The All new SIT-1 Mono Block (pair)£9,000.00
The first of a new generation of Mono-Block power amplifiers
The All New SIT-1
is the first of a new generation of power amplifiers using Static Induction Transistors (SIT) in single-stage, single-ended Class A circuits delivering superlative sound without feedback or degeneration. This is made possible by the unique characteristic of First Watt's custom SIT devices, which combines a square-law input character with a low impedance output to form the only solid state gain device which behaves like a Triode tube.This character has long been sought as a potential replacement for tubes, but the realised devices have several advantages. The Pass SIT device has higher gain and lower distortion and also conveniently operates at the voltages and currents required by loudspeakers. This means that an output transformer, with all its bandwidth and distortion limitations is eliminated. The SIT-1 has only one active device in the circuit. All the other components are passive
The All new SIT-2£4,500.00
First Watt J2 Stereo power amplifier 25wpc£3,595.00
The First Watt J2 25wpc
The J2 is a stereo power amplifier rated at 25 watts per channel. It has a two-stage circuit that operates in pure single-ended Class A mode, with signal JFET devices forming the input stage and power JFET devices for the output stage.
JFET transistors have long been recognised as having the highest audio quality of any transistor; the input devices of the J2 are known through the industry as the standard for low noise and linearity, and are found on the inputs of the finest phono stages, line level preamplifiers, and power amplifiers.
But for over 30 years robust power JFETs have not been widely available since the short-lived efforts of Sony and Yamaha. In the last few months, advances in Silicon Carbide (SiC) technology have resulted in new power JFET transistors with high voltage, current, and power capabilities – as high as 1200 volts, 30 amps, and 273 watts.
Created by SemiSouth Corporation of Mississippi, these robust new JFETs are designed for very fast high power switching in solar power and electric car applications. However, they also have a very low distortion characteristic that makes them superb for use in linear amplifiers. In apples-to-apples comparisons with comparable MOSFET type power transistors, they can achieve 10 to 20 dB improvements in distortion performance.
For over 10 years First Watt has been pushing the design envelope with simple high performance Class A amplifier circuits, and when a better transistor like this comes along, it can mean getting the same distortion performance with a lot less feedback, or lower distortion with the same amount of feedback. The J2 does amplifier does both,and that helps make it a better sounding amplifier than the best of its predecessors.
B1 Buffer preamplifier£995.00
First Watt Buffer preamplifier
B1 Buffer Preamp
So here we are in the New Millennium, and thanks to Tom Holman and THX we’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more.
Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.
Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control.
What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.
And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp.
I suppose if I had to floor the accelerator to drive 55 mph, maybe I’d think the life was being sucked out of my driving. Then again, maybe I like 55. Nice and safe, good gas mileage…
Is impedance matching an issue? Passive volume controls do have to make a trade-off between input impedance and output impedance. If the input impedance is high, making the input to the volume control easy for the source to drive, then the output impedance is also high, possibly creating difficulty with the input impedance of the power amplifier. And vice versa: If your amplifier prefers low source impedance, then your signal source might have to look at low impedance in the volume control.
This suggests the possibility of using a high quality buffer in conjunction with a volume control. A buffer is still an active circuit using tubes or transistors, but it has no voltage gain – it only interposes itself to make a low impedance into a high impedance, or vice versa.
If you put a buffer in front of a volume control, the control’s low impedance looks like high impedance. If you put a buffer after a volume control, it makes the output impedance much lower. You can put buffers before and after a volume control if you want.
The thing here is to try to make a buffer that is very neutral. Given the simple task, it’s pretty easy to construct simple buffers with very low distortion and noise and very wide bandwidth, all without negative feedback.
And here we are...
First Watt M2 Stereo power amplifier 25wpc£3,195.00
first Watt M2 stereo 25wpc amplifier
The First Watt M2 is a two channel audio power amplifier delivering 25 watts per channel. It uses JFET and MOSFET transistors operating in Class A mode without negative feedback so as to produce a more musically life-like sound. Negative feedback is a technique in which the input gain stage of an amplifier compares the input musical signal with the output of the amplifier and outputs a signal to the remainder of the amplifier which incorporates the original music mixed with corrections to reduce the errors made by the rest of the amplifier.
If an amplifier has high distortion, then negative feedback is very helpful in cleaning up the output going to the loudspeaker. Nevertheless many audiophiles view it as a necessary evil, affecting the musical quality of the sound since it involves mixing output errors and re-amplifying them. Excessive use of negative feedback creates issues with stability and although it improves the measured performance, is often associated with “sterile” sound character, and “subtracted” musical detail.
The M2 is a simple circuit whose output stage consists of a pair of complementary power Mosfet followers biased into pure Class A mode. These devices are the current gain stage of the amplifier, very linearly following the musical signal produced by the voltage gain stage. The voltage amplification is created Great attention has been paid to the linearity of the gain stages of the M2, resulting in a power amplifier whose performance is good enough to avoid negative feedback altogether. This is rarely achieved at a reasonable cost, and at this time the M2 serves as one of the best examples of the benefits of an amplifier with passive voltage amplification and no feedback.
The design is extremely reliable and will never need adjustment. It achieves a relaxed sound with a very organic character and dynamics well beyond the expectations of the power rating.
The simplicity and performance of the circuit allows a unique sonic experience that is likely to make you go through your entire record collection all over again.
an auto-former which magnetically multiplies the input voltage.
First Watt F1 10wpc Stereo power amplifier£2,395.00
First Watt F1 10wpc
The F1 is a 10 watt per channel stereo amplifier operating in balanced single-ended Class A without feedback. Each channel has only one gain stage and draws a constant 100 watts.
It is a power trans-conductance amplifier (or power current source, if you like), replicating an input voltage into an output current. A regular amplifier sends output voltage to the loudspeaker. This is not that kind of amplifier.
This amplifier ignores the elements in series with the load circuit, including back-emf, wire resistance, inductance and such, and creates voice coil acceleration in direct proportion to the input signal.
It is well suited to sensitive full-range drivers such as Lowther or Fostex, and allows easy use of parallel loading networks to tailor the driver response.
It has both balanced and single-ended inputs. The input impedance is nominally 80 Kohm, and the output impedance is 80 ohms. The output noise is around 100 picowatts (100 trillionths of a watt).
First Watt F5 stereo Power amplifier 25wpc£2,795.00
First Watt F5 stereo amplifier 25wpc
So far, First Watt has made a few different amplifiers: Very different amplifiers.
Quite a few people have asked me for a regular sort of amplifier, you know the kind you plug like any other, with some voltage gain and a real damping factor. Amplifiers that have low distortion and noise, and will drive a 4 ohm load.
The last time people asked for that they got the Aleph J, which satisfied most of those requirements. Single-ended Class A, the Aleph J is an easy-going design which is happy driving 8 ohm loads with a warm, relaxed presentation.
By way of contrast, I present the F5 (taa-daa!), a push-pull Class A amplifier, utilizing JFETs and MOSFETs in a very simple two stage complementary circuit – a little bit like a complementary version of the Aleph J. But like all theIn many ways, it’s an ordinary topology - the basic circuit is found in numerous preamp circuits and the odd power amplifier (Check out the Profet amp from Selectronics). But the F5 is the product of It has very wide bandwidth, DC to > 1 MHz.
No capacitors anywhere in the circuit. (except in the power supply, of course!)
It has a high input impedance – 100 Kohms, and a high damping factor (~40)
The distortion is very low, between .001% and .005% at 1 watt.
It will drive low impedances.
It’s very quiet, about 60 microvolts or so.
Did I mention that it sounds terrific?
decisions that set it apart.other First Watt amps so far – this one is different.