Tube FAQ
Why use vacuum tubes today?
The short answer is when used in audio circuits they just sound better than transistors.
These is quite a sweeping statement, but consider that if they did not have a considerable effect in the audio industry why after 85 years since their introduction we still use them today? Also consider that musicians (who should care) generally prefer tube amplifiers and tube microphones, and recording/mastering studios still feature many tube based components. A very strong argument indeed; tube products may not be the choice of the mass market but they are the choice of the discerning music lover and are still very much in use today.
We believe the true emotion of music and the feeling of ‘realism’ is enhanced by tube products. This is chiefly because they are low gain devices which have a very linear response, even without feedback. Tubes have an even-order harmonic response whereas transistors have odd-order harmonic response, which is why it is important for all transistor amplifiers to have very low harmonic distortion, as an odd-order response makes the sound very hard and sterile. That is why solid-state designs keep emphasizing the 0.0000000% THD measurements! Solid-state designs also implement huge amounts of feedback in the order of 50dB+, whereas tube designs are typically 10-15 dB.
Do you measure your amplifiers etc.?
Just because we design and manufacture tube amplifiers, which historically have not measured well, this doesn’t mean we don’t care about their technical performance. We trust our ears implicitly as there is no test equipment in existence today that can measure what we can hear. A distortion analyzer or Audio Precision piece of test equipment is a very useful engineering tool which we still use, but it usually confirms what we can hear. Our equipment typically measures very well, with most of our amplifiers still offering very competent 0.1% THD which is why they sound very clean and engaging.
How long does a tube last?
Vacuum tubes used in our products last between 5000 - 9000 hours depending on where they are used. Signal tubes (the smaller tubes) which are found in our preamps, DACs, CD players and the drive stage of amplifiers generally last up to 9000 hours, and power output tubes (the larger tubes in our amplifiers) about 5000 hours. They do not usually completely fail after this time, but gradually deteriorate as the cathode begins to loose its coating and cannot emit electronics at the maximum rate. The sound usually becomes less focused and 2D like lacking HF response.
I thought all tube amps sounded soft, because they glow?
A lot of people assume that tube amplifiers sound slow, coloured and soft. This may be the case of some of our competitor’s tube products but we can assure you this is far from the case with Tube Technology products. A well designed tube amp can offer a very fast slew rate and great dynamics with a clean presentation that is not coloured. The glow in a tube does not make them soft, this is simply a heating element, which heats the cathode so it can release negatively charged electrons which are attracted to the positively charged anode, creating conduction. So when you are listening to a tube amplifier you are literally experiencing electron flow.
Our circuit designs utilize the best combination of modern and classic design techniques, ensuring minimum distortion,, using very stiff power supplies which ensure accurate reproduction which is un-coloured and precise. We do not just re-make classic designs which have been around for the last 80 years otherwise they would sound coloured.
Other tube manufacturers do make much higher distortion products which are typical more of the older style circuits such as single-ended designs which can run into 5% THD, but because this is all essentially even-order distortion they can have a very pleasing sound but not necessarily accurate, this is where colouration is heard.
Do guitarists still use tube amps?
The Marshall or Fender guitar tube amp is still the most highly desired possession of a guitarist or even the good old HiWatt which is making something of a comeback today. Next time you see a band on stage, a Marshall or any of the above won’t be far away. Most of these products still exclusively use tubes because of their even-harmonic distortion, as a guitar amp over-drives the tube and the distortion component is most desirable.
I thought all tube amps were un-reliable & noisy?
Not the case with Tube Technology. After all Man went to the moon using tubes, tubes are used in guidance systems by the military (Russian Mig Fighter jets). The most unreliable and noisy item in older style tube amplifiers were the rectifier tubes, as they are doing a lot of work charging the power supply capacitors. Tube Technology does not feature rectifier tubes in its designs, we use solid state circuitry, which is reliable and low noise.
My tubes glow, but don’t seem to work?
Just because they glow, this does not they are functioning. The heating element is a very simple structure, effectively consisting of a spiral of wire passed through a tube, so this keeps working forever -virtually. A failure is usually caused by another breakdown in the tube.
Are tubes or valves still made?
Yes tubes are still manufactured today, in Russia, the Czech Republic, China and Yugoslavia. Some of these countries have purchased a lot of plant equipment from the British (GEC) and the Dutch (Philips) to continue this great tradition. The guitar industry demands many thousands of tubes per month and combined with the smaller HiFi industries needs, they will probably be around for many more years to come. Also many high power transmitters used in radio etc, are still tube based so these factories rely on this business too.
What tubes should I buy?
Not all tubes are suitable for use in our products. If in doubt, please check with us. Our website features replacement tubes, please consult it. Some double triode models which are available on the market can be asymmetric instead of symmetrical so be careful. Also do not always but the cheapest valves as these probably won’t give you the best audio performance, and since they last a long time in your unit why listen to a sub-standard product for an extended period of time.
Do I need someone like an engineer or my retailer to change the tubes?
No, not usually. Our amplifier products come with meters so you can change them yourself, and our preamps, DACs, CD players tubes can be just plugged in.
What is cathode bias and fixed bias?
Cathode Bias amps, which we do not manufacture use a capacitor to make the grid more negative and do not usually require any adjustment. The downside is they usually have more distortion which make them sound a little more coloured. TT amps feature fixed bias which requires tube adjustment but results in more accurate bias points and less distortion.
How often do I have to re-bias my amp?
It is important to re-bias your amplifier after you have fitted a new set of tubes, then check them again after approx. an hour then again approx. a week or so has passed. Check them once every few months after that, as they will have stabilized by then.
How important are cables?
Very important, if you use sub-standard cables, all the benefits gained by bettering the electronics will have been lost through the connecting chain.
What cables do you recommend?
Tube Technology now offers our own range if cables, which we highly recommend as they are compatible with our electronics and feature technology not available in other cable products. But like all audio products you should listen and try, to see if they work in your system and give you the results you want.
How long do tubes take to warm up?
A tube reaches operating temperature after a few seconds of switch on, however they can sound a little more controlled and focussed after approx. 20 minutes.
Should I leave the units on permanently?
There is no real reason to leave the units switched on permanently, but if you wish you can. The only advice is that if the units are left switched on permanently then the tube life will deteriorate at a faster rate.
What is triode, pentode or tetrode?
A triode is the description given to the type of tube utilised and refers to the amount of elements it has, which for a triode it has three, a Cathode, Anode and Grid. A tetrode has four elements, a Cathode, Anode, Grid and Screen Grid. A pentode has five elements, a Cathode, Anode, Grid, Screen Grid and Suppressor Grid. TT prefers pentodes in output stages as these extra grids stop the problem of secondary emission of electrons. This happens when electrons that have been emitted from the cathode bounce back and get re-emitted a problem with triode power tubes.
What is single ended, parallel single ended and push-pull.
Single ended means the amplifier tubes are operated in a single ended mode, the audio signal goes in one end of the tube and re-appears at the other end, very simple but it has its drawbacks because of increased distortion and noise problems. Parallel single-ended is the same thing but instead of one tube, more a used together in a daisy chain fashion. Push-Pull is the preferred use of circuit topology for Tube Technology because the audio signal is spilt between positive phase and negative phase, increasing power output with decreased distortion and reduced noise. This mode of operation is more complicated and involves careful transformer design to achieve good results; hence most companies opt for single-ended designs because they are easier to design.
I thought all tube amps only were 5 or 10 watts.
This again has been the norm. for many tube amplifiers in the past because of single-ended operation which is in-efficient and yields less output power, and usually requires much higher operating voltages to enable higher outputs. TT amplifiers offer higher outputs because of competent push-pull ultra-linear designs, which can deliver power in excess of 500 watts.
Are tubes dangerous, because they get so hot?
We often liken a tube to a light bulb, they also get hot but you don’t directly touch them! Covers are available for our amplifiers.
Why aren’t there any tone controls?
Tone controls usually are required to be placed directly into the signal path, therefore degrading sonic clarity. A tone control usually consists of o potentiometer which is a variable resistor, which does exactly that ‘resists’ the sound that passes through it. That is why a graphic equaliser is a bad thing, as there are numerous potentiometers in the signal path!
Is it safe to ship my amplifiers?
Yes, if using the correct packaging. Our products are built to a very high mechanical standard and are used to being shipped all over the world.
Can I change the voltage for another country?
All our products except those supplied to Japan, have multi-taps so can be changed for operation in any country.