ART SLA-2 hum

T

TheVede

Member
I've got a nasty case of "I'm-concerned-that-my-expensive-new-equipment-may-be-broken-even-though-it-probably-isn't-itus" and the only cure is you, the friendly and helpful denizens of the Axe-FX board. You guys already helped me with one such issue in the bug forum and I have just one more issue that I'd like to get clarity on and it's actually in regards to the ART SLA-2 rather than the Axe.

Based on the positive reviews on this board I purchased an ART SLA-2 to go with my new Axe-FX Ultra. The marketing copy for this power amp describes it as "extremely low noise". If they mean relative to an electric pencil sharpener then sure, my unit is extremely low noise, but sitting powered on in my very quiet room at night this unit seems to drive a surprising amount of hum through my 2x12 cab – regardless of whether or not a guitar is plugged in.

Running in stereo, Channel 1 and Channel 2 both drive a slight, tolerable hum through their respective speakers when their attenuation dials are both set to 0 dB (max volume). But whereas the hum in Channel 2 vanishes almost completely as you start to increase its attenuation, the hum in Channel 1 grows much louder as you begin to increase its attenuation – loud enough to hear it in an otherwise silent room from 10 feet away.

I know the loud hum in Channel 1 isn't caused by the cab or the speaker cables because I just plugged two different 100-watt heads into the cab using the same cables and it's all relatively quiet.

So, is my SLA-2 behaving normally or abnormally?

Thanks in advance for the help!
 
TheVede said:
I've got a nasty case of "I'm-concerned-that-my-expensive-new-equipment-may-be-broken-even-though-it-probably-isn't-itus" and the only cure is you, the friendly and helpful denizens of the Axe-FX board. You guys already helped me with one such issue in the bug forum and I have just one more issue that I'd like to get clarity on and it's actually in regards to the ART SLA-2 rather than the Axe.

Based on the positive reviews on this board I purchased an ART SLA-2 to go with my new Axe-FX Ultra. The marketing copy for this power amp describes it as "extremely low noise". If they mean relative to an electric pencil sharpener then sure, my unit is extremely low noise, but sitting powered on in my very quiet room at night this unit seems to drive a surprising amount of hum through my 2x12 cab – regardless of whether or not a guitar is plugged in.

Running in stereo, Channel 1 and Channel 2 both drive a slight, tolerable hum through their respective speakers when their attenuation dials are both set to 0 dB (max volume). But whereas the hum in Channel 2 vanishes almost completely as you start to increase its attenuation, the hum in Channel 1 grows much louder as you begin to increase its attenuation – loud enough to hear it in an otherwise silent room from 10 feet away.

I know the loud hum in Channel 1 isn't caused by the cab or the speaker cables because I just plugged two different 100-watt heads into the cab using the same cables and it's all relatively quiet.

So, is my SLA-2 behaving normally or abnormally?

Thanks in advance for the help!
Click to expand...

It seems like every once in a wile someone has an SLA with a hum issue. You didn't mention how you have things hooked up, are you using XLR or instrument cables from the Axe to the ART? And now for the obvious trouble shooting questions, have you tried different cables or sources to eliminate any other possibilities outside of the amp?

Assuming everything is hooked up correctly and the cabling your using is good you might try this tread...viewtopic.php?f=12&t=13264&p=125581&hilit=ART+SLA+hum#p125581
 
Thanks for the link, Sixstring. It "sounded" exactly like my problem, so this morning as soon as I read through that other thread, I unscrewed the top of my SLA2 and, sure enough, Channel 1's cable was touching the transformer. I pulled it clear and powered back up but unfortunately the hum was still there. Bummer.

Your question about how I connect my Axe to my SLA2 is moot because the hum is there even when the Axe is disconnected and I'm only going from the power amp out to the 2x12. I haven't tried different speaker cables, but I have tried swapping the existing two cables to no avail -- regardless of the cable, the hum is driven by Channel 1.

When I get home from work tonight I'm going to try bringing the cab and the SLA2 out into another room and plugging in there, seeing if it makes a difference.

Just so I understand what the SLA2 sounds like for everyone else, I should be hearing ZERO hum? The unit's fan should be louder than any noise coming out of my stereo 2x12 cab when the SLA2 is powered up and sitting idle with both attenuators set at 12 o'clock?
 
TheVede said:
Just so I understand what the SLA2 sounds like for everyone else, I should be hearing ZERO hum? The unit's fan should be louder than any noise coming out of my stereo 2x12 cab when the SLA2 is powered up and sitting idle with both attenuators set at 12 o'clock?
Click to expand...

That is correct you should hear the slightest (Hiss) with nothing hooked up to the inputs and with the outputs hooked up to a speaker and the masters wide open. I verified that with my rig just now so I know that is the case. If you have hum coming from just one channel it sounds like the amp has an issue.

Just to be sure try using a ground isolator on the power cord to lift the grounding lug. If you still have a hum it's time to have it looked at by a tech.
 
Sixstring said:
TheVede said:
Just so I understand what the SLA2 sounds like for everyone else, I should be hearing ZERO hum? The unit's fan should be louder than any noise coming out of my stereo 2x12 cab when the SLA2 is powered up and sitting idle with both attenuators set at 12 o'clock?
Click to expand...

That is correct you should hear the slightest (Hiss) with nothing hooked up to the inputs and with the outputs hooked up to a speaker and the masters wide open. I verified that with my rig just now so I know that is the case. If you have hum coming from just one channel it sounds like the amp has an issue.

Just to be sure try using a ground isolator on the power cord to lift the grounding lug. If you still have a hum it's time to have it looked at by a tech.
Click to expand...

Thanks again for the help. Tried different rooms/power outlets tonight -- even tried plugging into a Hum X -- but the hum remains. Thankfully, I'm still within my return period so I'm just going to exchange for a new unit and hope for the best. If the second unit still hums, I think I'll try a Carvin DCM1540L.
 
UPDATE

On a whim, I picked up a QSC RMX 850 because it's a SS power amp in my price range that all of my local guitar stores carry (I got my SLA2 from musiciansfriend.com).

On the plus side, zero hum. YES!

On the negative side, the fan is REALLY loud and the tone is relatively harsh with considerably less low-end punch compared to the SLA2. NO!

So, the QSC is going back and I'll be exchanging my SLA2 for a new one and hoping it doesn't hum. I may order a Rocktron Velocity 300, as well, so I can A/B them and keep the one I prefer. I'll report back on how everything turns out.
 
UPDATE 2

Figured I'd close the loop on this thread.

I did what I said I might and ordered a second SLA2 as well as a Roctron Velocity 300. Ultimately, I returned the Velocity 300 and the new SLA2 and kept my old SLA2.

First, about my second SLA2:

It hummed exactly the same way as the first one leading me to believe, either...

  • 1. All SLA2's hum and it's simply too quiet to bother most folks, or...
    2. When these units have a hum problem, it happens in batches (my new SLA2's serial number was literally 1 higher than my old unit), or...
    3. There's something about the SAL2 and the wiring in my home that generates hum, so every SLA2 I'd buy would hum in my home.

About the Rocktron Velocity 300:

  • 1. Doesn't hum at all; completely silent when not in operation
    2. Doesn't feel as solidly constructed as the SLA2; outer chassis seems to be made with thinner, more flexible metal
    3. Definitely adds extra tube "feel" to the Axe and adds some additional low-end, but...
    4. ...that low-end isn't as tight as the SLA2's low-end (important for distorted palm-muted riffs)...
    5. ...and, overall, the SLA2 seems to create a wider sound field with more presence and depth.

So, after a lot of time, effort, and A/B testing, I'm back to my original SLA2 and quite happy about it.

To my ears, it sounds much better than the QSC RMX 850 and subtly better than the Rocktron Velocity 300. AND I'm no longer wondering if there's a better-sounding option out there in my price range.

-G

PS
I opened up the second SLA2 and none of its wires were stuck underneath (or even sitting particularly close to) its transformer.
 
Did you make sure your groundlift switch on the axefx is turned off? I had a big hum in my ART and it just turned out to be that damn switch. Just a suggestion as now that the buzz is gone the SLA 2 sounds pretty fucking good.

PS Put in some Q-Tuner Hi Z's recently and they sound down right awesome with the axe/sla 2 combo.
 
I have EXACTLY the same problem with my Art SLA-2. Thanks to TheVede, I am going to return it. I have a Yamaha Stagepas 500 and when I hook it up to the Axe I have ZERO hum using the same power outlet, cables, etc.
 
Same for me. Mine ART Sla 2 is very quiet and surely NOT dead.

This is still the best solution (enough power, stereo or bridged, relatively cheap and high quality)
 
Check the shielded wire I had mine backwards and running under the transformer, my main cornern was overheating so I had to return it. The company has a very poor workmanship. Ihad loose screws too.
 
Be careful working inside these things guys.....they can still hold lethal charges unplugged! :shock:
 
You must log in or register to reply here.
Back
Top Bottom