Magnatone Giveawya

September 2014
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CAN YOU TURN THAT THING DOWN?

Hi Jeff,
I have a Fender Twin Reverb. I really love the tone of the amp with the volume set to about 5 or 6, but at that point it’s just too loud to play anywhere. How can I still get that great tone at a useable volume? Is there a safe way to do it? Is there a best way to do it? I don’t want to use pedals. Can you help?

Mike


Hi Mike,

Nice amp… nice loud amp. Ah, I remember the day when you could actually rock out on a Twin set on 7. Fortunately I still have my hearing! While a Twin is certainly a benchmark of tone, getting a naturally overdriven tone out of one in a small club environment can be a challenge. Luckily, there are quite a few options to accomplish this, some newer and some old school. Fortunately, these options are also reversible, so the full frontal assault of your Twin is still available should you need it for those bigger stages. Let’s start with a couple of newer options.

You may first want to explore an external attenuator, such as the Tube Amp Doctor Silencer, the Dr. Z Airbrake, the THD Hot Plate, or many other such devices. These can be inserted between the output jack of the amplifier and the speakers and function by reducing the amount of signal level sent to the speakers. There are many different units available and they do function in different ways—some with simple design, some more complex. They also vary in size, so do a bit of research and see which unit best serves your application. To return to normal operation here, simply remove the unit and plug the speakers directly into the amplifier.

The next option would be to explore a device know as the Yellow Jacket by THD Electronics. These adaptors plug directly into the output tube sockets of the amplifier and allow the use of 6BQ5/EL84 output tubes. These output tubes are capable of less power output, and the voltage and current supplied to them through the adaptor is limited accordingly so that the output of your amplifier is substantially reduced. Keep in mind that using a different output tube will substantially change the tone signature of your amplifier. This could open up a new sonic palette for you, but if you’re married to the tone of the current 6L6 output tubes in your amp, it may not be a viable option. To return to normal operation, should you choose this method, you would simply remove the units and reinstall the 6L6 tubes.

Okay, let’s visit a couple of old-school options, the first of which will require a trip to your local amp tech. Have your tech install a couple of different half power switches, the first of which would be a Pentode/(quasi)Triode switch. This switch reconfigures the operation of the output tubes by switching the screen grid resistor connection from the screen grid supply over to the plate of the tube. This simulates the operation of a tube in triode mode and will reduce the output of the amplifier by 40–50 percent. There is a bit of a change in the tone and feel of the amp, but to me it becomes a bit smoother, which is not necessarily a bad thing.

He could also install a switch that would disconnect the cathode connection of either the inside or outside pair of output tubes, thereby electrically removing them from the circuit. This will also reduce the output of the amp by 40–50 percent. Some might argue that this mismatches the primary/secondary impedance of the output transformer, but this method of power reduction has been used for decades with no known adverse affects. The above Pentode/Triode switch also theoretically mismatches the impedances, but again this method has been used for many years without cause for alarm. To return to normal operation here, simply place the switch(es) in their “normal” mode and the amp is returned to stock. If your amp is more of a vintage/collectable model and you don’t wish to adulterate the rear panel with switch holes, you could have your tech simply hardwire the changes internally. This would not, however, allow you to return the amp to its stock configuration with the simple flick of a switch.

The last, quickest and possibly most cost effective option I have for you would be to simply disconnect one of the speakers. This will also reduce the amount of clean output power that the amp is capable of producing due to the change in output impedance load, which will rise from 4 to 8 ohms. The one thing to keep in mind here is that while the constant output power of the amplifier has been reduced, it still does seem capable of outputting substantial peaks on the attack of the notes, so you might want to consider installing a different 8-ohm speaker with a higher power capability for use as the constantly connected speaker. Just because the amplifier volume control is set at 5 or 6 doesn’t mean that the amplifier is outputting only 50 or 60 percent of its output power. With most decent guitar/ pickup configurations, the amplifier has long since reached its maximum available power at those settings. The rest just tends to overdrive the output stage more… which ain’t necessarily a bad thing either! Of course, to return to normal operation here, simply reconnect the second speaker. By the way, two different types of speakers in an amp most times complement each other so the tone of the amp may actually improve. I hope that helps you tame the Twin.


Jeff Bober
Jeff Bober, Godfather of the low wattage amp revolution, co-founded and was the principal designer for Budda Amplification. He can be reached at pgampman@gmail.com.