Neal Gibbons' original WAD 300B PP with 3 clones

[Greg.]

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What a lovely group.

Neal's looks identical to mine (except for his CVC 300Bs) including the Pearl Coolers on the miniatures which add to the 'industrial and black' look of the original kit! (A public 'thank you' to Neal for his generous time and assistance with a problem I had with mine recently.)

The clones look lovely with their front plates, I'd guess that the one behind Neal's is yours Greg (I can just see the white bases of the EH GG 300Bs!). The two on the right also look interesting with their different PSU capacitors and the higher mounting of the GZ37, I'd considered getting my 300Bs higher to maybe improve appearance but will probably leave it.

Moving the on/off switch and fitting a front plate appeals though ...

[Clive]

I'm unclear why WAD originally placed the valve sockets so low down. I know that 300B's can use the spigot on the side of the base to ensure correct orientation but just about every 300B in use today has it's socket mounted close to flush with the top plate.

OK, there's a slight chance of installing 300B's the wrong way around with "high mounting" but this is offset but the dangers of having to remove the base plate and fiddle around when changing valves. There's a distinct possiblity of breakage too.

Also, low mounting simply looks wrong to me.

Are there other reasons for the low mounting?

Great picture!

[david counter]

the only reason that comes to mind is like my Glasshouse did WAD have a optional cover that went over the valves

Hi Clive,

I'm not sure why the sockets were mounted so low, the chassis height is determined by the other four large lumps of iron inside the case (well the two interstage TX's mounted on the sides).
I'd guess that WAD took advantage of the space and mounted the big valves low down so as to reduce overall height.

The chassis holes for the triodes do have spigot cutouts (for 300B and 300A) even though my 300Bs don't have a spigot!
However, it is impossible to install 300Bs the wrong way round as they have two pairs of pins which are different sizes, this is matched by the sockets like this (but round, not square!):
::

I've just tried and the only way the 300B valves will fit is the correct way.

David may have a point about an optional valve cover, which would tie in with my 'overall height' theory.

[Clive]

Maybe the height theory has it.

Re incorrect insertion of 300B's, it is possible with some sockets, obviously not with yours, so they seem like good sockets.

[Greg.]

Matt, once again your observation skills excellently well demonstrated Front right is Steve Grimshaw's and rear right is Mel's at the time fitted with Paul's TJ Meshplates. You may recall that in our tube test, we liked the TJ's the best although some of us are a little concerned that with the mesh design, recommendation is to drop plate dissipation to 18 to 22 watts. Our second choice was the EH gold grids which, when you consider their affordability has to be the current 300B bargain. It was interesting that our finding's correlated with Clive's earlier tube roll test published in the supplement.

The front plates were also made by the chassis manufacturer. Mark and Phil agreed for them to be silk screened with the WAD emblem as we expressed our wish that their pedegree should be recognisable and of course it brought appearance up to date to match other WAD kit we owned. They did this generously for free. The mains switch at the rear was, as with later WAD's to avoid AC wires crossing close to sensitive components. Look carefully and you will see the vents in the top plate are narrower and more pleasing to the eye (IMO) than on the original. In error, the fabricator omitted the vents either side of the GZ37, but as little heat is generated here, it's not an issue.

I was lucky enough to get some original blue LCR PSU caps, that I sprayed black with enamel, from Nick Lucas just before he left WAD. As far as I can tell, at the change over to Mark and Phil, alot of components were thrown in the skip (Nick told me they had plenty of stock). Mark could not find them so the other guys used motor run caps which work equally as well. The Tx covers are zinc coated although James and I got ours chrome plated. We had a few alignment problems with the GZ37 and it's PSU PCB, hence Mel's and Steve's mounting the valve socket direct to chassis top plate. I managed to get mine counter sunk but it was a hell of a fiddle.

Clive, counter sunk mounting of the 300B's is no problem. To remove valves, gently pull and rotate in a slight circular motion and the valve will pop out without any stress to the glued glass and valve base joint. Even quality UX4 sockets don't grip the pins that hard. Raised or counter sunk? It's personal preference based on aesthetics alone. I like them sunk. It looks more streamlined to me that way.

I'll post a picture of the innards and comment on other things we did.

Best wishes,

Greg

[Clive]

Greg,

I'm pleased and relieved that our findings on 300B's line up!

I am though a little concerned about the method of removing and inserting 300B's, are you really saying you're exerting even just a little pressure on the glass envelope? I suppose it's ok if you're not rolling lots of valves and therefore swapping them around a lot. I wouldn't do this with the WE300B's I have....and I have a loose GZ32 envelope from needing to do this on a Cornet2.

Cheers,

Clive

edit: by the way I don't use the WE's, still in line with the article, not my favourite 300B's but they are better in the WE91.

Thanks Greg!

I'd also noticed that Steve and Paul's TX covers were not as shiny, but didn't want to criticise their lack of polishing!

I hadn't spotted the vent sizes, do you have the same amount of ventilation though? This is where all the heat streams out of mine, and I think that heat may have had something to do with my recent problem (both R6s had gone high - Neal kindly sent me replacements for those and two new C2s too, to follow his advice and confirmations).

I remember from the original article that the capacitors were bright blue, which would have looked odd - Paint it Black indeed! Mine and Neal's both have the black ones with the WAD 300B PSU printing on them.

The clone's chassis is surprisingly close to the original even including the bottom plate seen in another thread, though it seems like some of the details around the GZ37 may have been a little 'out'. I assume that the chassis fabricators included mounting threads for the front plate and relocated the switch hole? I may have to PM you about the front plate ... !

To remove my 300Bs I grip them low down and gently rock them up and out, you may remember I bought six of them and rotate the pairs whenever the clock changes! My ceramic sockets do have quite a tight grip and Clive has a point about the glass envelope, was it you that could smell some glue curing (between glass/base) when you first got them?

I've realised that mine had a few tweaks in it (e.g. cathode resistors already upgraded and uprated to 1.5k) so I'm looking forward to an internal shot of your boutique components.

[Greg.]

Yes Clive, I'm pulling on the glass envelope, but the glue is good quality fish stock, judging by the smell for the first 36 hrs ( ) and being gentle it's not a problem. As you say, unless tube rolling, we don't need to do this often. Remember there are 300B PP owners out there who've never had a problem in ten years although I'm sympathetic to you sentiment as pulling on the glass goes against the grain and logically we'd be happier pulling on the valve base. One could pull on the glass a bit to reveal enough base which then could be pulled on if you're paranoid here.

I also would not treat WE's this way. As the sound is so poor, I'd have them on eBay pronto

As an aside, loose glass envolope to bases (I use NOS or good testing second hand so get this problem occasionally) can be well dealt with by drizzling superglue into the joint or in extreme cases use epoxy although, from a previous thread on the old forum, I think Richard has some alternative and good suggestions on this.

Matt, yes ventilation is fine. You are right that the cathode load resistors get really hot but the venting is fine. In contrast, Max who built his with a wood chassis and CAD Ali top plate has no venting and bolts his resistor type direct to the top plate for use as a heatsink and it works for him.

In a HFW article published in Sept 1994, Noel stated that the later PSU caps finished in black with WAD printing on them (C11/12) had been especially manufactured for their use. I don't think they were LCR's and the quote was 'polyprops are manufactured to our own specification using an audio grade metallised film.' I consulted Nick on this and he stated this was something to do with round spherical objects and that all that was different from the blue LCR's was the outside cover. I don't know, but I've listened to Neal's amp and I can't really tell any difference.

On the chassis fabrication, I did request new cutting for the mains switch at the rear using the application information of the component manufacturers. In particular we went for seperate switch and socket with the socket screw fixed to the chassis because with experience we didn't like the clip in options used by WAD which in time becomes insecure. The seperate switch was especially sellected for it's anti-surge properties with a view to avoid fuse blowing and to give the whole thing a softer time at switch on.

Your cathode bias resistors set at 1K5 is interesting by it's independance because that is the value I settled for in conjunction with a slight drop in HT to bring plate dissipation down to about 30W. That stopped plate glow on the EH's, although now I don't worry. I don't check either. I just play and listen. If the 300B's were to go down, I'll simply buy some more EH's. Cheap and sound excellent.

Best wishes,

Greg