Question about hum while using compressor's output gain

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Mahzin93
KVRer
Topic Starter
9 posts since 16 Jun, 2021

Post Sat May 14, 2022 7:15 pm

Hello. I'm an owner of Alesis 3630 unit and enjoy the sound it has flavoring the things it touches; currently I do a paralell comp. using it about the full mix and merging the recorded signal through it to the original thing. I can't use the output gain for using as a limiter this unit, hum comes. I am also an owner of a Teyun Q-24 interface that's surprising me due to low-noise, but it features 2 TRS INS + 2 TRS/XLR INS and 2 RCA INS + 2 RCA OUTS. I will buy one Edifier MR4 pair and decided for TRS being for them; what rests? RCA outputs ... I was thinking right now about one DI Box converting RCA to balanced signal, but not only the outs of the Q-24 are RCA, the ins of Alesis are unbalanced, so won't work possibily, but yes for less noise when going back to the XLR/TRS ins from the interface.

Question 1:
RCA always causes hum or not necessarily? If I buy another compressor for example, can I use it linked to the RCA outs?
Question 2:
I use adapters for linking the RCA cable to the ins of Alesis 3630, if I used a proper RCA to TS cable would be better than adapting?
Question 3: I heard about calibrating the Alesis, it helps a lot?
Question 4: It's possible to modify the unit turning it balanced?

Thanks people!

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BertKoor
KVRAF
13708 posts since 8 Mar, 2005 from Utrecht, Holland

Post Sat May 14, 2022 11:00 pm

A compressor is basically just an amp, which varies the gain all the time. If there is a tiny bit of hum in your source signal, it gets amplified to loads of hum.

Balanced cables won't help much with line levels and short cables. RCA cables and adapters don't introduce hum, unless they are broken. You might have a ground loop. Chances are the hum is hardly noticable in a full mix.

In short, this is why we work totally "in the box" these days.
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Mahzin93
KVRer
Topic Starter
9 posts since 16 Jun, 2021

Post Sun May 15, 2022 4:57 am

I saw and my PSU is 2-pin and perhaps low quality, thinking about buying one that I saw mentioning no-hum and 3-pin, worths?

lfm
KVRAF
5832 posts since 22 Jan, 2005 from Sweden

Post Sun May 15, 2022 5:16 am

Look for higher specs in regards to mA well over what is needed.
And for analog gear, better not to have switched PSU, that frequency can enter analog circuits. They often wear a bit, to older ones go down to audible frequencies sometimes when worn down.

Just normal transformer are better for analog stuff.

Mahzin93
KVRer
Topic Starter
9 posts since 16 Jun, 2021

Post Sun May 15, 2022 6:34 am

Thank you you 2, but do you all believe that this newer PSU with 3-pin poles with no-hum statement and same specs of the paralell one I am using (2-pin pole) will be better?

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BertKoor
KVRAF
13708 posts since 8 Mar, 2005 from Utrecht, Holland

Post Sun May 15, 2022 10:33 am

Hum free equipment can be made with 2-prong power plugs, no problem. It's a simple matter of good engineering. The 3rd ground prong is there for safety reasons only, to save you from electrocution in case of severe malfunction.

The 3rd prong can be responsible for creating ground loops (and hum) in certain cases. One cure of ground loops is cut it through or isolate it (which can be illegal)

So I do not agree with that. Not to say these can be fine. But for other reasons than that 3rd prong.
We are the KVR collective. Resistance is futile. You will be assimilated. Image
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Mahzin93
KVRer
Topic Starter
9 posts since 16 Jun, 2021

Post Sun May 15, 2022 1:31 pm

but the noise can be the powersupply ?

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BertKoor
KVRAF
13708 posts since 8 Mar, 2005 from Utrecht, Holland

Post Sun May 15, 2022 2:36 pm

Possible, but hard to prove (or debunk) from a distance.
We are the KVR collective. Resistance is futile. You will be assimilated. Image
My MusicCalc is served over https!!

Mahzin93
KVRer
Topic Starter
9 posts since 16 Jun, 2021

Post Mon May 16, 2022 2:34 pm

BertKoor wrote: Sun May 15, 2022 10:33 am Hum free equipment can be made with 2-prong power plugs, no problem. It's a simple matter of good engineering. The 3rd ground prong is there for safety reasons only, to save you from electrocution in case of severe malfunction.

The 3rd prong can be responsible for creating ground loops (and hum) in certain cases. One cure of ground loops is cut it through or isolate it (which can be illegal)

So I do not agree with that. Not to say these can be fine. But for other reasons than that 3rd prong.
Sorry my ignorance but I did not understand about the 3rd thing.

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BertKoor
KVRAF
13708 posts since 8 Mar, 2005 from Utrecht, Holland

Post Mon May 16, 2022 2:53 pm

Clarification:
Mahzin93 wrote: Sun May 15, 2022 6:34 am do you all believe that this newer PSU with 3-pin poles with no-hum statement and same specs of the paralell one I am using (2-pin pole) will be better?
3-prong power adapters are safer, but can (not necessarily) introduce ground loops.

Like lfm said, it's more important they can deliver enough juice. Then chances of hum are lesser. But no guarantee. More parts, more variables, more potential headaches.
We are the KVR collective. Resistance is futile. You will be assimilated. Image
My MusicCalc is served over https!!

Mahzin93
KVRer
Topic Starter
9 posts since 16 Jun, 2021

Post Mon May 16, 2022 4:13 pm

but my idea was not to use an adapter, but switch the paralell 2-pin powersupply I use for one 3-pin powersupply (not adapter) sold in Amazon, the problem exists for that case too?

lfm
KVRAF
5832 posts since 22 Jan, 2005 from Sweden

Post Mon May 16, 2022 6:56 pm

I looked at Alesis site, and power says 9V AC meaning external powersupply is just a transformer.

Doubt that will fix any hum making protective earth. You usually notice just touching chassis if any change in hum if that is the case. If a change you can even fool system by connecting chassis separately to ground on equipment. Just a cable attached to a screw on either part.

I would experiment with level for input and output instead. There is a switch for input between -10 dBV or +4 dBu and same for output level.

See where noise floor is on your daw when no signal through, you usually have peak indicator on a track. With line level stuff you usually have at least -80 dBFs or so.

Then raise make up gain on Alesis and see what happends and if altered touching chassis etc.

If you run +4 dBu out and interface is -10 dBV you might set levels on Alesis so noise floor way higher than needed, so you experience hum earlier.

Or check out specs for interface and set accordingly.

If persists and unit is really old, it could be some electrolytic capacitors inside is not that good anymore. They age and don't perform so well and create 50/60 hz ripple higher than when new.

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BertKoor
KVRAF
13708 posts since 8 Mar, 2005 from Utrecht, Holland

Post Tue May 17, 2022 2:53 am

Another clarification: a power supply is the same as a power adapter.

+1 to what lfm said above. Issues like these are hard to diagnose from a distance.
We are the KVR collective. Resistance is futile. You will be assimilated. Image
My MusicCalc is served over https!!

Mahzin93
KVRer
Topic Starter
9 posts since 16 Jun, 2021

Post Sat May 21, 2022 6:56 pm

I saw that my socket is 110v not 220v, the PSU was setted to 220v haha, it's working a lot better.

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