... a real sense of tubes

A tube headamps, handling and maintenance surface ...

Published: 25. 03. 2014 - 10:38

Why tube headamps?

Maybe quest for good sound?
There are many ways to reach it and using vacuum tubes is one of them. The constructor of such device is faced with few basic conditions:
-linear amplification throughout the entire audio range frequency with regarless of the load
-usage of feedback to the lesser extent (or without it) with transparent sound image and utter dynamics as a goal
-reliability and accesibility of the vacuum tubes used, use of quality parts, low impedance of the voltage source with good filtration
- Ability to drives wide impedance range 32 - 600ohm headphones.
Which is very demanding because low-impedance headphoness require a lot of current and high-impedance headphones demand enough voltage
For instance:

32ohm / 250mW   - signal has to be around 2.8 Vrms and 87mA
600ohm / 250mW - signal has to be around 12 Vrms and 20mA

- Low noise and hum. Noise voltage of  0.2 mV rms is barely audible, but it is audible at 32 ohms/98dB headphones. Headphones are acoustic magnifying lens.
- Preferably OTL design , even for high-impedance headphones..


A few words about handling with tube headphone OTL amp:

Each OTL tube devices are slightly unstable in the first minute at startup. It is due to set up tubes in the operating points. We recommend that during this period you don’t place or remove headphones from the connector. In particular, it is best to plug the headset into the connector, and then turn on the device, and if we didn't do so, before turning on the headset, wait a minute or two. Always use only clearly defined tubes for a particular device, or their exact equivalents. And of course, if you for any reason need our advice or assistance, please contact us using e-mail.

Tips about maintenance surface:

Cases of all models of HAD Audiolab devices are made from natural material - American walnut. Also, we have decided not to lacquer it but rather to smear them with natural walnut oil. We suggest to users to apply this oil on surface every 15-30 days. Buy walnut oil (eg. a fairly pure state is sold as a hair oil) and add to it a few drops of fragrant oil of your choice.
This fragrance will slowly evaporate...

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