Matched Quad for KaT6550

[jdd308]

Hi all,

Haven't posted here for a while, hope you are all well. I am certainly still enjoying my valve amp, and I ditched the surround sound system in favour of valves for film watching too!

I have just read the technology section on matched valves, and it suggests a matched quad for my 6550 amp as it is a push pull design.

Having just ordered and received a new set of Tung Sol valves, it looks like I have been sent 2 sets of matched pairs: 2 valves are 68mV and 2 valves are 76mV.

Before I send them back, should they all be the same value? The last lot were all 83mV for instance. Or can I get away with these 4 in my KaT6550? If so should I put identical values in each channel?

Thank you!

John

[John Caswell]

Hi John,
No it is not necessary to have a set of four identically matched valves for your amp.
Each side will however benefit greatly if the two valves are matched as closely as possible. This will balance the HT current through the output transformer therefore avoiding hum due to unbalance, and also reduce the possibility of DC saturation of the core which can lead to distortion.
So...
Put one matched set one side, the other matched set the other side, sit back and enjoy.

John - Dr John

[jdd308]

That's great, thank you Dr John as always!



John