THD Hotplate

[soulsonic]

 

Even speaker cabs themselves aren't accurate though. I challenge anyone to go measure their speaker cab and have it match--mine are always high (lower number).

 

 

You can't get an accurate measurement of AC impedance with a standard volt/Ohm meter, because it measures DC resistance - which is a different measurement. An 8 Ohm speaker has a nominal AC impedance of 8 ohms throughout a specific frequency range, but the actual resistance at any given individual frequency will likely be something else and it can change dramatically across the frequency range. My criticism of the Weber MASS in regards to impedance matching is based on my intimate knowledge of its design and its flaws, as one who has personally assembled over a hundred of them. I'm saying that the way it's designed doesn't correctly match the impedance.

 

Is the amp OK with that? Obviously, otherwise everyone's amps would blow up when they use one. But when you alter the impedance relationship between the amp and the speaker, you are going to change how the amp responds with that speaker, and therefore, alter the tone of the amp. So, if you have a particular tone you like going straight into the speaker, and you don't want that to change when you use an attenuator, then you should use an attenuator that maintains the impedance relationship. I think the altered impedance is a big (and often ignored) variable that is responsible for why so many people complain about any given attenuator changing their tone. Of course, there are other issues: the speaker not being driven hard, the change in a person's hearing response at low volume, etc... but I think you will be improving your chances of having a tone you will be happy with if you use an attenuator that matches impedance.

[Armitage]

High gain tube heads get most (not all) of their distortion from their preamp section, (the small tubes). They just run one tube into another, into another, into another and overdrive each section until you get the desired distortion. KT-88s, 6550 and 6L6s are usually used in the power section (the big tubes), because of their wide frequency response and clean output. EL34s of course get dirty faster.

Non master volume tube amps, get most of their distortion from the power section, you have to turn these amps up loud to get the distortion. Power tube distortion sounds different then preamp tube distortion. It's a matter of opinion which is better, but most people tend to prefer power tube distortion... when they can get it. And that's the kicker.

Transistor amps and modeling amps get their distortion in the preamp section and sound pretty crummy when their power section overdrive so I can't imagine anyone wanting to put a HotPlate on one.

I have a HotPlate and have tried it out with my 5150, ENGL Savage 120 (long gone), Steavens Poundcake, Soldano and Marshall TSL. All high gain master volume tube amps and am disappointed for this use. If you're planning on turning your amp up and crushing your volume down to bedroom levels you'll be greatly disappointed. High Gain heads have surprisingly clean power sections (so they don't get muddy when you turn them up). It's actually quite surprising. You also miss out on speaker to air interaction, speaker distortion, the shear volume, room effect, and your hearing curve is different for loud volumes then quiet ones (i.e. the Fletcher-Munson effect, that's why there is a loudness control on your stereo). It also affects your tone a bit, so you may not like it at all.

The HotPlate is great for taming a non master volume amp or running your amp at it's sweet spot, say 6 or 7, in a room you can only run at 5. But not cranked on 10 but only as loud as on 1.

Also consider wear and tear on your tubes. I don't think cranking your amp with a HotPlate is any worse then just cranking it, but you'll play your amp at much higher working levels then you normally would have, and that's a lot of wear and tear that those tubes may never had seen if you didn't have one.

I really recommend you try one before you buy it. Many people have one kicking around because it didn't suit their purpose, not because it's a bad product.

This is my opinion, from my experience with mine.