Fender Hot Rod Deluxe Volume Limiter
 

http://cgi.ebay.com/ws/eBayISAPI.dll...category=38074

Anyone ever use one of these? Just got a kickin' Hot Rod Deluxe. Playing a Guild hollowbody through a Boss BD-2 Blues Driver pedal. Managable volumes, the pedal seems to act as a volume limiter in itself, but don't know if I would be able to drive the amp more and limit the volume output.

There are two types: One inexpensive one on Ebay which connects between the preamp and power amp and simply inserts an audio taper volume control into the whole affair. The other is offered by Weber Speakers and is called the "MASS" which connects between the power amp and the speaker.

Here's the key: Tube amps sound best when the power amp is driven. As it begins to be driven, it begins to compress and put out a smooth distortion, unlike the preamp which can be a bit buzzy. With a high-powered amp (40 watts and up) cranked, that can be pretty loud in a small club/church environment. While the Volume Box on Ebay cuts down volume, it does so by cutting down the signal from the preamp before it gets to the power amp, thus preventing power amp distortion. The best way to get that sound and still keep the level controlled is to introduce a load between the amp and speaker. A load is a device which absorbs some of the power of the amplifier before passing the rest on to the speaker. The very best sounding type of load is a reactive load, which physically reacts to the amp's current like a speaker. The Weber MASS is a great, inexpensive example. It's more expensive than a Volume Box, but sounds much better.

Weber MASS homepage

Hope this helps!

Bob

A friend of mine in Cincinnati built me one of these when I had my black HRD. I sold the amp before I ever used the volume box. Now that I have the brown HRD, I keep telling myself that I'm going to experiment with it, but I never have. If it's half as cool as my buddy says it is, it'll be a keeper...

Steve

I actually built a box that does the same as the item shown on the eBay ad... it's just a passive volume control (potentiometer) that goes in the circuit between the preamp-out and poweramp-in connections. I wasn't really happy with the results.

Check the James Vandenberg mods web site, lots of other info on this amp on that site. I ended up installing the the audio-taper pot in the volume position to replace the linear pot that Fender puts in the amp, and it helped some. The HRD amp is just plain LOUD!

Bob W,
Does the MASS get hot? It must have to dissipate the energy someplace. Or is it that the internal speaker/motor absorb the work?
Thanks, just curious. I agree that tube amps need to be cranked up to sound good. I had a Blues Jr that was too loud to play in the house. Had to stick it in the closet to get it to sound decent.

I don't know whether it gets hot, but it looks to me as if the internal armature dissapates the energy through motion rather than heat. The non-reactive loads like the Scholtz Power Soak do it via a resistance network, and the resistance network gets really hot. The Mass and the Marshall Power Brake use motion, the Mass through a disconnected voice coil and armature and the Power Brake through a motor. While there is some secondary heat from fricton, I wouldn't think there would be much.

Why don't you write them an email and ask? I'd love to see the results.

Bob

Bob,
Thanks again for the additional info. I took your advice and emailed them; will post their reply when received.
aloha,
- roger.

Ted from Weber wrote back:
"It does get warm, but not hot to the touch. Most of the energy is
dissipated in the speaker motor and also in the power resistors that allow it to work at different impedances.
Thanks very much, Ted"

Great! That's what I figured.

Bob

So, I take it that this MASS outfit would need to be wired between the power output and the speaker? Does it create potential for damage to the amplifier?

Thanks for everyone's input.

I use a THD hotplate, the same company that make the Univalve amp and other custom amps. I think they sound much better than the weber. I do have a 1979 Master Volume Marshall 2204, but my 1971 sound 100% better when cranked wide open. But unless you use a power attunator, you better hope you have no one living close to you! Most young guys today don't even know what power tube distortion is..... they sure are missing a lot.

Yup, it goes between the amp and speaker, and nope, there is little potential for damage unless the unit is misused. The unit is basically a noiseless speaker which dissapates a selectable percentage of the signal level being sent to the normal speaker.

Bob