Valve swap EL84 to CV4043

normula1

So, I've always had a hankering to try a 6V6 valve in place of an EL84 but have always balked at the idea of cutting an octal hole in my chassis to achieve it.
Recently I came across the CV4043 which is a ruggedised version of the 6BW6 which in turn is apparently a 6V6 in a B9a bottle.

I've zero experience with beam tetrodes so before I bugger something up and get loud banging noises accompanied with the smell of fried electronics, am I correct that to fit the CV4043 in place of an EL84 I'd need to swap pins 9 to pin 8 on the socket or is more / less complex than that?

CV4043


EL84

I managed to get the CV4043s for £5 a pop at Langrex so thought it worthwhile a punt

ICBM

You also need to connect pin 9 (suppressor grid) to pin 3 (cathode), which is done internally in the EL84.

Be careful that there's nothing connected to pin 1 on the socket as well as pins 6 and 8 - this is IC (internal connection) not NC (no connection). Some modern amps use pin 1 as a component support, usually for the grid stopper resistor to pin 2, because many modern EL84s seem to be made with it as a NC… which works fine, until you put a NOS EL84 in the socket and it does something nasty, blowing the valve and sometimes damaging the amp.

Other than that I *think* it should work OK…

normula1

Thanks @ICBM. It was the pin 9 to 3 that was flumoxing me.
They're going into an old stereo hifi chassis from 1961 that many years ago I reworked into a stereo power amp along the lines of the Marshall / WEM 18 watt circuit so I'm pretty sure that pin 1 is unused, but I'll definitely check first.

Funkfingers

Interesting thread. I have always fancied making the same EL84 to 6V6 valve swap in my Boogie 20:20. 

normula1

So I finally found the bottle time to give this a go. I opened up the Lionheart as the socket is really easy to get to and work with and made the socket wiring changes which took all of five minutes.

Prior to the change I'd recorded a few guitar parts into my Ditto looper and recorded the EL84 output into Ableton and did the same with the CV4043 afterwards using exactly the same settings.

On a clean sound as I expected there's very little tonal difference to my ears at least although the EL84 is a tad louder as I believe the CV4043 is harder to drive.

Cranking the "clean" channel to full revealed a difference in that the CV4043 sounded a little clearer or maybe less congested in the lower midrange than the EL84 and sounded really nice.

Given that I rarely run the Lionheart this way and the CV4043 is shorter so the wire retainer is too loose without modification I think that I'll put the EL84 back in but in my stereo power amp where I'm looking for a clearer sound I reckon I'll make the swap.

normula1

Necro bumb !!
Finally got round to doing this in my stereo power amp and very pleased with the result so for. As with the Laney, they does seem a touch clearer than the EL84s even at the low volume I was testing them at.