AudioALT No. 1 amplifier

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by k4rstar, Jul 14, 2019.

  1. k4rstar

    k4rstar On a journey... somewhere

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    Many moons ago @Zampotech posted a link to the Moscow firm audioalt.ru who manufacture audio transformers in Russia. They also have a line of amplifiers and high current output discrete DACs. I was curious about their basic headphone amplifier, which was simply called the 'No. 1'. It seemed to use high quality parts, a simple circuit and their own transformers. The specifications listed on their website (using Google Translate) seemed promising.

    The link is here: http://www.audioalt.ru/product.php?cat=69&product=2357

    It is a transistor amplifier using two JFETs per channel, with transformer coupling on both the input and the output. The power supply is a toroidal transformer with a simple CLC filter. There are no coupling capacitors in the signal path. The list price is 24,990 rubles, or roughly 400 USD.

    Curiosity got the better of me and I decided to order one for shits and giggles. The ordering process was not easy, the sales representatives did not have the best English and it took 3 or 4 pro forma invoices to clarify that I wanted a 120 V unit with a non-locking 1/4" connector. In the end I paid and waited a few months for the amplifier to arrive due to production delays.

    Despite being shipped in a small wooden crate fastened by screws, the amplifier arrived heavily damaged. The power switch was jammed and there were loose parts rattling inside. I spent the better part of 3 hours taking the amp apart and repairing it. The internal build quality of the amplifier left a lot to be desired, it was pretty shoddy work. I am guessing this firm contracted out the assembly of their amplifiers to a third party. Here are a short list of problems I encountered:
    • Cold solder joints
    • The leads for the JFETs were too short, so the slightest tension caused them to sever
    • The connections at the volume pot were not wrapped in heatshrink. A millimeter nudge would result in a short circuit and possible damage to headphones/hearing.
    • The IEC inlet was way too close to the mains transformer. Again, potential for short circuit. I remedied this by inserting a piece of foam in between them
    • The standoffs for the output transformers were not fastened securely and came loose during transit
    • Although their web page advertises an ALPS potentiometer, it was nowhere to be found. Instead we got a cheap Russian POS
    Thankfully the simple circuit made it easy to follow what needed to go where without a schematic and I was able to fix the amp with a little soldering and glue. Here's a snapshot mid repair:

    [​IMG]

    And post repair:

    [​IMG]

    Of interest, the output transformers have split bobbins, which seems to be popular among eastern european manufacturers. The JFETs are mounted to the bottom of the chassis as a heat sink with screws.

    Once repaired, I actually plugged it in and gave it a listen with the HD650s. There are certain times where I get a curiosity about a component because I already have a pre-conceived notion in my head of how it will sound and I want to prove myself right (or wrong). This is one of those times where I was right. Because of the short signal path and the use of JFETs I expected a clean, resolving (for transistors) and slightly rounded sound. That is pretty much what you get.

    The No. 1 doesn't have the sheer grip and slam of a multi-stage circuit with MOSFET output or the clarity/immediacy of tubes. It does seem to stay composed at all volume levels with all program material. It is good at presenting detail in a natural and non-fatiguing way. Low bass and treble is a little rounded off but for me this is characteristic of JFETs. Gain is not an issue thanks to the input transformers, in fact there may be too much of it.

    Here is a review I agree with translated from Russian from the firm's website:

    Sound with a slight touch of analyticity, but not sharp. You can clearly track the location of the instruments on stage, but at the same time the integrity of the work is not compromised. Fast and clear bass frequencies, a beautiful middle, and clear high without rattling. A good scene in width, the depth is not too big (although very much depends on the quality of recording, on standard discs is not deep, but discs in HDCD quality sound just fine on stage and sound, added to the clarity of reverberation as well). Sound doesn't get tired of listening to music without getting tired of it for a long time. On low you can pick a little bit on the depth of bass and its saturation, but it's on the amateur, I love just such qualities of low that got. On volume I listen with the handle of the regulator not more than 9 hours, and even on 8. And at decrease in volume detail does not disappear, simply plays quieter and all, as well as at increase in a sound of distortions is not observed. In general, I was very satisfied with the amplifier for a reason.

    Overall this was an interesting experiment, though I am disappointed with the misleading advertising regarding the ALPS pot and the overall lack of attention to detail in assembly. If any members are interested in trying the amplifier I would be happy to send it out on loan.
     
  2. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    Interesting. Would be neat to compare it to the Shortest Way amp given similar design goals. Might be interested in a loaner if enough folks want to as well.
     
  3. Zampotech

    Zampotech Friend

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    I think I understand the damage problem. I know that.
    Probably chrome screws were screwed into the brass bushings. Very slippery threaded pair.
    If the amplifier was delivered upside down and plus vibration - the screws are unscrewed.

    PS And that was probably hard packing, without amoritzation.
     
    Last edited: Jul 15, 2019

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