FS WAD 300b with mods
World Audio Designs 300b push-pull (original)
These are pretty rare, even though 2 are for sale on here at the moment. I bought this one from Adam (Westlower) last year after he convinced David Coe to sell his own heavily modified reference amp. Adam had earlier bought the one for sale here on this site, and the listing below borrows from the original, but with additions as further work done before I bought it.
This is the original WAD 300b push-pull power amplifier, offered by World Audio Designs as a kit ... the one with inter-stage transformers ... and written about in HiFi World here:
http://www.hi-fiworld.co.uk/index.ph...html?showall=1. I can provide further documentation for any buyer.
This is generally regarded as the finest amplifier kit made available by WAD. A number of people built clones of the kit, but this was built from the kit (and is all the better for it from a visual point of view, even if it does not have the wow factor of Adam’s polished steel version).
It is relatively standard, except for schottky diodes, and a few boutique parts sprinkled about, including some Mundorf and Elna Silmic capacitors. The 300Bs are Electro Harmonix, which posters on another site believe to be a good compromise between sound quality, robustness and cost. They certainly sound good to my ears.
The amplifier has two switchable modes, with and without feedback ... the latter providing the best sound imo. The 5687 and 6072 input/drivers are relatively new and have not been stressed in recent years. The amplifier is currently set-up for 8 ohm speakers, but also has 4 ohm taps on the output transformers (reconfigurable).
Work done on the amplifier includes:
* set to correct operating point/dissipation for EH Gold valves of c.32 Watts/valve
* 11dB input attenuators fitted (Audio Note tantalums) to work better with active preamps (and also passives)
* replacement of old capacitors, incl. Mundorf ZNs coupling and Elna Silmics on cathode bypass
* hum reduction via: re-configuration of earthing arrangements; fitted DC supply on input/driver valves; shielded wire on input and feedback wires; etc.
* two additional small chokes better to decouple the input stage, for greater dynamics and image stability
* tidied up the wiring to improve the hum level, along with adding screened wiring to the feedback circuit
* converted to battery bias
* noisy humbucker potentiometers replaced
* cracked speaker sockets replaced with silver-plated, heavy-duty Audio Notes
After all that (and more!), the amp owes me £1500, but is now functioning beautifully. PM me with questions ...
Most of this work was done by David Coe, whose website illustrates his great proficiency in valve amps (and much else).
The amp is very heavy. Logically, collection only from North London (Finsbury Park) but I will deliver within c.100 miles.
One final thing to add is that DIYers still have work that can be done (such as boutique caps and resistors)
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Selling price £1500
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