amps, this could be through their audio connection, through their power connection- or through the air via RFI. Powerful GPUs draw huge currents- very short bursts of hundreds of amps at 12 volts.
 

sczm

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Corsair should be OK, yeah.


If the noise is coming over the power line, you might try plugging the computer into an isolation transformer - this one is good for 450 watts, check to see what your PC is drawing off the line when it is running, this unit may be large enough or you may need a bigger one https://www.amazon.com/dp/B00R5CDG8O/ref=cm_sw_em_r_mt_dp_E438D0NPNSZC7A3PH6G9

If you are hearing noises when the GPU is under load, this tells me that noise from the GPU drawing bursts of power off the 12 volt power bus in the PC as it is doing it's thing is generating noise that is getting into your speaker's amps, this could be through their audio connection, through their power connection- or through the air via RFI. Powerful GPUs draw huge currents- very short bursts of hundreds of amps at 12 volts.

My GPU and CPU can separately draw 450/400W peak at stock voltages. I would likely need to get a 1800W transformer and I'd rather not spend $600+ when the Jensen seems to work well enough. I don't know how the noise is transferring, whether through the connection or through the air as the receiver itself is located very close to the PSU as are any number of electronic devices. I know that the speaker itself isn't audibly affected by proximity to the PSU when connected to the transformer. At some later date I'll see if distancing the receiver has any effect.
 

levimax

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My GPU and CPU can separately draw 450/400W peak at stock voltages. I would likely need to get a 1800W transformer and I'd rather not spend $600+ when the Jensen seems to work well enough. I don't know how the noise is transferring, whether through the connection or through the air as the receiver itself is located very close to the PSU as are any number of electronic devices. I know that the speaker itself isn't audibly affected by proximity to the PSU when connected to the transformer. At some later date I'll see if distancing the receiver has any effect.
The problem is that there is a ground loop due to different ground potentials between components in your system. Once this happens all sorts of noise from many different souces can get picked up. You can never eliminate all the noise sources but you can break the ground loop. You have solved the problem by breaking the ground loop with a transformer which is one of the best solutions...The other solution is balanced connections. Enjoy your quiet system.
 

sczm

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Turns out the transformer did not solve my particular issue after all. It does attenuate the noise, but it seems the noise just simply wasn't very loud with stress test I was running. The noise was still obnoxiously loud while playing games at high frame rates while under load and the Iso-max did not make enough of a difference. Optical output from the motherboard carries the exact same signal noise as HDMI. So far, the only solution that has worked is connecting via USB to my JDS Element II. Unfortunately this can only work as a temporary solution. I'm going to try plugging in the computer power supply to an EBTech Hum X to see if it helps.
 
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