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mwhouston

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mwhouston last won the day on February 23 2016

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About mwhouston

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  1. Looks like a lot of old world caps caps in there. Probably PIOs. Looks super complex and expensive. Never really found the insides of amps and audio gear attractive. Personally I wood have had a wood or Al top and not Perspex. Tube gear with the hot bottles on top is different. Hope we the Xover lives up to its looks.
  2. Here is one of three Naxos Moyzes. Just might get the rest.
  3. I hope it gets you back into listening. Very important.
  4. The hybrid headphone amp (LeManja) is completed and sounding good. Still trialling the limiting resistor for the reg but all else checks out. With a universal front end any 12A?7 can be installed with no adjustments to bias etc. The backend is driven by a PT2308 - a dedicated headphone very low distortion driver chip (Class A/B). The chip runs on 7V max so I’ve used a 6V reg. About to have a be a big listen. Current tube is a new Ting Sol gold pin. After seven hours on the end of this new HP amp I am extremely impressed. So very pleased. It will go up for sale. PM if interested.
  5. Can anyone see what I have done wrong here TWICE! All values are correct but here is a hint - look at the red wire which connects the positive voltage. Only three guesses gents.
  6. Ta mate, I’ll have a chat with him. Haven’t caught up for a while.
  7. My main experience is with Class A tube amps (I’ve built and sold many) but have also built a number of Class A SS AMPS. THE hiragana “Le Monster” Class A is an example but the principle is true for tube and SS. Class A amps draw pretty well a constant current regardless of input signal level or volume plate at. Not usual for big Class A SS amps to be drawing many amps at turn on and to run very hot with no music on. Your assumption is correct.
  8. Without reading all of the above posts and some appeared to be way off the mark; In Class A operation with the power or output/driving device, tube or transistor, the control grid/gate/base is always throttling back (negative bias) the current flow through that device. In a tube the grid would stay negative compared to the cathode (or filament in a triode). In Class B mode the controlling element, in the power device, is more positive and allows higher current flow through the device. With a tube the grid would go positive the same with a NPN transistor. This occurs when the audio signal, being fed to the device, exceeds the devices negative bias. Image the device has a negative (-5V) bias but now the audio signal is plus 6V. The device is being driven beyond its negative bias. In Class A/B amps (take transistor amps) most high powered amps will deliver 30 or more watts (the output device remains in negative bias) until the input signal gets to the stage when it is pushing the transistor to higher conduction by sending the base positive (for NPN semi-conductors). When the bias is so positive it drives the output device into over-conduction, where it cannot handle the current, clipping occurs. Usually more noticeable in SS devices.
  9. I’ve found the same. Not much different after a while. Most testers don’t apply a very high voltage to the tube but the amp they are to go in may. Tubes can test OK then arc and hiss in the amp. Always watch a suspect tube as it comes up, If you see racing know tube is not suitable for the amp. Most times just dump them. Once suspect you don’t know what other damage they may cause. .
  10. I’ll be interested to see what you end up with. I’ve found good phones start about the $400 mark. I have three pairs at about the $400 point. Happy with the lot.
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