WAD 300B PP Clone innards

[Greg.]

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[Tony Moore]

Really nice build Greg!

[Greg.]

OK, this is the inside of my clone. Realise that from the outset I was not constrained by the limitations of anything original except the transformer set supplied to me by SP Wound components Ltd. Furthermore, I have to acknowledge an enormous contibution from Neal Gibbons whose help and direction brought me to this place I am now. All components were chosen based on experience of what would work well together. I used Rifa (RS) for low ESR electrolytic caps, and most resistors are Kiwame or Mills because I've previously worked out that these are good together. They meld in with Blackgates and Dynamicaps and even teflon V-Caps (remorgage caps) for coupling.

Studying the picture. Tx's are standard. I've fitted Richard's mains filter to the rear of the IEC socket.

The PSU board is non-standard having been inverted with a view to making more room for components, but in the end I still had to mount my C9/10 Rifa low ESR caps offboard because of size. These are double bypassed with polyprops but not visible because these caps are on the other side of the board. Incidentally, James made our boards out of quality material which really has to be as good as hard wiring if the product is right. You can tell the quality as soon as you apply the solder and iron The PSU board incorporates a small circuit to the side which supplies a tweak of DC heating for the two driver valves. The big PSU caps, C11/12 are double bypassed but not that obvious because the bypassers are stuck to the base of the caps. They are directly wired to the point of application, in this case being the Tx terminal. I've used Dynamicap and Rifa blue brick polyprop, but this is not snobbery; I just had spare Dynamicaps available.

Rectification is Fairchild 8A 1200V FRED available from http://www.percyaudio.com/

These elleviate the need for the snubber caps on the PSU board so these are omitted. Remember the GZ37 is not used for rectification, but as an ingenious soft start on the HT.

On the driver board, all low ESR electrolytics are double bypassed with Dynamicap and Arcotronics, not visible because they are on the other side of the board.

Battery bias has been applyed to the 6072 and these batteries are clearly visible. Note the Chris Venhaus (V Audio) V-caps for coupling the 6072 and 5687.

The driver board is populated with Blackgates and of course you'll note the use of Mills and Kiwame's in the cathode bias section.

All signal wiring is IPL IC2 or HU1...I like this stuff.

Please note the star earth busbar I created using tag strip at the rear of the chassis.

I think that's about it but no doubt questions will follow which I'll be happy to entertain.

Best wishes,

Greg

[david counter]

All credit to you Greg, it's really nice, make me quite envious

[Greg.]

I should also have mentioned that R2 are in my view critical input resistors and are Vishay small but expensive bulk foil also available from M Percy.

Best wishes,

Greg

[Clive]

Greg,

It does look good, I've been studying this pic (you sent a while back) for some months in the anticipation of picking up my hardware for my 300B PP build.

Cheers,

Clive

Greg, what value is R2.