What's so cool about Variable Feedback?
Global negative feedback takes a small portion of the output signal and re-injects it back into the input stage which greatly improves linearity and distortion performance of an amplifier. A tasteful amount of negative feedback is the key: too much and you're into poor transient response and phase shift problems. We generally use somewhere between 4 to 14 dB's of feedback in our line preamplifiers and within that window is a definite point of maximized stability with optimum sonic performance. So we give you the choice of where you want to be in several of our products. Changing the amount of feedback alters the overall gain of the amplifier as well as the slew rate (speed).
In the context of a hifi amplifier or preamplifier with the Variable Feedback feature, such as our 50 Watt Monoblock or Neo-Classic SE/PP 300B amplifiers, EveAnna uses variable feedback to suit different CD's and recording styles when she's listening to music at home. "For the most part I keep the variable feedback controls around the middle but sometimes when I'm playing a CD which is kind of harsh and aggressive sounding or I just want to mellow out, I just turn those control down and apply more feedback to get a smoother, richer texture. But when I'm the one in the aggressive mood, I crank 'em up for a faster, punchier sound. The bass gets tighter and the top end sizzles. Vocal placement; is more forward. And, oh yeah, it gets louder too!"
The "GAIN" switch in the Micpre section of the Voxbox is actually a variable feedback switch offering a range of 20dBs of global negative feedback in five settings of five dB steps to alter how much variable feedback is applied around the tube circuit. This GAIN switch can be used in the higher 55 and 60dB settings (in conjunction with turning up the Input Attenuator) to achieve maximum amplification for quiet singers or lower output ribbon mics. With most "normal" condenser mics and applications, the GAIN switch setting can be chosen at will for sonic variety for a "more tube-y" sound in the lower 40 or 45 dB settings, "straight forward" sounding middle positions, or "more agressive" "punchy" sounds in the higher gain positions. There is no right or wrong with this switch. Have fun playing around with it and we hope it brings you some interesting results.
Manley produced the first modern 300B high-fidelity amplifier, the first modern high powered tube power amps, the first new power tube design in thirty years, the KT90. Manley was also first to utilize the ULTRAANALOG™ converters in the USA and the first in the world to show a converter with tubes. Within this web site we show the first amps capable of switching topology between single-ended or push-pull and the world's first 300B preamp. We invented a new thing with the Passive Parametric Massive Passive... but hell, this is all old news....
"First" is exciting. "Best" is the real goal. "Affordable" is honest business. "Most Expensive" is for others, not us. We try to describe these products in basic terms with valid scientific and engineering data. We do, however, indulge in just a little "audiophilia nervosa": high purity wire, gold contacts, good layout, hand soldering and wiring, overkill power supplies, silver solder, 1% metal film resistors, film & foil capacitors, selected tubes, solid chassis, etc. We do this scientifically and sincerely: for the music, for you.
We're good honest folk!