We suggest you test the amplifier using just your music source, (iPad or CD player) and speakers. Keep it simple for a few days so you can see how you like what the amplifier can do. Then you can add a preamplifier if you prefer. Our amplifiers come with two volume controls so you do not have to use a preamplifier unless you want to. Once you connect a preamplifier just turn the volume controls all the way up and that will take them out of the circuit, and you can control everything using the preamp. This low power class A amplifier will perform best with efficient speakers. The power output to the speakers is only about 2 watts per side. You need to use 8 ohm speakers. There is a hum rheostat control located on the back of the amplifier or on the top. In some cases it has a screw driver slot, or a knob to adjust. To make this adjustment you first have the amplifier playing, then you cut the music source or turn the volume controls all the way down. Then with a screw driver or knob you turn the control to the left then to the right, you will hear a hum coming through the speakers, turn to the left then to the right until you find the sweet spot where any hum is at a minimum or gone all together. You only need to make this adjustment when you first set up the amplifier, or if you up-grade your tubes. The 6AX5 tube goes on the power supply it is a slow warm up rectifier and is a new old stock tube so it should last for years. The other tubes that come with your amplifier are used but test good. We suggest you purchase a set of back up tubes, the RCA brand is best. A back up set of tubes will come in handy for testing, and tubes like lightbulbs will wear out in time. For a trusted tube seller check out Jeffery on Etsy. Lowtechelec - Etsy https://www.etsy.com/shop/LowtechTwoo Enjoy your new amplifier!

No, we do not ship outside the US. However, many customers have used Planet Express (USA Address • Package Forwarding • Planet Express) package forwarding service with good results.

The 45 triode is the best sounding tube for all our amplifiers in our opinion. We feel that some sacrifice is made by moving to the higher power levels when you move to a 300B triode. At those power levels the components are able to handle the wattage produced by that tube and some sacrifice is made in fidelity, or other characteristics in the music that are present in the 45 & 2A3 tubes. There is no fidelity difference in stereo integrated 45, outboard power supply 45, or mono block 45 designs. They all use the same circuit and the same quality components. To help you make a decision on the 2A3 versus 45, consider your speaker sensitivity, the room you are listening to your music in, and the level of volume you prefer your music. Over the years NOT ONE customer has complained about lack of power even on a single 45 mono block. Most of our customers are boasting 97db sensitivity speakers. Factors to consider. Speaker sensitivity - The more sensitive the better. Room size and acoustics - Is this a large or small room to fill. Listening preference - Loud to rattle the windows or quiet to hear details.

The 6AX5 tube was one of the last rectifier tubes ever invented. It was a replacement for the 6X5 which was used in old wooden radios back in the late 1930’s The 6X5 was a poorly designed tube, although it was used for many years. It got the name transformer killer as it would short out in the non fused circuits back then, and take the power transformer with it. Then in the late 1950’s they invented the 6AX5 in my opinion the best rectifier tube ever made. It is a slow warm up rectifier like the 5AR4, only built much better than the 5AR4. It has a Huge cathode and strong plates with plenty of separation. Other slow warm up rectifiers sell for lots of money like the EL34 but are not as well designed as the 6AX5. A slow warm up rectifier tube will help the filter capacitors to last longer, it is like having a variac on the B+ voltage and slowly bringing it up, rather than hitting the amplifier and capacitors with the full B+ voltage at once. The 6AX5 tubes can sell for 10% of of the cost of a 5AR4 tube, as they are one of the best kept secrets in tube audio. Some of the high end power transformers Jason and I use offer a perfect 6.3 volt separate filament winding so we opt for the 6AX5 rectifier. If the power transformer we choose for the project has a 5 volt filament winding we may choose a 5R4 or a 80 tube for the rectifier. We always look for the best parts and transformers available, and change our circuit for the most benefit on sound and longevity.

I have been working on designing and building outboard power supply amplifiers lately. They are a throw back to the golden age of vintage audio. Some of the high end audio companies from the 40’s and 1950’s like Fisher, Capehart and others used this twin chassis design, in their top of the line flag ship offerings. The idea is to place on a separate chassis all of the transformers that can interact with each other or magnetic couple with each other. This can produce hum. This is especially important when dealing with 2.5 volt AC on the filaments using triode tubes, that we use in class A single ended design. With a separate chassis for the filaments, power and choke transformers on a separate chassis you have the room to arrange these parts far away from the sensitive areas of the amplifier that are known to pick up this unwanted noise, and place these transformers at desired angles in the power supply chassis and avoid magnetic coupling, and transformer interaction, that can produce hum and unwanted noise. With a single chassis amplifier you may not have the desired room to place these transformers away from the sensitive sound or noise pickup areas of the amplifier.

With a pair of mono amplifiers. Each one is an independent amplifier that can be used on its own. It is much easier to test and diagnose any symptoms if they should ever occur. Each amplifier has its own dedicated power supply, and rectifier tube. They do not share a common power supply like a single chassis amplifier would. So if something went out in the power supply on a single chassis stereo amplifier. Both the left and right channel would go out. Since each amplifier is directly connected to either the left or right channel speaker there is no chance for sound bleed crossover. You will get total channel separation. Some customers tell me that they seem to get more power and bass punch from the mono amplifiers, maybe because they do not share the common power supply. The draw backs are, do you have room for 2 amplifiers over a single chassis amplifier, Some of out customers place each on the speaker they are servicing. Since a pair of mono amplifiers uses almost twice the parts compared to a single chassis the cost is a little more. A pair of mono amplifiers require two of these parts, over a single chassis amplifier. Transformers, chokes, chassis, tubes, rheostats, are just a few of the items required in a pair of mono amplifiers verses a single chassis stereo amplifier.

Typically on our amplifiers, the rectifier tube, 6AX5 goes into the 8 pin socket directly in front of the power transformer. The power transformer will be the largest transformer on top and will typically have the AC plug directly behind it on the back of the amplifiers. The preamp tube, 6SN7 which is 8 pin tube goes into the other 8 pin socket which is typically on the other side of the transformer from the power transformer. There may or may not be a smaller output transformer mounted on top near this socket. The other indicator is the volume knob is always directly on the front of the amp where the preamp socket is located. The output tube either 45 or 2A3 is a 4 pin socket typically in the middle of the amplifier chassis. Be cautious however as the socket has two larger pins and two smaller pins. It will only go into the socket one way, typically we place the two larger pins on the power transformer side of the amplifier. The tubes should go in and out easily with out execessive force.