Friday, January 12, 2018

David Barrett's Small Harp Amp Reviews

David Barrett has been running a review series for small harp amps at his website, and it is still ongoing.  The Memphis Mini amp was included and got good reviews:  David said he could recommend the amp to all levels of players from students to pros, and that he would buy it himself.  We thank him for his generous review.

One measurement really jumped out at me:  Peak Volume in Decibels.  The MM amp was the second loudest amp in the review at 111 decibels.  The only amp that topped it was the Fender Blues Junior at 113 db.  The Blues Jr makes nearly 3 times as many watts as the MM and you would expect it to be significantly louder than the smaller MM amp.  At only 2 db the difference would probably not even be perceptible.

The Sonic Pipes Windy City amp – which is very similar to the MM amp – was measured at only 106 db.  That means the MM amps is about 1.5 times louder to the human ear.  (Differences in perception are logarithmic, not linear.)  That is a huge difference.

The Sonic Pipes Windy City amp is weaker because they decided to use a 6SJ7 single pentode tube in the preamp section, when the amp they are modifying was actually designed to use a dual triode 12A tube.  The 12A tubes actually are two tubes in one, with half of it managing the mic input and the other half managing the recovery of volume lost by the tone control.  The Sonic Pipes Windy City amp has no second gain stage to do that, so the volume is lost and the amp is significantly weaker.

Volume level in small amps is extremely important.  You need to be able to hear your amp on stage among the other musicians, and you can’t always count on the sound tech to get it right in the monitors.  That 5 db deficit can be the difference between playing a great set or flying blind.  Nobody wants to have a weak amp behind them and have to grope their way through a solo.