Tellurium Q Atom amplifier - Low cost modification for improved power and sound quality!

edited March 2016 in Amplifiers
The Atom is the little amp that can, it is a special thing. As originally sold, it was a class A/B transistor amplifier with a special sliding bias system to eliminate crossover distortion. While it is a modest 20W per channel it's other specifications are very much more interesting:

  • Out put maximum voltage swing; 30V peak-peak nominal
  • Maximum Gain: 19dB
  • Frequency bandwidth: 5Hz - 300Khz flat response
  • Frequency bandwidth: 2Hz - 300Khz -3dB
  • Phase angle change 0 degrees +/- 1 degree 85Hz to 300KHz
Not that many Atoms were made and of those that escaped the crusher at Tellurium Q, most that were sold found their way to Poland. I personally know of only two other people in the UK who have Atoms, but they seem well loved. In taking the Atom apart, the case appears to be very nicely made indeed although the aluminum front panel inexplicably feels cheap despite being a good deal thicker than I expected.

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Inside we find a cool little circuit in both senses, made to a very high standard indeed:

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Notice those two turquoise wirewound resistors nestled against the rear panel?

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These ones? I'm going to bypass them with little coils made of enameled copper wire, formed by wrapping around a pencil. The resistors appear to be there in order to limit the Atom somehow, for no clear reason I can understand. If I were to replace them with coils and the Atom will be more powerful, and sound nicer (I am told by it's designer Geoff Merrigan Colin Wonfor).


Here is a coil, shown with a 2p and a dinosaur for scale:

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Snipping the top of the resistors off, leaving their 'legs' mean it is easier to solder the coils into the circuit:


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This is them installed:

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This is a most robust amplifier circuit. I am told that during testing at Tellurium Q, an Atom was run short circuited on the output for two days! Eventually one channel failed, not the output device but one of the transistors in the circuit. This was replaced and the amp worked 100% perfectly once again.

The strangest thing is why this amplifier was deliberately limited in the first place, it seems at odds with the quality of the design as a whole. Personally, I suspect it was not so much a design decision as a marketing/business one (albeit a strange one).

If I have made any errors, perhaps Colin will kindly correct me? Also Col, would you tell us how the specs of the Atom changes with this little modification?

I hope that someone else with an Atom will find this information useful one day. How does it sound? A quick listen confirms much firmer bass and imaging is improved also. I'd definitely say it is a warmer sound and a more forceful one.
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Comments

  • That dinosaur for scale is the best thing I've seen today.
  • Nice write up Alan thanks for sharing
  • Love the dinosaur for scale. You could be on to some sort of international measuring scale there. Imagine the long jump measured in velociraptors instead of metres. Much more interesting.
  • edited March 2016
    image

    Here is the PCB in JPG

    All reference to the original manufacture have been erased from it's History.
  • Baby AB Amp known once as the "Atom" circuit.

    image
  • Circuit PCB for this can be bought from me, I need a min order of 10
  • AntiCrap said:
    image

    Here is the PCB in JPG

    All reference to the original manufacture have been erased from it's History.
    image
  • Who are the other two Atom owners Alan?
  •  
     These are lovely little amplifiers.

     I remember hearing one at Cols workshop, along with the mighty 100w SECA mono's.

     Put me down for two PCB's please :)


  • They are very nice. Especially bi-amped.

    Obviously not Class A, but plenty of grunt from a little package.
  • quickie said:
     
     These are lovely little amplifiers.

     I remember hearing one at Cols workshop, along with the mighty 100w SECA mono's.

     Put me down for two PCB's please :)


    OK done I will get costing and BOM sorted now the master builder Sir Quickie wants two thanks Paul
  • I'd recommend anyone have a crack at making this, kind of NAIT 2 fun but more serious and with more welly. It looks like an easy little thing to build from what I can see.
  • Alan said:
    I'd recommend anyone have a crack at making this, kind of NAIT 2 fun but more serious and with more welly. It looks like an easy little thing to build from what I can see.
    How does the  Ex Atom sound now Alan?
  • Are the Atoms bridgeable?
    :-?
  • With a external phase shifter yes. Why ?
  • Just thinking along the lines of more power, like Atom Ants!

    image

    Would the phase shifter effect sound quality?
  • So says the Metal fan :-)
  • edited March 2016
    uglymusic said:
    Who are the other two Atom owners Alan?
    Hi Dave,

    Yourself and Marc Whitmarsh. There area undoubtedly more, but these are all I know.
  • AntiCrap said:
    Alan said:
    I'd recommend anyone have a crack at making this, kind of NAIT 2 fun but more serious and with more welly. It looks like an easy little thing to build from what I can see.
    How does the  Ex Atom sound now Alan?

    Just lovely Colin, like a much more powerful amp. It's a real riot too, so much musical energy and verve. I could happily live with it as a final amp, especially with a SECA pre.

    This would be superb with some classic Royds!
  • Alan said:
    uglymusic said:
    Who are the other two Atom owners Alan?
    Hi Dave,

    Yourself and Marc Whitmarsh. There area undoubtedly more, but these are all I know.
    Do I know Marc Whitmarsh?
  • uglymusic said:
    So says the Metal fan :-)
    image
  • cj66 said:
    Just thinking along the lines of more power, like Atom Ants!

    image

    Would the phase shifter effect sound quality?
    A little
  • now 29W a channel Alan
  • AntiCrap said:
    quickie said:
     
     These are lovely little amplifiers.

     I remember hearing one at Cols workshop, along with the mighty 100w SECA mono's.

     Put me down for two PCB's please :)


    OK done I will get costing and BOM sorted now the master builder Sir Quickie wants two thanks Paul

    AntiCrap said:
    Cheers Col.

    Thanks for the link on the case.

    I've got a load of 160 va 2x18v transformers here, so have opted to mount the transformer off the pcb.

    Bought one of these, which look good.

    http://www.ebay.co.uk/itm/111144680258?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT
  • edited March 2016
    What is the Transformer diameter the PCB is 160mm * 160mm so you will have to mount Transformer in the front with this case, leaving about 120mm and a height of 49mm . Do Not allow Transformer mounting bolt to clash with the lid. It would give a shorted turn and get a bit hot, NO MELT.

    But you could put potting compound into the centre and drill it out and use shorter bolt.

    So Transformer Height and Diameter please.

    Now with 18-0-18V you should get about 18W into 8 Ohms and 35W into 4 Ohms
    22-0-22V is 24W 8 ohm 41W 4 Ohm
    25-0-25V is 36W 8 Ohm but 40W 4 Ohm only as we run out of current. Peak will be 70W 4 Ohm
  •  
     Transformer is 100mm diameter, and 45mm high, so will fit perfectly in the front of the case, if I doing away with the mounting kit
     
     and pot the centre.
  • In 2 week time I have a 12yr old going to make one of these I post results include vaporized kid he he

  •  Lol..........will probably be better then my effort :\">
  • edited March 2016
    What of vaporizing one self NO NO that my JOB the only one I have left.

    I have made the ideal tool will post one to Langport soon.




  • Here is a Mini Review Dave did a while ago


  • Gosh - that is a real mini review.
  • Yep Dave loves saving paper. But his links failed he he I will fix.

  • edited March 2016
    Colin can you count me in for two sets of amplifier boards please
  • edited March 2016
    FWIW, I'm listening to my Atoms at the moment. I listen to them all day at my desk, squeezed between my iMac and Missions.
  • NO do not pollute them with "I"issions
  • sovereign said:
    Colin can you count me in for two sets of amplifier boards please  


    OK James no probs
  • AntiCrap said:
    NO do not pollute them with "I"issions
    They sound pretty good to me. I've had them for donkey's.
  • edited May 2016
    So, another visit to Colin's pit and another maniacally genius tweak... My baby Atom is now something like 47 Watts! It started at 18 or 22 or something around there. It now gets warm when played loud, but no real downsides at all. It's been on steroids! (My personal struggle with steroid addiction only made me stronger.)

    Colin biased the Atom further into class A for me, and I have to say with it's clever sliding bias it is even more surprising than ever.  The bass impact and slam is only bettered by big class A stuff now, it really could be the last amplifier I'd ever need but just I've been spoiled with the really big stuff. The only place now the SECA is far ahead is imaging (namely projecting a soundstage far out into the room) and scale. The Atom really is a treat, keeping company with the SECAs for serious listening.

    It took Colin just a little while with a scope and a more precise meter than I have. Thank you Colin, great work! What a super little design the Atom was... I'm glad it could be back soon.

    Go on, get Atomized!


  • This gratuitous pic is posted at Colin's request (he likes to see where his babies live after they leave home). We are decorating and the HiFi sits in front of a newly painted feature wall.

    The baby Atom is there perched on the (larger) DAC, but the point is the wall colour sets off the stone on the SECAs rather nicely.




    image

    (Brown, you say? NOoooo, it is 'exotic spice', it said so on the tin. Besides, I was told "..any colour but Brown".  Fortunately it is liked - it really is a striking effect with the other wall-coverings.)

  •  Was there any interest in the PCB's ?

     I've got a nice little case here waiting :)

  • We have PCB,s yes, but some said yes but no action.
  •  
     Cool. Let me know how much for a couple Col :)

  • I'll take two boards if you have any to spare Col.


  • Nice progress Mr Brown.
    Has the increase in power etc. improved the sound of your system as a whole ?
  • sovereign said:
    Nice progress Mr Brown.
    Has the increase in power etc. improved the sound of your system as a whole ?
    James - hope you're well mate?

    It sounds great. Very fast, slightly 'cooler' sounding than Colin's SECA MOSFET gear. Sounds about as good as the prototype Atom (with old Magnum MF250 FETS) Colin gave me years ago, which displaced my shiny 'Statement' amp, but it has more grunt and bass 'slam'.

    I use it each day for TV/movies, also radio etc. It is also good enough for serious listening, but the SECAs are better still.
  • Col - we'll take an Atom board too, my son wants to build one. Hopefully we can mount a pot and source selector, to make a simple line level integrated.

    Does the new board have the 'piggy back' bi-amp facility the old Atom had?
  • Great news Alan, health is slowly on the mend, thanks for asking.
    I would have an atom board as well if I didn't have three of Colin's amps to build already :-O
  • That is great news James. I was just about to send you a message, but saw you'd answered my question.
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