Amps w/ built-in attenuators?

[arcadesonfire]

Short question: Are there any amps out there (combo preferred) with built-in attenuators? What's an el34 in a univalve or Bivalve like compared to a decent vintage plexi clone through a hot plate?

 

 

 

Long post:

Hiya folks, as you can see, I use a Marshall plexi clone with a Hotplate. Been using it for years, a bit above 12 noon on each channel. I love the way it reacts to pedals. I can't get something so perfectly compressed unless I go class-A, el84. But then I've got no brute force. I wanna stick with driving el34s. But the head/cab+attenuator is such a hassle to carry--and i have to carry it a lot. I see Univalve is out of business....

 

Are there any other brands out there with built-in attenuators? Anything particular you'd recommend? If I could get an attenuated plexi WITH reverb, I'd be in heaven!!!

 

Thanks everybody!

[WRGKMC]

There are a few but I'm pretty sure most are lower wattage amps. There are three main methods used in heads besides the master volume. One is to use tube bias reduction. This isn't much different then using a master volume and the amps I own that have it tend to sound darker and flabbier.

 

Tube removal switching is essentially the same as pulling one set of tubes and cuts the wattage in half. They also make Yellow Jackets that allow low wattage tubes to be plugged into high wattage amps.

 

The other is some use ceramic resistors to reduce output. I've only seen these in lower wattage amps below 25 watts though. Higher wattage amps have a serious heat issue and without ventilation you have meltdowns and fires. The wire wound resistors get as hot as an electric oven element inside.

 

I think Phil even mentioned one that has a built in rheostat to vary output but I believe its a lower lower wattage amp too.

 

Nearly all tube amps have to maintain a constant load impedance. Purely resistive loads don't vary in resistance with frequency the way a speaker does. Marshall transformers are especially venerable to improper impedances. Hot plates have additional circuitry that allows the impedance to fluctuate like a speaker does. I believe it has a light bulb that does this by substituting as an inductive load shock absorber.

 

The problem with having a hot plate built into the head is heat dissipation. Reducing bias or cutting off a pair of tubes doesn't increase heat because the wattage is reduced in both cases. A hot plate is different it acts as a load and the wattage gets converted to heat. Mounting those components in a head with tubes running hot would not only burn the components up, it would make the head allot heavier.

 

Building the hot plate into the cab would be more reasonable, after all its placed after the head and its attenuating what's getting to the speaker. I just haven't see it being done but it wouldn't be that hard to do. You have allot of space there too and heat dissipation would be much better.

[DeepEnd]

I don't know if this would appeal to you but Eminence makes a couple of 12" guitar speakers, the Maverick and the Reignmaker, that have built-in volume controls. The Maverick is US voiced and the Reignmaker is British voiced. Either handles 75 Watts RMS and has a street price of around $125. You could install one in the amp of your choice.

[WRGKMC]

I don't know if this would appeal to you but Eminence makes a couple of 12" guitar speakers' date=' the Maverick and the Reignmaker, that have built-in volume controls. The Maverick is US voiced and the Reignmaker is British voiced. Either handles 75 Watts RMS and has a street price of around $125. You could install one in the amp of your choice.[/quote']

 

I'd be curious to check those out. http://www.musiciansfriend.com/accessories/eminence-maverick-fdm-tone-adjustable-12-guitar-speaker--8-ohm

Since the speaker sensitivity changes I suspect the knob does something to move the magnet or stiffen the cone. I don't think its electronic.

 

I think it might be a screw mechanism that retracts the magnet in and out of the speaker coil. As the magnet is screwed out, there's less magnetic cone movement and less volume, the impedance stays the same all the time so there's no need for heat dissipation by big resistors like a hot plate.

 

The only drawback would be having these in a sealed cab. The cab would need an open back or a hinged door with hasps to keep it closed. Maybe even a removable door so you can run it as an opened backed cab and cut down on weight moving. Then you can just reach in and dial up the magnet strength.

 

If it works as I suspect it truly is a neat innovation.

 

The only thing that comes close were the old field coil speakers that used electro magnets instead of permanent magnets. You could vary the DC voltage to those and vary the field strength and thereby change the volume output. I understand they are some of the best sounding speakers for Hi Fi stuff because the distortion levels are much lower. They cost allot to build right too, but one day someone will make a good instrument version where you can just dial up the magnet strength and have a loose or tight sound with volume changes based on magnet strength.

 

 

[DeepEnd]

Frankly, I have no idea how it works but yeah, it seems like a cool idea. I think they're pretty obviously made for use in an open backed cab but hey, it's a guitar speaker anyway, not a bass speaker so an open backed cab would work fine. Maybe Phil or someone could review one and give us some technical info. Are you listening, Phil?