Attenuators: Passive-Reactive vs. Speaker-Thru?

[Ud Reks]

I'm looking at the way that different attenuators are described.

The maker of the Alex Attenuator describes the circuit like this:

My attenuator is a passive reactive load which maintains a load very near that of a speaker. By doing that this attenuator is extremely transparent. The limiting factor ends up being the response curve of the speakers at low volumes more so than any fault of the attenuator. In an attempt to compensate for the speaker response I have included a variable treble compensation switch. My attenuator will handle a 100 watt Marshall Superlead which can put out a 170 watts or more at full throttle. That is a lot of heat which means the unit will get warm. The handles don't get warm because they are isolated from the case so the handles are an extra cost option as not everyone will have to move the unit while it is hot.

The maker of the Aracom attenuator describes his circuit like this:

The key to the PRX150-DAG's natural sounding attenuated tone, lies within its patent pending SRT technology. Unlike the competition which alters, significantly reduces or completely isolates the speaker's reactance, the PRX150-DAG's step attenuation has NO impact on the speaker's reactance, allowing the speaker to respond naturally to the tube amplifier's complex signal.

Utilizing the proprietary SRT technology, the speaker is not loaded down and it is allowed to "breath" normally. Therefore, the speaker can react to the harmonically rich signal generated by the tube amplifier. In doing so, the speaker and tube amplifier are able to naturally interact. This adds up to a highly transparent, "cranked up" attenuated tone, that is natural sounding and full of dynamics.

Since the SRT technology allows your speaker's reactance to remain intact, the PRX150-DAG does not utilize an artificial reactive circuit or speaker emulation circuit. After all, what could be more natural than using your speaker's unaltered reactance to develop the tone from your tube amplifier?

Obviously there's an implied critique in there, but I don't want this to become a pissing match (nor am I interested in discussions of artificial artifacts, etc.).

Since the question about attenuators always relates to what's lost when the speaker isn't being pushed, it would seem to me that the Aracom circuit tries to address this. But can the difference actually be heard at those low levels? Is one method actually better than the other?

[Ud Reks]

If anyone can break this down for me, I'd appreciate it.

Looking to make a purchase soon.

[Seektone]

Sounds to me like Aracom is saying that it just allows pure unaltered signal to pass through, and that Alex is saying that his does that as well, but allows for adding treble if you like, or not.

I have an Alex and is it great knocking 3 or 6 dB off, very good at 9 dB, and good beyond that. Never heard the Aracom in person. I just think any time you take speakers which are meant to be cranked and put a tiny signal through the tone will be altered.

[Ud Reks]

Thanks, good info. I couldn't make out whether they were truly different or not.

[torquil]

The description of the first one sounds like something along the lines of this:

http://www.aikenamps.com/spkrload.html

The second is more difficult to guess at from the description, although it does seem to say that it doesn't do speaker impedance emulation like the first one.

I have calculated the impedance phase of the circuit I linked to above, but I have no impedance phase measurements of real guitar speakers with which to compare. The absolute value of impedance is displayed on the web page.

Anyone know the complete complex impedance of a typical guitar speaker cabinet?

[Ud Reks]

Thanks for the link, that was helpful. Wish I knew what Aracom meant by breathe.

[jkr]

I've owned most of the name attenuators out there (not the Alex though). Most attenuators sound decent for crunchy chords within the first few clips of attenuation. If you try to play lead lines, the dynamics are lost, the single notes sound thinner and often lose sustain. The Aracom unit (I actually prefer the DAG unit between the two), leaves single notes in tact, so when you play a lead, the note still sounds as thick as it did without attenuation, is still dynamic, and still sustains like it normally would without dying out. I don't know if that's what the manufacturer meant by "breathe", but that's my experience in doing a fair amount of a/b testing.

[Ud Reks]

Good stuff jkr, any experience with the non-DAG model? You wrote that you prefer the DAG, I assume because of the hi-cut switch. So, the hi-cut works, dials out any of the dreaded artifacts people were discussing?

I agree that other attenuators tend to suck tone and dynamics. But it seems many people were comparing the Aracom to the Alex and Faustine. I'm just trying to get a sense as to whether these 2 (or 3) top attenuators do things differently (in terms of the circuit).