Power Tubes Comparison

Telejester

https://youtu.be/mJ0M7Rpe2rI


Have a listen to this, I found it quite useful, wish he hadnt used a les paul but whatever. Havent had time for a good solid listen but immediately discounted the el84, what a ratty and shrill sounding tube and the kt66 sounds a bit lethargic to my ears.

Which one(s) did you guys like and not like ?

kreggs

Haha just read the youtube comments  that dude does look like McLovin haha

ICBM

Meaningless, since as far as I saw the circuit is not correctly set up for the different valves.

Being able to bias for different types is only a small fraction of it - the plate loading (via the output transformer impedance ratio) is at least as important and is totally different for different valve types. Without changing that, you will be hearing at least as much the effects of mismatching impedance as you are the valve types.

Typical muso misinformation about what really makes a difference. The circuit is vastly more important than the valve type. Which is not to say the valve type makes *no* difference... just that it's not the most important thing about an amp by a huge distance.

normula1

+1 on @ICBM 's view

I recently tried a 6v6 equivalent in my Laney Lioheart L5T with a correction to the bias component values. In theory the 6v6 has a similar impedance requirement to the stock EL84.

I recorded some guitar into a looper to eliminate playing differences and ran the amp into a reactive load and then into a DAW with one of the Celestion IRs and recorded the output.

There was no difference at all in the sound until the amp was cranked fully and even then whilst noticeable, the difference wasn't that massive. The 6v6-alike was clearer in the top end but that was it. I tried a few different versions of EL84 and unsurprisingly I suppose, a Mullard from the late 50s was the best sound by far.... but only when cranked. At normal levels there was sod all difference really.

I carried on the test to try different load boxes and again when cranked there was a massive difference between a reactive load and a purely resistive one. At lower levels the difference was still noticeable but the difference was less pronounced.

Modulus_Amps

These comparisons are only really relevant to the amp they are tried in, One cannot assume that one valve in one amp will sound best in another amp too, most people don't have the option of trying different OT's loading speakers etc

so different valves do sound different in the same amp, but they sound differenter in in another amp (yes I made up that word)

Doing a test with a restive load is also useless, speaker impedance is not constant across the frequency spectrum and nor is valve impedance.

martinw

+1 What you've already said.

The only  further thing to add is that some circuits highlight changes a lot more than other circuits. Further to that, some output valves are more differenter than others!

I've built a few amps with switchable output valves....that's fun, and demonstrates things nicely. Being able to A/B backwards and forwards allows you to hear what you would probably forget if you to physically change the valves.

DJH83004

martinw said:

+1 What you've already said.

The only  further thing to add is that some circuits highlight changes a lot more than other circuits. Further to that, some output valves are more differenter than others!

I've built a few amps with switchable output valves....that's fun, and demonstrates things nicely. Being able to A/B backwards and forwards allows you to hear what you would probably forget if you to physically change the valves.

The Egnater Rebel 20 does just that (2 x EL84 & 2 x 6V6) with a sweep control from EL34 to 6V6, I didn't find it made a massive difference to the sound, and came to the conclusion that the circuit topology & design made it far more 'differenter'   

ICBM

DJH83004 said:

The Egnater Rebel 20 does just that (2 x EL84 & 2 x 6V6) with a sweep control from EL34 to 6V6, I didn't find it made a massive difference to the sound, and came to the conclusion that the circuit topology & design made it far more 'differenter'    

The Mesa Blue Angel also had 4xEL84 and 2x6V6, which at first looks odd, when the available power and the impedance are quite different between the two sets - but I came to the conclusion that was actually the point, because a lot of what people think of as the 'characteristic 6V6 sound' (largely based on the Fender Deluxe Reverb) - that compressed, slightly flubby overdrive - is in fact a result of a low impedance mismatch, which the Deluxe has as stock and was deliberately designed into the Mesa.

If you swap the Mesa to running the 8-ohm speaker from the 4-ohm tap when using the 6V6s to mostly correct the mismatch, the sound is less different from the EL84 setting.