Mesa Boogie Rectoverb 25 with Two Notes Torpedo Reload (MOD)

A half year ago i bought a new Mesa Boogie Rectoverb 25 amplifier and a Two Notes Torpedo Reload to record my guitar with Impulse Responses. A problem occurred, the Reload made the Mesa go 'motorboating' with a constant low frequency rumble and flickering led on the Reload. By discussing this issue with Mesa Boogie and Two Notes resulted in a modification (switch with a MOD and STOCK setting) on the Reload which fixed the problem.

Last month i bought a new pair of el84 power tubes for the Mesa amp and guess what? The rumble and led flickering was gone just by using the STOCK setting on the Reload! So you would think the MOD was not usefull anymore? Last week i've experimented with the two settings on my Reload and found out that the MOD setting is overall better sounding with my Mesa amp.

According to Two Notes the MOD lowers some of the low end frequency (>200 Hz) by a max of -3db depending on the amp. I've read alot of info about reactive loads and how these compare with the impedance curve of a certain amp, speaker, cabinet and other load boxes. Pete Thorn for example wrote that the Torpedo Load has a wider area peak at the low end spectrum and higher peak at the high end spectrum of the impedance curve compared to other load boxes (Suhr and Fryette for example). I'm not a technical specialist so correct me if i'm wrong, and i don't know what the (cabinet) impedance curve of the torpedo's is based on, but by having a modded Reload which change the STOCK impedance curve makes it more useful for amps with more low end i suppose!?

By using the STOCK setting with the Mesa amp makes the amp sound darker and less defined in the lower frequency range. The MOD setting makes the amp sound tighter and less dark, great for riffs and slicing solo's Maybe Two Notes can make a Reload version 2 with some alternative load settings based on different speaker/cabinet impedance curves? Or a way to change the low-end and high-end of the STOCK impedance curve?

please tell us what the mod exactly is ?
can i do this myself ?
i do have an reload

Well, this makes sense

First, it's good to note that changing the tubes also addresses the same issue. Maybe they have less impedance at low frequencies, maybe it's another thing, but in any case, it's a relationship between the amp and the Reload, and not just the Reload, that causes the problem. So the problem can be addressed, to some extend, from both ends.

Basically, the impedance of a loadbox should be close to one of a loudspeaker, but loudpseakers have various impedance curves, so anyone building loadboxes makes a series of choices. The loadboxes in the Torpedo series are modeled after a mean of several measurements, in an attempt to find something that will work for as many people as possible. But of course, in a few particular cases, this may not be the choice the user would have made.

The impact of the impedance of the loadbox on the sound heavily depends on the amp itself. The higher its output impedance (and no, I'm not talking about 4, 8 or 16 ohms) the more the loadbox will influence the sound. Here are a few guidelines to estimate this :

1) Single ended amps have a higher output impedance than push-pull amps.
2) Adding tubes in parallel reduces the impedance, so a tube amp with 4 output tubes has a lower impedance than the same with only 2 tubes.
-> Basically, the more output tubes, the less output impedance. Through this and other considerations, we can usually assume that the more powerful the amp is, the less output impedance.

3) Feedback reduces the output impedance, so an amplifier with a Presence control may have lower output impedance than one without presence control (however, there could be feedback applied without any Presence control)
4) On a modern transistor amp, with a very low output impedance, changing the loadbox won't change the sound at all.

The Torpedo Studio actually embeds a way of changing the loadbox : it can be set as Reactive or Resistive. Doing the same on the Reload will make it more expensive, so it's not an easy decision.

Thanks for this explanation which i understand mostly because of what i've read online

The STOCK and MOD settings are both workable with the Mesa because you can change the BASS and MID EQ section easily. Overall the Mesa is a difficult amp when using a load box. I have had resistive load boxes in the past and still have the Mesa Cab Clone. A reactive load sounds and plays 'better' but the Mesa amp is not feeling completely comfortable with it if you know what i mean? Comparing it with my Orange Rockerverb with 4x 6V6 power tubes the amp feels more balanced and sounds really good with the Reload. More transparent and open so to speak. So as you describe a higher output impedance as with the Mesa (2x el84 power tubes) seems not to work as good as with the Orange amp with a lower output impedance i assume? I understand you can't get it all in one unit so in the end it's all about compromises. Yesterday i've experimented with the STOCK setting and the Mesa EQ section again. The STOCK setting on the Reload adds more warmth and depth which i also like. It's nice to have two impedance curve settings but it's not a 'must have' if your amp and Reload works fine. You can change alot with EQ also!

The output impedance of an amp is in no way related to any sort of sound quality, and neither is the fact that the loadbox influences the amp In your particular case, it seems you don't like how the Mesa behaves with the loadbox, but we don't know if this is due to its output impedance I was making more of a general point.

Basstyra":1oyjw622 said:

The output impedance of an amp is in no way related to any sort of sound quality, and neither is the fact that the loadbox influences the amp In your particular case, it seems you don't like how the Mesa behaves with the loadbox, but we don't know if this is due to its output impedance I was making more of a general point.

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Thank you, correct me if i'm wrong! I'm looking for some answers but you are right, it's not that simple.

Last week i bought a second hand Suhr Reactive Load box and i hoped the Mesa amp would sound better over the Reload. In some extend it does, but the problem with the Mesa remains the 25 watt setting with the so called Dyna Watt technology. When using the 10 watt setting on the Mesa with a load (Reload or Suhr) attached the sound is more relaxed, organic and open. With the 25 watt setting the sound is to busy and artificial in some way. For recording i now only use the 10 watt setting with the Mesa which gives the most natural response and best dynamics for recording guitar tracks. Imho this whole Dyna Watt thing is not as great as Mesa makes us believe

what do you think is the better/ transparant load , the suhr or the reload ?

joogi":37du97la said:

what do you think is the better/ transparent load , the suhr or the reload ?

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Both are great units and load boxes, but for tracking with my DAW and IR software i like the Suhr better because the feel and response is overall better. What i also like about the Suhr is the adjustable line-out. The Reload is really good as a load box and attenuator with a real cab attached and that's what i mainly use it for now.