Valve amp startup question...

Hello all,

I’ve just acquired a Mini De Luxe 609K that’s been in regular use with the previous owner since new.

It all seems to be working but there’s a 15-20 second delay from pressing the on switch to actually hearing anything. Is this usual? I’ve never owned a tube based amp before so not sure if this is part of the charm.

All but one of the valves are printed with ‘B&O 63’ in white (in addition to their manufacturer) so presume they’re original. Not sure if I need to source replacements - I’ve read that the ECC85 is a particularly hard working valve?

Any advice would be great.

Quite normal. The valves won’t do their job until the filaments (actually cathodes) are hot and start emitting electrones.

Common valve types aren’t particularly difficult to source, but it could be useful to have a spare If you want uninterrupted service. If they have lasted almost 60 years, they probably won’t give up this month either. Other problems may surface it the set has been sitting mostly unused for years.

Thanks mika - good to know!

As Tournedos says, quite normal for any valve equipment. When I was a child, we always 'waited for the radio to warm up' - literally - before listening to it.

I don't know where in the world you are, but here in the U.K. Watford Valves' website is currently showing all the valves for the Mini 609K 'in stock'. (My only relationship with them is as a satisfied customer - very helpful on the 'phone).

The 'small-signal' valves usually have a very long life, output valves less so. Depending on how 'stressed' they are - how much of the theoretical performance is being used - they may last only (say) 3000 hours or so. Your other problem, if not used to valve equipment, may be the need to re-bias the output valves (depending on the circuit used). Valves aren't always 'plug & play'.

Adam K, London.

Thanks Adam - that’s really helpful. I’m in the UK and have been on the Watford site whilst googling to check availability and cost etc. I’ll have to read up on valve biasing!

If you plan to work on that amp (or other valve kit) yourself, here's a great resource on technical literature:

http://www.tubebooks.org/

Sure they are old, but remember that all the theory you need in order to understand your 609 was probably known by 1950 - and mostly omitted from books written a couple of decades later