Q. How can I make my amp quieter for recording?

I have a Fender Hotrod Deluxe guitar amp that I love the sound of when gigging, but it’s far too loud for recording at home. I know about power soaks like the Hotplate and Motherload, but they’re as expensive as buying a smaller amp! Are there any other good ways to reduce the output level without sacrificing the tone?

Making an amp quieter for the purposes of recording is an ongoing problem for recordists who want an authentic sound.

Lloyd Parsons, via email

SOS Editor In Chief Paul White replies: 

Unless you’re good at electronics DIY and have a good understanding of the subject, the short answer is that there is no simple or inexpensive way to get the results you’re after. Tube amps have to be run into a load of similar impedance to the loudspeaker or the amp could be severely damaged, and that load has to be able to dissipate the output power of the amplifier without overheating. This is how power soaks work. There are specialist circuits that plug into your output tube sockets to reduce the power — again, quite costly (and only suitable for certain amp models) — but I’ve never tried these. I’ve also seen some replacement speakers that have a variable magnetic flux control to make them a few dBs quieter but, again, these would cost more than a power soak.

That leaves you with the option of trying to isolate the sound from your existing amp so that it doesn’t leak into the rest of the house. I’ve made recordings where the amp has been placed on its back on a block of foam, with the mic stand in place looking down onto the speaker, then I’ve used a clothes drying frame to make a small tent over the amp and covered this with blankets and duvets. This won’t kill all the sound, but may make it more tolerable.

Randall’s Isolation cab completely encloses a speaker, which is used instead of your combo’s speakers, then miked up through the cab.

At one time, I even considered putting a speaker baffle and a 12-inch speaker halfway up a plastic dustbin with a mic correctly positioned above it. The plan was to seal the lid with silicon rubber to prevent moisture getting in and then bury the thing in the garden just outside the studio, with appropriate connection cables in place! I never did get around to it, as I now do all my recording with a small Vox AC30 hybrid modelling, valve and solid-state amp that sounds good at any volume and is cheap as chips.

SOS Editorial Director Dave Lockwood adds: 

The specialised valve/tube adaptors that Paul is referring to are Yellow Jackets from THD Electronics, which allow an amp designed for 6L6, 6V6 or EL34 tubes to use lower-powered EL84-types running in Class A instead. This drops the output by about half and changes the tone fairly significantly to a more compressed, softer, typically Class-A feel, but still doesn’t get you into ‘domestically acceptable levels’ territory.

A completely different strategy involves the use of a fully enclosed speaker that is used instead of your combo’s speakers and then miked up internally. There are a few products of this type on the market (Randall’s Isolation cabinet and Demeter’s SSC1 Silent Speaker Chamber), but arguably the best of them — the UK-designed Hermit Cab — is, unfortunately, no longer made. The Hermit Cab used a ‘box within a box’ approach to achieve a serious degree of attenuation, whilst the others all tend to leak rather a lot of sound. (Confusingly, the Hermit Cab name is now being used by another company in the USA making single-skinned isolation cabs, primarily aimed at the live market.)

The Sequis Motherload (and its new affordable variant, the Motherload Elemental) is not just a power soak, it is also a very convincing, all-analogue speaker simulator, using entirely passive electronics. Similar units from other companies include the Palmer range (try the PDI03), SPL’s Transducer and the recently released, convolution-based Torpedo from French company Two Notes. Personally, I would favour this approach to solving your particular problem, as it would allow you to run your Fender amp with the exact settings that you use on stage, thereby achieving the same balance of preamp and power amp distortion. Getting these two out of balance, as people often do when cranking an amp into a power soak, will often result in harshness and a rather un-dynamic, brittle tone. Power-stage distortion alone is not the Holy Grail it is perceived as being by many; it merely plays one role within the holistic tone-shaping action of preamp, power amp, output transformer and loudspeaker. This is one of the reasons why simply using a very low wattage amp is not always the answer, as these are often designed to stay clean until the power stage is being driven hard, by which time even a 3W amp into a 10-inch or 12-inch speaker is actually very loud (way above the volume of a loud vocalist, for example).

A further option would be to run your valve amp into a simple power soak and take a line output from that (post output stage, not just preamp) into the speaker-simulation stage of one of the many software amp-simulation packages, or a dedicated, convolution-based software speaker simulator, such as Audio Ease’s Speakerphone. 

Published in SOS May 2010