FOR SALE: DXT Electro - Acoustics DXT-17
Pair of DXT 17 Power amplifiers
I Want to sale these amps locally only
Buyers are welcome to try before hand
I don't need to sell it but I won't need it anymore and don't want them to sit here unused
Vacuum Tube 17 watt
Monoblock power amplifiers
It is not in every situation that one finds a high efficiency speaker with a large woofer in a large cabinet to couple an amplifier to. With modern-day speakers they tend to be smaller in size and thus is less efficient. While the DXT-12 monoblock amplifier works extremely well with high efficiency speakers , the demand for more power is required to meet the needs of medium efficiency speakers. Thus, there was a need to conceive an amplifier capable of producing more power and higher damping factor than the DXT-12 Amp while still adhering to very similar design principles embodied in the original DXT-12 Amp. This new amplifier shall be designated the DXT-17 AMP, a monoblock amplifier.
The DXT-17 Amplifier is designed to be a Monoblock, rated at 17 watts. For stereo operation, two monoblocks are required. The DXT-17 Amp uses a Push-Pull configuration that operates in Class AB mode. The overall topology of the design utilizes triodes and triode-connected vacuum tubes for a warm, smooth, accurate and life-like sound. In one word, the listening experience could be termed as ‘musical’ to describe the overall sound.The output vacuum tubes are based on a pair of very linear triode-connected EL34s. Vacuum tube rectification is in the form of the rectifier tube, the GZ32/5V4 and a Pi capacitor/choke/capacitor filter. The vacuum tube rectification provides a soft-start to the rest of the vacuum tubes which in turn prolongs the life span of the rest of the tubes. However, although this is more expensive, it is preferred to solid-state rectification which exhibits hard-starting and noisier high tension voltage supply due to the higher harmonics ripple caused by the switching characteristics of solid state rectifiers. In our view, vacuum tube rectification is superior to solid-state rectification for the reason just stated.
output impedance of 74 Kilo Ohms or lower. The DXT-17 amplifier has a low
susceptibility to hum. As a result, there is no audible hum even when
placing one’s ear next to a high sensitivity 100dB speaker.
At the onset of the design, the goal was to achieve as low a distortion as possible without first applying negative feedback. It is with special selection and close matching of components that even without feedback, the distortion at 1KHz , mainly odd-harmonics is just under 1.5% at the rated output of 17 watts. In practice, it was necessary to strike a balance by applying the right amount of feedback to reduce the THD further without sacrificing the musicality. There is an overall or global negative feedback being applied from the secondary of the output transformer to the cathode of the first tube, the EF86.
The ‘right amount’ would then be a personal preference and hence the birth of the Variable Feedback Control (VFC).
The distortion figure then drops
further from just over 1.5% to these percentage figures depending on the
setting of the continuously Variable Feedback Control e.g. :-
Fully anti-clockwise : 0.45% THD
with 14.0 dB negative feedback,
Higher amounts of feedback give better frequency response but a narrower soundstage. On the other hand, lower feedback has more details and a wider, less compressed soundstage amidst a slightly mellower sound. Obviously, the choices are plentiful and the best way would be for the listener to experiment with the VFC to find an optimum spot. In essence, it is like utilizing the VFC to match the monoblock amplifier to a particular type of loudspeaker.
The output impedance to match the speaker is
factory-wired for 8 Ohms. For matching to a 1 Ohms, 4 Ohms or 16 Ohms
speaker, this requirement must be specified at the time of order and can be
factory-wired. The amplifier is a high quality handcrafted product that is
built to last a life-time. The only parts that will ever need replacement
are the vacuum tubes and no adjustment is needed thereafter. The time
interval required to replace the tubes will depend on the usage but it would
be typically in excess of 5 years for the small signal tubes and 2 years for the large
signal tubes, assuming a daily usage of about 5 hours.
The DXT amplifier is warranted for 3 years parts and labour except the Vacuum Tubes which are warranted by the manufacturers’ guarantee of 3 months.