Hi Guys,
I've heard from a couple of guys who think the G&W J1 is the best thing since sliced bread and report it sounds excellent (my one sounds excellent too) However........ I've also heard from quite a few people who say their J1's sound like total crud so this would suggest the parts in the J1 are not closely matched and you'll either get one which falls very close to the design tolerance or one which is well outwith the design tolerance... at £100 a pop they couldn't afford to match the transistors etc. and the parts are most probaby fitted off the shelf without matching.
A friend of mine bought one and more or less confirmed this to be the case... he had a very close look at the circuit and "then" listened to his J1 and found it to sound pretty awful.. the exact opposite from my J1 which sounds great.. here are his findings:
"Got my headamp yesterday. First thing I did was break the seal, take the cover off, and trace out the circuit. Did you notice that although the amp is made in China it was designed in the US? Clock the 'phone number of the designer on the pcb. I've got the full schematic traced out now and it was pretty much as I'd guessed from your photographs. The LF353 opamp in the power supply section is used to cancel ripple and noise on the output of the 7815/7915 voltage regulators. The headamp proper is an input differential pair of jfets ( 2SK30A junction field effect transistors ), a bjt ( 2N4403 bipolar junction transistor ) voltage amplifier, and a simple complementary ( 2SB647/2SD667 ) emitter follower output stage. The output stage operates in class AB with a quiescent current of 4-6mA per device. The output offset is adjustable with the 100k trimpots and was around 2mV on both channels of my amp. The output offset and quiescent current are interdependent, so that the setting which gives minimum offset is unlikely to be optimal for lowest crossover distortion. With class AB bjt output stages the quiescent current setting is critical for decent performance."
"After I'd done all of that I played my reference CD. Are we talking about the same headamp here?? Raw and in yer face; exciting for the first 10 mins and very wearing thereafter. I tried all of my headphones and it sounded awful with every pair of them. The mid range was raw, grainy, and muddled - the classic "transistor" sound of crossover distortion from a badly set up class B output stage. I found it impossible to separate out individual instruments and the stereo imaging was very poor. The extreme bass and treble were very prominent but not at all accurate. The bass was very rasping, "buzzy", and "one note". The treble was best done but came across as hissy on voices and wire brushes. The amp sounded best with the Grado 'phones; but even with them after 10 mins I'd had enough. I don't think I could listen to the amp for more than 30mins at a stretch with any of the headphones I've got."
"If all of the components were carefully matched and selected to give mimimum output offset at the same time as lowest crossover distortion then I believe that the amp could sound good. Obviously component selection and matching are out of the question for such a low cost amp. The amp has no temperature compensation so that as the output devices warm up the quiescent current will increase away from the optimum value for minimum distortion ( in the unlikely event it was at this value to begin with ). This will happen gradually over the space of 30 to 60 minutes so you won't be too aware of it. The sound of the amp will vary quite markedly from sample to sample - you were obviously very lucky and got one of the ( very ) few close to optimum performance."
Armed with this info I can no longer recommend the J1...... If they all sounded the same as the one I have then I'd recommend them without doubt but considering the sound varies (so widely) from amp to amp due to unmatched components it wouldn't be fair for me to recommend them to you guys... you could pick one up that has components that are pretty well matched (by luck) or you could pick up one with components that are way out of tolerance...... That's pot luck and I don't want you guys gambling your money on an amp which "may" or "may not" sound good when it arrives on your doorstep.
Those of you who have got J1's that sound like crap "could" replace certain components and hand match them but this is a costly and time consuming business and is probably "why" the J1 only costs £100.... if they were to hand match all the components when they were being made then it would cost a hell of a lot more... you'd throw more transistors in the bin than you would fit into the amp.
Those of you who are lucky enough (and it is pot luck) to have J1's with pretty closely matched components will be enjoying the music and probably oblivious to this thread..... I just wish the consistency of the J1 was close to 100% so that
everyone could hear this amp at its best but it obviously is more of a 50 / 50 thing and, as such, I can no longer give it the thumbs up
I apologise to any of you guys who read my report of the J1 and went out and bought one which turned out to be a bit of a kipper.... I should have realised that at £100 the components wouldn't have been hand matched and the parts would be fitted direct off the shelf with the only test being "DC offset" which is adjusted by the 100K trimpots. I wrongly assumed they would all be consistent, my apologies.
Mike.
