Tellurium Q Atom amplifier - Low cost modification for improved power and sound quality!
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:
Inside we find a cool little circuit in both senses, made to a very high standard indeed:
Notice those two turquoise wirewound resistors nestled against the rear panel?
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:
Snipping the top of the resistors off, leaving their 'legs' mean it is easier to solder the coils into the circuit:
This is them installed:
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.
- 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
Inside we find a cool little circuit in both senses, made to a very high standard indeed:
Notice those two turquoise wirewound resistors nestled against the rear panel?
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:
Snipping the top of the resistors off, leaving their 'legs' mean it is easier to solder the coils into the circuit:
This is them installed:
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.
Comments
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
:-?
Would the phase shifter effect sound quality?
Yourself and Marc Whitmarsh. There area undoubtedly more, but these are all I know.
This would be superb with some classic Royds!
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
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.
Lol..........will probably be better then my effort
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!
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.
(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
Cool. Let me know how much for a couple Col
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.
Does the new board have the 'piggy back' bi-amp facility the old Atom had?
I would have an atom board as well if I didn't have three of Colin's amps to build already :-O