5687 replacement tube.

[bikerhifinut]

They're in the post Bob

Andy

[bob orbell]

Thanks Andy, I will report back. Bob

[bikerhifinut]

Originally Posted by bob orbell

Thanks Andy, I will report back. Bob

Did they arrive safely?

Andy.

[bob orbell]

Not here yet Andy, don't forget the post is running short staffed because of you know what I will post on arrival. Thanks' Bob

[bikerhifinut]

Fingers crossed, usually parcels arrive safely via Royal Snail.
It was sent 2nd Class and I packed them in a stout cardboard box.
That said, It took over a week for a couple of AAAA cells to arrive finally yesterday. Odd size of battery, couldnt find any in the shops, used in a small "One for all" programmable remote that's perfect for the HFC board, once you work out which of the 10001 permutations does the job!
Regards.
Andy.

[bob orbell]

Arrived today Andy, all in good condition, I will let you know how I find them. Thanks'. Bob

[bikerhifinut]

Just Bumping this up Bob.
Have you tried them yet?
I have to say I think the specified 5687 are preferable.
But you could always have a play with the E182CC in a cathode follower maybe.
They weren't made for low distortion being industrial valves for stuff like early computers where resistance to cathode poisoning and general ruggedness were more prized. This might preclude their use in an amp with minimal feedback to tidy up any distortion.

Andy.

[bob orbell]

Hi Andy, yes I have had them in and to cut a long story short they just don't sound right, I will give more information soon but need to sit down and look at my notes and put a story together. Bob

[Richard]

Yes, see my earlier post 2, they didn't sound right to me either and I think Andy's reasoning may be correct.

Checking a few valves yesterday on the AVO I had the characteristic setting sheet out and 5687 vs E182CC settings are at different ends of the range.

Whilst they are pin compatable it could well be that they need to be run quite differently to give a good linear audio response.

This is a different situation to other near "equivalents" such as 6550 vs KT88 and 5751 vs ECC83 where the characteristics for testing suggest they are similar and they will still work well. (Other valves such as ECC83 vs 12AX7 are identical but just have different numbers from their different manufacturers or military part numbers etc.)

Perhaps someone has used them for audio from scratch at a design level and can shed more light on preferred settings but they are not a common audio valve and anything valuable audio-wise has probably been found by now.

[bikerhifinut]

I would agree Bob and Richard.
I didnt hear a marked difference but there was to my ears a kind of missing "mojo" to the sound.
But they really aren't meant for Audio and are not very linear, you have to use feedback to get anything like a linear response.
At least they didnt cost you Bob, I found a few in a box of ex BBC assorted valves I bought last year.
As noted by me earlier, I think they might make a reasonable Cathode follower as that uses 100% degenerative feedback and so most non linearitiy is cancelled out.
They're basically "industrial" valves designed for early computing and switching/control applications as far as I can find out. Constructed to resist cathode poisoning when running unbiased and no HT applied, again from what I can find out and maybe a bit off the bullseye there.

Richard, I think that with few exceptions, you're always better using a Valve either specifically designed for Audio, or a GP or other Valve with proven historical track record in audio circuits. One such valve is the ECC88, not one of my favourites admittedly but used a lot in serious Audio but designed for use in VHF radios. theres the caveat........ care needed to avoid oscillating but not a huge hurdle if known about.
Another valve that works better than it should on paper is the Humble ECC82 which considered on its own merits has a pretty poor distortion and linearity figure, but in a sympathetic circuit they make a good low gain line level amplifier and an excellent cathode follower.
The ECC81 again an RF Valve in design but makes a good medium mu AF amp with attention to grid stoppers etc.
There many others which I am sure we can all think of.
I see people reinventing the wheel all the time, and frankly at my time of life i can do without wrestling with RF transmitter valves and TV Line output pentodes when there's plenty of current production proper Audio "toobs"
Just my thoughts scribbled down.

Andy