ART SLA-1 is quite loud

[Chris Hurley]

I figured that the ART SLA-1 would be plenty loud in bridged mono mode. I normally run mono anyway, but if I wanted to run stereo in the future, I wasn't sure that 100w per side would be enough.

My SLA-1 arrived today and I hooked it up in stereo mode to my single 8 ohm cabinet and cranked it up. It is very, very loud. I never did turn it all the way up, but I was close and it was bone crushing. I normally play a 50W tube head and I never run it this loud.

Some people might need more, but I'm very happy with the output capability of this unit so far.

The SLA-1 might be putting out more than 100W in stereo mode with only one side driven. I'm not sure.

Tonally, it seems to reveal that my tube power amp accentuates high frequencies more than I'd thought. The SLA-1 (like my ADA Microfet 100) seems considerably darker on the same patches. Dialing up the presence on my presets brings the rig to life, though it blows the highs out of proportion on my headphones. I'll work that out with EQ easily enough.

So far, this seems like a nice 1U solution that has a surprising amount of power. It's very, very loud.

 

[rickboot]

That is good to hear. I bought an SLA1 but haven't had a chance to try it out with my Port City 2x12 cab with Celestion Century Vintage speakers. I think it will be enough volume for me too.

What cab and speakers are you running?

 

[joegold]

I figured that the ART SLA-1 would be plenty loud in bridged mono mode. I normally run mono anyway, but if I wanted to run stereo in the future, I wasn't sure that 100w per side would be enough.

My SLA-1 arrived today and I hooked it up in stereo mode to my single 8 ohm cabinet and cranked it up. It is very, very loud. I never did turn it all the way up, but I was close and it was bone crushing. I normally play a 50W tube head and I never run it this loud.

Some people might need more, but I'm very happy with the output capability of this unit so far.

The SLA-1 might be putting out more than 100W in stereo mode with only one side driven. I'm not sure.

Tonally, it seems to reveal that my tube power amp accentuates high frequencies more than I'd thought. The SLA-1 (like my ADA Microfet 100) seems considerably darker on the same patches. Dialing up the presence on my presets brings the rig to life, though it blows the highs out of proportion on my headphones. I'll work that out with EQ easily enough.

So far, this seems like a nice 1U solution that has a surprising amount of power. It's very, very loud.

1. Power amps that are designed to be used with guitar preamps typically have more high end emphasis than hi-fi oriented power amps.
In the case of a tube power amp which is designed to be used with a guitar-oriented preamp there is usually a Presence control which is part of the power amp's feedback circuit.
Many of the best guitar amp heads and combos used Presence in the power amp to make up for a lack of highs in the preamp or simply for a different type of top end than the preamp alone is capable of producing.
Guitar oriented power amps that do not have a Presence control often have some of that extra type of top end built in anyway.
Eg. Running a Mesa Triaxis into hi-fi oriented power amp will sound dull and lacking in Presence. Even though the Triaxis has a sort of a Presence control of its own it was designed to be paired with a power amp like the Mesa 2:90 which has Presence controls.
It would be very unusual to find a tube power amp made for guitar that had a flat frequency response.
Eg. I don't believe that there is any way to set the controls of a 2:90 (or any other guitar oriented tube power amp that I am aware of) to yield a hi-fi oriented flat response.
Since the Axe's power amp sims take care of all these types of sonic characteristics of a guitar oriented tube power amp, in general, you're better off using a hi-fi oriented power amp to monitor the Axe with when using its power amp sims.

2. If you're listening with headphones to the same signal path that you send to the SLA and a guitar cab (with the Axe's Cab Block bypassed), then there will be way too much audible top end compared to what comes out of your guitar speaker.
When listening with headphones you should normally have the Axe's Cab Block and cab sims engaged.

3. The SLA 1 in stereo @ 100 watts per side is still a total of 200 watts.
You will find it less loud if you're only running a single cab @ a mere 100 watts.
When playing in mono I usually use the bridged mode just to be sure I've got enough juice for any situation. But I use a EVM-12L which can handle the power. If you're using lesser rated speakers it might not be safe for them to run with the SLA 1 in bridged mono mode.

 

[Chris Hurley]

2. If you're listening with headphones to the same signal path that you send to the SLA and a guitar cab (with the Axe's Cab Block bypassed), then there will be way too much audible top end compared to what comes out of your guitar speaker.
When listening with headphones you should normally have the Axe's Cab Block and cab sims engaged.

That is correct, and I do.

 

[Chris Hurley]

That is good to hear. I bought an SLA1 but haven't had a chance to try it out with my Port City 2x12 cab with Celestion Century Vintage speakers. I think it will be enough volume for me too.

What cab and speakers are you running?

I have a homebrew 1x12 cabinet with a Celestion Seventy/80 in it. This is a deep 1x12, partial open back based around the slightly reshaped dimensions of an avatar 1x12 that I own. I've got a twin of this cabinet that has a WGS Veteran 30 in it, but I've not tried that one, my 4x12 or other cabs yet.

So far so good, though.

 

[Gasp100]

Excellent info! My SLA-1 gets here today so I can put my rig together tonight. I did a pseudo test last night using:

Guitar -> AxeFX -> Suhr Badger 30 FX return (uses EL34's) -> out of Badger into my Avatar 1x12 with Celestion Lead 80 (this is the same cabinet that I will be using with the SLA-1).
The CL80 is 80 watts, so I will be leaving the SLA-1 in stereo operation mode but only using one side. Should not be a problem because this is solid state.
Anyway, even at very low volumes and running through a very tube colored power section I see great promise from sticking with the AxeFX -> SS power amp -> guitar cab rig for a while. I still can't determine if I will be using power amp sims globally on or off; it seems to vary (really good to really dark sounding) per patch so I might just enable/disable the power amp sims via the SAG control.

 

[paulmapp8306]

Dont worry about an 80W cab. My 2x12 is a 60W cab, and I power it with my SLA-1 bridged. Its fine.

Rule of thumb is up to 5x you cab rating - so 300W for my cab. SLA-1 bridged is 260W so almost perfect.

Its not about volume though - its headroom. -3bd is half power, so when bridged, and the amp controls set to -6db its only kicking out the equivilent of 65W anyway and this is where I tend to run it.

 

[Gasp100]

Dont worry about an 80W cab. My 2x12 is a 60W cab, and I power it with my SLA-1 bridged. Its fine.

Rule of thumb is up to 5x you cab rating - so 300W for my cab. SLA-1 bridged is 260W so almost perfect.

Its not about volume though - its headroom. -3bd is half power, so when bridged, and the amp controls set to -6db its only kicking out the equivilent of 65W anyway and this is where I tend to run it.

Well, here is my situation. Home player (for right now, taking a lot of time off from even thinking about gigging again with new baby (third kid), etc...). I normally play at very tame volumes so I'm wondering if headroom is really going to be an issue (or even hinder my enjoyment). Might I get better results going non-bridged (to kick out only 100w total) so I can "push" the AxeFX output and power amp a little more? The volumes I'm talking are so low it's probably a non-issue, just wondering your thoughts.

 

[Chris Hurley]

Tonally, it seems to reveal that my tube power amp accentuates high frequencies more than I'd thought.

[attachment=1:1jjzgbut]50wpoweramp.jpg[/attachment:1jjzgbut]

I decided to grab an impulse of my homebrew tube power amp to see what was going on with the frequency response. I was surprised enough with what I got that I ran it several times with longer and shorter sweeps and got basically the same sort of results. The circuit is a typical 50W LTP-driven EL34 amp with a single 12ax7 triode recovery stage in front of it. In my case, there isn't much NFB applied, which may account for some of the craziness.

I took my existing patches that sounded off (and "dead") through the SLA-1, added a cab block with this impulse and the rig now sounds like it sounded through my tube amp. Lively, present... the usual non-specific terms.

This makes me want to look at the response of other tube poweramps...