Another tube newb

[fauxpas]

Took a splash on a chinese valve amp and am impressed. Sounds great compared to any of my modern amps a I imagine it doesn't come close to high end exotic valve amps. I have a few questions though.

The valves listed on the unit are 6F2 (ECF82) and 6P3P (6L6). With the 6L6 tubes, can I use any 6L6 as long as it fits? Can I use KT66 in place of the 6L6?

Regarding run-in and warmup. I've heard some outrageous run-in times (300 hours?) but when can I expect the amp to be run-in? Also I have heard ppl say 1 hr for a warmup? True?

Sorry to be a newb pain but I wanna get my basics right as I think I'll be keeping the amp for the duration and rendering all my transistor amps to doorstop duty.

[SY]

when can I expect the amp to be run-in?

About the time that the tubes give out.

Tube-rolling without appropriate circuit changes is unlikely to help performance, but it will give you lots of wrong things to tell your friends about.

If you want to seriously delve into it, get a basic set of tools together (meters, oscilloscope, signal generator at a minimum), read extensively (there's no better introduction than Morgan Jones's "Valve Amplifiers"), get a schematic for your amp, and start digging in. You'll find lots of help and support here on the forum. But willy-nilly substitution of tubes just because they're on top, look pretty, and can be plugged in and out is not the best way to optimize an amplifier's performance.

Do it right and you'll be hooked, I promise you.

[Kent Smith]

You can try different makes of the same type tube and get a little different overall sound.... I have tried a few different 6L6's. Which is best is a matter of personal preference and the circuit (and how it's adjusted).

Tubes (and just about everything else) do change over time. I adjusted my amp using new tubes, then had to re-tweak a few resistor values after awhile. My question would be: did the maker fine tune the circuit with new tubes or old.... and how old? That would answer the run-in time Q.

On warmup, I'm probably not as picky as some. I notice a little change over the first few minutes, not much after that. So I don't give it much.

Sorry, I probably give you more questions than answers. But things are more complicated than the non-technical guys tend to believe. It is fun to experiment with different tubes (and caps and other things), and sometimes you can stumble upon a combination of things (including speakers and source equipment) that just sounds "right". That's part of the fun of this hobby.

[Klimon]

ECF802 makes a great replacement for ecf82; same pin-out, different specs. In Dynavox vr-70e they sound better even without any bias modifications.

Simon

[fauxpas]

Originally posted by SY


About the time that the tubes give out.

Tube-rolling without appropriate circuit changes is unlikely to help performance, but it will give you lots of wrong things to tell your friends about.

If you want to seriously delve into it, get a basic set of tools together (meters, oscilloscope, signal generator at a minimum), read extensively (there's no better introduction than Morgan Jones's "Valve Amplifiers"), get a schematic for your amp, and start digging in. You'll find lots of help and support here on the forum. But willy-nilly substitution of tubes just because they're on top, look pretty, and can be plugged in and out is not the best way to optimize an amplifier's performance.

Do it right and you'll be hooked, I promise you.

Already hooked, just by sound, not even getting into the electronics of it yet...

I was asking about the different tubes in relation to ever having to replace them. I find some tubes easier to locate than others and just wanted to know if the manufacturer states 6P3P (6L6) and the tube itself is stamped 6P3P, if they give out can I replace them with 6L6 tubes? Are 6P3P & 6L6 the same thing?

I've noticed already the amp sound heaps better after half an hour to warm up...

[TubeHead Johnny]

There are several 6L6 variants you can use when these wear out, as long as each tube is biased correctly, and they're not operating well above the dissipation rating. These variants include 6L6GC, 6L6WGC, 5881, or KT-66. There are others but you will need to mod the bias supply (If it's fixed bias). Grid bias feed resistors may have to be changed as well.

[fauxpas]

Excellent. Thanks.