300B advice

[Lyndon Johnson]

The 300B's are up for replacement on my 300B PP (original, unmodified circa 1995).
Currently it is fitted with Electro Harmonix from Hot Rox and it looks like I can get a matched quad from them for £288 including postage, which seems reasonable.
Before I do, I thought it a good idea to consult the forum. Reading reviews it seems there are plenty of better-sounding valves out there but there isn't much consensus on which they are! Prices start to get silly as well.
Any advice appreciated.

[Greg.]

I was always happy using Electro Harmonix Gold Grid. The standard EH 300B’s sound a bit dull. There is a lot worse than the Gold Grids out there and as you say, some are also silly prices.

[Little Mick]

Another recommendation for Electro Harmonix Gold Grid bought some time ago from china arts on ebay from memory

[Lyndon Johnson]

Thanks both. The gold grid is dearer (£90 vs £72) but from your comments it sounds worth the extra outlay.

[Greg.]

Definitely. If you liked the basic EH’s, you’ve got a big treat coming with Gold Grids. Musically they are on another level and well worth the extra expense. I was with Richard several years ago when we made the comparison and we both acknowledged a marked difference in performance. As said before, the basic EH 300B is dull in comparison to the Gold Grids which make the music sparkle.

Interestingly, several years ago I and some others made a comparison of about five Or six different makes of 300B. I can’t now remember a couple of them apart from the EH Gold Grids, some JJ’s, and some GE’s (surprisingly disappointing considering their price) and a set of TJ Meshplate. Overall, I preferred the TJ Meshplates but they had disadvantages in that with a less robust plate, to avoid plate hot spots (plate glow), dissipation had to be reduced to at least 22W. That is a long way short of the max spec of 40W and consequently output is reduced. Also, the TJ’s are much more expensive.

Reducing dissipation is always helpful towards increasing valve life. I reduced the dissipation on my circa 1995 WAD 300B push pull clone from 40W (Andy Grove often designs amps so the output valves are operating at maximum dissipation) as my EH GG’s had plate glow, to about 32W without suffering from any noticeable effect from reduced output, but it did eliminate the plate glow. Dissipation is well worth looking at in all valve amps and simple to test. Simply run the amp for a while and then, in a darkened room, inspect the plates for any sign of plate glow. You are looking for any cherry red spots on the valve plate.

[pre65]

Not really on topic, but on valves like the 833a, a red spot on the anode is a sign they are in a good operating condition.

Sadly, my own amps using 833a have not (so far) got the red spot.

Another thumbs up for EH gold grid 300b, I've still got my pair somewhere.

[Greg.]

Indeed, but we don’t want plate glow on 300B’s especially as they will be in amps which are used day to day domestically and the owner wants to get the best affordable longevity out of the valves.

833a and some of the boat anchor builds sound best with the plates properly glowing, but this is outside the domestic criteria. It’s great fun at Owston etc but no regard in these circumstances is given to valve life and cost of replacement. It’s a very different scenario.

[Lyndon Johnson]

Just to say I have ordered this morning four EH Gold Grids from Watford Valves and I will report back on how they sound when the time comes. I'm not sure how much running in they will need before I can pass judgement?
Incidentally, plate glow is something that prompted replacement. I noticed that one of the four was glowing quite brightly in one patch, along with a projected pattern of blue 'plasma'. It was valve-specific in that the same valve showed it when I swapped it round with another.

[Greg.]

Excellent. EH GG 300B’s are a good price at Watford Valves at the moment.

[Richard]

Hi Lyndon,
If this was GerryB's amp I helped sort it when he first bought it secondhand. Did we meet briefly at Gerry's, sorry if I'm wrong, it was a while ago?
If so, we set it up with just the 1k5 cathode resistors in place and it didn't have any redness on the plates so it should be fine for all current 300Bs except perhaps meshplates. Hopefully the redness on one valve now is just old age.
From memory Gerry had Gold Grids.
I had a set of Standard EH in black boxes and Greg is right to say the ones he heard at my house did not have the same sparkle of a newer set of Golds, but mine were used by then and I don't think there was much between them when new. I did replace mine with Golds and they were for me the best of 4 types I used back then