One thing to consider on the previous post. It is from a web site of a company that sells a competing product. Of course, the verbage is very carefully wording to make it seem as if NO OTHER product will work correctly except the one they sell.
For any amplifier issue, the person I consider to be an ultimate authority is Gerald Weber. He is the king of amplifier makers (sorry Randall) and is pretty much the human encyclopedia of amp circuit knowledge, including speakers.
The following is an exerpt from a web site where he answers a simliar question. Notice, that he also mentions the "Kolbe" as a great product, but holds it up as an equal to the HotPlate... that is very telling, since Weber also sells dummy loads and attenuators, he is still extolling the virtues of other company's products.
Read and learn... The question:
From: Steve
"I have a 20/50 watt THD 'plexi' amp which I run either 2-EL84s or 2-EL34s. In order to get rich distortion and compression, it must be played loud. I would like to get that sound at lower levels, so I intend to purchase a THD HotPlate or similar attenuator. I understand that at lower volumes, the sensitivity of the ear changes according to a Fletcher-Munson curve, so I'm wondering what kind of speaker cabinet or system I should use to compensate at the lower volumes?"
WeberVST's response:
"Steve, that's true about the F-M curve and the correction needed at the lower volumes. I would have to recommend though, before using a power attenuator that you go through the calculations or have a professional amplifier technician advise you on its use with regards to steady state power handling and thermal dissipation capabilities of your output circuit. There's some 'sonic psychology' involved here, in that as you are listening comfortably to the lower, attenuated level of acoustic power, the output circuit is still giving it all it's got. So, since your ear hears the lower level, it isn't quite so evident that the output circuit is working so hard. The bottom line is that the output transformer is heating up, it might be in saturation alot of the time, you lose some bass due to the saturation as well as increased resistance of the windings due to heating, etc. As far as speakers go, depending on how much attenuation you want to dial in, you'll probably want to get the most effecient speakers you can find. Celestions and WeberVSTs are probably the most efficient speakers available at this time.
"great tone should be priority... so for that matter I'll have to steer you away from the GT Emulator, it's ok... maybe for recording. On a scale of 1 to 10, the Hotplate is a 10 and the emulator is a 4. No lie, it's that much better. I'm sure you will agree once you compare the two. And without extensive EQ treatment, the emulator is flat out useless."
"Nothing beats the sound of good output tube/output transformer saturation... makes my mouth water just thinking about it!"
"And like I said, you want to stay away from the GT Emulator... take my word for it, I used it for over 7 years. You can dial in a so-so sound, and probably get a good tone with some extra effort, but it's more of a hassle than it's worth. If I were you, I would be focused on the Hotplate or the Kolbe.
"As far as doing damage to your amp....I've never had a problem with any of my amps. I've only changed power tubes a few times in the last 15 years of playing and I only changed the tubes because I thought you had to do that at some point and I felt kind of silly with my old tubes. When I got new tubes, though, I could hardly notice a difference. Granted, I've played only, say, an hour a day on average over that period of time. However, I wouldn't hesitate to recommend using a properly designed attenuator to anyone as long as they're playing through a beefy amp.
In order to make your amp sound great through a soak or break you're obviously going to set the volume and tone controls a little differently than you would otherwise. With a high-gain amp like a JCM900 you'll probably notch the preamp gain down somewhat since the power amp section is likely going to be providing a large part of the overdrive and you don't want to fuzz the thing out completely. Just twiddle the knobs a bit and see what you like. On my Hiwatts I crank the HIgh, Mid, Presence, and Master up Full. The bass is about 1/2 and the two preamp volumes are on about 2/3. If I have the bass or preamps up any further than that the amp gets way overdriven and starts to compress too much."
