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Let's Tube'n'Roll

As many years since the introduction of the "Mini Dual Triode Headphone Amp" have passed it was now time to develop a worthy successor. Inspired by the experiences of the DIGNA II and the provided possibility of tube-rolling, Mr.Nixie now introduces a "cute" headphone amplifier to the market, which targets exactly this audience of "tube-rollers".

And whenever Mr.Nixie takes such a stuff into his hands, neither the sound nor the possibility of extensive tube-rolling is left behind. And so, for the first time an amplifier on the market can feature not only different brands of one tube type, but also a whole range of tubes - which are still manufactured today - namely the ECC81, 82 and 83 series.

These tubes are still in service today and were used in the past in almost every audio device or amplifier.
The AGNETA headphone amplifier now offers the willing audio nerd a nearly inexhaustible possibility to test his own tube treasure and finally to find out "his" tube with "the sound par excellence".

Which tubes exactly can be used?

Thanks to a careful voltage feedback, all double triodes of the types ECC81, E81CC, ECC82, E82CC, ECC802S, ECC83MG and 5751 and their international versions such as 12AT7, 6201, CV4024, CV455, 12AU7(WA) CV4003, CV491, 12AX7MG, CV4004, 6057, 6681, 7025 and many others, whereas the heater is connected to pin 4 and 5 plus the filament center tap to pin 9 and the heater current is 12.6 V @ 150 mA in series or 6.3 V @ 300 mA in parallel connection.

For this reason, the types 12BH7-A or ECC99 are not suitable because their filament power is too high or the ECC832 or 12DW7 because they have triode systems with different amplification.
Also Russian double triodes (e.g. 6N2P ~ ECC83) cannot be used, because these tubes do not have the center filament connection on pin 9, and have (like the 6N1P or 6N3P for example) different socket layouts.

With regard to the lifetime of the tubes, not only the low anode current of 2 mA per triode system (at stabilized 170 V anode voltage) but also the controlled preheating of the tubes with 2 x 150 mA constant current is to be valued as highly tube-friendly.
A two-color LED in the tube socket discreetly indicates the current operating status (red = preheating - no signal, champagne color = operation).

Goldpin tubes?

As each system of the double triode supplies its own channel of the amplifier, we recommend the use of gold pin versions for old NOS tubes, as these systems were selected by the manufacturer for low tolerance (for new tubes from European production this is normally no longer necessary due to today's lower manufacturing tolerances); or hand-selected tubes offered by the supplier are recommended, whereby special attention is given to low microphic.

And how does Agneta sound?

My dear friend Matthias has had the opportunity to check Agneta's heart and kidneys in advance...

I've had the opportunity to do some extensive tube rolling with Mr.Nixie's new Agneta headphone amp over the last few weeks. As expected, three NOS double triodes from early production were the most impressive in their sound.

But I will only comment on the RoHS compliant tubes as they are yet manufactured.

The listening impressions of course only describe my personal impressions with the six different headphones I used (from Ultrasone Edition 8 and Sennheiser HD 650 to Ultimate Ears - specially made in the USA for my inner ears).

The photo features my preferences descending from left to right.
All tubes were of course burned in for at least 20 hours before the listening sessions.
In my experience the amplifier also needs about 50 hours of operation to achieve its full potential.

Now to the essential point:

It had to compete against my reference from the USA, a Ray Samuels Raptor, which costs however three times as expensive as the Agneta. The sound is very spacious with good bass response and a musical midrange, which I like. At start-stop behavior is also nothing to complain about. The sonic characteristics came very close to my reference in some aspects. One thing Agneta did even better than the Raptor: It manages extremely well very low impedance headphones.

For the demanded price Jrgen alias Mr.Nixie has again developed what I consider to be a very well-rounded product.


AUX input on front

Normally you're listening during operation to the signal present on the Line IN RCA jacks. But when connecting to this front 1/8" TRS jack another audio source like iPod or other high quality player for example, than this AUX signal is feeded to the amplifier.

LINK output jacks on rear

These jacks feed the by Relais "hard wired" signal from the Line IN jacks, when the amplifier is turned off. During operation of the amplifier the LINK signal source can be selected with a slider switch on the top panel:

RCA = The Line IN signal is always feeded to the LINK jacks regardless if another listening source is connected to the 1/8" TRS jack.
The green LED is illuminated.

AMP = The tube amplifier's output signal (with athe adjusted volume level) is feeded to the LINK jacks. With this trick the AGNETA amp acts as a kind of "tube sound enhancer" of the Line IN signal, or - when connected another source to the 1/8" TRS jack - of this AUX signal.
The yellow LED is illuminated. The processed signal is decoupled via 2.1 kohms resistors from the power stage.

Headphone connectors on front

Beside to the standard 1/4" TRS jack there's another 1/8" TRS jack present for connecting a second headphone in parallel.

15 VDC jack

In addition to the included high-quality white switching power supply, further optimizations are naturally possible at this point, e.g. inserting the
DC-Cleaner Passive or the installation of the DC-Cleaner Pro Mr.Nixie power supply.
Linear power supplies also offer excellent results; a minimum of 1 A at 15 V must be provided at a 5.5/2.1 mm plug with positive pole inside.

And last but not least: Designed and handcrafted in Germany

Hand-soldered in small quantities with lead-free silver solder, assembled with through hole components which have been acquired - wherever possible even though this corona crisis - in Germany: For example, all aluminum profiles are made by Fischerelektronik in Luedenscheid, the polymer parts are bought from Leipzig - like most of the electronic components - and are laser-cut in Berlin, JJ-Electronic tubes are supplied by BTB-Elektronik in Fuerth/Bavaria, etc.


Due to the lot of combinations please contact me first.

The AGNETA headphone amplifier is available in black und champagne-colored and the price without tube is
546 EUR incl. worldwide DHL priority shipping.

Don't hasitate to ask for tubes which Mr.Nixie's kitchen and cellar can offer ;-)

Shipping costs
Shipping and handling costs are already icluded in the product price. The prices for shipping within EU includes the German VAT.
Import duties, taxes etc. are not included. These charges are the buyer's responsibility.
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